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Page AR-15 » Rimfire and Pistol Calibers
AR Sponsor: bravocompany
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Posted: 2/16/2017 10:09:55 PM EDT
I recently finished my 9mm AR build and put 250 rounds through it. Gun is running great. Not a single hiccup, good accuracy and quick handling. Came home and to clean it and inspect things over. This is what I found, the buffer is smashed in and the quarters I used for spacers top coin is dented.

Honestly I'm surprised it didn't malfunction. I'm running a carbine extension with milspec buffer and spring + 7 quarters. I guess I need less in there.

Anyone else experience this type of damage before? Guess ppl are not kidding 9mm ARs are rough lol.



Link Posted: 2/16/2017 10:13:20 PM EDT
[#1]
What weight buffer and which spring?
Link Posted: 2/16/2017 10:39:42 PM EDT
[#2]
3oz buffer according to the scale I just put it on. No idea on the spring.
Link Posted: 2/16/2017 10:41:26 PM EDT
[#3]
That's your main problem. You should be using a 5 to 7oz buffer with the 9mm blow back action.
Link Posted: 2/16/2017 10:46:58 PM EDT
[#4]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
That's your main problem. You should be using a 5 to 7oz buffer with the 9mm blow back action.
View Quote

This. You're WAY under weight for a 9mm.
Link Posted: 2/16/2017 11:08:26 PM EDT
[#5]
Link Posted: 2/16/2017 11:25:18 PM EDT
[#6]
I run a hydraulic buffer.
Link Posted: 2/17/2017 9:42:57 AM EDT
[#7]
Rock River Arms 9mm buffer,
Sprinco red spring
NFA rubber spacer
Link Posted: 2/17/2017 10:02:07 AM EDT
[#8]
To me, that looks more like a POS buffer made of wrong material.  It didn't stop functioning or make any unusual sounds?  I can't imagine how the spring could move over the buffer without binding and causing all kinds of issues.

I've run a standard mil-spec ~3oz carbine buffer and never had one end up like that.  5-5.5oz is all you need for SA non suppressed.
Link Posted: 2/17/2017 11:12:28 AM EDT
[#9]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Sprinco red spring
View Quote

No, do not use an extra power spring with a blowback 9mm.
Link Posted: 2/17/2017 12:44:10 PM EDT
[#10]
Discussion ForumsJump to Quoted PostQuote History
Quoted:

No, do not use an extra power spring with a blowback 9mm.
View Quote


Depends on what loads your using & buffer weight, on my 16" with an 8.5oz buffer a Wolff xtra power spring is great with +P ammo but chokes on light loads. But overall a std. weight spring runs OK with everything. An xtra power spring will put more stress on your bolt catch.

If I was strictly running hot loads I'd upgrade to a 10 oz buffer before going to a stronger spring. On my rifle the heavy buffer & xtra power spring had more felt 'recoil' when the buffer slammed home than when it came back.

IMHO 5 oz is the minimum weight for a 9mm blowback. I don't know of any manufacturer of one that comes with less.
Link Posted: 2/17/2017 3:46:20 PM EDT
[#11]
In no way shape or form is spring power a substitute for reciprocating mass in a blowback  system.

The main function of extra power springs in a 9mm AR is to beat the crap out of the firearm, as illustrated in two different threads just this week.

It takes very little energy to strip a 9mm from the magazine and chamber it in a 9mm AR. That's what the spring does.
Link Posted: 2/17/2017 3:57:29 PM EDT
[#12]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
In no way shape or form is spring power a substitute for reciprocating mass in a blowback  system.
The main function of extra power springs in a 9mm AR is to beat the crap out of the firearm, as illustrated in two different threads just this week.
It takes very little energy to strip a 9mm from the magazine and chamber it in a 9mm AR. That's what the spring does.
View Quote


This.  Mass keeps the bolt closed, and has an order of magnitude more effect on the initial bolt velocity than the rate of the spring.
You just need a spring that is strong enough to strip and chamber without being sluggish.
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