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Switched Barrels And Have A Question


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#1 JimFromFL

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Posted 25 July 2003 - 08:09 PM

As you can tell from my numerous posts that I have been working on my Thompson.

Anyway, I have the barrel changed and getting ready to head to the range in the morning.

Just for grins I placed an EMPTY .45 brass casing into the chamber and pulled the trigger and it jammed shut. Had to use a dowel through the barrel to push the bolt open. Pulling back on the actuator knob would not budge.

Thinking the brass was expanded too much from being an already spent round, I tried with a .45 caliber snap cap. Placed this in a mag, pull the trigger and this stuck too. Had to use the dowel once again to push the snap-cap out.

I have a feeling I may have to polish out the back end of the barrel.

Anyone else experienced this? Is this typical with new barrels?

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#2 Whiskey Brother

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Posted 25 July 2003 - 10:48 PM

Well, the first time I read your post I thought extractor, then I reread and realized that something else is sticking. Even a fired brass casing should go in the chamber and out without resorting to wooden dowels through the barrel. You may want to try a chamber casting to measure the chamber exactly. Chamber casting material is available from Brownells. The trade name is cerrosafe, and you can order it here:
http://www.brownells...tail.aspx?p=384

The casting you make will allow you to compare specs on a .45 ACP. (Full instructions should be included) This will tell you if something is wrong or not. You will also need a good set of calipers or a micrometer. If it is undersize, the next step would be reaming to proper dimensions, but you might want to let a gunsmith do that if it is even necessary.

My second thoughts on the matter are how you went about installing the barrel, and is your Thompson the 27 A1C? (Aluminum) It is possible a light burr has built up in there when you screwed on the barrel. See if you can get a glance inside the chamber and check for burrs or even something else caught in there that would cause a jam such as you describe. What did the empty brass look like when you pulled it out? It should be shiney or scratched where it was caught up at, and this might be an indicater of the problem.
Hopefully you can solve this little problem without to much hassle...
Good luck!
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#3 LIONHART

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Posted 25 July 2003 - 10:55 PM

Jims Gun is a TSMG.
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#4 Whiskey Brother

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Posted 25 July 2003 - 11:03 PM

Well, not much chance of an aluminum burr then. rolleyes.gif

It sounds like it's really getting stuck in there, for some reason. I'd still recomend a chamber casting, as that will give you an exact duplicate of what that chamber looks like.

I also will assume normal headspacing and other such precautions were taken when installing the barrel.

Maybe a slow chambering with a snap cap to see if you can tell where the hang up is. Maybe a little of the old "magic marker" trick to get an idea where the snag-up is...
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#5 JimFromFL

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Posted 26 July 2003 - 08:56 PM

Thanks for the suggestions. Here is what I found out today.

The Thompson worked for the most part, but did experience the symptoms as described above.

I took the rounds home that caused the problems and used my gauge to test them out and sure enough just about each stuck out about 1/8 of an inch or so from the end of the gauge.

I tried the snap-cap in the gauge and this too stuck out.

Conclusion:
========
It appears the new barrel has a very tight tolerance.

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#6 Whiskey Brother

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Posted 26 July 2003 - 10:20 PM

I'm not quite sure if I'm understanding you as regards your gauge. Are you saying you have .45 acp rounds and a snap cap that are 1\8 of an inch oversize? Or do you mean a chamber a whole 1\8th of an inch too tight? I'm thinking you are using a standard case gauge, where whatever sticks out needs to be cut off. Is that what you mean?
I'd be a little cautious firing it till you figure out what's causing the cartridge to hang up. Remember that a .45 Acp headspaces on the mouth of the brass, and if your bolt isn't closing on that last 1\8th of an inch.... Hmmm, I wish I could take a look at it, you got my curiosity aroused anyway.
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#7 catnipman

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Posted 27 July 2003 - 01:23 PM

I bought a new barrel from Numrich for my 1928 overstamp TSMG so I could set aside the original barrel for preservation. After installation, I had major jamming problems. I did a chamber cast with bondo after I made sure the chamber had a very thin layer of oil so the bondo wouldn't stick, which worked good enough to find out what I needed to know, though I wouldn't necessarily recommend doing this since it was kind of a pain trying to do this with the barrel attached to the gun. (Though this worked great with the original barrel that had already been removed.) The upshot was that the Numrich chamber was undersized by several thousands of an inch in diameter and I had to have it removed, reamed, and replaced by my gunsmith.

The lesson for me was to always have aftermarket barrels checked and/or reamed *before* installation. In the case of Numrich, it looked to me like the SOBs used their factory reamers long after they had worn out, thereby producing undersized chambers.
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#8 Whiskey Brother

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Posted 27 July 2003 - 05:18 PM

I am unfamiliar with the properties of bondo, never having used it before. As long as it does not expand or shrink when it hardens, it should be all right. Cerrosafe is extremely accurate, and is the preferred chamber casting material for gunsmiths as well as tool and die makers. It also can be used again and again, so the initial investment should last a lifetime. It is also easy to use. Isn't bondo like a spackle paste? That must have been a real bear packing that stuff in there with the barrel still attached.

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#9 JimFromFL

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Posted 27 July 2003 - 06:48 PM

QUOTE (Whiskey Brother @ Jul 26 2003, 10:20 PM)
I'm not quite sure if I'm understanding you as regards your gauge.

It is the .45 caliber gauge used when reloading to enusre the bass is sized correctly and the round is not too long.
Basically, you drop the bullet in and it should drop right in, but the snap cap and other rounds that caused a problem did not fit all the way in. These would get stuck about 1/8 or so sticking out the end.
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#10 The1930sRust

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Posted 27 July 2003 - 07:01 PM

The tight chamber conclusion has already been made, but here is a quote from Steave Wayman, Class III Firearms, (in some email he sent me last year) regarding just this problem with some West Hurley guns (read bbls)"

"Occasionally you will find a WH with a tight chamber, it isn't way off spec., maybe a .0001 of metal needs to be removed, but the barrel must be removed from the receiver to do this. Solution, remove the barrel and run a std. .45 ACP chamber reamer through the chamber, just a couple of twists of the reamer should do it. I would also advise giving the chamber a bit of a polish after this has been done. This is really the only aspect of WH that you may not be able to do yourself as you will need to have an action wrench to do this. Luckily this problem is rarely encountered."

FWIW
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#11 LIONHART

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Posted 27 July 2003 - 07:40 PM

Steave really is a great guy. Always goes the extra mile in his dealings!
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#12 Ron A

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Posted 28 July 2003 - 03:09 PM

I had the same problem with a WH28 - the edge of the chamber was sharp and dug into the brass round causing a jam - when it did go into the chamber which was undersized the bolt would not closed all the way.
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