integrally suppressed old French .22LR pistol

[quietoldfart]

I've acquired a 1950's Unique D4 pistol. The manufacturer's stamp reads MANUFACTURE D'ARMES DES PYRENEES FSES - HENDAYE -. It was initially in reasonably good shape. Some previous owner replaced the grip with a two-part walnut affair which was oversized and quite wobbly, so I trimmed that and glued the halves together and generally carved it into something usable. Also done a number of small modifications to the mechanics of the pistol to make it function more smoothly. There were feed problems owing to a sharp lip on the feed ramp and worn lips on the magazines but these are sorted and it seems very reliable now.

As I'm near other properties and don't get out much I wanted to make the pistol quieter for practice at home, and so decided to make a suppressor. I am not residing in the USA, not a US citizen. The finish of the pistol was rather rough, not exactly battered but not in a collectible sort of condition either, and since it has an unusually long barrel I decided to go ahead and port it for quieter operation even with regular, non-subsonic ammunition. I initially drilled with a 1/8" twist bit and trimmed inside with a small carving burr, but as these holes weren't terribly neat and suppression with rated 1280fps .22" LR was still borderline supersonic I re-bored using a 5/32" square endmill and again dressed the inside edges to de-burr using a carving burr and a half-round diamond file. cloth doesn't catch when cleaning the barrel and it appears smooth, and accuracy attests to the porting not being a factor at close range. I've not yet managed to get out to the woods for a proper longer range test, but I'm happy with the results so far.

The materials:
- 1" OD aluminum seamless tubing 12" long from a hardware shop, with a 0.87" ID
- 6061 aluminum vent plug at the reduced muzzle step (the pistol held a factory compensator previously)
- high temperature acetal resin rod turned for rear plug over the barrel and front plug
- 6 K baffles of 6061 aluminum, turned to my specifications by a fellow member here - rrdstarr - who made 8 to give me extra baffles to experiment upon; these were left quite thick with no vents and a 1/4" face, each bored to 0.25".
- 6061 blast baffle I turned and bored initially to 0.235", but after some concerns about excessive heating bored again to 0.25" which seems to have resolved the issue - bored a 1/16" 'Dater' hold after some use.
- 0.050" aluminum tube spacer 0.5" long before blast baffle, again to reduce heating
- 2 x 10-32 set screws to retain the plastic front plug, 2 x 1/4-24 set screws to retain the suppressor in a shallow detent bored into the bottom of the barrel near the muzzle and the rear plug on the tube
- copper plated stainless scrub pad stretched and twisted, beaten flatter and wound around the barrel on assembly

I've played with dimensions of the K baffles a number of times, gradually reducing wall thickness and trimming face curvature, fitting them together, tapering the backsides of the faces to an angle, cross-venting as is commonly shown in these forums, and finally boring a series of small holes in the first K and carving bleed holes in the outer edges of the K cones to increase flow to the spaces outside the baffles as deposits there were not adequate. Each of these steps has reduced blast volume a bit. The net effect is a suppressor which is somewhat quieter than my Brocock Atomic PCP pistol in .22" shooting at about 600fps with 14gr pellets. In this video I fire 2 shots from the suppressed Unique using Remington subsonic (very quiet!) followed by one shot from the Atomic, suppressed using a 7 K baffle stack made of acetal rod - this pistol is quiet enough for squirrel hunting without disturbing neighbours, when suppressed, but very loud to the point of being somewhat painful unsuppressed. Click the image to go to a page where the video should play:



Here's the 3 shot result from that test, at 5 metres from a putty trap, the lower two shots being from the firearm and the upper one from the air pistol:

So accuracy doesn't seem to be a problem. It seems the bore is reasonably concentric to the outer barrel resulting in decent automatic alignment between the plastic rear plug and aluminum vented muzzle plug:

I considered threading the barrel for this part, but decided for now just to use a set screw. Eventually I'll likely build another version, probably an inch shorter and with shorter K baffles without the waist, bringing the number of K's up to 7 and using a stainless blast baffle. At that point I'll likely use a M23 x 1mm tap and matching die to cut threads in each end and plastic end plugs to thread in, and perhaps at that time I'll thread the reduced barrel section for a new muzzle plug with simpler, more open venting. Thanks to this venting there is zero FRP.

Here are some photos of the various parts and the pistol:


















This last is the baffles at one stage of trimming after about 60 shots. It's quite obvious how the outer cones are not getting very dirty at all, just smoked a bit. Now with the vents trimmed into the outer cone edges the outside filth is slightly worse than that inside, making it more difficult to dismantle for cleaning but obviously doing a superior job of quieting the blast.

Thoughts on a future K baffle (in MS Paint) derived from some of the more professional types seen in forums, though I'm not sure my tiny hobby lathe is up to machining complete K baffles in aluminum. It does fine in acetal rod, but tends to be a bit scary when trimming the aluminum at times. But keeping the tools sharp and feed rate slow I can usually manage without chatter at a medium speed, unlubricated. Cutting stainless for the blast baffle might be something I have to have a friend do for me.


I know over-the-barrel integral pistol suppressors are commonplace for Ruger owners, but thought this unusual pistol and somewhat funky home-made assemblage might be of some use for other hobbyists. Obviously I'm less than satisfied with the set screw solution, but the plastic at each end doesn't seem to be a problem. Distance for the front plug makes for very little heat getting to it. And the rear plug did overheat a little with the smaller barrel ports and no metal scrub 'yarn' around the barrel, but with that mesh in place sound is slightly reduced and the plastic suffers not at all. There is some carbon build-up on the over the barrel portion of the tube as the ports are quite close, but as long as I remove the suppressor every hundred or two hundred shots and wipe the barrel and put a film of lithium grease on it again the barrel itself doesn't have any build-up. Shooting 1280fps rounds is now just a little bit louder than 950fps subsonics, and both make similar impressions on the electrician-type duct seal trap so it seems I've brought regular velocity ammunition down to below 1,000fps. A chrony test with the 950fps ammo showed it averaging 925fps with smaller ports. I used a rather bad ball endmill in a drill press for the venting of the K baffles, tending to smear as much as it cut. Now have a proper set of mill cutters so the next version should prove a little easier and tidier. I'll be investing in some new carbide cutters for my tiny lathe as well which should make K carving somewhat more practical.

[Historian]

Bienvenu.

Thank you for showing your classic pistol and the
fine sound reducer you made for it.

Fine machining.

You prove the old adage that length and volume crucial to sound
reduction. More is More in this category.

Out of curiosity what are the popular lathes in France?


Best wishes.

[quietoldfart]

I'm actually an English variety of old fart, now mostly retired on the Continent, just lately moved over, so I'm not terribly familiar with what's popular here. I acquired a TAIG micro lathe from Lee Valley tools in Canada some years ago along with a 1/4 horsepower motor to run it. Between the tiny V belt with a tendency to slip and the rather less than rock steady tool holders for the 1/4" tools it is not really what one would shop for if one were contemplating suppressor manufacture! Hence my reliance for now upon a friend for the basic turning of the aluminum K baffles. I did manage the blast baffle and vented muzzle plug, with moderate difficulty. I expect the most challenging element will be turning the inside of a new K cone from rod. Have to look into what sorts of countersinks are available to render this a bit less chattery on a low-power lathe. Or perhaps I'll simply drill the centre bore then gradually eat away at it until there's a hollow K baffle, rinse, repeat... Seems likely to be very tedious but then again most of the fun in suppressor building is in the experimentation, so I'll try to be patient.

As for length; yes indeed, a foot long suppressor is somewhat lengthy! The D4 has about a 7.5" barrel measured from breech to crown and I've hidden about half of that inside the tube, so the part in front of the muzzle is about 7.5", only about 2" longer than a normal commercial 6" long can would be on this pistol, counting the roughly 0.5" threading. Still long, with the pistol's length coming in at about 18.5" overall, but with the weight including 10 round loaded magazine at about 2 pounds 2.25 ounces (about 970 grams) the pistol feels very light.

[windchaser]

Very unique and interesting. Thanks for sharing.

[quietoldfart]

I've been further playing around with suppressing the pistol above, and have found some success and a couple of interesting, not exactly intuitive results. Briefly, I'm tending to favour an 8" tube over the 11", both for handling the pistol (it is VERY long with the 11" tube in place!) and for the fact that the 8", with superior K baffles, is almost as quiet. Further, with Remington CBee rounds (which now cycle the action of my Unique, as I found a Glock 17 firing pin spring plus an 18mm preload spacer was just the right amount weaker than the original spring) the 11" tube with 11 baffles about 0.55" long plus a blast baffle tend to cause slight clipping, enough to get keyholing at fairly short range but not enough to damage the aluminum baffles. I don't like the CBees as they're very dirty, but they certainly are quiet. I'll be getting some CCI Subsonic soon and those should be about right. Federal bulk rounds still cycle perfectly with the lighter spring arrangement, so I'm happy with how the pistol is working. Anyway... quantifying noise levels is more interesting to me at this stage:

A friend of mine who also likes to experiment with baffles, mostly on air weapons, decided to buy a pair of cheap digital sound meters, so as to enable easier comparisons of our latest results from two different cities, as we've yet to shoot in the same place. Here's the one:
http://www.ebay.ca/itm/Portable-Digital ... 27d482bcfe

It's about $17 on eBay, a bunch of Asian sellers peddling the things. We didn't have very high expectations considering a decent meter costs in the thousands, but what the heck. I've been very pleasantly surprised with how close to accurate mine seems to be. This meter has been discussed in at least one earlier thread around here, with the expert consensus being that it's quite useless... but perhaps not, at least for comparing against another meter of the same make and comparing different suppressors/baffles on the same host.

Though it's only rated up to 130dB, and the manual says it only samples 2 times per second, I've yet to see it read more than a couple of dB difference during a session with a given weapon and power level. My friend's unsuppressed Ruger MkIII 22/45 measures about 94.7dB chambering a round, and Paulson says a MkII measures 108dB. He's measuring 1 metre to the right of the muzzle and that's what I'm doing as well. So perhaps safe to say my meter is measuring 13dB low in that range? For some reason he doesn't mention firing any 22lr from a pistol in his table comparing dB levels in Volume 1, but his rifle metering for .22" standard velocity (a Ruger 10/22) is 139dB, and my meter's saying about 128dB for the Federal standard velocity. From what I see elsewhere here in discussing the subject it looks like about a 10dB increase in metered blast is to be expected for pistols over rifles, so perhaps his 139dB becomes 149dB? In which case my 128dB is about 20dB low at this highest pressure. Checking my meter's levels against common household noises it seems to get more and more accurate the lower the volume, but at these higher sound pressures it is perhaps close enough to be interpreted based on Paulson's numbers and other sources which align quite well with his.

So taking that bit of guesswork, and adding in that Remington Subsonic meters 125dB out of his Ruger, I can start comparing my suppressor results for the Unique D4 I've been testing baffles on for a while. Here's what I'm using now in the 8" tube, which my friend threaded for me as well as making a pair of end caps which I then drilled and finished on my little lathe. I'm using a 0.030" wall stainless tube around the ported barrel now, with a few dozen 1/16" holes drilled in rings away from the ports to force a round-a-bout path for the initial gas pressure. A bit of lithium grease on the barrel makes it easy to get off for cleaning. These are the baffles. I'm not using the O-ring now, it wasn't necessary. I've also taken to switching the interlocking baffles 180 degrees from one to the next as it's slightly quieter.





Here's what the can looks like on the pistol:


So these are obviously nested, the fronts of the cones turned down smaller to just fit inside the faces of the ones ahead and the last one nestling into the front cap snugly. I've gone slightly further today, testing a dense rubber sheet of sorts to make a small wipe between the front K and the end cap. There was a substantial drop in volume, especially on this 8" tube (considerably less significant on the 11" - another reason not to use it), enough to make me cut out a couple of dozen little wipe discs for later use. They cup over the exit hole nicely, pressed into place by the inside of the front cone, and on this smaller suppressor cause no apparent change in accuracy at short range, at least with the Federal. With the CBee it's hard to say, they're just not very accurate out of this pistol.

Anyway, back to the sound meter. I'm getting a metering of about the same unsuppressed from the Unique as from my friend's Ruger; 129dB for this one with the Federal. Without a wipe the 8" tube gives me an average of 116.8dB and the 11" tube gives 112dB. Adding a wipe to each, I get 109.6dB and 108.4dB respectively. with only 1.2dB between them wiped, the choice is obvious, the shorter tube wins for convenience in handling and storage. Testing with Remington Subsonic I get 108dB for the 8", 106dB for the 11". So the quieter the round, the less difference between cans. Going to the CBee, it's 106dB and 103.5dB. Wiped, I get 100.5dB and 101.6 for the two cans. Now to adjust those numbers, guessing at the relative error in this range as compared to a proper meter. I'll go with 17dB worth of error, about midway between the lower action-closing error of 13dB and the unsuppressed firing error of 20dB.

Federal SV:
8" goes from 116.8 to 133.8dB, and wiped goes to 126.6dB
11" goes to 129dB, and wiped it's 125.4dB

CBee:
8" reads 123dB and 117.5dB
11" reads 120dB and 118.6dB (actually consistently LOUDER than the 8" in this combination!)

I ran out of Remington Subsonic.

To my ears it seems perhaps these numbers are being a bit harsh in terms of interpreting the meter. My unsuppressed PCP carbine shooting .22" at 610fps from a 10" barrel reads 117.4dB, and it's painful to hear indoors, where the CBee through the 8" tube is about the same measured volume, but doesn't hurt at all. Perhaps a frequency thing, as I'm more sensitive to higher frequencies and the pop of a PCP is definitely high pitched. At any rate, it's obvious I'd need access to a high end meter to get proper results. Just playing around with relative volumes, and for this purpose the meter seems very useful as it tracks even small design changes very reliably. Going from 5 short K baffles in the 8" tube to 6, by nesting them instead of butting them cone against skirt dropped the volume by about 4dB. That's useful information, telling me I'm on the right track. And knowing that there's so little difference between the short and the long tube, especially at lower velocities, provides an easier decision as to which length to pursue further. The baffles are identical between them except that I've not nested those in the 11" tube. And considering how little powder and scorching makes it to the last few baffles in the longer can, it seems a bit of wasted length.

Ah, here are a couple more images to flesh out what I've made with these shorter K baffles:



The drawing I sent my friend to use in doing the bulk of the lathe work on those for the 11" tube. I've actually found I can make approximately the same K baffles on my small lathe using the same 7075 aluminum rod, and while it was challenging it proved at least possible. About 1 K every half hour, including detailing with a ball end mill on my drill press. I made a simple 6061 collet to hold each for the detailing of the face and ports.

[Capt. Link.]

I like seeing this type of stuff showing up.Not sure why you deviated from a traditional K type baffle but if your happy with it I'm happy for you.
Just so you know the meter is a wild card and will not give you accurate information at suppressed levels it just can't respond fast enough to catch the peak sound pressure level and no mathematical adjustment can be used to compensate for data not heard.

[quietoldfart]

I like seeing this type of stuff showing up.Not sure why you deviated from a traditional K type baffle but if your happy with it I'm happy for you.
Just so you know the meter is a wild card and will not give you accurate information at suppressed levels it just can't respond fast enough to catch the peak sound pressure level and no mathematical adjustment can be used to compensate for data not heard.

No argument here regarding the capacity of the sound meter. I understand that for measurement of absolute volume levels such a cheap 'toy' meter is useless. However it does seem to be consistent, very much so, for measurements of given volumes in a string with the same host and suppressor and ammo, and for comparison of the differences between them, and in terms of making improvements in baffle systems that's really all I need. As my ears tell me that NONE of the suppressors I've made so far causes any pain (or even remotely close to pain) with indoor firing of SV or SS rounds, and that one shot of an HV round DID cause moderate ear discomfort, I'm on the right track in terms of absolute noise reduction. Comparison head-to-head with a commercial suppressor and the same meter might prove useful, or not, but probably no more so than judging what I hear subjectively. It's just a whole lot easier to check as to whether an improvement has been made by metering and seeing a 2dB or better reduction being recorded by the peak measurement setting.

Regarding the why I deviated question; quite simply, I wished to have more aluminum to play with in making the face contour deeper, then making a deeper face port to perhaps more effectively direct the cross-bore pressure stream into the waist port. Maximizing effective use of the space in the short 8" over-the-barrel tube was my priority. There's only a bit more than 3" available, including a 0.50" thin tubular spacer for the blast chamber. 3" isn't a lot for K baffles, not really much room to confound the pressure which is trying to get out the front plug. So to my way of thinking, more is better, provided the wall thicknesses are minimal but sufficiently strong, and that the porting and profiling are efficient in design. By nesting 6 small K baffles together in this way I've achieved a very 'dense' pattern of cross-bore interference with the primary blast stream. Installing them at 180 degree rotation one to the next causes each cross-bore stream to strike the face profile of the next baffle and diffuse there, rather than directing it into the region of the next baffle's cross-bore port and perhaps interfering with efficiency of gas movement through that port. The net effect seems to be a greater stifling of pressure for a given air volume available.

It seems from my testing that, as has been stated in these forums quite often, it is a case of diminishing returns when going to longer baffle stacks. While the un-nested short K baffles in the 11" tube run to just over 6" in length, plus a 0.870" blast baffle, there is not much perceived improvement in suppression with SV rounds and only a measured improvement of about 4dB. Hardly worth the extra length. Going to Remington subs the advantage is further reduced, only a 1.8dB measured improvement with all that extra length and not really any perceived difference, or perhaps a hint, it's hard to say. Considering I'll mostly be shooting around 900fps to 1050fps ammo, there is little if any point in using the longer baffle stack. While I might find some slight further advantage in nesting the K baffles in the longer tube and adding 2 more K baffles as a result, the increased suppression is not likely to be significant.

Considering the shortness and somewhat similar cross section of the K baffles used in the quite successful AAC Element 2 suppressor (yes, the face detailing is considerably different, theirs being shallower and more complex), it doesn't seem my overall pattern is too far off the mainstream.

[gunny50]

looks bit like th eAAC x bafle, Winsor did a rendering from the Patent dwg a while back.
US7987944B1






http://patentimages.storage.googleapis. ... D00004.png
Face is completely different but good work there in France.

Gunny

[quietoldfart]

Ah, those are interesting. They look somewhat more 'bulletproof' than my relatively thin-walled efforts. Perhaps important for high velocity stuff, but I've no intention of using that, only tried it once and it was plainly too loud for my tastes.

[Capt. Link.]

Rebuilding the pistol suppressor package and returning to a standard K baffle would net you major increases in suppression and handling.While your baffles have the overall silhouette of a X baffle the design details alters function.

[quietoldfart]

Rebuilding the pistol suppressor package and returning to a standard K baffle would net you major increases in suppression and handling.While your baffles have the overall silhouette of a X baffle the design details alters function.

Forgive my obtuseness, but... wasn't my initial post showing a fairly 'standard K baffle' in use? A bit longer than average at the waist perhaps, but otherwise very close to what I've seen from dozens of makers including a number of commercial suppressors. What particularly makes these so different that you'd think them louder? Especially considering that the pistol is actually quieter with the 8" tube and stack of 6 nested short K baffles than it was with that initial 12" long tube and a more standard set of long K baffles? Going back to something louder to make the gun quieter makes no sense to me, so plainly I'm missing your point.

[Capt. Link.]

What particularly makes these so different that you'd think them louder?

Proportion port size and placement.

[quietoldfart]

Not really big on specifics, are you Capt.? Oh well. Seems to me that proportion could mean just about anything, same goes for port size and placement. I probably will some day get around to making a set of 'average' K baffles based on what I see from manufacturers, but that'll be a project for a very idle day indeed.

[quietoldfart]

Tried a small modification to the 8" suppressor's baffle stack; drilled a 0.125" Dater hole in the first K, 90 degrees offset from the cross-bore vents. Testing this with the Remington CBee (650fps out of my pistol) my impression was that it was significantly louder on the first shot, and my cheap SPL meter confirmed this, showing 110.5dB, where the average prior to the Dater hole was 106dB. Second shot dropped to 107.9dB, then it was down to about 107dB for following shots. So I made another K to replace that one and put that in place, tested again, and what had obviously been FRP was now gone. First shot was 104.3 (without a wipe), with following shots hovering within 0.5dB either side.

So apparently this hole in the first baffle introduced first round pop, where normally my suppressors have none. Interesting. I ought to have tried a 1/16" hole first I suppose. No matter, it seems a Dater hole in this case is a bad idea when it's 1/8", so maybe just half as bad an idea for 1/16". Or not. Don't really feel like making too many K baffles to find out, but I suppose I've learned something. I did this one experiment because I wanted to use a steel initial K baffle anyway, so the aluminum one was on the way out regardless.

[gunny50]

Tried a small modification to the 8" suppressor's baffle stack; drilled a 0.125" Dater hole in the first K, 90 degrees offset from the cross-bore vents. Testing this with the Remington CBee (650fps out of my pistol) my impression was that it was significantly louder on the first shot, and my cheap SPL meter confirmed this, showing 110.5dB, where the average prior to the Dater hole was 106dB. Second shot dropped to 107.9dB, then it was down to about 107dB for following shots. So I made another K to replace that one and put that in place, tested again, and what had obviously been FRP was now gone. First shot was 104.3 (without a wipe), with following shots hovering within 0.5dB either side.

So apparently this hole in the first baffle introduced first round pop, where normally my suppressors have none. Interesting. I ought to have tried a 1/16" hole first I suppose. No matter, it seems a Dater hole in this case is a bad idea when it's 1/8", so maybe just half as bad an idea for 1/16". Or not. Don't really feel like making too many K baffles to find out, but I suppose I've learned something. I did this one experiment because I wanted to use a steel initial K baffle anyway, so the aluminum one was on the way out regardless.

The dater hole is used when using a direct thread silencer for normal barrels, Not in combination with Ported barrels.
The pressure after the ported section is already lower than when shot without the ported section.
First chamber for 22 with dater is approximately 1/4" (6-7mm) long, yours is as long as the ported barrel.
Try good packaging of ported section, single roll or donuts with shims in between.
Your x baffles have other angles, the extra scoops deeply machined in the original are important, also make the 2 scoops as in a normal K as deep as possible for early crossflow.

Gunny

[quietoldfart]

Thanks for the notes gunny. Here's the steel baffle I made yesterday, for what it's worth. A bit smeared as my carbide cutter for cutting the face contour was getting a bit dull, and the little lathe was complaining a lot about working steel. It's just mild steel, but the tiny rubber belt on the TAIG tends to slip when stress gets too high. Anyway, you think this face contour is deep enough? The cross-bore vents line up alright I think, only 1mm between where one ends and the next begins as measured along the bore.






As it's a tougher material than 7075 I went a bit deeper, and hollowed out the cone into a rounded surface. Might have gone a bit far with that but it seems still strong enough. While I was at it with the modifications something that'd been bothering me about the grip finally put me over the edge. Just too bulky still for a tiny pistol. So I carved it down into a simpler, slab style grip. Feels good in the hand. No real need for a 'target' grip on this little thing with almost no recoil.





Oh, and the area around the ported barrel seems quite under control, as the thin-walled stainless tube covering all the ports is drilled fairly conservatively. I'm seeing dramatically less carbon build-up on the inside of the aluminum tube as compared to tightly winding it in copper scrubbing pad, wound out into a sort of 'yarn' as I did for a while (per Paulson's recommendation). I may at some point try adding a mesh to the outer area as well, compare to see if that makes any difference.

[quietoldfart]

After posting comments in another thread it occurs to me I've not updated this thread to reflect the current state of things with my pistol suppressor. I decided last month to do away with the short aluminum spacer between muzzle and first K baffle, and added one more aluminum baffle to the front of the stack making a total of 7 0.55" long K baffles. Each is nested into the next, the last nested into the contoured end cap. I've also put another coat of baked epoxy paint onto the 8" tube. And if I hadn't mentioned it earlier, I'm now using a bronze vented plug which is threaded onto the stepped down section of the barrel with a 7/16" coarse threading. Much less fussy than the set screw mount I'd used previously. So there is still a set screw, but it holds only the bronze fitting. Here is the finished project showing the 7 small baffles and end cap, which is face contoured like the K baffles to make it effectively an 8th baffle.





The result is now measuring at about 2 to 3dB quieter than previous iterations with the 8" tube and is certainly sounding quieter still to my ears. It seems that within reason, more baffles is better. I've discontinued use of the 11" threaded endcap version as even with 11 K baffles it did not get sufficiently quieter to justify the greater weight and awkwardness in handling of the much elongated pistol. I've put those baffles into an 8" tube on my PCP carbine which I use for pest management and they work very effectively there.

[quietoldfart]

Well I gave up. The 7" ported barrel with integral suppressor was quiet to be sure, but accuracy was sometimes off. Just could not group consistently for long strings. So I concluded that the very slight off-centre bore was just too big a problem to overcome with shimming of the muzzle plug. I made a number of plugs, but always it seemed the proximity of the projectile to one edge of the baffles was causing inconsistency, if not strikes. So I elected to cut the barrel down to 4" total length and re-crown it, thread it to 1/2"-20 and go to a simpler suppressor design. It would make for a more compact, lightweight pistol for shooting un-suppressed and perhaps eliminate accuracy problems, even though it meant putting more baffles ahead of the new muzzle.

Though I lack tooling to machine-cut threads I am a patient fellow and have worked out ways of preserving alignment. The core of these involve use of a modified hole saw shank with a steel rod secured to it then soldered over all and then turned down to a snug oiled fit into the bore. Some hole saws use a 1/2"-20 thread, and this seemed a practical and cheap tool to work around so I purchased a 1/2"-20 die as well. Threading the die onto the modified hole saw shank provided concentricity and it was fairly easy to cut about 1/4 turn at a time until slightly over 1/2" of barrel was threaded. I actually considered making some sort of bolted-on fixture to make a shoulder for a suppressor to press against, but this seemed too ugly a solution. Instead I opted for indexing from the outside of the 1/2" barrel, after hand truing it to round; the barrel proved to be about 0.003" out of round with the long oval being vertical. Once filed and polished it was exactly 0.50" diameter in every direction, and the new bore end at 4" just happened to be well-centred! I smiled broadly upon finding this, as running a hacksaw through the old French steel was quite a nerve-wracking experience.



I didn't record any photos of the new build in progress, but it's fairly simple really. The core of the hole saw provided a 1/2"-20 threaded mounting hole, and I cut a 15/16"-20 thread onto the reduced OD of that steel plug using a hand turned die. This, obviously, was the least precise of the steps, but I went slowly and kept checking from every angle, correcting with slight downward pressure where needed to correct the angle until reaching the small flange I'd left when turning down the steel plug in my small lathe. After cutting a relief behind the thread and re-checking the squareness of the flange, the next step was to braze on a large hex nut to provide material for a barrel-indexed short sleeve. I carved away most of the nut, used a boring tool to gradually shave the inside until it was just a hair over 0.50", then tested it on the Unique's barrel. Fit like a glove. Inserting a 0.55" long aluminum spacer for the blast chamber, a 0.30" long blast baffle (hollowed on both sides, a sort of inverse toroid, Dater hole 1/16" to one side) and 7 K baffles approximately 0.50" long, then a threaded contoured end cap, I peered down the bore and found everything was aligned perfectly! So I dismantled and cleaned it and sprayed with epoxy paint, roasted it at 350F for about 40 minutes, then reassembled and went to bed.

This morning I'd intended to do a bit of testing on paper to check accuracy but a different opportunity presented itself. A grey squirrel. The thing had been stealing dozens of walnuts all morning and when I went out to water the garden it had the audacity to come right down the tree trunk and stand, not 10 feet from me, and proceed to munch one of the 6 nuts it had just picked in a cluster. I hesitated only a second wondering if I ought to go get an air rifle, but my neighbours seemed absent so I took out the Unique. Just a second to line up my new brass front sight (soldered to the barrel then carved - gives me about 3/64" of the post over the 1" tube, enough to see the brass clearly through the small rear sight blade. Dropped his nuts, kicked once, and was done with a shot to the heart. Seems I shan't need to adjust much when I go to sight in at a longer distance. I had CCI Quiet loaded, which come from this 4" barrel at about 570fps for 29fpe. I'd say the report compares almost exactly to that of a can of soda being opened. Here is the completed suppressor, wrench flats filed into the two sides so as to facilitate making it very tight into the tube.

[V8Astro]

Brilliant! Thanks for sharing

[DKDravis]

What you have there looks very much like the "DGSE Speciál" The French version of the Rugers with integral suppesssion ..used for "special purposes" by various "intelligence agencies"

[quietoldfart]

A few searches have netted me nothing like my little pistol... it would seem I lack the 'Google-fu.' Perhaps you have an image of such a French special operations pistol? All I've been able to find is modern pistols used by this group, mostly the Glock line of pistols with suppressors mounted and of course some short barrelled rifles.

The thread just ending in the barrel was bothering me so I used a small Swiss file and carved a relief behind it. Changes nothing in terms of how the suppressor clocks on the pistol but is a more satisfying end to the thread.


And here is a different angle on the finished project. I don't see anything else I could do to the poor old thing, unless it were to mount a small laser somewhere. But I doubt that will happen. Too ugly and complicated for such an elegant little weapon.

[Kanook]

Could you explain how the single shot lever works and how hard was it to make?

[quietoldfart]

I explain it and show close pictures in this thread:
viewtopic.php?t=121181&start=25
It was not easy, but I have long years of experience in improvising with metals and woods and was able to make it work very nicely even though there were moments when I thought I'd ruined the pistol. Taking a torch to the delicate rearward prongs of an old semi-automatic pistol isn't something I'd recommend for the feint of heart. But it came out alright and doesn't look too terrible. After several hundred rounds of mostly SV ammunition fired there is about 0.5mm of rearward play, owing to compression/smearing of the carved-to-shape bronze inside the two caps which were added to the slide. Some could also be due to compression and/or slight bending of the stainless steel peened pin running through the stirrup and the duck bill on the back of the frame. Not certain, but it's not enough to worry about yet. At some point I shall probably have to add a bit of silver solder to each and re-carve the pockets, if it gets much more play rearward.

Making the stirrup was in itself a bit of a challenge and involved a lot of beating on a steel block to get the rounded prongs shaped just right such that they slip upward/rearward and nestle perfectly into the pockets.

If I were suggesting such a modification to anyone else I'd say to start by making a mock-up of the stirrup out of sheet metal, folding it and filing it until it seemed about right with the slide removed. Then drill the hole for the pivot and test again with this model. Once satisfied with the geometry, make the proper one out of good steel. Then measure very carefully and carve away the slide as needed, starting rearward of the final position and slowly adjusting forward until the stirrup prongs just barely push into place with some force. Then polish. Then make a pair of steel caps and have them TIG welded into place, to avoid the severe heat stress to the upper. I think that'd be a very tidy solution.

[quiettime]

...It was not easy, but I have long years of experience in improvising with metals and woods ...

And it shows, I'm impressed what you have been able to do with your modest tooling.

Great thread old chap!

[DKDravis]

Sorry .. I have never seen photos of the "DGSE Speciál" I have only read about it somewhere, and I used to own and shoot a Unique DES-69 target pistol, which was the successor to the DES target pistol that was "converted" The reason this gun was used was because of its raised rear sights (mounted on a "bridge" over the rear of the slide) and long barrel, with a ramped front sight. (this was soldered on, so could be removed, or moved back to make room for the threading.)
The walnut target grip shells were cut down and flattened, to make the gun concealable, much like you have done. There were two types of grips on the old target DES, yours looks like the oldest type which was quite simple, with no movable palm rest.

Again, I only have this info from reading about it quite some time ago. I sold my Unique DES-69 over 10 years ago ..