Seating depth variation and dies

[brewer12345]

I have always just used Lee dies because they are inexpensive and serviceable for what I do. Lately I have been fooling with 6.5 Grendel and the accuracy potential of the cartridge is making me think about some gear upgrades. The most urgent is maybe a seating die. When I am seating bullets with the Lee seating die, I am getting OAL variations of 5 to 8 thousandths over a batch of 50 rounds. For a 2 or 3 MOA lever rifle or a hunting load that I want to be MOA-ish for big game, that seems to be fine. When I am chasing the smallest sub MOA groups, I am guessing it starts to matter. So a couple of questions given my lack of experience with closer tolerance stuff:

- Does 5 thousandths of seating depth variance really matter?

- I am looking at the Forster benchrest seating die as an upgrade. Any of you use these? Will it solve my problem?

 

[ParallelCode]

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

Personally I wouldn't be concerned about a variance of +/- 0.0025. Others might see it differently of course.

 

[JFrank]

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

 

[Varminterror]

First, you’re correct to question whether 5-8 thousandths variability in COAL is actually influential downrange or not. It may simply be variability in bullet meplats.

But let’s pump the brakes for a moment here - you absolutely can’t blankly assume the Lee dies are the REASON for the variability in your COAL’s, nor that Forster dies will yield greater consistency.

In other words, you really have to decide IF you have a problem, and IF a problem is determined, THEN you have to deduce the root cause for said problem. If the variability is due to inconsistent meplats or variable ogives, changing dies won’t “fix” anything.

Given that process of deduction here - what about the Lee die could be introducing variability in COAL? Is your die stretchy? Is the seating stem screwing itself in and out between rounds? Are you getting gunk build up in your seating stem which is flaking off occasionally? None of these seem very feasible, eh? Why not? Because they aren’t. Dies aren’t rubber, and you’re not adjusting the stem between rounds, nor do you have sand floating around gumming up your stem…

Most likely, you just have variable bullets, whether meplats or ogives, and nothing to do with your die, so you’re chasing the wrong rabbits… well… REALLY most likely, you don’t need to chase any COAL consistency rabbit at all.

Measure your BTO’s, if THOSE are moving, you have a bullet problem. It ain’t gonna be the fault of the die.

 

[brewer12345]

Interesting. I am using Barnes Match Burner bullets and factory new Starline brass. Measuring tip to bottom of brass, which I guess is primitive enough that I am probably not able to attribute anything to the variation that is meaningful.

 

[Laphroaig]

I just started loading 6.5 Grendel too, and bought some 120 gr. Match Burners. I measured seating depth to touching lands, and the COL variation for 3 Match Burners was 0.015". For comparison, 3 V-Max measured exactly the same. I'm thinking the difference that you are seeing is due to the bullet, not the die.

My first trip to the range revealed that the MB's shot incredibly well with all 3 powders that I tried and the seating variation doesn't seem to matter on paper. Shoot them before you pass judgement. The most important part of a bullet is the base and Barnes seems to have that figured out.

I do have a Forster micrometer benchrest seating die for .223 and love it. I'm thinking of getting one for the Grendel too. You might not get an improvement in the COL but I bet your bullets will be seated straighter.

 

[edwardware]

When I am seating bullets with the Lee seating die, I am getting OAL variations of 5 to 8 thousandths over a batch of 50 rounds.

So, everything that @Varminterror said, but let me emphasize. . .

If you're measuring to the tip of the seated bullets, you can't expect any sort of consistency at all because you're mixing seating variation with necessarily high ogive-to-tip manufacturing variation. Bullets are seated from relatively far up the ogive, and should be measured with a comparator that rests low on the ogive near where the bullet hits the rifling.

Now that we're clear on what you're measuring. . . I really doubt that a gas gun will show any benefit from reducing seating depth variation below +/0.005". I'm certain that I can't discern that benefit in my bolt guns, but I'm just a rube pushing on 0.5MOA.

All that said, I really love my micrometer seating dies, not because they're more consistent than the Lee, but because repeatability between different COALs is trivial. I think the Lee is every bit as consistent as my Redding Competition Seater, but probably not quite as concentric.

 

[Cacas ex Fortuna]

All my super match are .003 or less. I figure a human hair is about the right sloppiness.

Mr Wilson and my ole man were best buddies.
This is the most accurate equipment Ive ever used.
Been using it since the mid 60s.

https://lewilson.com/

 

[AJC1]

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.

 

[brewer12345]

I just started loading 6.5 Grendel too, and bought some 120 gr. Match Burners. I measured seating depth to touching lands, and the COL variation for 3 Match Burners was 0.015". For comparison, 3 V-Max measured exactly the same. I'm thinking the difference that you are seeing is due to the bullet, not the die.

My first trip to the range revealed that the MB's shot incredibly well with all 3 powders that I tried and the seating variation doesn't seem to matter on paper. Shoot them before you pass judgement. The most important part of a bullet is the base and Barnes seems to have that figured out.

I do have a Forster micrometer benchrest seating die for .223 and love it. I'm thinking of getting one for the Grendel too. You might not get an improvement in the COL but I bet your bullets will be seated straighter.

Heh, I shot a ladder already and got a tiny group with 27 grains of tac. Was very impressed. Wish they were hunting bullets.

 

[ParallelCode]

Heh, I shot a ladder already and got a tiny group with 27 grains of tac. Was very impressed. Wish they were hunting bullets.

Gotta love TAC

 

[brewer12345]

Gotta love TAC

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.

 

[BWS]

At touch length and shorter, .005" probably isn't gonna show up too much on paper(target results).....

But get to jam,plus .005 and it almost always shows up..... good AND bad.

 

[BWS]

Short story on seater dies;

On another forum someone talked me into trying an RCBS case flaring specialty die. Was reluctant because we are FULLY engaged with Lyman M dies. Turning our own spuds to specs/tolerances that I'd be called a liar for even writing.... just say we're splitting some serious hairs on the M spuds.

So I get the RCBS and it just is NOT gonna work at the level of precision we were already "at" with the M setup. So now I'm looking at this die like WTHeck are we going to do with this?

Took awhile.... like way too long but;

I made it into a 223 seater die for exactly the cast bullet diameter #'s that a particular R700 in this chambering was utilizing. CRS but,let's say .2245 on diameter. I patterned this die like a Hornady with the sliding sleeve arrangement except.... it was for one specific bullet nose(Lee 225-55RF) at that specific diameter....

Yes,custom turned seater stem.... just sayin,this die is a hybrid of sorts between an inline hand seater and the sliding sleeve type typ press dies. It not only "worked"... it works perfectly. The precision at this step in the process can not be overlooked. And will even go so far as to say from that die experience, that seating alignment/precision is where a whole lot is being "left on the table".

Good luck with your project.

 

[emb]

.005 may make a difference if you're loading a specific distance to the lands of approximately .0030 or less. Variations at distances to the lands greater than that probably won't make much difference. But from one of your posts, it appears that you're measuring COAL rather than to the ogive. Both measurements may vary from bullet to bullet. In your example the COAL differences are probably meaningless and won't be solved by a new/better die. If your goals are "hunting accuracy", you're probably fine. From your later posts, it appears to make little difference.

 

[Varminterror]

For what it’s worth - I don’t like bullets which are jump sensitive. No reason to tolerate another insensitivity which can be avoided. Loading in a node and using a jump-forgiving bullet will let you breathe easier knowing you’re not as vulnerable to these kinds of production errors.

 

[Bcwitt]

Get something like an empty 22lr case & slip it over the bullet tip. Use that to compare the rest. You might find it is closer then you think.

 

[Varminterror]

At touch length and shorter, .005" probably isn't gonna show up too much on paper(target results).....

But get to jam,plus .005 and it almost always shows up..... good AND bad.

Clarifying on this - if the variability is happening because of variable meplats, even when jamming, 0.005” may not actually show any negative effect, because the ogive and bearing surface jam in the leade may still actually be exactly the same.

As I said above, determining what dimension is actually causing the variability in COAL is critical in this discussion, and running around blindly changing dies and processes might not actually fix the problem - if even a problem actually exists.

 

[jmorris]

I am getting OAL variations of 5 to 8 thousandths over a batch of 50 rounds. For a 2 or 3 MOA lever rifle or a hunting load that I want to be MOA-ish for big game, that seems to be fine. When I am chasing the smallest sub MOA groups, I am guessing it starts to matter. So a couple of questions given my lack of experience with closer tolerance stuff:

This sounds like a great chance to learn something. If you load a batch of ammunition, you can sort out a group of perfect ones and shoot them against the “variation” group and then will be able to quantify exactly how much difference it makes, if any.

One thing I would do first (to possibly learn even more) would be to not only measure OAL (that can change just with different tip lengths) but from a “datum” (a repeatable diameter along the ogive) to the base.

You can also just measure projectile consistency tip to base/datum on ogive to base.

Like these SMK’s that have different OAL’s in the bullet.



but if you measure them from a point along the ogive, they are identical.



So an Overall measurement of a completed round is less than useful, if I wanted to know if they were all seated to the same depth.

If you measure different OAL’s with just projectiles, you might pull the seating stem from your die (might put a witness mark on the two parts to put it back in the same spot first) and use it as your “datum” point to see if your rounds still have the same variation from one another.



In other words your .008” variation could be a big deal or it could have absolutely zero negative consequence’s.

 

[CQB45ACP]

Get something like an empty 22lr case & slip it over the bullet tip. Use that to compare the rest. You might find it is closer then you think.

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.

 

[Varminterror]

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.

It’s standard practice, which is why ~10 of us here immediately brought it up. But for some reason, doesn’t make it into most “how to reload” editions of YouTube videos or reloading blogs, or even most reloading manuals - at least not directly.

I assume largely for 2 reasons 1) it’s an admission by the manufacturers that they don’t actually produce consistent bullet profiles, and 2) they don’t sell the tools to measure ogives, so they don’t profit in marketing them.

COAL really only matters for mag length. The tips of our bullets don’t touch anything, ever, until they run into something down range.

 

[CQB45ACP]

It’s standard practice, which is why ~10 of us here immediately brought it up. But for some reason, doesn’t make it into most “how to reload” editions of YouTube videos or reloading blogs, or even most reloading manuals - at least not directly.

I assume largely for 2 reasons 1) it’s an admission by the manufacturers that they don’t actually produce consistent bullet profiles, and 2) they don’t sell the tools to measure ogives, so they don’t profit in marketing them.

COAL really only matters for mag length. The tips of our bullets don’t touch anything, ever, until they run into something down range.

I didn’t see others mention it.

Using the correct size case would get you a decent ogive measurement device to use with calipers, no? For cheap.

And, from what you say, this is why seating dies aren’t on the tip?

 

[brewer12345]

This is all very interesting. I need to think about how far down the rabbit hole I want to go with this. I am completely comfy admitting that the variations I introduce as a shooter are way beyond what is likely introduced by my reloading practices. Might be worth picking up a comparator and seeing what it tells me in practice.

 

[JFrank]

Oh my goodness, you definitely need a comparator that does NOT contact the meplats… Base to ogive is the standard for setting and monitoring seating depth. Probably less then $30

Just for information , the best hand made bullets in the world Vapor trails and Barts hold .003 tolerance in overall length, .001 base to seater stem and .002 base to ogive. …Most other bullets are just that.

 

[AJC1]

I didn’t see others mention it.

Using the correct size case would get you a decent ogive measurement device to use with calipers, no? For cheap.

And, from what you say, this is why seating dies aren’t on the tip?

A 22 lr would likely show you a measurement very close to the contact point of your seating stem.