Bolt Catch

[survivalshop]

I answered a thread on another forum , because of a problem with a CMMG bolt catch . I also have had the same problem as the poster & finally got time to play with repairing it .

The problem is not holding the bolt back on last round consistently or not at all ,even though the rifle functions properly as far as feeding & ejecting .

Using both a 308 or a std M15/16 Bolt catch doesn't make a difference, still no hold back.

Also the catch when manually operated will not hold it for a second ,if that .

With a empty mag in the rifle ,it is not much better.

I started by comparing the lift that each mag (different manufacturers ) produced on the catch with an unaltered DPMS lower that's on my 20" rifle ,because it has worked flawlessly.

I than, of course, measured the CMMG lower to compare . Measurements were taken with a DPMS 308 Bolt Catches.

I than took material off the stop area of the Bolt catch ( where the spring buffer comes in contact )to match the height of the DPMS lowers Bolt Catch.

DPMS (unaltered)--CMMG (before)--CMMG(alt)

PMAG--0.449"  -----0.424"  --------- 0.4665"

Cprod.-0.399" ----- 0.378" ---------- 0.4015"

DPMS--0.456" ----- 0.431" ---------- 0.4750

It looks like there is not much difference ,but it made a big difference in function. The catch even holds after mag has been released & works manually & holds .

I will take the CMMG to the range tomarrow to test some new loads with the Chrono .

The  308 BC & AR 15/16 catch. Material already removed

A AR15/16 catch & 308  catch side by side .

And the Bolt catch blued with Brownells 44/40.

[Matt.Cross]

Nice job! Do-it-yourselfers rock!  ;D

[survivalshop]

Thanks . It seems some CMMG 308  lowers are not to proper spec's . If they were, I or we would not have to do any kind of special fitting.

I do not think I will ever buy any Major part from a manufacturer that makes uppers or lowers & doesn't make complete rifles as was the case of early CMMG 308 lowers.

Hay , Doc , are you reading this .

[TacBlade]

Good Stuff!!!!

[survivalshop]

Testing was done today with three different manufacturers mags.

All mags worked, with the bolt catch working on all three different manufacturers .

Two Pmags, two Cproducts & two DPMS mags. I used these mags because ,they all would not work the bolt catch  after last round.

I will be testing new mags of each manufacturer in the coming weeks .I will be unwrapping them & testing .

If I could only get Pmags to fire a complete 20 rds with out a FF , I'd be Happy with this CMMG lower , but hay ,I got the Bolt catch to work. Its a start .

Rifle has no problems with DPMS or Cproducts mags.. WTF