PDA

View Full Version : Marks Armory AR Pistol question


GRmilitia88
03-19-2012, 10:35 AM
I recently purchased an AR pistol upper from Marks Armory.
Everything looks great, but after taking it out to Az this weekend to run some rounds through her I had a ton of ftf & fte.

I used 6 different PMAGs and a some USGI steel mags as well, and had the issue with all mags.

I remember reading something in a thread about Mark's pistols being awesome, but having to trim a coil or two off the spring to account for this issue. I can't find the thread anymore. Can anyone point me towards this thread, or help me out? Thank you.

Flintlock Tom
03-19-2012, 11:37 AM
Do you have it mounted on a "pistol" lower? Using a "pistol" buffer and tube?
It might be "short-stroking", the bolt carrier not moving rearward enough to eject the casing or chamber the next round.
Maybe a mis-aligned gas port.
Maybe the buffer is too heavy.

RookieShooter
03-19-2012, 12:15 PM
Do you have it mounted on a "pistol" lower?

Beside the legal issues, what is the physical differences between a "pistol" lower & a standard lower?

Lych
03-19-2012, 12:31 PM
Beside the legal issues, what is the physical differences between a "pistol" lower & a standard lower?

absolutely nothing

GRmilitia88
03-19-2012, 12:37 PM
It's mounted on a brand new LWRC pistol lower which has the shortened pistol tube.
The upper is a pistol marked upper w/ a chrome BCG and no forward assist.
The shortened buffer tube uses a spring that actually goes over part of the BCG (which on a side note is kind of a hassle when marrying the upper to the lower).

crf250x
03-20-2012, 10:27 PM
This might be a dumb comment, but I had an AR that was extremely picky about lubrication. I had problems if it was dry, so I always kept it lubed.

Carnivore
03-21-2012, 1:54 AM
absolutely nothing

Not true: some of them say pistol on them:kilt:

nrakid88
03-21-2012, 2:43 AM
It's mounted on a brand new LWRC pistol lower which has the shortened pistol tube.
The upper is a pistol marked upper w/ a chrome BCG and no forward assist.
The shortened buffer tube uses a spring that actually goes over part of the BCG (which on a side note is kind of a hassle when marrying the upper to the lower).

You dont mess with what mr. Browning made. You don't mess with what mr. Glock made. You don't mess with what mr. Stoner made.

Those shortened pistol receiver extensions, in my honest opinion (formed by reading forums), only serve to make the gun unreliable.

Anything under 11.5" doesn't make much sense to me either for a 5.56, and from what I understand a AR has a minimum barrel length of 11.5" to be reliable.

Flintlock Tom
03-21-2012, 7:02 AM
absolutely nothing

I was thinking that a buffer system that was tuned for a rifle or carbine length barrel may not operate properly with a pistol length gas system.

FeuerFrei
03-21-2012, 8:33 AM
These issues come up time and again.
Do more searching.
Try http://www.calguns.net/calgunforum/showthread.php?t=482730

GRmilitia88
03-21-2012, 1:55 PM
Thank you for the info guys. I love Calguns.

marksarmory.com
04-04-2012, 8:38 PM
I recently purchased an AR pistol upper from Marks Armory.
Everything looks great, but after taking it out to Az this weekend to run some rounds through her I had a ton of ftf & fte.

I used 6 different PMAGs and a some USGI steel mags as well, and had the issue with all mags.

I remember reading something in a thread about Mark's pistols being awesome, but having to trim a coil or two off the spring to account for this issue. I can't find the thread anymore. Can anyone point me towards this thread, or help me out? Thank you.

Grmilitia88,

I have had several people same issues you are talking about. The pistol upper you bought from us is actually the young manufacturing upper. They sent some out with some bad ejector springs. If you contact them, they will fix it no problem.
sorry for your troubles if you need contact info email me at mark@marksarmory.com

glenntuc
04-05-2012, 10:09 AM
i use carbine lenth buffer tube and ymh bolt with stronger extractor spring no more problems no fte's. keep bolt lubed,

h0use
04-05-2012, 10:24 AM
i was wondering what weight buffer needs to be used for a ar pistol?

MrPlink
04-05-2012, 11:49 AM
You dont mess with what mr. Browning made. You don't mess with what mr. Glock made. You don't mess with what mr. Stoner made.

Those shortened pistol receiver extensions, in my honest opinion (formed by reading forums), only serve to make the gun unreliable.

Anything under 11.5" doesn't make much sense to me either for a 5.56, and from what I understand a AR has a minimum barrel length of 11.5" to be reliable.

Im sorry, but this is dogmatic nonesense and fail.


Stoners original design is far from what is used today. Ever notice how Glock is on their 4TH generation? Ever heard of the Browning HighPower? The final version was modified by NOT JMB.

Cant run a barrel under 11.5in? You should probably tell those dummies DEVGRU that the MK18 wont work because the internet says so.

CHS
04-05-2012, 1:49 PM
It's mounted on a brand new LWRC pistol lower which has the shortened pistol tube.


Those systems have no buffer, so you can get a LOT of bolt-bounce which is bad for the system and cause all kinds of issues.

I would try a standard pistol receiver extension, carbine spring, and carbine buffer. If you've got an H buffer, give that a try first.

Foresight88
04-26-2012, 7:27 AM
Im sorry, but this is dogmatic nonesense and fail.


Stoners original design is far from what is used today. Ever notice how Glock is on their 4TH generation? Ever heard of the Browning HighPower? The final version was modified by NOT JMB.

Cant run a barrel under 11.5in? You should probably tell those dummies DEVGRU that the MK18 wont work because the internet says so.



Pwned.

chead
04-26-2012, 7:48 AM
Colt made tons of 10.5 ARs in 5.56, what more evidence do you want that short rifles work just fine? You won't lose enough velocity out of a short rifle barrel to really matter until you get REALLY short. Check out the MAC video where he chronos a Draco vs Mini Draco. They're AKs, but it's the same idea.