[Case Damage] What part is crushing the cartridge?

[Guest LLArms]

After a while at range today I started having some serious jamming issues. Even after cleaning and re-lubing.

I think its either short stroking or extractor failure.

Most of the time the spent round would not make it all the way out and it would feed the next live round in line, resulting in a nice V double jam.

[Livnoutdoors6.8]

Could be that the rounds are coming off the mag at too steep of an angle causing them to hit the barrel extension. Did you try different mags?

Looking at the spent case in the front, the two dents look appropriately spaced to match the lugs on the ext.

[Guest LLArms]

What I tried so far and what I know:

Mags:  2 DPMS 1 PMAG

Ammo: The good brass and the cheap steel

Extractor does not appear to be showing any oddities (but gonna order a new one anyhow)

Lightly polished the ramps and throat, think Im going to do a bit more.

Rims of the cases look good.

Also read some people doubling up on AR-15 size o-rings (AR-10 platform normally only has a spring and tiny rod) with good success.

[Tripledeuce]

    I got similar jams/marks on my lar8 befor I opened the gas port in the bbl.

    Respectfully

    Terry

[Guest LLArms]

Enlarge the hole on the barrel?  I guess thats an idea...

[MikedaddyH]

I have had this problem with low power {starting} loads during load developement. As the pressure of the load increased the brass deformaties vanished.

Like Terry stated opening the gas port may solve the problem, but check your loads first. Once the gas port is open the next bandaid is an adjustable gas block.

Buffer Spring changes and Buffer weight change are other options you will need to play with to dial in the ejection. Are the shell casings exiting at 3 o'clock ? If not , where?? Are they landing in a pile? or all over the place ?? Too much pressure or not enough.

I am doing the same type of T & E with the magnum AR, so I get it.

[Retired JM]

You might also want to check the carrier key for obstructions and also check that it hasn't become loose. Check for obstructions in the receiver extension and check the buffer spring for excessive wear. Check the gas tube for a gas leak.

[seasprite]

You might also want to check the carrier key for obstructions and also check that it hasn't become loose. Check for obstructions in the receiver extension and check the buffer spring for excessive wear. Check the gas tube for a gas leak.

This is what I'm thinking that you developed a gas leak some ware also check your gas block for tightness and leaks and are the gas rings staggered?

[unforgiven]

Just came from the Crown Point In. gun show wanted to add a RRA star ambi-safety and winter guard on RRA 5.56 lower.Also took my spent brass 1300 5.56 mixed mostly lake city,1200 9mm mixed,and 340 .308 mixed mostly mil surpl.The guy [who is a RRA dealer and works on them don't know if I'd call him a smith] looked at the .308 cases. Said they were beat up because of to much lube causeing maybe the rifle to over gas.Guy walking by heard this and said "thought your suppose to run them wet" RRA rick said "not RRA".So I'll put gunscrbber in gas tube and blow it out with computer air in a can,wipe it down and see what happens.I usaully just use CLP for lube last 3 cleanings have put oil on bolt rings under chargeing handel and under carrier so I will eliminate that an stay with light lube and see what happens.Also mentioned primers flat on spent cases,not sure if it was bullpoopy to give me less for brass or what <dontknow>.In the end got ambi-safety and winter guard and put in with $5.00 back to my pocket.Returned with Lar-8 lower and he polished the 2-stage trigger and man what a difference noticeably lighter.

[Guest LLArms]

Problem has been discovered.

Apparently my gas tube has ninja type skills and and loosened up after I had checked it. (quite a bit).

[Jgun]

I'm curious, do you mean your gas tube or your gas block? I'm trying to understand what you mean by the tube loosening up, are you saying the roll pin that retains it in the gas block came out?

[Guest LLArms]

The gas block came loose. Sorry about that.

Was loose enough where it could freely move and get out of alignment with the hole on the barrel.  I knew something was wrong right away when I got the shroud off and saw a bunch build up on the barrel around the gas block.

My guess is (reason it was so sporadic) was as the rifle was vibrating sometimes it would be aligned properly and other times it was getting knocked and twisting left or right of the hole.

[survivalshop]

The dents in the case are caused by your bolt slamming into the partially fed cartridge on the feed ramp ( bolt lug marks ), from short stroking or it can be a magazine problem also .

Looks like you took care of the short stroking ,lets see if it eliminates a potential mag problem also .

[NoFail]

The dents in the case are caused by your bolt slamming into the partially fed cartridge on the feed ramp ( bolt lug marks ), from short stroking

This, exactly what I imagined by the looks of those dents.