Consistent Seating Depth

Discussions covering the components and techniques of reloading for your long gun.
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Macd
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Consistent Seating Depth

Post by Macd »

While loading 25 rounds for my test of the effect of bullet jump in my M96 Swedish Mauser I met that constant PITA of trying to maintain a constant seating depth. I long ago gave up on COAL as there is just too much variation in bullet length even in premium bullets. Also seating stems engage the bullet on its curvature as opposed to its tip and even minor variations in diameter or centricity translate into changes in depth. I use a Hornady comparator to check seating but again these variations will cause the comparator to seat at different locations in relation to the base of the bullet. The only way I have been able to precisely establish seating depth is to measure each bullet with the comparator from base to the insert contact and then using simply arithmetic figure out the comparator to case base distance measurement for each bullet. That to me is bordering on obsessive but for my jump test I am trying to control every variable but there has to be a better way.
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Re: Consistent Seating Depth

Post by horseman »

A seating die should seat using the ogive of the bullet. You're right on the coal being a poor measuring place as tips can be deformed (soft points). If you are using the Hornady comparator set then you know the math involved in setting OAL so no need to go there. Any good seating die "should" be able to give consistent lengths within a couple thou of each other seating from the ogive and that's good enough. Not sure where your issue is. Perhaps the seating stem on the die is hitting the bullet tip before the "cup" part is engaging the ogive. Guess an easier way to say it is the seating stem doesn't fit the bullet. I'm just guessing here.
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Re: Consistent Seating Depth

Post by RBHarter »

You could remove the bullet form variations by removing the multiple form die variations with a swage die of your own . Wear and press flex would then be the only variations of bullet dimensions .
Sort of out of the Lee league of tool prices but there's a guy using the classic cast as a base for his kits over on Castboolits .
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Re: Consistent Seating Depth

Post by Macd »

horseman wrote:A seating die should seat using the ogive of the bullet. You're right on the coal being a poor measuring place as tips can be deformed (soft points). If you are using the Hornady comparator set then you know the math involved in setting OAL so no need to go there. Any good seating die "should" be able to give consistent lengths within a couple thou of each other seating from the ogive and that's good enough. Not sure where your issue is. Perhaps the seating stem on the die is hitting the bullet tip before the "cup" part is engaging the ogive. Guess an easier way to say it is the seating stem doesn't fit the bullet. I'm just guessing here.
I am not a benchrest shooter but I am keen on getting the very best accuracy out of each rifle I own. As you know controlling the variation in the components and construction of ammunition is vital to this objective. Consistent seating depth is one area that frustrates me. You are right that the seating stems in my Lee dies in almost every case are not made to accurately and consistently seat the long pointed bullets I generally prefer for serious paper punching. Often the bullet tip bottoms out before the bullet ogive comes into contact with the mouth of the stem. To correct this I have made or modified stems. However, even with modified stems, variations in the distance from the base of the bullet to the point where the bullet ogive mates with the mouth of the stem introduce variations in seating depth. I just measured 10 Hornady 168 grain HPBT Match bullets using a comparator. The measurements varied by a maximum of .006. This is when I can carefully control the alignment of the bullet to the comparator insert orfice. Inside a Lee die with a floating steel stem that bottoms on the curved surface of an aluminum cap I am not so sure that perfect alignment of the stem and bullet always occurs.

There is a saying that lifes imperfections are what keeps it interesting. Solving imperfections is what makes handloading, as opposed to reloading, so interesting to me.
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Re: Consistent Seating Depth

Post by mr surveyor »

My experiences may not be exactly relevant, but close. As much as I like the old standby 30-30 bullets in Rem Core-Lokt, they have to be the most inconsistent in loading to the same oal. I'm pretty sure the issue centers around the the length of the soft tip itself in regards to the cannelure. I don't have any issues with the Sierra Pro Hunters or any of the various cast boolits in maintaining decent oal ..... just those danged Core-Lokt bullets.

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Re: Consistent Seating Depth

Post by horseman »

Macd I really don't have the answer for you without being there with you as you load. I just went in to my reloading room and measured 15 rounds, using an RCBS precision mic, of 7mag rounds I recently loaded using 160gr. Sierra HPBT bullets. Thirteen measured within .002 of each other and the other two were within .003. These were seated using a Forster comp seating die and my Co-Ax press but I'd bet the results would be the same on my Lee Classic SS. I also think if I had taken a "bit" more effort when loading these I could get those numbers even closer. Perhaps the dies make the difference, I don't know ?? These are the only dies I have for the 7.

By the way, .003 is about half the width of a human hair... :D
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Re: Consistent Seating Depth

Post by Macd »

horseman wrote:Macd I really don't have the answer for you without being there with you as you load. I just went in to my reloading room and measured 15 rounds, using an RCBS precision mic, of 7mag rounds I recently loaded using 160gr. Sierra HPBT bullets. Thirteen measured within .002 of each other and the other two were within .003. These were seated using a Forster comp seating die and my Co-Ax press but I'd bet the results would be the same on my Lee Classic SS. I also think if I had taken a "bit" more effort when loading these I could get those numbers even closer. Perhaps the dies make the difference, I don't know ?? These are the only dies I have for the 7.

By the way, .003 is about half the width of a human hair... :D
Don't think it is my reloading technique but a product of bullet variation and dies. It is impossible to get precision with a bullet lot that doesn't have a consistent ogive radius. It also is very difficult to use dies that will seat the exact same bullet in the same case to the same depth only 8-9 times out of 10. I am seriously considering micrometer adjustable options. Unfortunately nothing will fit Lee dies. Since I am only interested in 6.5x55 at the moment, that isn't a big issue.

It depends on what human and what hair :D
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Re: Consistent Seating Depth

Post by RBHarter »

Forming a seating stem to precisely match the desired ogive might remove issues as well .

The tools on the bench can only be as precise as the tools that make the components or tools .
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Re: Consistent Seating Depth

Post by Macd »

RBHarter wrote:Forming a seating stem to precisely match the desired ogive might remove issues as well .

The tools on the bench can only be as precise as the tools that make the components or tools .
Agreed. I have made a seating stem for most of my regular bullets. It definitely helps as long as the tip area is relieved enough to prevent bottoming out.
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Re: Consistent Seating Depth

Post by horseman »

I think you're correct with the inconsistent bullets and dies. Mainly the bullets being inconsistent, you'll obviously not be able to get consistent CBTO using bullets like that. One other thing I've noticed but using primer seating as an example is how "hard" you lean on the press handle will/can/may make a difference. I've not "tested" this with bullet seating but I can seat a primer in a case just taking the machine to it's "stop" position vs stop position and then lean on it a bit more. Using the RCBS bench primer, Co-Ax press primer, RCBS Pro 2000 primer seater, well you get the idea here, and "move" the primer up to .010 deeper quite easily depending on how hard I push the handle after the stop position of whichever I'm using, and it isn't all that much difference in pressure. This is AFTER the press hits it's "stop". Pretty sure I could do the same with bullet seating. Easy enough to check I guess, I'll take a couple of loaded rounds, put them in the press and give it a firm "push" after the stop position (not on a cam-over press) and see what kind of changes I get. May end up being nothing, but I'd wager it'll change some. I shall return....... :D

I'm back. So much for that "theory". Using the Co-Ax press, Forster comp. seating die. Measured before and after all I could get is .001, and I "leaned" on it hard. So, back to bullets or die. Probably more so the bullets.
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