B&T TP9 - Suppressed use, mags, impulse, and general inf

[TOOL1075]

well, I've been shooting my TP9 with my Trident. It's pretty great, but I am having some issues.

I started a thread on Uzitalk, because I thought it would get some hits from owners of this gun, but apparently there isn't that high of a concentration of TP9 owners that frequent that particular part of the forum.

I believe the gun is over-functioning with the suppressor. There might be slightly too much duration on the chamber pressure, which is increasing the impulse.

The reason I say this, is that I am getting some slight erosion of the ejection port on the top receiver cover (from ejected brass. I'm pretty sure it's from suppressed use, because it only happened after shooting suppressed; not after many rounds of unsuppressed fire)

Also, when using the 30rd mags, I sometimes have failures to feed. I believe it is because the bolt is moving back too quickly, and the magazine can't raise the next cartridge in time.... but I'm not 100% sure.

The magazine followers, if you are familiar with the gun, have a small tab that activates the bolt release lever, so that the bolt will stay open on the last round. That tab compressed back into the magazine body when rounds are loaded into the magazine and the follower is pushed down into the mag body. This results in friction between that part of the follower and body. This seems to be by design, as I see no way around this friction force occurring.

So, I took a small file, and I filed down some material from that tab. It still engages the bolt-release lever, but now the follower moves much more easily through the magazine body. I'm hoping that this decrease in resistance will enable the follower to move up more quickly in the magazine, thereby getting the next cartridge ready to feed before the bolt gets there.

I'm also trying to find a stiffer recoil spring. I took some measurements of the existing spring, but I have been unable to locate a similar spring. I believe I need one that is slightly stiffer, as the increased pressure duration that occurs with suppressed use imparts more impulse on the bolt than what is ideal.

Any TP9 owners (or anyone in general) have any ideas/thoughts/suggestions?

Thanks guys.

(I know the internet gods wish pics to be offered, so here ya go):








oh, and by the way - this is the quietest 9mm host I have shot (but the only other 9mm hosts I have shot are a 226 and an MP5....)

[ThePatriot]

If it's quieter than a P226 it must me damn quiet.

[hjustein]

I own a TP-9, and have been wanting to suppress it BUT, I have been waiting to hear from the early adopters IE you

You are correct in that the design does not lend itself to increased back pressure.

this is also probably why the B&T can for the TP-9 is so huge, to decrease backpressure.

I know this doesn't help you, but my current plan is to do a large diameter, short length Form 1 can. I doubt it will be as quiet as your setup, but it should reduce the intensity and duration of the pressure pulse on the barrel face, which is effectively a large piston.

Another suggestion which may be more useful to you is to take up reloading. A small amount of fast burning powder behind a 147gr plated bullet would significantly lower the gas pressures and volume at the muzzle.

hope that helps.

[TOOL1075]

I think all I need is a stiffer recoil spring.

The recoil spring is a very simple spring.... it shouldn't be hard to just get a stiffer one.

I found this, but it's probably too strong (it's stiffness is 50 lb/in... ):



I was thinking about the B&T suppressor, and I guess it is pretty big (in diameter, at least). That probably explains it.

The gun still shoots well suppressed, and it's a lot of fun... but it would be great to just get a stiffer spring... It really does need one....

Of course I emailed B&T and they didn't respond, and I called DSA, and getting a hold of someone with technical knowledge at DSA is like finding a leprechaun. (it's not that they aren't there, it's that they are apparently too busy to talk to you. which, I guess isn't like a leprechaun at all.... whatever, you know what I mean )

[bellamy67]

I use this combo. I have fired well over 300 rounds with 147 gr with a trident 9. I never had a failure and it always locks up after last round fired. The noise all i hear is from the spring because thats pretty much all the noise the gun makes. Super quiet. I was shooting a glock 19 and the tp9 and all my firends said the tp9 was more quiet when they stood behind. It was a noticeable difference.

If you own the gun I strongly feel this is a great suppressor host. Only knock is the trigger. Talk to tros and get an adapter and your ready to go.

[TOOL1075]

also, keep in mind, suppressors aren't increasing the chamber pressure.

they only increase the duration of the chamber pressure (so, they increase the total impulse).

I called Wolff today (the gun spring people) and they said they didn't have any springs for this gun, but if I give them measurements, they will see if they have anything "close." Pretty nice people on the telephone actually.

I googled for springs, and I ran across some spring manufacturers (not for guns - just springs in general) but whenever I run across a spring relatively close to the size I need, its stiffness is very high, or the outer diameter is too large, etc.

The spring is approximately 5 13/16" long (5.8125"), uncompressed.

Its outer diameter is approximately 7/16" (0.4375")

It has to fit in a hole in the bolt that is approximately 1/2" in diameter (0.5")

The guide rod that goes into the spring has a small retention flange that is approximately (0.361") in diameter.

The best measurement I can get on the inner diameter of the spring is somewhere between (0.355" and 0.365").

The wire diameter is approximately (0.048").

All of these measurements are approximate, and I have a feeling that this is a metric spring anyway.... but this is the best I can do right now.

Plugging these parameters into Century Springs, Lee Spring, and McMaster Carr, I can't quite get a match that isn't ridiculously stiff, like I posted above.

I'll call Wolff with the dimensions tomorrow...

[TOOL1075]

I use this combo. I have fired well over 300 rounds with 147 gr with a trident 9. I never had a failure and it always locks up after last round fired. The noise all i hear is from the spring because thats pretty much all the noise the gun makes. Super quiet. I was shooting a glock 19 and the tp9 and all my firends said the tp9 was more quiet when they stood behind. It was a noticeable difference.

If you own the gun I strongly feel this is a great suppressor host. Only knock is the trigger. Talk to tros and get an adapter and your ready to go.

do you notice any erosion on the top cover near the ejection port, from brass hitting it?

which 147gr ammo do you use?

you have never had a failure to feed with the 30rd mags?

[JohnDS]

Tag for interest - been wanting to do one of these myself. Heard they have excellent suppression. Please post back if you find a source for springs.

[TOOL1075]

I will.

Just so you know, you can click "Watch this topic for replies" at the bottom-left of the page, and you will receive an email when someone replies to the thread.

bellamy67:

I'm very interested in your answers to the questions I asked in my last post, because if you aren't experiencing any erosion of the top receiver cover ejection port while shooting suppressed with your Trident, that would mean:

A. your ammo has lower impulse than mine
B. your recoil spring is stiffer than mine
C. the way you connect the Trident (TROS adapter to SWR threaded mount, vs. TROS adapter to TROS 3-lug adapter to SWR 3-lug mount like I did) results in lower pressure duration
D. all or some combination of the above

[bellamy67]

I will.

Just so you know, you can click "Watch this topic for replies" at the bottom-left of the page, and you will receive an email when someone replies to the thread.

bellamy67:

I'm very interested in your answers to the questions I asked in my last post, because if you aren't experiencing any erosion of the top receiver cover ejection port while shooting suppressed with your Trident, that would mean:

A. your ammo has lower impulse than mine
B. your recoil spring is stiffer than mine
C. the way you connect the Trident (TROS adapter to SWR threaded mount, vs. TROS adapter to TROS 3-lug adapter to SWR 3-lug mount like I did) results in lower pressure duration
D. all or some combination of the above

I'm using dirty american eagle 147. Yes I'm using an adapter to a fixed mount. I'm planning on buying from tros an all in one that fits the gun and the trident. My spring is totally stock. I did have to return the gun to get fixed prior to using the suppressor. Non related. No damage to any part of the weapon. Everything looks just like being fired without suppressed.

I run several 30 round mags and they ALWAYS work.

[TOOL1075]

if you don't mind me asking, why did you have to return the gun?

Is the ammo you are using the flat point, or conventional ball rounds?

So... you don't get any increased function when firing suppressed? Doesn't your brass eject much further?

[HandyMan]

I have access to and have examined the factory B&T silencer for the TP-9. I have also fired a factory SMG with the silencer and have noticed a few things.

The B&T Rotex silencer has a very large initial expansion chamber, perhaps up to a third of the available volume. The baffles are standard B&T fare, namely machined versions of the crimped cone. There are five baffles in all.

The first two baffles have largish ports machined into the outer diameter of the baffle. Six ports total per baffle with dimensions roughly 3/16" width by 3/8" length. It is pretty obvious they were trying to depressurize the blast chamber very rapidly.

I believe a modern pressure driven silencer will tend to over-function the TP-9 pistol. My personal bias is to use a co-axial design with a large primary expansion chamber. Something akin to the Gemtech MK9K would likely work well.

I plan on building a form 1 can to use on my TP-9, which will be SBR'd. As soon as I get my trust worked out I will file both form1's. Without a silencer, my personal TP-9 has had no issues with either the 15 or 30 rd mags.

[TOOL1075]

That confirms my suspicions. Thank you so much for that first-hand information. That makes sense, and is exactly what I thought might be the case.

Now, what doesn't make sense to me.... is why bellamy67's gun is not over-functioning when suppressed with the same suppressor as mine is (or maybe his is over-functioning?)

I was thinking that the 3-lug adapter I am using (you can see it in the picture in the first post of the thread) might be too restrictive. Perhaps when using the SWR Trident thead mount (as bellamy67 is doing), the pressure bleeds off faster, because it doesn't have to travel through the 3-lug adapter shaft, i.e. there is a shorter path for the gas to travel to get to the Trident's expansion chamber.

It is interesting that this pistol already has a "built-in" expansion chamber (the barrel guide). So, what I'm basically doing with the 3-lug adapter you can see in the first post.... is sending gas out of the barrel, expanding into the barrel guide, then though a 3-lug adapter shaft, then into the SWR 3-lug mount, THEN into the Trident expansion chamber.

Think there is any merit to the theory that the extra length of small diameter shaft of TROS adapter (relative to the barrel shroud diameter) is too restrictive to the gas flow?

[HandyMan]

It may be the constriction of the 3-lug adaptor creating a chamber that pressurizes the front of the barrel. As you have noted, the barrel has a lot of surface for pressure to work against.

Perhaps an adaptor that goes from the 26.5 X1mm of the barrel shroud to the Trident directly. This would eliminate the constriction and at least one threaded joint.

Problem is the market is so small for the TP-9 at the moment. No one wants to invest in a new design for such a limited distribution.

Oh, one other thing. The TP-9 is very quiet when fired as a pistol. But when you add a stock, the ejection port is pretty close to your ear. The factory Rotex silencer is around 128-130 at the muzzle. But it is 138 or so when measured at the ear. A little snappy.

Do you think the brass catcher has any effect on the ejection port noise? I haven't picked one up yet. It might knock the sound down a bit at the ear. My goal is a compact, cool little SBR that is quiet with a silencer and fun to shoot. I thought about an MP5 clone, but like this platform a little better.

[TOOL1075]

You may be right about that restriction.

But, if I can get away with solving the problem by unscrewing the TROS 3-lug adapter from the other TROS adapter (you are looking at two adapters from TROS screwed together, seamlessly, in the first pic in this thread), and just using a Trident fixed-mount directly to the large TROS adapter instead (like bellamy67 is doing), then that would be fine.

But yes - TROS I think is going to make an adapter that connects the Trident DIRECTLY to the gun. See this thread:

viewtopic.php?t=47357

Bellamy67 - how long is the wait for that TROS adapter you are having made, and do you need anyone else to go in with you to reduce the cost? I take it Mark at TROS is making more than one, right?

Regarding ejection port noise... I don't know if the brass catcher really reduces that noise, because as you say, I fire the gun as a pistol (putting the sling in tension for stabilization).

I suppose it could help redirect the noise, maybe. I may mess with that tomorrow when I go shooting.

I am apprehensive about continuing to shoot this gun suppressed though, due to the over-functioning. I need to either get a stiffer recoil spring, use underpowered ammo, or get a less restrictive adapter/mount combination.

[David Hineline]

Do not have this gun but my experience with stronger recoil springs is they delay the opening of the bolt, which keeps ejection port noise reduced, will effect the ejection of the case pattern and how far the brass ejects, but then you have a stronger spring to close the bolt faster so bolt speed related magazine feed problems is made worse, and bolt bounce is made worse if it matters in the operation of your type of gun. If a tungsten weight could be added to increase the mass of the bolt that would slow it down in both directions, but of course could dork up firing when not silenced.

[TOOL1075]

...but then you have a stronger spring to close the bolt faster so bolt speed related magazine feed problems is made worse...

David,

I thought about that.

I have the sneaking suspicion, however, that my feeding problems are related to my ammo. I have feeding problems, while suppressed, with American Eagle 147gr truncated cone FMJ and Winchester Ranger 147gr truncated cone FMJ. (with the 30rd mags)

Yes, both types of ammo are truncated cone designs (flat point) but the Winchester Ranger ammo has a longer overall length than the American Eagle. (The American eagle is right at the minimum recommended cartridge length from B&T for reliable function with this weapon).

Normally, I would think it was the ammo that was causing the problems, right away (as both those ammo types are truncated-cone, flat-point designs) but the following really makes me think at least the Winchester (due to its longer length when compared to the AE) is not the problem. Look what is on this list - there's all kinds of stuff on here, with hollow-points, etc:



On an aside... I know that HK fills bolt-carriers with tungsten granules on their 9mm roller-locked weapons (MP5) to stop bolt-bounce. (kind of like a dead-blow hammer). I don't think I'll get any bolt bounce with this gun. (especially since it's only semi-auto).

I think my ticket is reducing the gas flow restriction.....

I need to test some 147gr ball ammo with the suppressor, as well.

Suppressing weapons is apparently not always straight forward

[HandyMan]

Suppressing weapons is apparently not always straight forward

You got that right. Adding a silencer to any gun can change the operating parameters significantly. Silencers are always an afterthought in the design.

[TOOL1075]

Very true.

I sent a check off to Mark at TROS for one of the remaining direct TP9 to Trident adapters that he just made. (he made a small batch)

He's going to make another batch again, so more will be available this year, actually.

We spoke about this stuff at length on the phone... he's such a great guy - truly a treasure for the firearms community, in my opinion.

If it ends up that the new direct adapter does the trick, I'm still going to keep the adapter(s) I have now, because it will enable me to connect other suppressors to this gun in the future.

Hell, my possible options right now are:

1. Use the stock B&T 9mm suppressor
2. Use any 1/2"x28 threaded 9mm suppressor with my TROS adapter
3. Use any 3-lug mounted 9mm suppressor with my TROS adapter(s)
4. Use my Trident with the direct-connect adapter I'll be getting from TROS

The silencer community (and this forum, specifically) has once again stimulated important conversation about a relatively obscure weapon system that will benefit users everywhere.

I like the internet.

[TOOL1075]

okay.... I was thinking more about this, and I'm pretty sure it will make a difference.

if I had AutoCAD on this home computer, I would have used it........ but I don't, and therefore I didn't.

So I used Paint. Hell, if you haven't used Paint in Vista or Windows 7, it's improved over the old versions at least.....

Anyway... don't you guys think the schematic on the bottom would result in less restrictive gas flow?

Seems like a no-brainer, right? or am I off base?

[HandyMan]

The bottom setup will reduce the back pressure on the gun for sure. It will also reduce the ejection port noise.

When you recieve your adaptor from TROS, give us a review. I am interested if it improves things in your view.

[TOOL1075]

I think so too. Keep in mind that my crude schematics are not to exact scale, and I'm not sure of the exact geometry of the new adapters Mark at TROS is making, but I believe the rough representation given does the basic concept justice.

I'll report back, for sure.

It may be a week or two. I believe the adapters just got back from black-oxide treatment, and my check should get to Mark on Tuesday. If he still has one or two, I'll get one from that batch. If not, it will be a few weeks, until the next group is created and shipped.

I'll be shooting the piss out of this gun, unsuppressed, tomorrow. Won't shoot it suppressed again until I have the new adapter in hand. I think I have about 400 to 450 rounds through the gun, total, with the large majority being suppressed with the Trident.

[csfirearms]

I have about 500 rounds through mine (no can) and it only jammed on the second round. Been using the stock on it then shooting it as a pistol. Runs great.

CSF

[TOOL1075]

I got the TROS direct TP9-to-Trident adapter (M26.5x1 to 1- 3/16-24)

I apologize for the clarity of these photos, compared with those I posted previously (only have a cell-phone camera available at the moment):




Very nice. Very solid. Shortens the overall length..... can't wait to try it!




Oh yeah, I made a lanyard connection for the sling. I took an old (strong) cord I had, and cut it to size. Then, I slipped some heat-shrink tubing over it, and joined the two free ends with a reef knot.

I stretched and finagled the tubing over the reef knot, and used a lighter to shrink down the tubing. Then, I cut off the excess lengths and fused the fray with the lighter. Using a lark's head knot, I connected it to the receiver sling-hole. It can be removed, of course, because you can always remove a lark's head by threading the line through itself.

It makes attaching/detaching the sling easier, and the sub-gun variant (the MP9) and the Canadian semi-auto built-in pistol grip version (would be an SBR in the U.S., but the U.S. SBR does not have the built-in pistol grip) actually includes one:



(that's where I got the idea )

[HandyMan]

I like it. Very clean looking setup. Can't wait for an after action report.