questions about bullet seating depth

[nra-for-life]

hi everyone...

i am loading up some rounds to test in my 22-250 to see what seating depth this rifle will like the most. i am using a hornady bullet comparitor with a mitutoyo caliper to check the length of the cartridge (from the base to the ogive). after seating the bullet and checking the length, the seating depth of the bullet seems to vary a lot even though i haven't adjusted the seating die. the seating die is a forster with the mic.

i seem to get routine inconsistencies of 15 thousandths although i have had much more, up to 90 thou on the most, although that was quite a bit higher than the norm. so my questions... is this normal?? is this this acceptable??? what causes this...? i suspect that the difference can be accounted for because the seater is pushing the bullet into place from a different place on the bullet, where as the comparitor is taking the measurement right at the ogive (or closer to it anyway) or possibly just differences in the bullet??

Is it safe to assume that my bullet seater is working properly? give me your opinion please. thank you

here is a couple photos...two different cartridges, two different measurements, same seating depth on the die.

 

[LRPV]

.015 difference in seating depth would not be acceptable to me and is nowhere near the consistency I have seen with my Forster seating dies in any caliber. There are a lot of variables to be considered one is consistent neck tension, has your brass been fired very many times and is all the brass the same brand and/or been fired the same amount of times. Not sure which bullet you are using. If the base/boat tail of the bullet is getting down into the neck shoulder junction and is right there in the unsweet spot I have seen some variations there before. The same would hold true if there is only a small amount of bullet in the neck. The example you pictured is only .0045 different but even that is more variance than I'm used to getting in my loads. I don't normally more than .001 difference between a whole batch.
Jason

For what it's worth, I've had good luck with most Hornady bullets around a .020 jump.

 

[Martin52]

A few things to check:

Your seating die is secure in your press, any slight looseness will easily result in a few thou variance.
Powder load is not too high in the case ie a compressed load (if so, try a long drop funnel).
The loaded round is sitting vertically in the caliper ie not off centre.
Your primers are seated correctly, ie no high primers, this will affect the measurement.
Try a dusting of powdered graphite around the hole in the Hornady comparator, this will stop the projectile sticking and impacting measurements.
The caliper is sensitive to how much pressure you apply, don't close the arms with force, use a constant pressure or "feel"
Constant pressure also on the press arm, make sure it goes all the way, every time you seat a projectile.
When raising the ram, allow the projectile to partly seat in the case then lower the ram, turn the case through 180 degrees and raise the ram again and complete the seating.
Are you experiencing resistance when seating projectiles, what brand and type of sizing die are you using, Forster can hone the neck to avoid over-working the brass and to get the neck tension you require (I use 0.0015)

I also use the Hornady comparator and a Forster BR die, I have experienced variances in seating depth, and still do, but not as large as you report. I always check seating depth in all loaded cases before a match. I have just changed the spring in the seater die and also the seater stem but I am doing this to reduce very minor variances compared to those you are reporting.

Martin

 

[6BRinNZ]

I have found the following affects the Ease of achieving Seating Depth Consistency.

1./ rate at which the handle is moved
2./ amount of pressure at the end of the stroke
3./ Donuts in the neck (if seating that low)
4./ > .002" neck tension, especially with long bearing surface bullets
5./ Consistency of neck thickness, > .0005 - .001 variance from 1 case to the next will be problematic
6./ Consistency of the brass - annealing seems to help

I used to sort projectiles to try and achieve seating depth consistency, but I found the factors above play a greater part. I use a Redding Instant Indicator to measure the seating depth of every single round I fire and I am comfortable holding the seating depth to .002" ES (could probably achieve better but don't see the need at this point) by being careful with the above.

YMMV

Good luck

 

[nra-for-life]

hi guys, thank you for the replies thus far.

the brass is all the same (hornady, twice fired by me from the same gun)

the bullets are sierra 50 grain blitzkings (sorted by wieght to the nearest 10th)

the casings were all sized with a forster full length die. the seater and sizer are both used on the co-ax press... (the neck tension is a little high at .030, im waiting for an expander mandrel and will try to resolve this on my next reloading attempt with the forster bushing die)

the dies in the forster press have a little bit of play...unlike a regular press they slide in and are not tightened in as in a rock chucker or similar press. This is normal for dies to have some play in the co-ax press????

neck thickness has not been addressed, ie i have not turned or reamed the necks.

the loads are not compressed. the primers definitely` are not high, and i do believe i am taking pretty accurate measurements with the caliper, the measurements are repeatable.



based on what you all have told me thus far i should address neck tension and possibly the looseness of the die in the co-ax press.?

 

[6BRinNZ]

neck thickness has not been addressed, ie i have not turned or reamed the necks.

Since you have loaded rounds, measure the OD of them, then measure the seating depth. I found that cases with the thinner necks, invariable the projectiles seated up to .003" deeper. From what I can gather guys using no turn necks with Lapua brass have very consistent brass right out of the box.

Anyways, measure the OD of your loaded rounds (use a micrometer) and you will get a pretty good handle on whether or not the neck thickness is a culprit and needs to be turned. I would expect a relationship of thinner walls = greater seating depth to come out on average.

 

[LRPV]

With the Co-ax press the dies do fit a bit sloppy but that's just part of it. The die will be pushed up and stops against the part that holds the die. This is normal and I use the same press with the same dies. I got to thinking today and I remember having a similar problem and it was with a 22-250 and 50 Vmax when loading for a friend. His dad had re-sized the brass and it was all different headstamps and just a hodge podge of a mess with different neck tensions. Sounds like this isn't exactly your problem as the brass is all the same but I'm betting it comes down to varying neck tension.