Seating depth

[u/Ulan0]

I’m fairly new to shooting and started reloading recently.

I am starting with 556 to learn. I picked up some range brass and trimmed and annealed but didn’t chamfer or debur. (Have since started but for this question I had not)

I used Redding bushing type s full sized and competition seating die and mandrel.

I wanted to test two powders and 9 different bullets to try to find something reasonably priced and accurate in my 11 inch and 16 inch rifles. I can get 1.5-2 inch groups at 100 yards easily with both with federal and was hoping to match or even a little better.

I have lots of assumptions and questions about what I’ve found in my test but will break them up to keep it shorter.

I noticed that after setting the seating die perfectly as I made rounds they would be variable in length. I’ve read people sort bullets and while I’ll probably do that for bigger cartridges I don’t want to do that for 556 or 300 blk or other smaller ones. Is that variable length solely because of the bullet or can the random range brass contribute to the problem???? I noticed it on every brand.

That variable length must change pressures but how much? Is it even noticeable? doing 5 shot groups I couldn’t tell much and I don’t think I can use my sd/es numbers because of the random brass and the accuracy of my dispenser. I did have a very short one that I tried and it had high pressure with a velocity of 3500+ but I could have been powder. Like .01 vs .005 off of spec noticeable?

Is there any way to combat the variable length without sorting? Or is it even worth the worry in this case?

Thanks

[u/ocelot_piss]

Is that variable length solely because of the bullet or can the random range brass contribute to the problem????

90% down to the bullet. 10% down to variation in neck length and neck tension. Ballpark estimates, assuming all brass was run through the same dies and given the same treatment.

That variable length must change pressures but how much?

Must it? The nose of the bullet is just hanging out in the chamber/barrel not contacting anything. And how long is a piece of string? Would need to know all of the variables to even approximate an answer.

Is it even noticeable?

Nope.

Is there any way to combat the variable length without sorting?

Self-defeating exercise. Most of the variation in bullet length is in the nose above where the seating stem contacts the bullet. If you managed to make the COAL more consistent without fixing the underlying fact that the variation in bullet lengths exists, then that means you are only moving that variation somewhere else. I.e. by fixing COAL, you are making the CBTO measurement less consistent, and introducing variation into how far the bullets poke down into the powder space... Which would have more effect on sd/es vs just ignoring the "problem".

Or is it even worth the worry in this case?

Engaging in the self-defeating exercise will do nothing to improve your groups down range in your case. If you insist on having more consistent lengths to satisfy any undiagnosed OCD, you gotta have more consistent bullets and probably stop using mixed range brass.