Advice requested

[Pwrbomb1970]

I am having a bit of an issue with my Grendel AR. I’m getting ejector swipes and marks on the brass from loads that are way under max. I have a standard gas block and carbine spring and buffer. JP Enterprises enhanced bolt. Can I get some advice? I’m thinking of going to an adjustable gas block. Should I look into the spring/buffer combo too? If so what should I go after? Thanks in advance for any advice.

[grayfox]

What is the barrel length, and what is the gas system length.
Several threads on this type of phenomenon, it could be due to more or less normal things.
The ejector swipe can be from the sharp cylinder edge on the ejector plunger, many have polished or even chamfered it slightly on the inner part of that edge towards the firing pin. For the "marks on the brass" do you have some pics or describe it further.
Primers can flow some into the firing pin hole during firing so this does not necessarily mean cratering.
Brass markings on the side... usually need pictures, some milkiness on the sides - some guys don't like, usually from a rough chamber wall.
Small nicks on the rim can come from extractor radius points being too sharp. You can try to carefully sand or file them down a bit to get rid of the sharpness.
If I have this correct... others may chime in also.
Pic's are worth a 1000 words.

[Bigs28]

Pictures please

[Pwrbomb1970]

22 inch barrel. Rifle length gas tube. Otherwise brass looks fantastic. Nothing to see on it. Just the ejector mark....it isn’t deep or a burr...but it’s there.

[1Shot]

What barrel do you have? Are you measuring how far off the lands your bullet is? Some people have gotten barrels with really short throats and they were jamming bullets into the lands and really getting pressure with lighter loads.

[Pwrbomb1970]

I do my due diligence in the measurement area. I use a Hornady comparator with a mod case made for my chamber. Use the hornady tool for finding where the lands are for the bullets I’m using. I’m working loads for 123 gr bthp bullets. I’ve worked back from .010 and currently at .015 off the lands.

[Lemonaid]

Does factory ammo have the same marks on the brass? more pronounced or less? Pics will aid in diagnoses.

[Popeye212]

I had a similar problem with an AR10 in 6.5 Creedmoor. Turned out the bolt was coming out of battery too soon. Put a heavier spring in it and and adj. gas block.