Thompson Barrel Torque

[ws556]

I'd like to replace a barrel on my 1928 upper. I canno find the torque specifications. Does anybody know? Any help would be greatly appreciated. Thanks, Walt

[Grey Crow]

I've never seen any stats on barrel torque. However there are other issues involved with barrel replacement such as head space.

 

If you search through this board you will find that this topic has been discussed before.

[Bisley45]

Doug Richardson has a three page article about it in his Thompson Tecnical Vol#1 and sells a head space gauge in his catalog with complete directions.

 

BB

[BASS6621]

ws556,

 

When I did a rebarrel job on my Stembridge movie gun a couple years ago I didn't use a torque wrench. All I had was some of Doug Richardson's tools (loaned to me by another TSMG owner) and a demilled '28 kit with the barrel still attached.

 

The index mark on both the barrel and receiver nose of the kit lined up. I found once I took the barrel off the receiver stub and then hand tightened it back after cleaning the threads, it would hand tighten to where the barrel index mark was about .10 inch from the index mark on the receiver stub.

 

When I mounted that take off replacement bbl to my Stembridge gun, I found it was about .20 inches out of index line alignment. I removed enough metal from the barrel shoulder (IIRC maybe about .01) to get the barrel index mark to be within .10 inches of lining up just. When I finally tightened it, the index mark and receiver mark aligned _perfectly_. I did use Doug R's headspace gauge to check h/s; you'll need a set of feeler gauges to really do it right with the gauge. All was within acceptable parameters so I was good to go.

 

Anyway, that barrel has been on the gun for several K rounds now. Never a misfeed or stoppage. My method was somewhat unscientific (save for breaking out the calipers for measuring), but it worked very well.

 

My advice when removing the barrel, use a fairly long breaker bar (maybe 2-3 feet). You may need the leverage to get the old barrel off the receiver. However when re-barreling, use a short (maybe a foot long) bar. You'll have a better "feel" when you go to tighten the replacement barrel in the receiver. You'll also be less likely, in my opinion, to over torque the barrel. Practice a little if you can on a old barrel and receiver nose to get the feel for it.

 

Hope that helps!

BASS6621

 

[JimFromFL]

QUOTE (BASS6621 @ Dec 12 2003, 08:34 PM)

When I did a rebarrel job on my Stembridge movie gun...

Who did you purchase your Stembride from and what movies was it in?

[BASS6621]

Jim,

 

I purchased my Savage 28A1 from LMO (Long Mountain Outfitters) when they closed out the Stembridge gun rental collection (like in '98 or '99 can't remember right now). Lots of choice pieces including a good selection of TSMGs (all variants). Many blank adapted like my TSMG. Wish I had more money back then, I would have bought a few more things.

 

Some of the NFA guns they sold off came with a COA (Certificate Of Authenticity) citing which movie they were featured in. My "Red Dawn" AK has that COA as it was used in that movie, but not the TSMG. Apparently only some of the guns, which include items like the Lewis guns used in "King Kong" to M60's used by Schwartzenegger and Stallone, were tracked back to specific movies.

 

IIRC, there was some effort underway to try to tie the TSMGs that were sold off back to specific movies or to get additional history on them. I don't know of any other details on that effort or if it is still ongoing.

 

So unfortunately I really don't know which movies it may have been in. That gives me lots of "flexibility" so I can watch movies like "Battleground", "Back to Bataan", "To Hell and Back" or "Them" and say to my wife... "Look! There's my gun!" ... You never know... I might be right one of those times. ;-)

 

BASS6621

[gijive]

Bass6621,

 

Your gun sounds interesting. The Stembridge Thompsons appeared in so many movies it would be diificult to pinpoint exactly which ones which gun appeared in. Suffice to say it appeared in movies in the 1940's through the 1980's.

 

By the way, when you replaced the barrel from the parts kit the witness or index marks on the receiver would not have lined up correctly on the new barrel. Doug Richardson has written on this topic. The witness marks may have been placed on the barrel when originally fitted and replacement barrel marks will rarely line up with the mark on the reciver.

 

It wasn't necessary to remove any metal from the barrel flange. The barrel should just have been tightened to the proper torque and the feeler gauge used to measure head space. I am not a gunsmith but I don't know if removing metal from the barrel was necessarily a good idea.

 

If it works, fine but I would realign the compensator on the next barrel change, if there is one, instead of removing metal to make the witness marks line up.

 

Thompson researcher and collector Gordon Herigstad is currently looking for information on the former Stembridge Thompsons. If you care to email me privately I can put you in touch with him if you happen to have any further information about the locations of some of the other guns. He is primarily interested in the Colt guns but may have some information for you about the history of your gun. He has the records from Stembridge regarding the productions that rented Stembridge guns and may be able to provide some specifics about what productions your gun was used in.

 

[LIONHART]

Bass, is your "Red Dawn" AK Semi? I know someone up here that purchased one of those as well, complete with documents from Stembridge. Norico Type 56, Semi. Just curious.

[JimFromFL]

BASS6621,

 

Mine was supposed to have been used in the Dick Tracey movie (the one with Warren Beatty).

I have called Stembridge but they were unable to associated the Thompson with a specific character so it could have been used by anyone or even sat on the side as an extra.

[BASS6621]

gijive,

 

Agreed, it would be difficult to tie the gun to any particular movie. Like I said, it gives me some flexibility to dream of what might have been.

 

I did the rebarreling job a few years ago. Didn't really have any access to Doug R. at that time (he was frequently out of the country) and this excellent forum wasn't around then. I even had to borrow the tools to do the job as unfortunately his excellent rebarreling wrench and receiver fixture were available (I would buy those tools today if I could).

 

I took the rebarreling route I did based on direct observation between different demilled receiver parts and different barrels. Suffice to say I removed, with a flat hand file, no more than .01 inches from the collar by rotating the barrel by hand. This was fairly time consuming; taking me the better part of two evenings to "hand lathe" the barrel. No metal was removed from threads in the area surrounding the chamber, so structurally, there should be no loss of strength. Had I been removing metal from there I am sure the strength of the barrel would have been negatively impacted.

 

With regards to the comp alignment? No need to realign as the front sight lines up and is vertical. Headspace was fine as well; I've got all the measurements written down in a journal I made of this effort, but I recall it being right in the middle of the acceptable range.

 

Without any torque measurements at my disposal, I took a shot. If there is a torque setting I would like to know the number in the event I have to do this again. Maybe I just got lucky on this, but I did pretty well. The TSMG was the first, and only gun, I have ever rebarreled. Truly a labor of love for me and the gun has never failed me in any way since I swapped in a real barrel. It was a joy to see that Savage reborn to fire live rounds again.

 

Thanks for the confirmation Gordon Herigstad had been doing some research on the SGR TSMGs. I thought I had heard that at one time, but wasn't sure. I am aware of the location of 3 other SGR TSMGs in addition to mine (1 28A1, 1 M1A1 and 1 Colt 21). Maybe I'll drop him an email and see if he has any insight he can share.

 

BASS6621

[BASS6621]

LIONHART,

 

No, my SGR AK is f/a. It's a Steyr Maadi conversion done by Pearl Manufacturing for the movie and is one of the two made up for "Robert". Beat to heck externally, but runs like a clock and has all the "kill" marks cut into the wood.

 

BTW, I had to laugh when it was announced that the op to capture Saddam Hussein was called "Operation Red Dawn" and the two target sites were "Wolverine 1" and "Wolverine 2". Someone had a sense of humor. :-)

 

BASS6621

[Arthur Fliegenheimer]

In regards to barrel alignment marks:

 

After 1928, Colt guns ordered, or returned to the factory for the 2nd pattern Cutts Compensator installation, also had new barrels with a heavier muzzle end installed on the Colt 1921AC's and 1928 Navy's. This would account for the slightest misalignment of the barrel and receiver marks. Naturally, original Colt 1921A's , or 1921 AC's with first pattern Cutts should have perfect alignment marks, or it would indicate a barrel change sometime after the gun left Hartford for good.

[BASS6621]

Arthur, .

 

That's good info re Cutts and barrel replacement, thanks.

 

I still have a question though after this discussion. Can someone explain to me

why alignment marks are found on new-in-wrap mil surp barrels?

 

Every new surplus barrel I've examined always has them. If they're are not

used for alignment (to indicate when the torque and/or h/s is about right), what

are they used for?

 

Thanks,

BASS6621

[gijive]

Arthur,

 

I would be interested in your theory about the 1928 Navy Thompsons with the first type Cutts compensators. Are you suggesting that they were all 1921AC's that were returned to the factory to be converted to Navy models?

 

I believe the second type compensators were introduced around 1932 and the different thread pitch and heavier muzzle end would be characteristic of Navy models produced after that. Would you agree?

 

Bass6621,

 

Yes, drop Gordon an email. I know he would be interested in the whereabouts of the former Stembridge Colt Thompson.

[PK.]

The alignment mark question has been raised before and I don’t think a good answer has been discovered yet. Mil surplus parts barrels are noted with and without the alignment marks, but the prints for receiver and barrel that I have seen make no note of thread timing and there is no cut for the front sight or compensator pin. Re-barreled guns are noted with the alignment marks in all sorts of positions, the sights and comps are straight however as they were obviously installed after the receiver was re-barreled.

 

The headspace dimension is measured from the shoulder of the barrel and if the parts (barrel, bolt and receiver) are in spec, headspace is assured regardless of the position of the mark. Some guns had no marks on either barrel or receiver.

 

I am still hoping to obtain further military prints for the barrel and perhaps this might shed more light on the matter.

 

[Arthur Fliegenheimer]

GI Jive,

As that idiot Fred Durst said, "I am in agreance." Sorry I was not clear in my post. 1921 A's, or AC's converted to the Navy model (whether they were returns, or initial factory orders) before the 2nd pattern Cutts became available, you think would also have perfect alignment marks since there would not be any barrel change. There are few reported examples of Navy models without any Cutts. Since Auto-Ord did not sell TSMG's in any sequence with regards to serial numbers, it is difficult to to determine when a TSMG (if it is not a 1921A) went back to the shop for the upgrades i.e., first pattern Cutts, 2nd pattern, or Navy overstamp, or never left the factory until an order mandated the change from 1921A to AC, Navy, etc. What we do know is that the original 115 TSMG's ordered by the FBI between 1934 and 1939 were Navy models with 2nd pattern Cutts. The serial numbers range from 4471 to 14427. Cox estimates that 63 of these survived the FBI's torch. I guess it is rather safe to conclude that the latest serial numbered Colt's were not returns for upgrades, but left Auto-Ord initially with the desired parts.

[gijive]

Arthur,

 

Thanks for the reply. I am also in "agreance."

 

PK,

 

Interesting reply to the witness marks question. I wonder why the replacement barrels were marked if they weren't going to line up to the receiver mark anyway? Maybe the specifications called for it to be marked on the barrel and they just manufactured them that way, regardless of the usefulness.

[PK.]

GI Jive

 

I think you are right. The whole question has haunted me for some time and as I said, I am seeking further documentation to help illuminate the situation. It is certainly not inconceivable that parts were made “to spec” even if the spec didn’t make any sense.

 

[SecondAmend]

I speculate that the barrel mark was some sort of proof test. I have no evidence to support my speculation.

[BASS6621]

SecondAmend,

 

Could be, but I think it's probably not a proof mark. Those "seem" to be well established as "P" stamps or pin prick punch marks.

 

Could just be part of the specs of manufacture, but I wonder if there is some consistentency in it's placement. Why do I say that? When I got my SGR TSMG, the blanked barrel had it's witness mark out of alignment with the receiver mark (comp/front sight was aligned). The replacement barrel I put on it initially had the witness mark go to the same space/distance from the receiver witness mark as the blanked barrel witness mark that had been on it during its movie life. Not trying to draw any conclusions from my limited experience, but I find that interesting as it suggested some limited consistency.

 

Maybe I need to take some measurements on some of the pulled and NIW mil barrels I have with regards to the placement of witness mark in reference to the start of the barrel thread to see if there is some consistency.

 

BASS6621

[PK.]

If you have several spare parts barrels (take off’s should be considered 2ed echelon) with witness marks and a receiver (or section of one) handy, screw the spares into the receiver and see if the marks on the barrels go to the same point on the receiver (regardless of the place on the receiver). If they do, it would indicate that the barrel threads are, indeed, timed. It wouldn’t make sense to time them though as the mil prints for the receiver do not indicate thread timing for that part.

 

The sample (number of parts) should be as substantial as possible and the makers of the barrels recorded.

 

I have wanted to do this for a long time but haven’t figure a way to get a large quantity of parts barrels here at the same time.

 

[PK.]

Phil,

 

Some interesting and quite plausible theories.

 

Others more adept at research than I have failed to discover manufacturing records sufficient to clarify this question, I don’t know why I maintain hope that I would be able to find such, but I fear the question will haunt me still.

 

The bottom line is proper headspace- wherever the witness mark falls. If you machine to line up the marks you will likely have to re-chamber.

 

[PK.]

http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/laugh.gif Phil- yer killing me with laughter! http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/biggrin.gif

[ws556]

I was just wondering is you can put new semi-barrel on a full-auto?

[Arthur Fliegenheimer]

The question is why would you want to?