Other than in -20 weather, does it cycle properly for you?
Did you ever try any Federal Gold Medal 168gr sierra ammo?
Thanks for the feedback ... so far, you are the first I have heard from with a Mk4
Yeah I was also scrounging the Internet looking for information before I ended up buying it. Not much out there yet.
The gun cycles great over -20. I only had about 300 rounds through it between testing groups and barrel break in with cheap pmc ammunition so it very well may still work in.
I was too excited to wait out the cold snap when I first got it and the problems happened in the first 30 or so when shooting it after it's out of the box clean and breakfree clp application just before hand. Since then it has warmed up and has been fine for accuracy tests at -10 to +2.
I should note that it would only fail to go back into battery. Didn't have an issue with extraction. Just pushing the charging handle forward passed the little red dot was all it took to fix the issue.
I think I had a box of it. All I remember is that the CX outfitter was what I was hoping would work and it was the first ammunition I tried after 200 rounds of pmc break in and deep clean and it ruined the target paper as the rounds were 6" spread at 100. All the other ammunition like nosler ballistic tip 150, 165, barnes ttsx 150, pmc bronze 147, Winchester copper impact 150, federal premium tsx 165, and Hornady sst in 150,165 grains all shot within 2.5". 3 sets of 3 rounds and the eldx was the only one to not have a flier and stay consistently at 1moa or under.
It's also the only ammunition that's the heaviest so this could be why. It's a 1-12 twist. Maybe it just likes heavy ammunition. I did not test anything else above 165 grain. Next time I see a box of barnes ttsx in 178 grain I'll try it.
I tested the ammunition mono copper first since gilded copper jackets mess with accuracy. Unfortunately it didn't seem to make a difference.