Headstamp marked

[Grimmy]

[ATTACH]6.5 Grendel 002.jpg[/ATTACH] I am getting a mark on the headstamp it's sharp and at the the exstractor location. I know this is a hot load but it shows the mark well. It also happens with factory ammo. any thoughts?

[rasp65]

If you tried to put a load meant for Hornady or Lapua cases into those fire formed FC cases you will more than likely get high pressure. There is usually about 2 gr less volume to 7.62x39 cases so you should adjust you load accordingly. I took the extractor and the ejector out of the bolt and polished the bolt face, it keeps the sharp edges of the bolt face from cutting in. I too have had factory ammo leave marks on the case head.

[ChellieWiles]

I don't like the look of that at all. It could be a cheaper softer brass, but anytime I see that mark I back off at least a grain. But, something conflicting in the image is that the primers aren't oozing out of the primer pocket which will normally happen before the extractor marks from my experience, but not always. I am leaning towards what rasp said, it might be the brass. What is the load/bullet/charge and all that mess? Are your loads compressed? If you seated the bullet out a few thousandths further will it still fit in the mag? There are a few things you can do to change pressure characteristics, i.e. seating out further to lessen compression, but these are only nominal pressure changes 1-2k psi. If you haven't been weighing each charge independently and those loads come from just throwing charges, I would be very careful, the Grendel isn't very forgiving if you go too far over pressure. I've broken a few gas keys off with higher pressures in my 18" and that was at about 1.2 grains over a suggested max. You might be getting into dangerous territory.

[Grimmy]

I get the same marks just not as defined with Wolf ammo. The load was 28.2 grains of xbr with 123 amax's. 28.0 I don't get the marks but still have the sharp egdes on extractor side of the case just not as pronounced. I weight every charge always. Rasp what did you use to polish the bolt face?

[ChellieWiles]

I like to run hot with some of my bullets as well, and I reach the point where those marks show up then back off .5grains. It will greatly extend the life of your barrel, bolt, extractor and gas tube by backing off when you see these signs. It will be different for most different types of brass. As for Wolf Ammo, if you want to see you gun get eaten to shit, then by all means, you can shoot that inferior rusky ammo all you want. Me, personally, I care about my rifle so don't use anything in it that isn't American made.

[Smoke]

Back off .5 grains and try again.. getting the ejector marks is bad news for you and the gun as chille said if you are not weighing each charge I would do so and see if you have some consistancy issues there

[Grimmy]

Out of the eight ar's I own this is a first for me. I've blown primers before but never had pressure signs like these. Maybe as stated the Grendel is more touchy than other ar chamberings. Thanks again for the input. Still in all it's a new learning curve and a great caliber.

[sneaky one]

Grimmy-I just read an article today about the swipe-It also involves timing. I tried an H2 buffer last month, what a difference!( Ironically, on the same range trip-I used my tweaked ejector also= metal removed from bottom, and rt. side-then polished=no swipes,) smoother gun action- feel. The ejector mod.- Smoothed out the trip from mag. to chamber, on the rear of the brass. No more fleks of brass on the boltface! I win! That has been an issue since day one with this stupid gun, hee. The H2 tamed the GRrrrr !!!! BTW- recheck that load data, and your scale-against another at least!

[Grimmy]

Well I'm running a Magpul PRS with rifle buffer I'll weight it to see were it's at. Also took bolt apart and polished the extractor pretty much as you said. Lucky for me all my knife making equipment lends it's self to polishing this stuff up quickly. Hope to shoot on Friday and do some more testing. Also weighed my fire formed brass it's definetly heavier than hornady brass by about ten grains roughly. As always thanks for all the info guys.

[sneaky one]

Grimmy-the Ejector on the Lt..... not the extracter. on the Rt... how does your scale -compare to another? Knife making equip., you say?????? hmmmmm.......

[rasp65]

Rasp what did you use to polish the bolt face?

I chucked a case with a used primer in it into a drill and used 600 grit lapping compound at slow speed in both directions. Just want to polish the face not increase headspace. You can also use 600 grit emery paper cut into strips and use a dowel to polish the face. You will have to remove the extractor and ejector to do this. While you have the ejector out you can chuck it into the drill and polish it against the emery paper. Also polish the underside of extractor's claw to remove sharp edges and remove and sharp edges from the part of the extractor that contacts the case head.

[Grimmy]

Thanks for the info.

[rasp65]

Grim This is where I got the idea to cleanup the bolt to reduce case wear:http://www.snipershide.com/forum/ubb...Number=1943980

[Grimmy]

After you had stated that you polished everything I did a search and found the same site. I did the same thing just used my equipment in my knife shop to get the same end result. After looking at the bolt under a maginifier (actually I looked at all my bolts) Most of them have alot to be desired in the finish area. But it's the best part of this forum that we share all this info. Anyway my bolt looks like the photos in the link you posted. I'll shoot Friday and look at the results. As always thanks for the help.

[Grimmy]

Well shot on Friday the work to the bolt and new Hornady brass payed off all looks good. 97 Degrees out did make for the best shooting conditions. But overall a step forward.