Playing with seating depth

[Labrat198]

So far in my reloading journey I have been seating to whatever the books and manufacture suggest and adjusting my powder charge. I am measuring the jump, just have not been adjusting it other than to fit the magazine. I have a dozen or so different bullet and powder combinations that I am starting to go back to and getting more exacting in my process.

Working back from the lands, or the longest the magazine will allow, it looks like increments of .005 is a good place to start.

So I could just keep seating each bullet deeper until I feel the powder getting compressed, velocities start saying "pressure", or the bullet falls in the case.

I am wondering if there is a better way.

[Harpoon1]

So far in my reloading journey I have been seating to whatever the books and manufacture suggest and adjusting my powder charge. I am measuring the jump, just have not been adjusting it other than to fit the magazine. I have a dozen or so different bullet and powder combinations that I am starting to go back to and getting more exacting in my process.

Working back from the lands, or the longest the magazine will allow, it looks like increments of .005 is a good place to start.

So I could just keep seating each bullet deeper until I feel the powder getting compressed, velocities start saying "pressure", or the bullet falls in the case.

I am wondering if there is a better way.

Kind of depends on what the goal is too?

There is another half dozen or so articles in this series. Gotta start somewhere!

https://precisionrifleblog.com/2020/03/21/bullet-jump-and-seating-depth-reloading-best-practices/

[imaguy3]

I don't think I'd start with .005" increments.. you may waste a lot of ammo doing if you're far from a good node.

I have used Bergers method with good success with several diff loads...just scroll down to the "solution" section... https://bergerbullets.com/vld-making-shoot/

[grayfox]

I find my node MV first, then adjust seating depth by 0.010 increments to look for the best grouping. The reason is that once you find a node, the next thing is to find the correct timing for bullet exit from the muzzle, when the longitudinal wave is far from the muzzle tip. that way each bullet exits the muzzle at same MV and same initial trajectory. You adjust the timing of the bullet exiting by the coal adjustments. = tight group.

[A5BLASTER]

I find my node MV first, then adjust seating depth by 0.010 increments to look for the best grouping. The reason is that once you find a node, the next thing is to find the correct timing for bullet exit from the muzzle, when the longitudinal wave is far from the muzzle tip. that way each bullet exits the muzzle at same MV and same initial trajectory. You adjust the timing of the bullet exiting by the coal adjustments. = tight group.

I'm with grayfox. That's how I work my loads as well.

[imaguy3]

That's also how I did mine..

[Klem]

LR,

What sort of gun is this OAL testing for, and AR?

[Labrat198]

This will be for an AR.

Goal is to see just how tight a group I can repeatedly get and learn a good methodology for getting myself there. I don't want to make too big of jumps that could miss a node or waste time and money shooting miniscule changes either.

I have a lot of MV data that I am currently confirming with the LabRadar and selecting those nodes from there.

So I see .005 iterations recommended from the precision rifle blog, but suspect that is more geared toward bolt guns. The consensus here appears to be .010. Berger Bullets is .040 per stage and then going back trying and fine tuning with smaller adjustments. I also read Barnes recommends .025 increments when working with the LFP's.

I like that the Berger Bullets link gives a range, that is one thing I was hoping to find more of.

[Klem]

In an AR I doubt if you are going to see any noticeable differences in group size that you can guarantee belongs to seating depth. The system is just not precise enough plus the mag limit stops you from experimenting seating closer to the lands where if there is going to be a difference this is where it will be.


Maybe mag limit and one OAL shorter but anything shorter is robbing you of velocity. Varying bullets and powders is enough for me.

[grayfox]

Yes, in my case also, for an AR, there isn't

much room to work with

until mag-limiting.

For me and 123 class or below, I've got up to about 2.270.

So I can look at lengths from say 2.240 to 2.270. One of those typically has the better grouping, so I go with it.

Bolt guns are different, they can have a tighter chamber plus allow longer oal's.
An AR isn't going to get the same level of accuracy as a bolt, you're trading reload/firing speed for pinpoint accuracy.

I'm not trying to over sell the technique, so these, and Kelm's, caveats are applicable.

I don't use 0.005 b/c unless I'm going to be totally anal about primers, neck turning, micro-nano-bullet seating of bullets that are btw match grade..... in short for my bullets I can see up to =/- 0.003-0.005 differences in Oal while seated, since I don't do cbto measurements. Thus a 0.010 step-wise oal will allow the target to indicate a measurable difference, if any is there.

[Labrat198]

Sounds good. I think I'll try three intervals adjusting my seating by .010 just to see what happens.

Thanks everybody

[imaguy3]

I disagree with the guys about the AR. Sure you may not be able to go towards the lands as far, but you can increase jump and still get good results. I am currently sitting at a base to ogive measurement of 1.654" on my loads. My base to ogive to hit the lands is 1.748". That gives me a current bullet jump of 0.094".

When I settled on my powder charge (26.96gr IMR8208xbr). My SD numbers are single digits and I have no pressure signs. When I did my length tests I started at 1.626 and ran it to 1.686". I settled on my measurement bringing me down from 1.5moa to 3/4moa.

[A5BLASTER]

I disagree with the guys about the AR. Sure you may not be able to go towards the lands as far, but you can increase jump and still get good results. I am currently sitting at a base to ogive measurement of 1.654" on my loads. My base to ogive to hit the lands is 1.748". That gives me a current bullet jump of 0.094".

When I settled on my powder charge (26.96gr IMR8208xbr). My SD numbers are single digits and I have no pressure signs. When I did my length tests I started at 1.626 and ran it to 1.686". I settled on my measurement bringing me down from 1.5moa to 3/4moa.

Have to agree myself. I thinking playing with seating depth in increments of 5 thousands is a good thing.

Both my 12.5 and 12 inch grendels 120 gold dot load shoot well inside 5 shots under half inch because of doing a good ladder and then playing with seating depth till I found what it wanted.

Realistically the argument that a bolt action grendel has more room for loads is just that a argument. I have owned a howa grendel and now a CZ grendel and the difference in useable mag space isn't enough to say it's a difference.

My thinking is if I do something for my bolt grendel handloads too get the most out of them, then why would I not use those same techniques when loading for my ar grendels.

[Happy2Shoot]

Sounds good. I think I'll try three intervals adjusting my seating by .010 just to see what happens.

Thanks everybody

Please do report back with your findings.

Also, do you plan to go out to single hand loading lengths, or stay within you magazine length?

[Labrat198]

Please do report back with your findings.

Also, do you plan to go out to single hand loading lengths, or stay within you magazine length?

I plan to stay within the magazine length at this time. Depending on how many components i have left, I might try it now that you mention it.

Probably will be awhile before I report back, but I will post my findings.