Integral P38/P1 for best performance : length ratio?

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calinb
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Integral P38/P1 for best performance : length ratio?

Post by calinb » Tue Oct 11, 2011 11:39 pm

I'll be using a Form 1. I'd like to reduce handgun length as much as possible in a 9mm or larger caliber. From my review of existing designs, it appears that a ported barrel with an integral is the way to do this. I've searched high and low on this forum and the P38 forum and I can't find a definitive confirmation that the limited barrel movement P38 will work well without a impulse / recoil / Nielsen device. I guess it would be possible to build it into an integral but I'd like to avoid it. I'm planning to build light (titanium). Any other ideas are welcome and appreciated, but I'm trying to select a platform that's not too terribly obscure.

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Re: Integral P38/P1 for best performance : length ratio?

Post by Selectedmarksman » Tue Oct 11, 2011 11:51 pm

Is short your highest priority? Short generally != quiet.

If it has to be short and has to be 9mm, the shortest I can think of is a product that still isn't on the market: boberg XR9. The barrel appears to be fixed, so probably no cycling concerns, but as they don't exist yet it is definitely obscure.

EDIT: Check that... in their animations the barrel is fixed, in some slo-mo vids of it firing, it appears to move. Who knows what production models will be like.
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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Wed Oct 12, 2011 1:16 am

Selectedmarksman wrote:Is short your highest priority? Short generally != quiet.
Well...short is relative. ;) Short is not the highest priority, but I'm willing to dedicate a suppressor to single application use (integral) to gain short(er), if necessary. It doesn't have to be a 9mm, but going much smaller isn't terribly desirable. It's easy to find examples of integral designs for .22LR pistols that seem to be very quiet at around 7 or 8 inches of integral barrel length, but I'm not terribly interested in a .22LR for my first Form 1 project (though one could argue that a .22LR would be the more sensible first project).

I'll keep my eyes on the Boberg, regardless. The animation looks fixed, as you say. We'll see how it really works later, I guess. Thanks so much for the link!

Edit: Okay--I see the barrel moving in the animation now. Compare the muzzle position to the forward face of the frame or compare the breech of the barrel to the position of the rim of the topmost cartridge. It doesn't tilt, but it does move a bit.

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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Wed Oct 12, 2011 2:09 am

I found this P38 integral:
http://www.waltherforums.com/forum/clas ... 38-sd.html

It doesn't appear to have a Nielsen / inertial decoupling device and it sure doesn't look to be terribly light weight! The museum piece and the figures of the pistol below the German text appear to be quite short in length. My high school German is pretty rusty and I wonder how well it worked. If I knew that this pistol cycled reliably, I think I'd have no trouble updating the design with a lighter weight implementation.

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Re: Integral P38/P1 for best performance : length ratio?

Post by jlwilliams » Wed Oct 12, 2011 7:33 am

You can skip the porting and just cut the barrel off at about 2-1/2" or so. Without diggin it out and measuring, mine is shortened enough that the sight is re-attached in front of the slide, has about 3/8" of thread past that and that's it. Keeps 125 grain subsonic. It works well with a Gemtech Trinity, no booster. It's not the quietest set up dry. Better with a little water in it. With the barrel that short there is a hell of a blast to suppress. It's hearing safe dry but you aren't going to pull any James Bind slick shooting without alarming the neighbors.

In general, the P38 cycles well with out a booster.

Don't use a P1, definitely get a real WWII P38. The P1 has a barrel liner pressed into the barrel and will screw you when you go to thread it. The early ones were not sleeved. You can get a Russian refurb for reasonable money and it will be fine.

A 22 will most definitely be a better 1st project. You will get better suppression and end up with something you will shoot a whole lot more than the 9mm. 9mm is a great suppressor round, non't get me wrong, but 22 is quieter. When you have it all done you are going to want to shoot it all the time, so the economy of 22lr is a strong attraction. That said, a dedicated P38 SD unit will be the balls too. Do what you want, but I think a 22 first makes more sense. If you don't do the 22 first, file the form 1 asap and do it a soon second. You will be glad you did.

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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Wed Oct 12, 2011 1:40 pm

jlwilliams wrote:<snip>
In general, the P38 cycles well with out a booster.

Don't use a P1, definitely get a real WWII P38. The P1 has a barrel liner pressed into the barrel and will screw you when you go to thread it. The early ones were not sleeved. You can get a Russian refurb for reasonable money and it will be fine.
<snip>
Thanks for the excellent information! I'd read about the sleeved barrels and that worried me. I've also read about less than perfect barrel P38/P1 cross-compatibility so I guess I'll be shopping for a WWII steel pistol and I'll look for Russian refurbs.

And I am thinking about making a Ruger .22 Mark series pistol my first project. It's the perfect candidate for an integral suppressor and it'll give me time to shop for a WWII P38.

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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Wed Oct 12, 2011 8:46 pm

I thought of a couple more P1 questions.

1. Are the sleeved P1 barrels too thin for all appropriate threads or are they only problematic with "standard" threads (1/2 x 28, etc.)? I'm interested in doing a Form 1 build so I could use any thread that I desire.

2. If the sleeved P1 barrels are too thin for threading, why couldn't I just turn the front sight shoulder round and thread the barrel there, where it's thick? The barrel might be longer than desired, but would it work?

Thanks, again!

-Cal

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Re: Integral P38/P1 for best performance : length ratio?

Post by jlwilliams » Thu Oct 13, 2011 8:44 am

Call Mike at Tornado Tech. He threaded mine and told me about the issues. I got the impression that he's threaded more than a few and has run into the various pitfalls. Maybe a call or an email to him would be worthwhile. Since you aren't sending him the work, he may not want to spend a bunch of time telling you the ins and outs. If you are straight forward about your intensions he can either take the time or say no. No harm asking.

He posts here from time to time. I'd try PMing him through ST. Maybe link to this thread.

Going with a 5/8 OD thread does sound on it's face like a good way around the barrel issue. I'm not sure if the aluminum frame would be a problem, but the barrel sounds like you can work around.

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Re: Integral P38/P1 for best performance : length ratio?

Post by Artful » Thu Oct 13, 2011 2:27 pm

sleeved P-1 barrel can be threaded but you have to make a bushing
Image
drove my machinest friend to drink I think.

Small pkg - is 11" too long?
Image

works fine with DTA NANO titanium can.
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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Thu Oct 13, 2011 6:00 pm

jlwilliams wrote:Call Mike at Tornado Tech. He threaded mine and told me about the issues. I got the impression that he's threaded more than a few and has run into the various pitfalls. Maybe a call or an email to him would be worthwhile.
<snip>
Thanks! Turns out Mike is local. 8) I work only two or three miles from Tornado Tech's address. :) I'll tell Mike about my intentions (Form 1 hobby project), but I might be interested in sending some of my project his way--especially given that he's local.

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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Thu Oct 13, 2011 6:39 pm

Artful wrote:sleeved P-1 barrel can be threaded but you have to make a bushing
drove my machinest friend to drink I think.
Is the bushing welded onto the barrel? I thought about finding someone who can run a TIG.

I've also been thinking about doing an integral with a ported barrel. I'd port the barrel just forward of the slide and support the can behind the port on a taper-fit endcap (perhaps the taper of the P1 barrel would be appropriate. The design would be very similar to a John's Guns integral .22LR Ruger. Though this guy wasn't terribly happy with the fabrication of his John's, the design seems sound: http://www.brokevw.com/newruger.html Of course I'm planning a 9mm.

If I could use the extra thickness of the front sight shoulder for threading, the barrel would be nearly unmodified (just the threads and ports). Although the P1 has some taper, it might not be enough taper to permit the rear endcap to slide past the threads in assembly. In that case, I could turn two "halfshell" taper bushings to fit under it and make the endcap ID larger. The ported section would be filled with packing (braided ChoreBoy like Dr.Dater's AWC RST or screen). Baffles of TBD design would be used forward of the threaded midsection barrel "nut" to the front endcap of the can.

With about 2-1/2" of ported / expansion / packing length forward of the slide, it might turn out to be somewhat long. Even five K-baffles would require about 5+" more length so that adds up to about 7-1/2+" from the end of the slide and 11+" total pistol length. I'm sure it could benefit quite a bit with another baffle or too and even more length.
Artful wrote: Small pkg - is 11" too long?
works fine with DTA NANO titanium can.
11: total length. Not at all! I'd even be happy, if it were a bit longer--say up to a foot. Hmm, maybe the integral design I describe above would meet my length goals at 11-12 inches total. I wonder how it might compare in performance to a thread-on non-integral can.

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Re: Integral P38/P1 for best performance : length ratio?

Post by Artful » Fri Oct 14, 2011 1:22 am

liner was threaded and bushing was threaded to match in a close interference fit (Ie heat one cool the other and they thread great but when same temp not coming off) he also said he used locktite - he's worried about the thin liner snapping at the junction of the old barrel and the bushing but over 200 rounds and no problem so far. :)
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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Fri Oct 14, 2011 2:37 am

Artful wrote:liner was threaded and bushing was threaded to match in a close interference fit <snip>
That makes sense. Great idea and the photos look great too. Thanks!

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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Mon Nov 07, 2011 7:43 pm

I got my P1 but need to finalize some aspects of the design before I'll know the length for my Form 1. Mike didn't answer my PM here or my email to Tornado Tech so I'll just need to jump-in, with the help forum members have already provided to me.

There appears to be plenty of "meat" on the front sight band for threading there, or I could cut the barrel the about 3" and thread just forward of the slide (providing clearance for barrel movement). I really don't see any reason to use a bushing, if I'm machining my own supressor, because I can use non-standard threads. The barrel O.D. is 0.585 just forward of the slide and the sleeve appears to be around 0.475 O.D. so I could cut a 0.585" major thread diameter on a 3-inch barrel. A 0.585" x 36 TPI would have a 0.558 minor thread diameter. Even a 0.585" x 28 TPI would have a 0.550" minor thread diameter. There should be plenty of barrel thickness, given a 0.475" I.D. sleeve. Sure, if 1/2" or 5/8" commercial supressors are the application, I see the obvious need for a bushing.

A 3-inch barrel should be about right for 124 grain subsonic loads. So the big question is what will work best--integral or thread-on can? Should I port the barrel at about 3" and design an integral that's supported by threads cut on the front sight band and a taper bushing just ahead of the slide or should I cut the barrel to about 3" and just thread it with a 0.585" major diameter thread and make a screw-on can to fit? I'm kinda favoring the screw-on can, because it's simpler.

-Cal

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Re: Integral P38/P1 for best performance : length ratio?

Post by jlwilliams » Mon Nov 07, 2011 10:02 pm

That sounds like a good start. You have 'till the stamp comes to think about it. In fact there is no time limit after the stamp comes (I think there is no limit) anyway, you have plenty of time to decide what you will do. As long as you design a rock solid, square mount then scre on should be fine. Simple is good.

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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Tue Nov 08, 2011 4:31 am

jlwilliams wrote:That sounds like a good start. You have 'till the stamp comes to think about it. In fact there is no time limit after the stamp comes (I think there is no limit) anyway, you have plenty of time to decide what you will do. As long as you design a rock solid, square mount then scre on should be fine. Simple is good.
I'm really only concerned about deciding on the length, at this point, though an integral isn't necessarily any shorter than a screw-on can, which I'm favoring right now. A 3" barrel is about right for subsonic 124 grain and it will probably be lighter overall than an integral using a longer ported barrel. I can work on the details while I'm waiting. I've read that it's possible to revise the length on a Form 1 too, if necessary, but I'd rather not complicate the process. I'll probably just submit with a typical length and design to it.

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Re: Integral P38/P1 for best performance : length ratio?

Post by jlwilliams » Tue Nov 08, 2011 8:48 am

OK, how about this approach. The registered silencer has to be the length you register it at. The barrel length is irrelevant from the law's point of view. So, you can go with a muzzle can and cut& thread the barrel a little longer than you think you need. Then trim back 'till there is no more sonic crack, then a little more to account for variables in factory ammo. More lathe time but if it's your lathe and your time, so why not.

Then, you can post here and tell everybody what the optimum lenght is for keeping 125gr 9mm subsonic from a P1.

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Re: Integral P38/P1 for best performance : length ratio?

Post by calinb » Wed Nov 09, 2011 6:10 am

jlwilliams wrote:OK, how about this approach. The registered silencer has to be the length you register it at. The barrel length is irrelevant from the law's point of view. So, you can go with a muzzle can and cut& thread the barrel a little longer than you think you need. Then trim back 'till there is no more sonic crack, then a little more to account for variables in factory ammo. More lathe time but if it's your lathe and your time, so why not.

Then, you can post here and tell everybody what the optimum lenght is for keeping 125gr 9mm subsonic from a P1.
I could optimize the length, but the shoulder and thread relief behind the barrel threads limits the "granularity" of the barrel trimmings to the width of the threads. According to Quickload, three inches is about right, which is about the shortest barrel possible with room for threads and barrel movement clearance. I don't know how much the suppressor will affect the velocity, but I guess I could do chrony work as I progressively shorten the barrel before threading. I'll have plenty of time while I'm waiting for my Form 1 approval.

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