I bought a 1927 A1 a month ago. I also bought a 250rnd box of 230grn Magtech .45ACP. I have had a problem with this rifle short stroking. The recoil springs are very stout, it takes a lot of force to pull the bolt back. This Magtech ammo chrony's at about 830FPS, fairly slow and I'm thinking this is the reason for the short stroking. I am going to reload the brass and I was wondering if any of you fellows have experience with the Thompson and could recomend a load that would make it cycle properly. Thanks

Guts, a friend of mine has an original full-auto Thompson. I'll email him and see what he uses. Might be a day or two before he responds.

Let me first state that my knowledge on the Thompson is not that great.
( although I would love to own one )

Most standard 230 gr. loads are in the 830 fps range.
Some go higher but are usally well under 900 fps.
Some Cor Bon +P loads have been clocked over 950 fps.

With that said my thinking is this .........
Back when the Thompson was made, all they had was standard ammo. I also belive that the ammo had less pressure. (lower velocity)
So don't spend a whole lot of money and time trying a bunch of different loads. Try something you know thats hotter and see how it goes.
Hopefully I'm wrong in my way of thinking and theirs nothing wrong with Tommy !!!!!!!!!!

One last thought ....... When was the last time it had a good cleaning and oil change !!!!!!!!!!!!!!!!!

Yeh...While Pumpkinslinger goes for the needed information why don't you completely disassemble that Tommy and clean it. Then reassemble it with a good lubing. Both sound good to me.

One thing. The velosity for .45 ACP rounds was measured using a 5 inch barrel. Even in those days. the 830 fps is derived from such a barrel. From the Thompson it should be a bit faster (longer [not much] barrel)...

I have a Thompson 1927A1 and use Lee home cast lead 230gr bullets with Lee liquid alox lube over 5.0gr Bullseye powder with no short cycle at all.
This load shoots great out my STI Trojan and does not do bad from my Thompson.

From my friend:

"I have no trouble using 6.5 grains of Unique and a 230 grain cast lead bullet or 5.0 grains of Bullseye with a 230 FMJ. I don't know what the bolt weighs on the semi version, but those loads work just fine in an M1928A1."

Once again, I'm tickled with the folks I've met on the internet and the knowledge they have.

Thanks a lot fellas, as always you guys are here for each other(me), makes me feel warm and fuzzy. It's a new rifle with approx 150 rounds through it. I am one of those crazy anal guys about cleaning my rifles, after I'm done shooting they are tore down and completely gone through and oiled up like a $10 stripper. I used to shoot a little 1911 in indoor range competition back in the 70's and it seems like we loaded the rounds down to almost squib rounds(850FPS) where the 1911 would barley cycle. It was a long time ago and I haven't had anything that shoots .45ACP for many years, that's why I thought the standard .45 was a little hotter right out of the box. This rifle has really tough springs behind the bolt, it will leave a mark in your flesh from cocking it back. I thought the 16" barrel would run them out a little faster too, but the loads are so weak it dosen't seem to speed them up at all through the longer barrel. I'll load them up to around 900 and see what it will do. Once again, thanks a bunch.

GUTS, in my .40 S&Ws, a Browning HP and a Ruger PC4, I saw a gain of 300+ ft/sec in the carbine. Now that was with a light bullet (135 gr JHP over Hodgdon LongShot) loaded to the max in the manual. Near as I can remember heavier bullets (180 gr) showed maybe a 200 ft/sec gain.

I have an M1 Thompson and had a 1927A1. They did well with hard cast bullets and a healthy dose of Unique. Neither gun would chamber bullets with a light roll crimp. They demanded a taper crimp. All the best...
Gil

I agree with Gil. Take care...
Joe