buffer face is getting chewed up

[4150bandit]

what's going on is the buffer face is getting chewed up its seems to be hitting the retaining pin  and it has bent it over some the buffer tube is tight and where it suppose to be the upper is a 16 inch cmmg and the lower is a pof  has anyone ever had this problem and what can be do to fix

Edited September 10, 2014 by 4150bandit

[98Z5V]

Your buffer isn't getting pushed off the retaining pin by the upper receiver, when the upper receiver closes on the lower receiver.  Everytime the bolt carrier goes all the way forward, it's not keeping the buffer from running into the retaining pin.  It's a machining issue.

 

Pics are necessary, of the buffer face, for confirmation of this.

 

We have seen this before - the first time it occurred here, it was on a IRA matched set (lower and upper). 

 

The CMMG part and the POF part are not playing well together.  I thought the POF stuff was proprietary?  Meaning, they're stuff doesn't match any other manufacturer out there.  Gonna have to see pics of how those two mate together.  If they match up, and it's machining differences, you can use the Tubb Carrier Weight System to fix the problem.  If they don't match up perfectly, you need to pick which one you like the best, and buy the corresponding "other part."

Edited September 10, 2014 by 98Z5V

[shibiwan]

 

The CMMG part and the POF part are not playing well together.  I thought the POF stuff was proprietary?  Meaning, they're stuff doesn't match any other manufacturer out there.  Gonna have to see pics of how those two mate together.  If they match up, and it's machining differences, you can use the Tubb Carrier Weight System to fix the problem.  If they don't match up perfectly, you need to pick which one you like the best, and buy the corresponding "other part."

 

 

Could be the entire upper is a little forward of where it should be. Probably a factor of the different tolerance from different manufacturers.

 

BTW, is this a 308 AR or an AR15/M4?

[4150bandit]

had to use some spacers that I got from Hogan arms because of the pin size they mate up well and the gun shoots and cycles fine never had a jam yet there's been about 700 to about 800 rounds though it  just seam  this has come up in the last 100 or so rounds

[98Z5V]

Tubb CWS.  Keep that buffer, once you use the CWS it won't take anymore punishment.

 

http://www.davidtubb.com/carrierweight-ar15

 

Writeup about it:

Edited September 10, 2014 by 98Z5V

[Robocop1051]

Wait a minute here... do you mean to tell me this is a thread about rifle issues, and CMMG parts were used. What are the chances of that??

[blue109]

seriously, can we get a locked CMMG sticky consisting of only those memes?

[survivalshop]

  It could very well do the same with any other manufacturers upper when mated to a POF lower . Doesn't matter if you use a spacer set up or not . Those spacers are made to get tolerances close to what a POF upper would fit , don't mean they will work with every upper manufactured.

 

   POF uses ( as was stated above ) proprietary components & if you use there Lower , you should mate it up with there Upper & this issue will not come up . I know that doesn't help you much , but now you have to rig something to make up for those tolerance differences. The kits above will help & seem to work. We have seen this before here , same outcome .

[FaRKle!]

Late reply, but just got back from a business trip overseas.

Your issue is a result of the buffer retainer hole being too far rearward. When the upper is closed on the lower the back of the BCG is supposed to push the buffer off of the retaining pin. When the firearm cycles with the upper on, the buffer should never touch the buffer retainer. You can visually inspect this two ways, the first is to separate the upper and lower. You should be able to see the buffer protruding beyond the rear of the receiver (towards the fire control area) where the receiver extension threads into. The second way is to look for the rear of the bcg pushing the buffer off of the buffer retainer when closing the upper on the lower. A light helps with this.

If you really want to try fixing this yourself you'll need to try to extend the buffer retainer hole more towards the fire control pocket and then use a shim to keep the buffer retainer towards the front of the receiver. The hole is 1/4".

I've seen other reports of this issue on POF lowers before (and that's with matched POF uppers too).

Edited September 21, 2014 by FaRKle!

[Robocop1051]

The Tubb (Superior Shooting) Carrier Weight System will fix the problem for less than $60

[shibiwan]

I must be the only one out there that got a CMMG with no issues and runs like clockwork. Wonder if that's a sign to buy a lottery ticket.....

[survivalshop]

I must be the only one out there that got a CMMG with no issues and runs like clockwork. Wonder if that's a sign to buy a lottery ticket.....

 Are they miss matched manufacturers upper & lower receivers ?

 Any time you use miss matched uppers & lowers , you can run into this , really does matter who's parts you use.

 After tightening up my friends CMMG 's Barrel Nut , she has been working like a swiss clock , but that is a later model CMMG factory rifle .

 

 I would not recommend modifying the Buffer retainer hole , the above recommended fixes work with out any modification to the rifle .

 

  Here's a thread about Iron Ridge rifle doing the same thing , these receivers are out of spec's with each other with the same results as your miss matched receivers.

Edited September 22, 2014 by survivalshop