Dented shoulder / occasional not cycling 22 nosler

[TX mountain hunter]

1 out of 5 or 10 rounds the round will jam while trying to cycle and result in looking like the round below.

Also occasionally it will only lightly dent the primer.

I bought this used on here, and am not too familiar with ARs yet. Any help as to why this could be occurring would be appreciated.

 

[Rosebud]

Those look like groves from the magazine lips. Maybe someone more knowledgeable than me will step in.

 

[LRhunter514]

Looks like a bolt over base malfunction. The dents are from the feed ramps, this is usually a magazine problem.

 

[Reelamin]

Those are from you bolt locks. Now just need to identify what ones to start problem solving.

 

[Rosebud]

Those are from you bolt locks. Now just need to identify what ones to start problem solving.

I don't know ARs from my A#$. Explain that using small words.

 

[Reelamin]

Your bolt or BCG has a male star pattern on the front. These are the bolt locking lugs with a squared front.
The back of your barrel has the female "receiver" locking lugs with a smooth feed ramp area in the bottom center.

The female side has taper, so they don't usually create the sharp squared gouges in your case.

When the bolt goes forward it picks up the base driving the case forward into the feed ramp.
The case will go far enough forward the mag feed lips will release it to go inside bolt face and feed into chamber The bolt locks when it turns slightly locking it together.

Look up bolt over riding and it will cover all the options on what causes it. Compare to what you have going on and it will start to make sense.

 

[26Reload]

Is the "bolt over riding" hitting the 'next cartridge to come up' or is the malfunction happening to the run to be injected into the chamber....???

Looking at the cartridge....seems to me the bolt is going down into the magazine after the first round is pushed forward......???

 

[Reelamin]

Is the "bolt over riding" hitting the 'next cartridge to come up' or is the malfunction happening to the run to be injected into the chamber....???

Looking at the cartridge....seems to me the bolt is going down into the magazine after the first round is pushed forward......???

Or bad mag allowing case to raise up forward. Bolt misses base due to angle catches case 3/4 way up jamming it against feed ramp.

Just have to run it by hand or crank some off to recreate it.

 

[26Reload]

Yeah..I could see that too....
Feed lips slightly open....
Extra spring pressure...??...possibly shoving on the magazine cartridges....
Glad mine doesn't do that....I get to reload all my 223....I use a net to catch the cyclers.....better than bending over...

 

[TX mountain hunter]

It seems very random when it occurs. The dents seem to match up with the feed ramp:

I haven't yet been able to replicate it with a manual cycling.

 

[TX mountain hunter]

It's such a shame. It shoots great with several loads including this one with a 73 eldM even in 27-30 mph winds:

 

[waveslayer]

That looks consistent from a Type III malfunction. Are those rounds feeding ok? or are you seeing two cases stuck in the action?

 

[26Reload]

Pull the bolt and check the bottom stars...
If two aren't well worn you can exclude the bolt stars.....then you will know its ramp interference....

 

[jamie eaton]

Do you have anyway to check the bcg ? I had the same problem with my upper from White Oak Armament . Swapped parts back and forth with buddies upper . Things worked fine . Ended up sending it back to White Oak . They looked it over , up and down could not figure it out until they tried to shoot it . To their surprise , they shipped it with a 6.8 spc bcg . Sent it back with the nosler bcg and it shoots lights out . Love this caliber .