LD - Seating Depth Testing Increment

Baron23 · Aug 3, 2021

HI guys - quick question from brand new metallic reloader.

I have settled on a charge weight and MV, and now would like to explore impact of seating depth.

Its Berger 140 gr Hybrid Targets in a 6.5 man bun Proof SS barrel with 1,400 rounds on it. Seating .010 off of max mag length gives about .060 off of lands.

I have read a number of folks who have expressed that this bullet is pretty jump tolerant and that many are running .100 off or even more.

Right now my plan is to increment up by .010 from .060 to .100 off of lands with ten cartridges loaded at each depth to allow two five shot groups....yeah, I'm not good enough of a marksman to utterly eliminate my shooting from ammo performance so I'm thinking shoot two groups of five.

But, is this too big of an increment between depths such that I'll miss the best depth. Do I need/should reduce the depth increment to maybe like .005?

Thanks

nn8734 · Aug 3, 2021

I’d start at .020 and go to .90 at .010 increments. My guess is that you will see minimal difference through a large portion of that range as all Berger hybrids like jump and thst range has always done well for me. Whichever the node happens to be, load at the top of it so you won’t see any difference in precision as the throat erodes until that erosion passes through the bottom of the node.

Side commentary, I have no idea why people refer to the 6.5 creedmoor as a “man bun” sounds retarded (not directed at you, just remarking on the coining of the term itself).

Baron23 · Aug 3, 2021

nn8734 said:
I’d start at .020

Can't....will far exceed mag length. Closest that I could get is .050 off and that's right at mag length while .010 back from max mag (.060 jump) is more comfortable to me.

nn8734 said:
Side commentary, I have no idea why people refer to the 6.5 creedmoor as a “man bun”

hahaha...yeah, sort of preemptive self-defense after being accused of shooting man bun here on the Hide a few dozen times! LOL

For what I do, I actually like the 6.5 CM. I know PRS guys are going to smaller calibers and lighter/faster projectiles but at 69 y.o. I'm not competing and at best would shoot positions for recreational fun. So, for just a long range shooting challenge, 6.5 CM is good with me on barrel life and former wide availability of ammo/components.

Thanks for taking the time to reply.

Cheers

nn8734 · Aug 3, 2021

Baron23 said:
Can't....will far exceed mag length. Closest that I could get is .050 off and that's right at mag length while .010 back from max mag (.060 jump) is more comfortable to me.

Gotcha. .060-.1 is a good test range then. Ideally your groups shoot tight across that range.

Yea anyone accusing you of shooting a “man bun” outside of spirit of good fun/ball busting is an imbecile, whether it occurs on here or elsewhere.

KnowNothing256 · Aug 3, 2021

I actually like the idea of shooting two shots and moving on if they don't touch, that's kinda brilliant as far as I can tell. It requires an arbor press and separate mic seating die, though, and OP may or may not have that setup.

Curious to hear others' thoughts on the "shoot two and move on if they don't touch" approach though, seems like it would be a quick and low-cost way to check a huge range of seating depths while still maintaining fine resolution.

OP, another method if you aren't looking for F-class accuracy (because that's a rapidly diminishing rate of return on time/headache investment) is to do exactly what you propose. Longer jumps have been shown to be more tolerant of jump variation, at least in a few examples (link below), so it's reasonable to expect that you could find a good jump in 0.010" increments. You can choose to seek even tighter groups by varying 0.003-5" off of that if you like, but my thought is that once you commit to that level of precision on jump, you have to start chasing the lands. I'd rather run a jump that looks basically the same at +/-0.010" at least so I can minimize how much time I spend re-establishing jump as the barrel wears.

Baron23 · Aug 3, 2021

KnowNothing256 said:
I actually like the idea of shooting two shots and moving on if they don't touch, that's kinda brilliant as far as I can tell. It requires an arbor press and separate mic seating die, though, and OP may or may not have that setup.

Curious to hear others' thoughts on the "shoot two and move on if they don't touch" approach though, seems like it would be a quick and low-cost way to check a huge range of seating depths while still maintaining fine resolution.

OP, another method if you aren't looking for F-class accuracy (because that's a rapidly diminishing rate of return on time/headache investment) is to do exactly what you propose. Longer jumps have been shown to be more tolerant of jump variation, at least in a few examples (link below), so it's reasonable to expect that you could find a good jump in 0.010" increments. You can choose to seek even tighter groups by varying 0.003-5" off of that if you like, but my thought is that once you commit to that level of precision on jump, you have to start chasing the lands. I'd rather run a jump that looks basically the same at +/-0.010" at least so I can minimize how much time I spend re-establishing jump as the barrel wears.

Thank you. My issue with two and move on is that my shooting is not quite consistent enough for me to have full confidence. I'm not bad, but I'm not one of these "in the .2's on demand" guys.

And I do not have an arbor press with compatible micrometer seating die....so there is that.

You mentioned a link but I don't see it....did you forget to paste it in???

Thanks for your input!

KnowNothing256 · Aug 3, 2021

Haha, I always forget the links. Here it is:

Bullet Jump Research: Executive Summary & Load Development Tips

This is the last post in a series of articles focused on bullet jump research that has been conduct...

precisionrifleblog.com

nn8734 · Aug 3, 2021

KnowNothing256 said:
I actually like the idea of shooting two shots and moving on if they don't touch, that's kinda brilliant as far as I can tell. It requires an arbor press and separate mic seating die, though, and OP may or may not have that setup.

Curious to hear others' thoughts on the "shoot two and move on if they don't touch" approach though, seems like it would be a quick and low-cost way to check a huge range of seating depths while still maintaining fine resolution.

OP, another method if you aren't looking for F-class accuracy (because that's a rapidly diminishing rate of return on time/headache investment) is to do exactly what you propose. Longer jumps have been shown to be more tolerant of jump variation, at least in a few examples (link below), so it's reasonable to expect that you could find a good jump in 0.010" increments. You can choose to seek even tighter groups by varying 0.003-5" off of that if you like, but my thought is that once you commit to that level of precision on jump, you have to start chasing the lands. I'd rather run a jump that looks basically the same at +/-0.010" at least so I can minimize how much time I spend re-establishing jump as the barrel wears.

IMO, two shots is way too small a sample for load testing. If you are wanting to do minimal shots per target, I’d prefer a straight up dot drill. That helps let you see your mean radius as well as conditioning you to focus squarely on hitting a very small target vs just trying to group. Again, just my opinion

KnowNothing256 · Aug 3, 2021

nn8734 said:
IMO, two shots is way too small a sample for load testing. If you are wanting to do minimal shots per target, I’d prefer a straight up dot drill. That helps let you see your mean radius as well as conditioning you to focus squarely on hitting a very small target vs just trying to group. Again, just my opinion

So, a couple things. First, it’s been established ad nauseum that anything less than about 30 shots is statistically dubious, so the difference between two shots and five isn’t as much as it seems. Second, it’s not two shots only, it’s two shots followed by 8 more if a depth seems promising. If two shots are an inch apart, they’d have been an inch apart even if you fired three more, and it STILL wouldn’t be an attractive group and you’d have burned three more shots to find out exactly the same info.

Agreed on shooting at dots or some other very fine aiming point; my range has rolls of free paper, I just draw crosses on a big sheet in normal-sized Sharpie. Finer aiming point than a 1” dot and basically free.

spife7980 · Aug 3, 2021

.010 may be too much, but it also may not be.

When I have a new bullet Ive not used or a new chambering I do a test in .010 increments just to find out the bad spots and what doesnt work. Ill then go in .005 increments inside the promising spots just to see where its actually "best". Usually once I find that sweet spot it stays shooting well from there regardless of throat erosion Ive found.

nn8734 · Aug 3, 2021

KnowNothing256 said:
So, a couple things. First, it’s been established ad nauseum that anything less than about 30 shots is statistically dubious, so the difference between two shots and five isn’t as much as it seems. Second, it’s not two shots only, it’s two shots followed by 8 more if a depth seems promising. If two shots are an inch apart, they’d have been an inch apart even if you fired three more, and it STILL wouldn’t be an attractive group and you’d have burned three more shots to find out exactly the same info.

Agreed on shooting at dots or some other very fine aiming point; my range has rolls of free paper, I just draw crosses on a big sheet in normal-sized Sharpie. Finer aiming point than a 1” dot and basically free.

The thirty shot minimum generally refers to sample sizes needed for meaningful SD/ES so if you’re going to apply it to group sizes, then 2,5 or 10 shots aren’t enough either unless you plan on burning 30+ rounds at a given seating depth to validate it’s good to go.

There are multiple ways to skin this cat so if that method works for you and others then it’s just as valid as any other. I’d rather use less rounds per group to find the width of my seating depth node.

Dots, x-hairs; again whatever works best for you.

nn8734 · Aug 3, 2021

thestoicmarcusaurelius said:
An interesting, at least to me, test that I did recently.

The “Zero” load development method. Brand new barrel, proof steel prefit in 308 with no testing or shooting prior to this test on this barrel.

I loaded up 308 rounds to mag length at 2.96.” 155 TMK’s. Virgin Lapua Brass. 46 grains of IMR 4895. Expanded necks with .3065” pin gauge. CCI 450. Powder throw with RCBS matchmaster. No sorting or uniforming or neck turning of any kind.

Installed an EC tuner brake. Tried a few setting on the tuner brake and then picked one and did a 10 shot 200 yard group. Can’t really think of many ways to get simpler or less rounds for “load development” than that. View attachment 7679339 View attachment 7679340 View attachment 7679347

Thanks for sharing, seems as though the EC Tuners are effective. Admittedly, I don’t know much about them - are they compatible with any suppressors or is it only a brake with no ability to attach a can?

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