Thinking about SBR'ing  my 1927A1 and I keep reading seemingly conflicting information all over the web. I plan on swapping the barrel out, but most of the people selling 10.5" bbl's say things like "Full-Auto Chamber", or "For full auto Thompsons only".
I know this is a pretty common conversion as far as they go, is that all "We don't want to get caught selling our barrels to non-NFA/illegal  conversion thugs"? Or is there a mechanical difference that I need to be aware of (once I receive my stamp and am all GTG with the Feds)?
Additionally, I have read conflicting things about how to remove/install the barrel as if there is some serious "gotcha" there. It looks like all you need to do is remove the foregrip supporting plate and spin it off/on. Is there something else? What about headspacing?
Of all the rifles I have that are SBR candidates, this one SCREAMS about it most, so I really think it needs to be done. Any help here (especially for a DIY'er) would be appreciated.

The full auto Thompsons Fire from an open bolt - the semi's are closed bolt. My guess is that there is a difference.

As far as the replacement of the barrel - I looked into this years ago and was told that it was a tough job even for a competent smith. I have no other info - only what info I was fed about 10 years ago.

Good luck and post pics!

I have done it for my thompson sbr.  The chambers are the same.  The trick is in retiming front sight to line up with the rear.  I took a Savage made Thompson 1928 parts kit and married it to a Kahr Commando.  My barrel came real close so I used a .006 washer to bring it to alignment.  I went to Thompson original patents and copied his method of using a lock screw through the bottom of the receiver to lock the barrel in place.  Works like a charm.

All you need is the correct barrel wrench. The process isn't hard at all and doesn't require any other special tools. You remove 1 screw, take off the handguard, used an old leather belt and a vice to hold the 'nose' of the receiver, clamped on the wrench on the bbl as close to the receiver as possible, and unscrew it from the receiver. It's simpler/easier than an AR bbl swap. Of course, if you DON'T have the right wrench or you lock the 'body' of the receiver in a vice, you can screw it up.....so don't do that. It's easy. Less than 10 mins.

As far as barrels go, just buy an SBR bbl from Kahr. They sell them separately.

Re: the front sight timing, I was going to negate that by using a 1921 profile barrel with a press on front sight ring...
Who's a good source for Thompson barrel wrenches?
I looked into the Kahr barrels, and I might be more interested if they weren't nearly TWICE what other venders are selling barrels for.
In particular, I was looking at products offered by Green Mountain, or better yet, Thompsonbarrels.com.
Any Tommy gunners have info on their product?

I used aluminum blocks for the barrel and a large adjustable wrench for the receiver.

Submitted E-Form 1 and $200 tonight. Now the LONG wait.
Still haven't decided on where to buy the new barrel. Any recommendations from people who have done it? Just web searching now, and see that IMA has a few for $160, but they specifically say they aren't compatible with Kahr semi's. I can understand them not wanting to sell to non-stamped people, but from what you all have told me here, they are flat out lying. I guess they don't need the business.

Tha "LONG" wait for E-Form 1 is about 35 days or so.

ETA-As for the IMA not being compatible with semi-auto Kahrs, perhaps contact Kahr and find out from them. Perhaps Kahr did change some aspect on the semi-auto Thompsons.

BS on the non compatibility issue.  I did my conversion in 2008 with a Kahr Thompson 1927 Commando and a Savage manufactured 1928 kit.  Both are blowback in operation, the 27 is closed bolt while the 28 is open bolt.  The only changes that Auto-Ord/Kahr made was to reduce the height of the receiver by 1/10" to prevent a full auto bolt from being used, and a new lower set up to utilize semi auto trigger assembly for the new closed bolt.  The reduction in height of the receiver is why military magazines will not lock in.  In my conversion, I kept the upper frame and semi internals and threw out the rest.  Everything else came from the Savage kit.

Finally completed this build. once I got the weapon engraved, and got my tax stamp approved, I ordered a 1928 profile barrel from http://www.thompsonbarrels.com/, and received it very promptly. I am very impressed with the quality, and recommend this guy 100%.
When it came time to do the job, I disassembled the Kahr as well as I could, and drifted the handguard mounting plate out by rapping it with force against the stem of my vice. Several good wollups and out it came. Next I clamped the barrel in the vice and put an old leather belt around the fore-end of the receiver where the profile is reduced and the barrel mates with it so the adjustable wrench wouldn't mare the finish. It came out stiff, but not too hard. I cleaned out the old red Locktite inside the receiver (Good one Kahr!), and reversed the process for assembly. It really was a snap. All that remains is to drill press the pinhole in the press-on front sight band, and it's off to the range!


I can't emphasize strong enough what a difference in feel, heft, and balance this makes. Who'd have thought six inches of steel would make so much difference?*
It's like a whole new gun. If you own one of these, and live in a free state, DO THIS!

That looks awesome!

The handguard hanger is held on to the receiver by a flange that is pinched between the barrel, & the receiver. "Drifting it out" likely ruined it. The correct way is to remove the barrel with it in place.
That's what makes it a PITA job.
I'll lay odds that your handguard will come loose in the near future...

It does look nice though.

You caught me. I screwed up in the order of my procedure. I DID remove the old barrel first, and then the hanger. It was the round hanger protrusion knub on the top of the hanger that I caught against the vice to remove it by wacking it. That would not have been possible with the barrel in place. I went to dinner and had a few drinks between completing the exercise and writing about it here, that may have been the issue in relating my account.
I did hold the old barrel in the vice and spun the receiver, not the other way around. I remember having to clamp the barrel out more near the muzzle so the entire hanger would clear the vice as it turned (didn't care about old barrel). I didn't have to take the hanger plate out at all I guess, but I didn't know that at the time. Once out I noted the flange you're talking about and figured that out. When I reassembled, I got it as tight as I could before "choking up" on the barrel with the hanger sticking out the top of the vice for the last @ 1/8 turn until it snugged up. I don't know if that makes sense to anyone who hasn't done it...Wish I'd taken pictures.

Yup, makes sense to me.
Glad to hear you didn't mess it up...