THE ACCURATERELOADING.COM MODERN MILITARY RIFLES FORUM

Go
New
Find
Notify
Tools
Reply
  
AR15 9mm upper
 Login/Join
 
one of us
Picture of ramrod340
posted
My B-I-L is wanting to put a 9mm upper on his rifle lower.

As I read it as long as the barrel is 16" or longer he is legal. Correct?


As usual just my $.02
Paul K
 
Posts: 12881 | Location: Mexico, MO | Registered: 02 April 2001Reply With Quote
One of Us
Picture of lee440
posted Hide Post
Correct.


DRSS(We Band of Bubba's Div.)
N.R.A (Life)
T.S.R.A (Life)
D.S.C.
 
Posts: 2246 | Location: Houston, TX. | Registered: 18 May 2004Reply With Quote
One of Us
Picture of dpcd
posted Hide Post
He will need magazine adapter, unless he gets a dedicated 9mm lower which has a mag well specifically made for a Glock mag. I just built one last week. Fun to shoot.
 
Posts: 17008 | Location: USA | Registered: 02 August 2009Reply With Quote
One of Us
posted Hide Post
He will also need to replace two pins with stainless steel pins and will need a different recoil buffer.
 
Posts: 2744 | Registered: 10 March 2006Reply With Quote
One of Us
Picture of dpcd
posted Hide Post
Which pins? I used standard parts except the lower which has the ejector and mag release in it. And which buffer? I have a standard CAR buffer in mine; the bolt carrier is weighted to accommodate the unlocked, no gas system, blow back operation.
 
Posts: 17008 | Location: USA | Registered: 02 August 2009Reply With Quote
one of us
posted Hide Post
Stainless fcg pins are/were standard on Colt factory 9mm ARs. They're not a bad idea, but you don't need them.

Pistol cartridges (direct recoil operation) usually generate greater hammer velocity in ARs than does the in-line piston design and 5.56. Sufficiently high hammer velocity impact loads fcg pins. Result is pin breakage and/or wear on the receiver fcg holes. Trigger slap is the subjective correlate.

Parenthetically, it is indeed possible to make Stoner's design overcycle with 5.56. An overgassed, worn, pistol upper can generate trigger slap and break pins.

Back to 9mm, to prevent your lower from beating itself to death you want a ramped (beveled) carrier, and/or proper hammer, buffer, etc. My understanding is most makers - including Colt - now ship properly properly ramped bolts. Supposedly DPMS mitigates overcycling via hammer design.
 
Posts: 670 | Location: Dover-Foxcroft, ME | Registered: 25 May 2002Reply With Quote
One of Us
Picture of dpcd
posted Hide Post
The one I have, has a bolt carrier that has a big steel weight welded into the back of it, I assumed to prevent what you are describing. The bolt velocity does not appear to be more than a gas operated one.
Anyway, even if the SS pin is harder than a standard pin (which are pretty hard), the impulse is still transmitted to an aluminum hole; same result. So far, they are still tight, after 500 rounds.
 
Posts: 17008 | Location: USA | Registered: 02 August 2009Reply With Quote
one of us
posted Hide Post
quote:
Originally posted by dpcd:
The one I have, has a bolt carrier that has a big steel weight welded into the back of it, I assumed to prevent what you are describing. The bolt velocity does not appear to be more than a gas operated one.
Anyway, even if the SS pin is harder than a standard pin (which are pretty hard), the impulse is still transmitted to an aluminum hole; same result. So far, they are still tight, after 500 rounds.


Increased carrier mass is another approach. And agree stainless pins are unnecessary if you pay attention to carrier velocity. FWIW, I feel the same about those so-called anti-rotation pins. FCG holes do not wear because of pin rotation, anyway.
 
Posts: 670 | Location: Dover-Foxcroft, ME | Registered: 25 May 2002Reply With Quote
  Powered by Social Strata  
 


Copyright December 1997-2023 Accuratereloading.com


Visit our on-line store for AR Memorabilia