cycling problems

[deermill]

I had a Mega maten .308 ar built. And it is not cycling every round, the bolt is not locking back when the mag is empty, when you lock it back by hand then bump the gun, the bolt goes home. this gun would be considered a carbine because it has a collapsable stock. what should the length of the buffer and buffer spring be? And also when the shell is ejected, there is a dent in the neck of the casing. The barrel is a DPMS 18" 762x51, and I am using Magpul Magazines.

[Matt.Cross]

What kind of bolt carrier was used on your build, and what kind of bolt release did the builder use?

[deermill]

as far as I know it is a DPMS. I am just learning about the ar and the guy won't admit to any mistakes. this was the first .308 that he built. He has only built the ar15. I called Mega Arms, and they told me that he put the wrong buffer and buffer spring in it, but what else could he have put in there that don't belong?

[edgecrusher]

The bolt catch, buffer, spring, could all be suspect. Armalite bolt catches are beefier than the DPMS catches (he could have put an ar15 catch in which is also smaller). Armalite springs are the best ones going for any 308ar, I have several. A great ( no understatement) buffer is one by our site sponsor Clint at Heavybuffers.com. I only run his buffers in my ar's, and they never fail, reduce recoil, and are superbly machined. Here's a link to a thread I started regarding them for some info for you, I hope this all helps.

http://308ar.com/forum/heavy-buffers/don't-think-there's-a-difference/

[washguy]

Hi  Deer      magpul mags should be no problem...they work great....look to the buffer spring and buffer both should be car length in 308....get the dpms bolt cathc and put that in,but first look at the buffer spring/buffer......he could have put an 15 spring and buffer in there?  locking back is the first function check on these ar's.....its gotta lockback....and bumping causes bolt into battery ....yikes  :)Wash

[98Z5V]

If it's the first 308 the guy has built, look at the bolt catch first (make sure it's not the AR-15 part), then the buffer, and then buffer spring.

[Matt.Cross]

If it's the first 308 the guy has built, look at the bolt catch first (make sure it's not the AR-15 part), then the buffer, and then buffer spring.

I was thinking the exact same thing, thus my line of questioning. The other possibility I was thinking was that maybe his bolt carrier wasn't a common type, and doesn't lock back like my SI Defense NiB carrier.

[98Z5V]

I agree, Matt. 

And also when the shell is ejected, there is a dent in the neck of the casing. The barrel is a DPMS 18" 762x51, and I am using Magpul Magazines.

Here's another piece of the puzzle - that BCG is moving way too fast.  Could be a weak/incorrect buffer spring, too light of a buffer, or overgassed.  It shouldn't be denting cases.  <dontknow>

[washguy]

Hi  Deer  this might help    a 308 car buffer spring is 13.750" long where as an ar15 car buffer spring is 11.250 long....so check your spring ...also make sure your buffer is for a 308 car  I think it should weigh in at 3.4 oz's <thumbsup>Wash

[survivalshop]

Here's the difference in an AR 15 & a DPMS 308 bolt stops.

The dented case could be from several things , wrong buffer/spring , sticking extractor ( holding the case too long ) , over gased (if they ported the gas port in the barrel wrong , not likely ,but possible, this could be related to a wrong buffer/spring )

And there is more that could cause cycling problems. Bolt bounce comes to mind & may be related to wrong components also ,  make sure you have the right components in there first.

[deermill]

I thank everyone for their input, I have a new buffer/buffer spring on the way. I will let you all know what the out come is.

[unforgiven]

Welcome from Indiana brother deer,dear,deer <lmao> <laughs> :cookoo:

[deermill]

its been awhile since i have been logged on. Thanks for the advice the buffer/buffer spring was the answer to all my problems!!

[racerken70]

the maten comes with the bolt catch already installed. if it releases when you bump it i would say that you are catching the carrier (which has very little area to catch) it should lock all the way back with the catch holding the bolt face i have seen this a few times with new guys. if it cant pull all the way back to catch the bolt face then it is deffinately a problem with the buffer or spring bottoming out.