Seating depth changing?

[Ol' Red]

Easy test, take 20 of the exact same load, and adjust the COAL on each cartridge so they are all EXACTLY the same. Take the next 20 using the last seating die setting and seat those using the exact same load and batch of brass. Same number of firings, same since last annealing. Shoot 2 5 shot groups from each batch at 300 yards, preferably first thing in the morning with no wind. Shoot the next 2 sets of groups at 500 yards. Single load all rounds, do not use the magazine.

That is how I have tested everything over the last 50 years to come up with what I need to focus on and what is irrelevant. Consistency of bullets, brass, primer pocket and flash hole uniforming, and consistent load, right primer, same neck tension as well as seating depth are all relevant but the variance in exactness is where the material versus don't matter live. So for example, powder to 1/10 produces nearly the same SDs and ES as powder to 1/100th, in loads over 50 grains and over 80 grains it is totally irrelevant. The less powder you have, the more measuring to 1/100th shows up.

Come back and tell us if you can see any difference at all after firing the 40 rounds.

I should have read this before I posted.

 

[Rick Richard]

I've read on a couple of post where "neck tension" can effect seating depth…..how so? You are using a ram with WAY plenty of force to seat a bullet with little resistance to a stopping point that can't be exceeded. Thus, traveling a specified distance. Sorry, I just can't wrap my head around this one.

 

[MJN030]

Have you seen seating depth change from round to round, when using a seating die? Am I doing something in my process wrong or why would I see a variation of 0.001-0.004 using a Hornady Micrometer seater on a Hornady Custom Seater Die?

My assumption was once set, lock ring tightened, they should all be really close after using my dummy round to verify length with comparator. Ideas? I basically have to check every round right now and am seeing more variability than I'd like, so I just don't trust it. Do you really need to measure every one?

One thing to check on , is please make sure that the cartridge cases are all the same length .

That certainly can contribute to this issue.

Thanks
Marc

 

[Brent40]

I agree with the others post. Shoot and see if it makes a difference.

I can't, I check every round; my OCD will not let me do anything else. When you have a flier or when groups open up, I like to know the problem didn't come from me being inconsistent. At the very least make everything as consistent as possible when testing/ developing a load.

I would recommend a great set of calipers (Mitutoyo or the best your budget will allow) and a bullet comparator tool. If the measuring tool you are using is not accurate then nothing else will be.

 

[RD57]

It's not uncommon to see an OAL variation of around .004-.006" from bullets taken out of the same box/same lot. I've seen up to .008" with Berger Match bullets. Just when you think everything is good to go in your handloading setup and start loading with a new lot of the same bullet, you'll notice another change. Like others have mentioned, if you're measuring/sorting your bullets first from Base-to-Ogive the variation in Overall Length can be pretty small, depending on how the tip was made (HP, lead spear, plastic, etc.).

 

[Rick Richard]

One thing to check on , is please make sure that the cartridge cases are all the same length .

That certainly can contribute to this issue.

Thanks
Marc

I don't understand your comment. Seriously, please explain your reasoning . Thanks

 

[DuckHunt]

Some folks measure bullet base to ogive - because there are differences - and set aside to load in those particular groupings. I tried that for a while but that is just too tedious for me. Now, I load a few rounds and measure cartridge base to ogive to check seating depth difference. When I find one that seats a few thousands deeper than my target depth tolerance, I back off on my seating die to bring the seating depth in line with my target depth for that round - leaving the longer rounds set to the side for further seating later. Those that are seated at target depth are complete and placed in storage box. But, those that may be longer than target depth I set to the side to further seat later. Then I do the following for the round(s) seated too deep:

- I use a kinetic bullet puller to make the bullet longer only - I do not completely pull the bullet.

- I adjust seating die and seat the bullet again and measure. If I am on my target depth, I will then seat all my rounds with seating die at this setting, measuring each one for target depth consistency. Those that are longer than I want, and there should be some, I set to the side and reseat those after I have my total rounds reloaded

So,
(1) seat a few bullets
(2) measure for seating depth and find any seating too deep - I am only seeking those seated too deeply
(3) set longer seated bullets to side - to be seated to proper depth after all other rounds are loaded
(4) use kinetic bullet puller to lengthen round seated too deep
(5) adjust seating die generously so I don't have to use kinetic puller again
(6) reseat bullet and verify correct to target ogive depth, adjusting seating die until it is
(7) seat all remaining rounds - checking each one for target depth. Repeat step 3 & 4 if rounds are found seated deeper than tolerance allows
(8) when total rounds being loaded are completed, then adjust seating die to make the longer rounds (set aside during loading process) seat to proper depth
(9) seat all other rounds (set aside) adjusting seating die as necessary to reach target ogive

This all sounds a bit "busy" but it really flows well after you get started. Been working really well for me. And, I do this for hunting loads... so glad I don't shoot competition! LOL

Have fun! :)

 

[bigbulls]

Me too. I keep 20 or so next to my scale, and a pair of tweezers.
Most powders I get to within .02gr (1/3 to 1/2 a kernel variation). So say 46.00 to 46.02. Only N570 do I strive for .04gr (still 1/2 a kernel variation).

Does it help? It sure doesn't hurt.

Wow, I feel a lot better now I thought I was the only one. I start out with kernels cut up on a plate to get 58.515 gr to 58.535 gr. N570 I'm sure it doesn't make much difference on target but it sure makes me feel better knowing what's on target is me. Lol As far as seating depth I had the same issues as OP and could never find a fix til I went to a wilson micro and arbor press that helped most of what I was seeing. I like to seat bullets long after each powder throw and then come back after powder is done and seat where I want them within a .0005-.001 I do think most of the variance comes from the hold on the measuring device.

 

[Rotten]

I've read on a couple of post where "neck tension" can effect seating depth…..how so? You are using a ram with WAY plenty of force to seat a bullet with little resistance to a stopping point that can't be exceeded. Thus, traveling a specified distance. Sorry, I just can't wrap my head around this one.

The way i can see how neck tension will change oval length is by a tight neck will have more pressure that will move the case down ward it will spring back but the length will be off. Just the opposite on a lighter neck press will not compress the brass downward and will end up being longer . Just my thought on this as I also was wondering about it. I haven't yet tested this out yet just me thinking.

 

[Dean2]

Neck tension variations affect accuracy. The only way neck tension would affect seating depth is if you were loading compressed loads and the tension was insufficient to maintain the compression, as in the push back of the powder pushed the bullet back up. If you had variable tension, some would push back out, others not. Also, really light neck tension may not hold a bullet securely and you could get variable movement of the bullet as it is handled, measured etc, especially if the necks have not been uniformed. Final point, a lot of people cannot measure accurately the COAL with a caliper, but error due to inconsistent measuring with a .001 accurate caliper should be .001 to .002

Rotten - There is no where near enough pressure when seating for the brass case itself to be compressed by the press.

 

[Rotten]

Not the entire cass just the neck junction. If the brass is expanding 001-.003 at neck why wouldn't their be enough force to also move the neck downward. 001 or so at the same time.
Not saying it would as I haven't measured it. Just a thought.

 

[memtb]

I have a friend, I know hard to believe, that is a board certified psychiatrist…….you guys would drive him to drink! memtb

 

[Alibiiv]

I don't know how to articulate what I'm thinking, so I'll type like I talk.

I'm very much into the why and details of things and don't believe in a free lunch. That said, if I'm doing unnecessary worrying about things that don't matter, I don't want to. But if there are things I SHOULD be worrying more about than others, I want to.

I'm seeing a couple trains of thought here. Adjust every load and make sure it's what I want, and the other don't worry about it. Being new, if I incorporate measure every load now to my process, it will seem normal to me. If I don't and get great results, was it useless worrying or will I eventually see something I need to tweak in my process? Seriously asking. My reptile brain is very process and detail oriented. I tend to overthink stuff and get lost in the weeds and tend to go overboard. My kid reminds me every time we reload, this is supposed to be fun, not f-ing calculus Dad.... I believe in doing it the right way, I just don't know what that is yet.

This is a long thread and I have not read all of the replies. I get what you are saying. There are a number of variables that go into reloading ammunition, far more than what is incorporated in this thread. The ogive of the bullets can vary, the neck tension on over all length can cause a variation, are the case annealed or not, do you crimp or not crimp (?), powder charge can cause a variation "ESPECIALLY" if seating a heavy bullet and it is a compressed load, or any combination thereof; and...I am certain that I have missed a few in here as well. In my opinion unless you personally have machined every single piece that you are assembling and if you have set your quality control acceptance to a very high standard getting a .001-.004 is acceptable. Once my COAL is established after a ladder load development then that is it for my load data for that particular firearm. I have seen where an extractor mark on the back of a case will raise up .005 thousandths of more. With this situation it prevents the base of the case from sitting squarely against the shell holder, a piece of burned powder, or case lube can cause the same results. How close is the measurement for how far a bullet is off of the lands, how is that measured?? It is measured with a bullet, that gets jammed into the lands, then is measured while it is in a "special" case, that is screwed into a piece of plastic, that is placed inside a comparator sleeve, a sleeve that is screwed to a set of dial calipers that have been calibrated by zeroing out the dial calipers. Try to take into account how many variables there are within this operation.

I can only suggest that you are in charge of the decision as to how close you want to be. Reloading refinement is in your wheelhouse and no one else's. Along with reloading refinement there is the huge variable, and that is the cost variable that is very real as well. I anneal my brass with an AnnealEez, would I prefer an AMP annealer, yes but...I do not believe a $1400 investment is going to improve my reloads enough to warrant that investment. I do the very best that I can do when I reload with what I have to work with. If I can find another operation that I think/know that I can do then I do it. If it pans out and it is an improvement great, if that operation does not show any improvement, oh well I tried it, it didn't work out and lets move on. I am ADD/HDD/OCD/ANY DD that one can have, so I do understand what you are trying to get an answer to. Keep following the reloading tips and threads that you can and keep doing what you are doing. I hope this reply helps you out and helps to get you where you are trying to get.

 

[TennJed]

Have you seen seating depth change from round to round, when using a seating die? Am I doing something in my process wrong or why would I see a variation of 0.001-0.004 using a Hornady Micrometer seater on a Hornady Custom Seater Die?

My assumption was once set, lock ring tightened, they should all be really close after using my dummy round to verify length with comparator. Ideas? I basically have to check every round right now and am seeing more variability than I'd like, so I just don't trust it. Do you really need to measure every one?

Using a comparator, measure the bullets (unloaded) on the ogive and separate them by length. The ogive can vary slightly from bullet to bullet. Once separated load the same size ones by groups adjusting for each group. This will reduce the variance. But for the very precise ones out there I agree a different seating depth even .0001 will affect pressure LOL