Is anyone noticing their Hornady Creedmoor ammo loaded super hot?  I just finished a new Mega Arms Creedmoor build with a Mega Barrel and Mega Bolt that is headspaced to the barrel.  I also have a SLR adjustable gas block set to lowest setting.  I am blowing about 4-5 primers out of 20 rounds and the rest of the cases have big extractor marks along with volcano primers (i have pics but not sure how to post).  This is for BOTH the 120 amax and 140 ELD.  I heard and read that hornady is known for juicing them up and that i shouldn't use the ammo for semi auto rifles.  it sucks since i bought a case of each.

Should i have a friend chronograph the ammo and then call them?  I really don't want to buy a bolt rifle to shoot the ammo.  

Also, I was going to try prime ammo.  Anyone have good results with them?

Hornady chronos hot for me also.  I'm using it in a bolt gun so it doesn't really bother me, but I can see where it would be problematic in a gas gun.  

I've never tried prime.

Hornady is even hot for me suppressed in a bolt. There is a current thread on a LR forum about prime in a semi. Mixed reviews so far.

What position is the brass being ejected too? also do you get the same results when the SLR is completely closed off (it should completely cut off gas flow)

The brass is ejecting about 90 degrees to the rifle.  When i did shut off the block i was still getting the marks.

Also, i forgot to mention i do have a jp heavy duty 308 buffer with the stiffest spring in the buffer tube.

Sounds like its a hot ammo problem then, or at least for you gun. From my experience semi auto's tend to start showing pressure signs before bolt actions, so while the ammo might be fine for a bolt gun is might

be too hot for your gun. Contact Hornady and send pictures of your brass, maybe they well refund you for the ammo

I have seen very well-behaved performance in a gas gun using the new Winchester 140gr HPBT 6.5 Creedmoor ammo, in a very limited setting though.

I do have a lot of praise for Hornady products in most cases, but have heard of the same thing happening with 6.5 Creedmoor in gas guns.

A lot of the time, it's the gas system, firing pin aperture, and buffer weight.

What gas system and barrel length are you using?

There are some barrels out there that are MLGS 20" that will be abusive on brass.

The problem is your Mega Arms barrel. They drilled a way to big gas port(mine is .097) and it causes the bolt to open prematurely. I popped two primers in the first five shots. After I finished the five shot string I noticed a blown primer laying on the bench. I installed an adjustable gas block and with it almost shut off it still leave ejector swipes from the pressure.  I have done several Creedmoor gas guns and have not had any issues firing Hornady ammo till I bought a Mega Arms POS.

I was blowing primers on factory and hand loaded ammo until I got the small pin bolt.  Now I can even shoot the Superformance stuff without pressure signs.

I did some writing about it a year and a half or so ago, essentially I was blowing primers left and right, superformance was totally out of the question.  Had the firing pin turned/bushed and now I can shoot handloaded Superformance powder slightly above max loads without pressure signs.  

I have the small firing pin High pressure bolt and it still popped the primers right out of the cases from premature bolt opening.  I got an adjustable gas block and turned it almost off. It just barely ejects the cases and still has Ejector swipes. It's just the combo of the Hornady ammo and the Mega Arms barrel. The other manufactures barrels had no issues with a smaller gas port. I did three or four Ballistic Advantage Creedmoor builds and the all functioned just fine. I did not measure the gas port diameter on theirs but it looked pretty small and I had my doubts that it would function. They obviously did their homework and they functioned great and were real accurate.

Interesting.  Wasn't there some complaints about the MEGA .308 barrels not performing well too?  Also chamber issues iirc.