I've been thinking about a 9mm AR SBR.  I have one registered SBR lower that will be serving a 300 BO and a 5.56 upper.  Thinking about adding a 9mm upper, just because.  I already have a TNW ASR carbine in 9mm and 10mm, but have not and probably won't SBR it.  I am really only interested in another 9mm as an SBR and use of Sten mags would be a big plus (I have a Sten semi-auto and plenty of mags).  Also plan to supress whatever I build/buy.

I was just about to buy a cheap PSA SBR/Pistol upper with their hybrid BCG and was going to play around with trying to get it to work with a Sten mag block.  But then I did more research and realize that will be quite a project and I certainly don't want to do anything that would damage my SBR lower.  I would play around with it in a cheaper pistol lower to start with.  Upper $300, mag block $85, plus parts and tinkering and no certainly of success.  Fallback would be using a mag block for Colt-type mags.

In 9mm, I understand the true Colt guns are kind of the gold standard:  pinned mag block, factory tested and tuned, warranty, etc.  A boxed Colt carbine can be bought for under $1000.  Then I could use it "as is" in carbine form and put in to SBR it.  Then I could have the barrel shortened when the SBR stamp comes in.  Or I could BUY an SBR version for about $1150, but then I wouldn't be able to play with it until the SBR papers come through.

And the "final" thought is to buy a built complete Colt upper group for about $700 and use it on my SBR lower after buying a Colt-style mag block for it ($100).

Or just bag the whole idea, SBR my ASR and be done with it.

Any other considerations?  Thoughts?

Rob

Colt factory SBR. If a factory sbr is available it is always preferable IMO. That Colt offers a factory SBR, the decision is an easy one. No need to engrave your info and it will hold value better than a form-1 sbr. This may not seem important to you now, however what if you decide to sell it in 10 years? What do you think will be more valuable - a form-1 parts gun or a factory made Colt sbr?

I bought a Colt 6951. Shot it a bunch while waiting for my stamp. When the stamp came back, I sent it to ADCO and had them shorten the barrel. The thing has run 100% with all ammo both full size and after being cut down (suppressed and unsuppressed). May cost a few dollars more that way but works great.