I was reading in Guns&Ammo a comparison of the .45ACP and the .45GAP.  Since the .45GAP is so much shorter would the rounds go into a Colt mag?  I was wondering if anyone out there was building a .45GAP set up for the AR.

Scott

I made one by taking a Thompson SMG barrel, cutting down the end of the barrel till the chamber was .45 GAP length, and then making a new barrel extension from scratch. It uses 9mm Sten mags with a KKF magwell block. I made my own Oly type pistol caliber upper receiver by ordering Olys ejector spring package and drilling out a flat top receiver I had lying around.

Runs like a raped ape. It is currently being parkerized. I will be using a LaRue free float hand guard with flip up front sight that sits on the hand guard as the barrel is too thin to machine for a .750, standard front sight base and it would add to the cost to machine it to .625, A1 diameter and then I'd have to search for A1, front sight base.

I haven't had a chance to check accuracy or velocity yet but it feeds, extracts, and ejects very well. I can get 16 rounds in a Sten mag.

Sorry the pictures are out of focus.

Wow, that is very cool.  Did you make that yourself or had it done?  What are you using for a bolt and buffer?  Thanks for the pictures.

Scott

Bolt and carrier are Oly Arms. Buffer is standard AR. It doesn't need a heavy buffer as the lower is a standard aluminum lower.

A local machine shop made me a new barrel extension and shortened the Thompson barrel for me.  

Is there a reason to do so in the first place other than for the hell of it?

My inerest is because I have a Colt M16 RR.  Grease gun mags won't fit in my magwell.  Since the .45 GAP is shorter, I thought maybe that round would work in my Colt system.  So I thought I would ask.

Scott

Is there a reason to do so in the first place other than for the hell of it?

For the exact reason .45 GAP was invented. To shoot .45 out of a 9mm package. Remignton is loading 230gr .45 GAP to .45 ACP levels so there is nothing lost to the .45 ACP round and in this case it uses 9mm magwell block, 9mm magazines, and a standard AR15 lower. All that is needed to be changed is the barrel and bolt if you have an Oly 9mm AR setup already.

I've been shooting M16s and AR15s for 24 years now. I got bored.

I understand. I didn't realize that there was a magazine size problem with the AR.  I'm a big fan of the .45GAP round in pistol for the reasons it was created, but not having a .45 upper for my M16, I just didn't realize that there were no cheap magazines made that would fit the magwell.  And just to add, "for the hell of it" is plenty good reason for me in the first place.

I stand corrected. Remington is loading .45 GAP to .45 ACP + levels according to their own ammo chart.

Quoted: Is there a reason to do so in the first place other than for the hell of it?

The Tommy gun barrel probably got a whole lot sharper/ cleaner/ shiny rifling than the Oly barrel.. I seen a 40 barrel on a new Oly/Glock, it look like crap inside.