Seating depth variation and dies

[jmorris]

I am completely comfy admitting that the variations I introduce as a shooter are way beyond what is likely introduced by my reloading practices.

The point I was trying to make was that you might not be introducing them, components can and do. It’s just as important to understand what you can’t correct as it is to correct those things you can, if they are important.

 

[Varminterror]

I didn’t see others mention it.

The rest of us didn’t (literally) depict how to take these measurements, but the recommendation to take the BTO measurements rather than COAL’s was painted all over the first page…

Out of curiosity, are you measuring COAL or cartridge-base to ogive?

Does 5 thousandths of seating depth variance really matter?
if you are measuring from the base to the pointy end then I would say .. no

Measure your BTO’s,

I'm thinking the difference that you are seeing is due to the bullet, not the die.

The first step is to get a good measuring tool that checks seating depth by ojive.

it appears that you're measuring COAL rather than to the ogive.

 

[JFrank]

Too funny, I like my post best.

 

[Laphroaig]

Oddly enough, 27 grains of tac was also the money load with 123 grain SSTs, but I just didn't get enough velocity for hunting.

You never said whether you are shooting a bolt or gas gun. I'm shooting a Ruger American. I've been looking for, but not finding, some more 6.5 Grendel friendly powders, namely Benchmark and 8208. Probably should consider some TAC too. Anyway I found data for some powders I had on shelf and tried them. IMR4198, IMR 4895, and Rl 15. Other than the Match Burners, I had some .264 95 gr. VMax and 120 gr. ProHunters which I loaded up also. All 3 powders shot some impressive groups with the MB's, the other bullets not as good but still under 1" 5 shot groups for the most part. The best was 28.5 Rl15:



Factory Nosler 120 Ballistic Tips shot very well too.



I'm chomping at the bit to get back and fine tune some of these loads but I'm going to wait until the deer hunters all get sighted in. Other data; Nosler brass, CCI 400 primers, RCBS dies, shot off of a bipod with a rear bag, 100 yds.

 

[brewer12345]

You never said whether you are shooting a bolt or gas gun. I'm shooting a Ruger American. I've been looking for, but not finding, some more 6.5 Grendel friendly powders, namely Benchmark and 8208. Probably should consider some TAC too. Anyway I found data for some powders I had on shelf and tried them. IMR4198, IMR 4895, and Rl 15. Other than the Match Burners, I had some .264 95 gr. VMax and 120 gr. ProHunters which I loaded up also. All 3 powders shot some impressive groups with the MB's, the other bullets not as good but still under 1" 5 shot groups for the most part. The best was 28.5 Rl15:

View attachment 1112157

Factory Nosler 120 Ballistic Tips shot very well too.

View attachment 1112158

I'm chomping at the bit to get back and fine tune some of these loads but I'm going to wait until the deer hunters all get sighted in. Other data; Nosler brass, CCI 400 primers, RCBS dies, shot off of a bipod with a rear bag.

Gas gun. I keep thinking about a Ruger American in this cartridge, but other expenses keep popping up.

I have thus far played with H335 and Tac. Tac is very accurate with both SSTs and (especially) match burners with 27 grains, but the velocity is less than I am looking for in a hunting load. I got the minimum I was looking for with SSTs and H335 for a deer load this year, but I think I can do better with other powders. I found a pound of 2520 and a pound of CFE223. A lot more excited to work with 2520 as 223 has a reputation for a high level of temp sensitivity.

One of these days I will get some 123 grain ELD-Ms to work with. The factory Hornady Black is very accurate and fast, so I think they have good potential. In the meantime I am playing with the match burners because midway was blowing them out for a hair over 20 cents a piece a couple months ago and thus far they are very accurate.

 

[JFrank]

I feel like typing so bare with me for a moment, seating depth testing is part of the tuning process (seating depth adjustments make subtle changes to the pressure curve) depending on the discipline you may not even find enough value to bother with it. Or the platform isn’t accurate enough to show the differences and we can get adequate groups with just powder bullets and neck tension testing etc.
Higher end platforms will benefit or reflect every little detail or change, seating isn’t always about the smallest group, sometimes the window is so small that .001 off can be a disaster or the winning combination that day’ some guys will select a depth of no harm meaning the seating depth may not produce the smallest but it won’t spit rounds rather agg it out. An example below where .004 -5 and 6 thousand jam are not the smallest but they are steady with low vertical dispersion.
Another example below where .010 11 and 12 are smaller and .011 is great BUT you better get it right or take a chance on spitting a round.

 

[AJC1]

I feel like typing so bare with me for a moment, seating depth testing is part of the tuning process (seating depth adjustments make subtle changes to the pressure curve) depending on the discipline you may not even find enough value to bother with it. Or the platform isn’t accurate enough to show the differences and we can get adequate groups with just powder bullets and neck tension testing etc.
Higher end platforms will benefit or reflect every little detail or change, seating isn’t always about the smallest group, sometimes the window is so small that .001 off can be a disaster or the winning combination that day’ some guys will select a depth of no harm meaning the seating depth may not produce the smallest but it won’t spit rounds rather agg it out. An example below where .004 -5 and 6 thousand jam are not the smallest but they are steady with low vertical dispersion.
Another example below where .010 11 and 12 are smaller and .011 is great BUT you better get it right or take a chance on spitting a round.

Some people limit themselves to a seating depth variation of the cannalure or the crimp grove. Target shooters are generally more willing to venture into real changes like the berger seating depth test.

 

[JFrank]

Some people limit themselves to a seating depth variation of the cannalure or the crimp grove. Target shooters are generally more willing to venture into real changes like the berger seating depth test.

Truth be told I prefer not to mess with it at all. Just stay with magazine length like our hunting rifles

 

[JFrank]

@AJC1
Just between you and me, I see as much variations from case volume as any other part of the puzzle.

 

[AJC1]

@AJC1
Just between you and me, I see as much variations from case volume as any other part of the puzzle.

I keep pondering a round of volume sorting a batch of cases but just the idea seems excruciating. Might do it when the weather gets stupid cold just to have done it once. If nothing else I might see what a brand worth of variation looks like but I don't know if tenths is enough resolution.

 

[JFrank]

I sort cases by feet per second. Set the unexplained high a low aside for further testing. I learned it from Bart

 

[Bcwitt]

That’s an ingenious technique and actually doable by simple folks like me. Obviously someone else told you about it But seriously I’m going to try it.

No, I came up with that when I was faced with the need. Im sure im not the first one.

 

[Bcwitt]

Any tubular material w square ends should give a decent measurement. A short piece of brake line, pipe or similar. A comparator is just an expensive version of the same concept.

 

[AJC1]

Any tubular material w square ends should give a decent measurement. A short piece of brake line, pipe or similar. A comparator is just an expensive version of the same concept.

A comparator uses standards for datum.

 

[Bcwitt]

Now the other important part not covered is seating depth has a good window like powder has nodes. If your seating depth is in the middle of a tuning window that variation is probably OK. The cause of your variation may be neck tension variation as much as the seating die. The first step is to get a good measuring tool that checks seating depth by ojive. That same tool can be used to measure bullets. You can see the bullet variation and sort them. With sorted bullets you can test your process to see where the variation is coming from.

"OGIVE"

 

[Howa 9700]

Well this rabbit hole just got deeper.

I have same desire as OP to be able to fine tune bullet seating depth using a variety of dies, none of which have micrometer seating adjustments. So figured I would make an attempt to calibrate what I do have. If I know how much deeper one full turn of the seating scew seats the bullet, I can work from there. But in order to do that, you need a constant. Measuring COAL of loaded round is no good due to bullet variations. Have already tried that and have seen as much as 12 to 15 thousands difference in COAL. This using soft point bullets like Interlocks, where tip is not uniform like a plastic tip might be.

So decided to find out how much variation there is in just the bullets alone. Following advice here, got myself a Sinclair bullet comparator and set out measuring both overall length of the bullet (tip to base) and using comparator, ogive to base. Results were a bit scary. Measured two different 6mm bullets........100 grain Hornady Interlock BT, and 100 grain Nosler Partition. In both, overall bullet variation from only 5 bullets was 6 to 7 thousands.........and ogive to base 4 to 5 thousands. Unless I made a grave error somehow, one Hornady bullet was off on the ogive to base measurement by a full 10 thousands. If true, that might explain some of the fliers I get now and then.

Next step is to take what is left of the box and sort them into piles......then when doing my seating depth turn tests......pick all bullets from the same pile.....same exact length......so as to get a constant. See if those will seat to the same depth. If yes, I will have found my constant. If not, accept that my equipment and components do not allow for that level of precision.

I also have some Hornady SST bullets with plastic tips. Need to measure those....both overall and base to ogive to see if they are more consistent. If so, may be able to calibrate die seating depth with those. They are in a different caliber, but a screw turn may be a screw turn.

 

[AJC1]

Well this rabbit hole just got deeper.

I have same desire as OP to be able to fine tune bullet seating depth using a variety of dies, none of which have micrometer seating adjustments. So figured I would make an attempt to calibrate what I do have. If I know how much deeper one full turn of the seating scew seats the bullet, I can work from there. But in order to do that, you need a constant. Measuring COAL of loaded round is no good due to bullet variations. Have already tried that and have seen as much as 12 to 15 thousands difference in COAL. This using soft point bullets like Interlocks, where tip is not uniform like a plastic tip might be.

So decided to find out how much variation there is in just the bullets alone. Following advice here, got myself a Sinclair bullet comparator and set out measuring both overall length of the bullet (tip to base) and using comparator, ogive to base. Results were a bit scary. Measured two different 6mm bullets........100 grain Hornady Interlock BT, and 100 grain Nosler Partition. In both, overall bullet variation from only 5 bullets was 6 to 7 thousands.........and ogive to base 4 to 5 thousands. Unless I made a grave error somehow, one Hornady bullet was off on the ogive to base measurement by a full 10 thousands. If true, that might explain some of the fliers I get now and then.

Next step is to take what is left of the box and sort them into piles......then when doing my seating depth turn tests......pick all bullets from the same pile.....same exact length......so as to get a constant. See if those will seat to the same depth. If yes, I will have found my constant. If not, accept that my equipment and components do not allow for that level of precision.

I also have some Hornady SST bullets with plastic tips. Need to measure those....both overall and base to ogive to see if they are more consistent. If so, may be able to calibrate die seating depth with those. They are in a different caliber, but a screw turn may be a screw turn.

If you use the locking ring on your die, you can use calipers from the base of the seating die to the top of the stem for very accurate adjustments. A timing mark on the die may help. On my Wilson chamber seater I do the same thing from top of cap to bottom of seating stem.

 

[CQB45ACP]

Well this rabbit hole just got deeper.

I have same desire as OP to be able to fine tune bullet seating depth using a variety of dies, none of which have micrometer seating adjustments. So figured I would make an attempt to calibrate what I do have. If I know how much deeper one full turn of the seating scew seats the bullet, I can work from there. But in order to do that, you need a constant. Measuring COAL of loaded round is no good due to bullet variations. Have already tried that and have seen as much as 12 to 15 thousands difference in COAL. This using soft point bullets like Interlocks, where tip is not uniform like a plastic tip might be.

So decided to find out how much variation there is in just the bullets alone. Following advice here, got myself a Sinclair bullet comparator and set out measuring both overall length of the bullet (tip to base) and using comparator, ogive to base. Results were a bit scary. Measured two different 6mm bullets........100 grain Hornady Interlock BT, and 100 grain Nosler Partition. In both, overall bullet variation from only 5 bullets was 6 to 7 thousands.........and ogive to base 4 to 5 thousands. Unless I made a grave error somehow, one Hornady bullet was off on the ogive to base measurement by a full 10 thousands. If true, that might explain some of the fliers I get now and then.

Next step is to take what is left of the box and sort them into piles......then when doing my seating depth turn tests......pick all bullets from the same pile.....same exact length......so as to get a constant. See if those will seat to the same depth. If yes, I will have found my constant. If not, accept that my equipment and components do not allow for that level of precision.

I also have some Hornady SST bullets with plastic tips. Need to measure those....both overall and base to ogive to see if they are more consistent. If so, may be able to calibrate die seating depth with those. They are in a different caliber, but a screw turn may be a screw turn.

That is really enlightening. So we’re all doomed to uncertainty regardless what we try.

 

[AJC1]

That is really enlightening. So we’re all doomed to uncertainty regardless what we try.

No just buy better bullets.

 

[CQB45ACP]

No just buy better bullets.

Okay so like me just buying Berry’s and Extreme plated pistol bullets, I’m doomed. (But I guess I’m okay with that since I’m just a casual shooter anyway)

 

[AJC1]

Okay so like me just buying Berry’s and Extreme plated pistol bullets, I’m doomed. (But I guess I’m okay with that since I’m just a casual shooter anyway)

This is one of the things we get very caught up in here. If your quest is absolute accuracy there is a path and the br guys do most of it. There are some differences between 200 and 1k br. Using those processes show you the quality of your materials. If your not agg shooting for score it's not worth your time.

 

[JFrank]

Well this rabbit hole just got deeper.

I have same desire as OP to be able to fine tune bullet seating depth using a variety of dies, none of which have micrometer seating adjustments. So figured I would make an attempt to calibrate what I do have. If I know how much deeper one full turn of the seating scew seats the bullet, I can work from there. But in order to do that, you need a constant. Measuring COAL of loaded round is no good due to bullet variations. Have already tried that and have seen as much as 12 to 15 thousands difference in COAL. This using soft point bullets like Interlocks, where tip is not uniform like a plastic tip might be.

So decided to find out how much variation there is in just the bullets alone. Following advice here, got myself a Sinclair bullet comparator and set out measuring both overall length of the bullet (tip to base) and using comparator, ogive to base. Results were a bit scary. Measured two different 6mm bullets........100 grain Hornady Interlock BT, and 100 grain Nosler Partition. In both, overall bullet variation from only 5 bullets was 6 to 7 thousands.........and ogive to base 4 to 5 thousands. Unless I made a grave error somehow, one Hornady bullet was off on the ogive to base measurement by a full 10 thousands. If true, that might explain some of the fliers I get now and then.

Next step is to take what is left of the box and sort them into piles......then when doing my seating depth turn tests......pick all bullets from the same pile.....same exact length......so as to get a constant. See if those will seat to the same depth. If yes, I will have found my constant. If not, accept that my equipment and components do not allow for that level of precision.

I also have some Hornady SST bullets with plastic tips. Need to measure those....both overall and base to ogive to see if they are more consistent. If so, may be able to calibrate die seating depth with those. They are in a different caliber, but a screw turn may be a screw turn.

The best custom/hand made bullets can vary .003 in overall length.
To adjust a non micro seating stem can be a little trial and error for sure, remember the seating stem contacts the bullet in a different location than your ogive comparator.
I sort non custom bullets by base to ogive, base to seating stem and overall length.
I load those within a thousand each side of my number ; for example .631 base to ogive as a base number I would only load those .630-.631.632 and consider that pretty darn close.

 

[Howa 9700]

OK......for grins measured all 5 of my Lee dies sets. On 4 or 5.....one full turn screwed seating knob in 0.055 to 0.057 thousands. So if one wanted to divide the knob into 4th's and then 8ths......half o 1/8 turn would be 1 /16 turn and that would be 0.004. If that turned out to be correct, it would be accurate enough for my use.

But what about the fifth one? The 308 Win? Measured it 3 times and one full turn raised or lowed stem 0.156......or over twice what the other 4 seating dies did. Either I screwed up or something is entirely different with the 308. If seating stem is moving that far, that fast, will be no fine tuning that one.

 

[AJC1]

OK......for grins measured all 5 of my Lee dies sets. On 4 or 5.....one full turn screwed seating knob in 0.055 to 0.057 thousands. So if one wanted to divide the knob into 4th's and then 8ths......half o 1/8 turn would be 1 /16 turn and that would be 0.004. If that turned out to be correct, it would be accurate enough for my use.

But what about the fifth one? The 308 Win? Measured it 3 times and one full turn raised or lowed stem 0.156......or over twice what the other 4 seating dies did. Either I screwed up or something is entirely different with the 308. If seating stem is moving that far, that fast, will be no fine tuning that one.

What do you think the adjustment is on your sizing die and don't you expect the same level of control.

 

[JFrank]

Maybe just order a micro adjust seater, they’re cheap.