11-21-2023, 01:32 AM
I can't speak to the mkz bullets, they have a cavity at the base right? But for a 100 gr ttsx 29.0 gr of xbr is an ok load, it's max is 29.5 by the book.
You don't say what OAL you are seating the mkz/cartridge to, is it 2.230? 2.250? 2.290? or what...
If a load is compressed but rather resistant to compression then yes the oal can grow, whether it is cycled or just sitting in the tray.
You don't say if the growth is from a bolt release, or following a fired round (bcg complete cycle) or what...
You also don't mention what type of lube/dry flake you might be using on the inner side of the neck, if any.
All these things can impact what you're doing.
But to address the general question of oal growth for ARs my solution was to get the Lee factory crimp die (fcd) - don't have to have all the brass trimmed to exact same length as you do for roll and die crimps and as for pistol loads. You set it once per instructions, lock in to that, then use. I don't have numbers but it has improved my oal shifts and also the groupings. Not an expensive die, the fcd, but worth it, it does cause an extra step in the reload process but I'm willing to do that for better shots.
Those who go all-out on neck tension do the neck bushing-thing... I just haven't brought myself to that level of ocd, lol.
by the way, imo the fcd die is the only die from Lee that I would recommend, I'd say throw out those LEE resizing/seating dies and get either hornady, forster, rcbs or some set that has better quality. I use hornady and they work well enough for me, but like I said the Lee factory crimp die is the only one of theirs I'm using. I have a mix of rcbs, hornady resizing, and those plus a couple forster seating, dies for all my calibers.
You don't say what OAL you are seating the mkz/cartridge to, is it 2.230? 2.250? 2.290? or what...
If a load is compressed but rather resistant to compression then yes the oal can grow, whether it is cycled or just sitting in the tray.
You don't say if the growth is from a bolt release, or following a fired round (bcg complete cycle) or what...
You also don't mention what type of lube/dry flake you might be using on the inner side of the neck, if any.
All these things can impact what you're doing.
But to address the general question of oal growth for ARs my solution was to get the Lee factory crimp die (fcd) - don't have to have all the brass trimmed to exact same length as you do for roll and die crimps and as for pistol loads. You set it once per instructions, lock in to that, then use. I don't have numbers but it has improved my oal shifts and also the groupings. Not an expensive die, the fcd, but worth it, it does cause an extra step in the reload process but I'm willing to do that for better shots.
Those who go all-out on neck tension do the neck bushing-thing... I just haven't brought myself to that level of ocd, lol.
by the way, imo the fcd die is the only die from Lee that I would recommend, I'd say throw out those LEE resizing/seating dies and get either hornady, forster, rcbs or some set that has better quality. I use hornady and they work well enough for me, but like I said the Lee factory crimp die is the only one of theirs I'm using. I have a mix of rcbs, hornady resizing, and those plus a couple forster seating, dies for all my calibers.
"Down the floor, out the door, Go Brandon Go!!!!!"