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bolt will not lock back on empty mag


RAM2940

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As the topic states, this is a 6.5 creedmoor, 20" Wilson combat barrel.  I do have the armalite gas tube.  Tried adjustable gas block, did not work, purchased a non adjustable gas block, it will chamber rounds from mag, but will not lock back on empty mag. Ejects shells okay. This is a rifle stock and aero precision M5 rifle buffer kit.  Rifle buffer 5.3" long, Spring measures 12.6 with 39 coils, it is a lot stiffer than my AR15 springs.  I was looking at slash's buffer table and wondering if the spring could be the issue.  Link to M5 buffer kit that is installed.

https://www.aeroprecisionusa.com/m5-308-rifle-buffer-kit

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51 minutes ago, jtallen83 said:

Will it lock back manually?

How many rounds down the pipe?

 

Yes, when you pull the charge handle back it will lock.  This is my first Dpms 308 large frame rifle, feels like a lot of spring tension but I guess this could be normal.  About 25 rds fired.

Edited by RAM2940
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Shouldn't be a lack of lube then.  "Good amount" for an AR15 isn't a good amount for these big things, though, so that's subjective.  They need to be almost dripping.

You also need to carbon seal the gas tube to the gas block, and the gas block to the barrel.  To a lesser degree, you carbon seal the end of the gas tube to the carrier key on the BCG, as well.  25 rounds usually isn't enough to do that.  More things to consider, when you're looking at the tolerances in manufacturing.  Loose gas block?...  Gonna take alot of carbon fouling to seal that one up, if it just slid right onto that barrel.  Just an example.

Edited by 98Z5V
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  • 4 weeks later...

I got back onto the issue, the Wilson combat barrel came with a .071 gas port, so I drilled the port out to .078 (5/64).  With a non adjustable gas block, fired several rounds one at a time testing, and all rounds locked back.  Recoil felt better.  Now the next step is to get on a target and check accuracy and find what it likes.

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5 hours ago, RAM2940 said:

I got back onto the issue, the Wilson combat barrel came with a .071 gas port, so I drilled the port out to .078 (5/64).  With a non adjustable gas block, fired several rounds one at a time testing, and all rounds locked back.  Recoil felt better.  Now the next step is to get on a target and check accuracy and find what it likes.

My sentiments, exactly.  They ship the 20" rifle-gas .260 Rem barrel with a 0.070" gas port diameter, and I've stated that it's just too small.  I punched mine up to 0.080".  :thumbup:

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  • 2 weeks later...

Gee , another Barrel that has a Gas Port too small , that's new 🙄

I have had LR PMags since the first one came out & I don't remember a Gen. two , I thought they went right from the first original LR PMag ,right to the Gen 3 . I have so many of them , how do you know it's a Gen. two ?

This is also the first I have heard of a Mag issue with the Small Framed 308 AR's . I had plenty of issues with one build with mixed manufactures Upper & Lower Receivers , but it wasn't a lock back issue , it was Tolerance stacking issue ( intermittent FTF ) , rifle also worked with all other Steel Mags & L7 Lancers, but would not work the the Org. LR PMag . The Gen. 3 LR PMag. when it came out ,worked fine in this particular build ( its why you should always use same Manufacturer for Receivers ) , so something did change in the two Gen. LR PMags ..

If thats all it takes is to alter the Follower to make it work in your particular SF 308AR , thats an easy fix , but it's probably not the PMag , it is the tolerances of the Rifle, IMO.

 

Edited by survivalshop
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12 hours ago, RugerNiner said:

What? No updates?

His problem was solved and updated before you chimed in.  What are you looking for an update on?  “Day 26 and the rifle still works after drilling the gas port out.  If you don’t hear from me for a few weeks- I never came home from the range. Send my love to everyone at 308AR”. 

 

Now we’re updated. 

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The follower on the mag contacts the bolt catch when it’s empty and pushes it upward. The bolt then contacts the bolt catch.  That’s why if you have no mag in the rifle and pull the charging Ing handle and release, it won’t lock back.  You can manually lock it back by manipulating the bolt catch by hand.  Put an empty mag in and perform the same pull and release, the bolt should lock back as the follower has pushed up the bolt catch.  This is another area of the 308 that caused some headaches for a while and if anyone is having bolt catch issues there a lot of posts on the topic that can be searched.

 

I had to stop watching the video halfway through. That guy drug a 30 second concept out for 11.5 minutes. 

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On 6/7/2019 at 4:22 AM, survivalshop said:

Gee , another Barrel that has a Gas Port too small , that's new 🙄

I have had LR PMags since the first one came out & I don't remember a Gen. two , I thought they went right from the first original LR PMag ,right to the Gen 3 . I have so many of them , how do you know it's a Gen. two ?

 

The Gen 2 5.56 P-Mag was already released before MagPul made the original LR-20 mags.  All original LR-20 mags followed the "Gen 2" developments of the 5.56 mag designs.  Then, they updated to the Gen 3 revisions.  There was never a "Gen 1" MagPul .308 mag, because they'd surpassed that technology by the time the released the LR-20s.  :thumbup:

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  • 2 years later...
4 hours ago, CCCERAKOTE said:

It is 100% a mag problem. I know This is old but if anybody is having the same issue the following is not pushing the mag release up far enough to hold it.

It could also be you used the WRONG bolt catch. Also your mag catch could be wrong. It's not always the magazines.

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