Low Price Guns
Buster Beaver Cerakote
Oregon Arms & Ammunition
Gun Deals
J&B Firearm Sales
Advertise on Northwest Firearms
Oregon Rifleworks
Sporting Systems
Defensive Arts
Southwest Firearms Forum
Welcome to Northwest Firearms
Join our community, sign up for free today!
Sign Up

AO Thompson M1SB

Whilst browsing around the Auto-Ordnance site, I came upon their <broken link removed> :


It is basically their semi-auto M1 with a 10½" barrel. It looks pretty interesting.

Anyone have experience with these? Good, bad, or ugly?

  • National Rifle Association
No experience, but the short barrel matches the original TSMG specs. (Note: very few receiver parts interchange between a Kahr or West Hurley semi and a GI M1 or an original 1921/27/28, largely because of the redesign required to go closed-bolt and otherwise comply with "not readily convertible to full-auto." This is why original 1927 semis are cheap: they have all the arse-pain of NFA MG since they were factory converted from full-auto 1921s and "once MG always MG," but none of the rock-n-roll fun.)

DB, Thompson nut who has owning a live Colt 1921AC on his bucketlist
I had one about ten years ago and it was very finicky with magazines. You have to modify military surplus magazines in order for them to work in the AO Thompsons. The magazine catch/release is different. You have to dremel the hole on the surplus magazine for it to work in the AO Thompson. If you do it right, they work fine. Even the AO supplied magazines were problematic. I also had an extractor break. Once I got the magazines tuned so to speak it ran fine. It was an expensive plinker though so I sold it. Mine was an alloy frame and receiver version. Much lighter than original but the internals were the same. I had also SBR'd it as they did not offer them from the factory like they do now.
  • National Rifle Association
The alternate option is to replace the mag catch with modified GI--if I had budget for a Thompson, that's the direction I'd go, in no small part because modding the mags for semi guns makes them unusable in the originals.

Dunno if he's still in business, but back in college when my Thompson geekout first started, my very first move other than taking it out for a "diagnostic" shoot would have been to ship the gun off to Paul at Diamond K and the drums off to Merle "Drum Doctor" Bitikofer for top-to-bottom tune-up.



  • Supporting Vendor Cerberus Training Group
    5.00 star(s)
    Armorer 1911 Course This was a 2 day course devoted to the iconic 1911. You might own a 1911 but, I assure you, you don't know it until you've...
    • Hueco
  • Supporting Vendor Oregon Rifleworks
    5.00 star(s)
    As a recent owner of a PTR91 a friend mentioned to me that Oregon Rifleworks has surplus magazines on hand for $3.99ea. I drove from Vancouver to...
    • svxr8dr
  • Rapid Fire Arms
    5.00 star(s)
    Great place friendly service always take time to help you, great knowledge of products
    • RJSouth
  • Supporting Vendor Copeland Custom Gunworks
    5.00 star(s)
    Perfect install of peep sight on my cz 527 carbine. Price was right, was expecting it to be more. Will be my go to for anything I can't handle...
    • cd90caprice
  • Adaptive Firing Solutions
    5.00 star(s)
    I've been party to a couple transactions with Steve and he is a great guy to deal with.
    • titsonritz