Jamming Tommy

[zultar]

I just received my 1928 a1 tommy, its a NAC and looks as if its never been fired. It started out jamming 2 out of three rounds on all clips. I've greased it, cleaned it, and got some steal wool after the chamber ramp. It better now, the 20rd mags may go through a whole clip but the 30rds are still bad

 

It jams in two ways. 1) the first bullet will not fire- there is a light strike on the primer, and watching the bolt as someone fires it you can see the bolt slow down some at the mid travel location. the bolt appears to close, but obviously not all the way. 2) some bullets (those that jam while firing) are getting crooked in the chamber ramp and bolt closing on it- scatch marks on the brass near the distal end- apparently from the ramp. I have put about 700 rounds through it. At first when ever I good get a 10-15 round burst out of it it was variable in its rate, but no it fires a nice constant rate. Also the recoil spring has a slight (5-10 degree) kink in it. I have also noticed since I have fired it some the tip of the spring rod is wearing rapidly and unevenly from entering the bolt block off centered.

 

My tommy gun friends have never had or heard of tommy guns jamming, but we think it is because the gun needs to be broken in. I think it may be also because of the spring and have ordered a few, but not received then yet.

 

Anyone have any ideas or heard of this problem?

 

[TSMGguy]

My '28A1 is a nearly new NAC gun as well. It's run like a champ from day one. I have No. S- 3329xxNAC.

 

PhilOhio is right; don't make any changes to the gun before you've replaced the mainspring. That kinked (and weakened) spring is slowing down your bolt, as evidenced by the light primer strikes. The first round of your magazine will not fire because the weak bolt spring is having trouble overcoming the healthy spring of the fully loaded mag.

 

If you have an original matching USGI receiver (as mine does) it left the Savage factory with the feed ramp right. You should be able to see original slight horizontal milling marks on the ramp. Don't attempt to polish these away. Dremeling perfectly servicable feed ramps is the first thought that springs (for some strange reason) to too many minds when these guns have problems. It's nearly always a mistake.

 

My gun is absolutely reliable and has a 750 rpm rate, which is correct and is some 100-150 rpm slower than a '21. I think that it is so reliable because the feed ramp is unadulterated, the springs are straight and strong, the mags and drums used are original and in excellent shape, and I use only original WWII ball ammo out of Russian and American spam cans, not underloaded modern commercial stuff. I'll run out of this ammo in a few more years, but for now, it's a blast!

 

So, troubleshooting any TSMG starts with springs, mags, and ammo, in no particular order. There should be no need to start replacing parts at random. The original USGI componants, if in good shape, should last for your lifetime of sport shooting. I have the obligatory spare parts, but have not needed to replace anything. Ever.

 

To determine of your barrel is original to the gun, first, you should be able to find a small 'P' proof mark somewhere on the cooling fin nearest to the receiver. Also, there should be a small dimple (index mark) on the top of the receiver, centered, nearest the first large cooling fin of the barrel, which should have an identical mark. These should align. If these marks are present, all to the good. The real test comes when you move the rear sight ladder to the vertical and fire single rounds from a sand bag or rest at a known distance target. The rounds fired should impact the aiming point on your target with some precision, or the original factory targeting (which was quite precise) has been somehow disturbed.

Edited January 3, 2008 by TSMGguy

[zultar]

Ive have used new winchester and aguila ammo so far, both performed equally. I am going out to look at it and shoot it in a few seconds after I deer hunt. If I recall there are multiple milling marks on the chamber ramp. it is parkerized and did have some small pitting on the ramp from manufacturing. But I'll check on the other marking when I get out to the deer lease. See my post on tommy nac about further description of the gun. There were no marks on the bolt or spring guide, all other parts had 'S' marked.

 

as for new bolts, R Gun in shot gun news has complete bolt assemblies 'original GI' for $200, does anyone know if these are good?

 

Thanks

[zultar]

checked it out. no marks on the barrel. but my brother is the most informed I know of older guns (ask him a dragoon or walker serial number and he can off his head tell you which unit received it originally.) He said that my barrel if definately a colt blueing, that it is distinct and hard to copy. There is a tick mark on the right side of the receiver near the barrel but no proof marks. And of most curious is a 'water stain' appearence to the area around both serial numbers of the upper and lower. And there is definate logitudinal mill marks on the chamber ramp.

[Motorcar]

The add in SGN from R Guns is typical of the USGI '28 parts kits that have come back from Lend Lease guns shipped overseas during the war. The complete kit I purchased from another supplier was unfired and in advertised excellant condition. Much has been written on the forums on these kits. Get 'em while you can for spare parts.

[TSMGguy]

Detailed photos of your gun will get you some concise answers as there's some serious Thompson experience hanging around these boards.

 

If your barrel has square cooling fins, it wasn't made by Colt.

Edited January 3, 2008 by TSMGguy

[zultar]

if you mean by squared off corners, no its not they are rounded. My main computer is dead and waiting on replacement from dell (has been shipped) as soon as i am up i will place some photos.

 

shot it last night went through a 30 round clip with only one jam, so doing better- i stretched the spring some.

[zultar]

ok got a complete bolt assembly kit from r guns and have installed it today. I shot it last weekend aftering cleaning again, 2 3o round clips fired with only one jam, the third clip (and same one) jammed almost every bullet on the first trigger pull. bolt not closing all the way I guess, light pin mark on primer.

 

now that i have replaced bolt group, the bolt slides well, except if i gently let it down it will not close all the way, about 1-2mm more after i push it, but with half force it will close. have not fired it yet.

 

the bolt, actuator, and spring guide had no markings, except the actuator had a knurled knob. all 'new' parts in kit from r guns are marked 's'.

 

pictures to follow of gun.

 

well crap, how do you insert pics, it wants me to give an http address for pics????

[FireMerc]

Posted on behalf of zultar:

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-1.jpg

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-2.jpg

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-3.jpg

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-4.jpg

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-5.jpg

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-6_edited-2.jpg

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-7.jpg

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-8.jpg

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-9.jpg

New Bolt Assembly

 

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-10.jpg

Old Bolt Assembly

 

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-11.jpg

Original Bolt Assembly

 

http://i139.photobucket.com/albums/q304/class3nfa/NACSAVAGE-12.jpg

Edited January 12, 2008 by FireMerc

[motorgun]

I had similar jams with a 1928 and it turned out the "U" shaped bracket at the back of the receiver that has the felt oil pads on it (and a hole the spring rod goes through) was in upside down. Turned it over - friction was gone and it ran perfectly from then on.

[zultar]

Thanks for posting my pics. Does anyone know what the caused the 'stain' around the serial numbers?

[jim c 351]

Zultar,

I have a A.O. 28A1 NAC gun. For the most part the gun has run flawlessly. One of the first things I noticed after field stripping was that my bolt spring and guide was off center from the actuator hole just like yours. I removed the buffer,spring, and oiler and then checked alignment of actuator hole to spring guide. It was perfect. I was baffled. Since I had two extra bolt assemblies I began switching parts. I noticed that one of the spring guides ( both Savage) was 1/16" longer than the other -- i used the longer one. It helped. I found that by using a certain Savage bolt and a certain Remington actuator the alignment was near perfect. Nice thing about having extra parts, you can swap untill you get perfect fit. While interesting I don't believe this has anything to do with your problem of failure to feed and fire.

 

If you find one magazine that works perfectly all day and another mag that constantly screws up , then you have a magazine problem not a gun problem. Be especially suspicious of Crosby mags. I've had more trouble with these mags than with Numrich drums.

 

If your barrel is a Numrich replacement with a tight chamber, then this could be you problem. This would be solved by opening the chamber to military spec. or installing a military barrel.

 

If you live near someone who owns a military TSMG try to pay him a visit and compare guns. If you can find someone with a CEINER 22 conversion kit , try inserting the 22 barrel into your barrel. If it won't go in all the way, then you probably have a replacement Numrich barrel with a tight chamber.

 

Hope this helps.

Jim C

[adlake]

Unless its bad photography I place my pen and a straight edge to the pilot and it looks a little bent. ( on the original photograph) But you've seen to cover that in the purchase of a new bolt. I have several re-coil springs for the 1928 from WWII. I will let you have one if it works for you. You pay shipping. May I suggest WOLFF Gunsprings. Check there website. I love them!-adlake

[giantpanda4]

After reading this whole thread I'd say there is no question at least one mag needs help. I have had a few bad mags cost me a chance in the pepper poppers shootoffs (thats my story - I'm sticking to it!).

 

Search these posts for a thread about mag anvils, like the ones made by Glen Whittenberger. The thread has the dimensions of what the mag should be, as well as ideas on how to fix them.

 

I have about 50 mags I got for a buck or less each, and was able to straighten out several of them and they are good shooters. It can be done.

 

When trying to solve any problem, you should eliminate variables, so use the same mag (one that works best) and I always start from the cheapest possible solution and work in the more expensive direction. Not to say that you shouldn't have a spare parts kit around, that is always good insurance that a trip to the range isn't a bust. And - PhilO mentioned it twice - swap/trash the spring, it is crap. Get a new one. Start cheap, remember?

 

Good luck and good shooting!

[zultar]

I have only 6 mags, all jam. But the 20 round mags seem to worl slightly better. Will shoot it tomorrow with new bolt group/spring and keep ya'll informed. Thanks for the help so far. I think I really had two jamming problems, one on first round where it seem not to close well and just barely dent the primer, and the other during cyclic fire when the round would get malaligned in the feed ramp. I do like the chamber idea above- the gun jams much less when just cleaned, after 30 rounds or so it begins to jam 2 out of 3 tries. I have a few tommy friends nearby so far, i can check with about the barrell.

 

hays

[zultar]

after looking at my pilot pin again, it might be the oiler. I'm going to shoot it as is first and then change out the oiler and see sometime tomorrow afternoon.

[FireMerc]

You can shoot it without the oiler on a limited basis and not hurt it as well.

 

Without the frame but all internals, when you slide the bolt back using the actuator does the spring and pilot go into the actuator smoothly or bind? Sit down, with the open internals facing up, keep your thumb over the bolt and pull the actuator back with your finger.

 

Take out the spring and pilot, when you slide the bolt forward can you see or feel any area's that cause the bolt to bind.

 

I certainly don't have the experience of others in this regard just an idea.

Edited January 15, 2008 by FireMerc

[TSMGguy]

Thanks for posting the photos.

 

The gun has been refinished, with the receiver parked rather than blued. The barrel was removed (and perhaps replaced) as it is blued and polished.

 

You might find and fix a single problem by replacing parts at random, but the gun doesn't shoot right as it's out of spec somewhere. Take Phil's advice and don't do anything else until the mainspring is replaced. If still no luck, I'd send the gun to PK for proper sorting out. No one knows these guns as Paul does. He's that real rarity: an engineer who is also an artisan. He can also rectify that finish.

[zultar]

I tried to shoot today after replacing the entire bolt assembly and new spring/guide. It was much worse. I tried all 6 of my mags, 3-4 rounds each mag and only 3 fired, none cyclic. I am asking firemerc to post a few photos of the shells. There is a scrape mark on the underside of the cases (as seen in the pics to come) and a slight scrape on the up side just at the edge of the case on the bullet end. None had a firing pin mark, these are the ones that tried to feed after the initial bullet fired. There is also barely visible on the pics a small tic mark on the case rim- which i have not seen until now (new bolt??).

 

The initial ones that did not fire seated but not enough to allow the bolt to close completely, one even would not extract. These had light firing pin marks.

 

I cycled the bolt with the lower off and watched the pin guide, it was malaligned as seen on the previous pics (new spring/guide) but as it cycled it straighted up. the bolt cycles without snag or difficulty.

 

I am convenced that there is a problem in my chamber, feels smooth, but i have big fingers and can only get some in the chamber, can't see in well but will go get a dental mirror from my dentist tomorrow and look in. I think i will need to get a new barrell and try it out. Any good sources for barrells? I did find out there is an old marine armorer in town that worked on tommys back in the day, call him but no returned call yet.

[FireMerc]

Posted on behalf of zultar:

 

http://i139.photobucket.com/albums/q304/class3nfa/JamminTommy1.jpg

http://i139.photobucket.com/albums/q304/class3nfa/JamminTommy2.jpg

[full auto 45]

That stain looks suspicious to me, but it may be harmless. Maybe somebody else has thoughts.

 

 

Looks like somebody was a little excited about a new Thompson............................a little DNA?

[DINK]

Regarding your "stained" Tommy, it looks like there were other marking on the receiver that were removed via welding. The receiver may have been "recycled" when built into a gun. The latest batch of photos seems to indicate that your ammo is not going smoothly into the chamber. This could be a problem with the chamber, but it could also have to do with the bolt assembly. Things changed (for the worse) when you changed out the bolt, so you might want to check the bolt face out. The base of the cartridge has to slide across the bolt face and then push the extractor aside and drop into place as it's being rammed into the chamber. Anything that interferes with this will keep the round from chambering.

 

I would suggest that you look around and find one of the Russian import parts sets that are still floating around. You will then have a full set of like-new parts, including a barrel.

[zultar]

Who is a good source of barrels? tommy gun shop has new ones. tommygunner has some old ones and R guns has the whole parts kit. I take it I do NOT need a threaded barrel, but whats the trick to taking off the compensator and barrel. I thought i saw a post somewhere on that subject. And who is PK 'Paul'? Where is he located?

[zultar]

how do i get hold of PK?

[TSMGguy]

pk@gwe.net

 

Paul Krough, who is the best thompson smith going!