I need some help as im trying to get together a 9mm sbr build. Should I get a dedicated 9mm lower or buy a cheap lower and get a mag block? Id rather have the glock mag compatible because i already have several mags.

What kind of bolt should i get? I know i need one ramped correct? I also read something about sending the bolt off to have it cut for a glock mag? is that true?

Are there conflicting uppers that wont work with certain lower or triggers?

I plan on running a 7 or 8 inch barrel. Suppressed in the future. Thanks!!

Why not just buy the SP5K and have the best 9mm submachine gun?

Really dont want to drop that kinda money

Get the Glock mag lower.  New Frontier lowers can be found for fairly cheap.  Most bolts available today are ramped and a good majority will be cut for glock mags.  Just make sure to check the product description before ordering. 

There are so many amazing options these days, I would buy a proven design before building. My personal preference list:

1.) HK SP5K
2.) B&T TP9
3.) B&T APC9
4.) Kriss Vector KV90-PBL20
5.) B&T USW A1
6.) CZ Scorpion EVO 3 S1
7.) Sig MPX
8.) Colt AR6951
9.) IWI Uzi Pro UPP9SB

as Josh commented... my NFA small Glock lower is very nice... I just ordered a sister unit made by them from PSA...I have both a 16" upper built from parts, and a 16" complete from PSA, additionally a PSA 10.5 for my SBR uses a Macon Armory bottom load mag block with Colt mags....the bolts from PSA are hybrid working with both Glock and Colt magazines, the original bolt is NFA modular...only problem was that the 16" from PSA had a short leade area, and I had to throat ream to shoot 1.130" hand loads... worked fine with jacketed...I use mine for USPSA PCC and am pretty particular as to what fore end, trigger group etc I use, so going the DIY route was natural for me...

a friend built a PSA 16" for around $620 less match trigger and scope

Topic Moved

Most what you mention are not AR15 type

Just go buy a PSA 9mm carbine.
Then just get another upper with a short barrel when stamp arrives.

Or...put in some time searching and reading what others have built, what parts they used, what works, etc.
Tons of info available if you just look for it.


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I would use a standard lower and go Colt if you are going to have a registered lower.  That way, you can take out the mag block and use any other caliber upper on your SBR.  If you register the glock lower, we'll you're stuck with 9mm or 40.  If you weren't planning on registering as an SBR, I'd go with Glock lower.

When I built mine, I wanted to go Colt style.

I debated getting a dedicated 9mm lower versus a 5.56 lower and a quality mag block.  It turned out that it was cheaper for me to get the 9mm dedicated lower.  

I would recommend going with a dedicated lower, of which ever style (Colt or Glock) you choose.