Hi all,

starting a side project as i am soon starting into retirement

The plan is to manufacture some parts for a AR pistol setup.
Starting with the barrel soon, BCG will come later.

Would be great to get some support from this knowledgeable community.

Can someone help me with the dimensions for the barrel?




According to my research b should be 0,98"
Any guidance on the other dimensions?

Thanks!

Do you currently have an AR-15?  

Those measurements will be the same for 9mm as any other AR extension.

Are you building it with a blowback action?  If you are nifty, you might be able to make your own delayed blowback system.

Blowback is simpler.

The hole in the receiver tenon should be 1.000", so the diameter of your extension should be close to that.

Some make the receivers' hole tighter for barrel fit, but since you have control over the barrel you might want to snug up pretty close to an inch.  You can always put a torch to it  

From Colt's Technical Data Package, the dimensions for the extension are (using your Letters):

A = 0.9987 (+0/-.0008) dia.

B = 1.170 dia.

C = 0.990 L

C+D = 1.121 L  (that's the way it's dimensioned, this makes D = 0.131 L)

There is also an undercut at the locating pin.  It's 0.993 (+0/-.005) dia. X 0.16 W.

I'd post a section of the drawing, but my laptop is not co-operating today.

I don't have any information on your E for the 9mm.  But, on a .556 A1 barrel, it's approximately 0.636 (+/- .030) L.

Thank you so much, really helpful!

Will post some pictures once the barrel is done. Might take a few weeks though as my lathe refuses to work atm


Regarding the bcg i will rather keep it simple and stick with blowback.
For me this is already quite a complex project  ...