I have a question I feel like I should already know the answer to but have never thought to ask before: how much do you bump the shoulder when resizing brass for an ar15, or is that even a valid concept in a gas gun (or is the case being ejected “too soon” for this concept to work)?
Here’s the impetus for my question. I have a 6.5 Grendel AR that I use for hunting and occasionally shoot in a local 300 yard “AR Tactical” match. I plan to shoot that match more next year. This weekend, I cleaned my Grendel dies up and then set them back up. To ensure reliable feeding, I have always just used the factory instructions when setting up dies for my ARs: 1/4 turn past the shell holder. I did that again here, but I also took some measurements using a Hornady headspace comparator.
As currently set, my dies are bumping the shoulder back 0.015.” That seems like a lot to me. I measured some factory ammo with the same comparator, and it matches what my resized brass measures. I also have a case gauge, and my resized brass is sitting right at the minimum headspace measurement in the gauge—right where I’d think it should be for a semi auto. So the die is setup by the book.
I should probably leave it alone, but Grendel brass isn’t quite as common as some other calibers and I’d like to prolong my case life as best I can. I’ve read things on the internet about bumping the shoulder on brass for AR15s 0.003” - 0.005,” which would be substantially less than I’m currently doing and I don’t want to lose reliable feeding. I’d like to hear your thoughts and experience. Thank you in advance.
Here’s the impetus for my question. I have a 6.5 Grendel AR that I use for hunting and occasionally shoot in a local 300 yard “AR Tactical” match. I plan to shoot that match more next year. This weekend, I cleaned my Grendel dies up and then set them back up. To ensure reliable feeding, I have always just used the factory instructions when setting up dies for my ARs: 1/4 turn past the shell holder. I did that again here, but I also took some measurements using a Hornady headspace comparator.
As currently set, my dies are bumping the shoulder back 0.015.” That seems like a lot to me. I measured some factory ammo with the same comparator, and it matches what my resized brass measures. I also have a case gauge, and my resized brass is sitting right at the minimum headspace measurement in the gauge—right where I’d think it should be for a semi auto. So the die is setup by the book.
I should probably leave it alone, but Grendel brass isn’t quite as common as some other calibers and I’d like to prolong my case life as best I can. I’ve read things on the internet about bumping the shoulder on brass for AR15s 0.003” - 0.005,” which would be substantially less than I’m currently doing and I don’t want to lose reliable feeding. I’d like to hear your thoughts and experience. Thank you in advance.