Bullet length/seating depth

[FLINT]

Hi all,

quick question. About to load up some 250 savage rounds.

I have a box of Sierra Varminter 87 gr. and a box of Speer Hot-cor 87 gr.

I was originally thinking that they would be interchangeable as far as loading. However, I held two of them up side by side and noticed that the sierra looked a little longer. So I measured 10 Sierras and then measured 10 Speers.

The Sierras were 0.014" longer on average.

Does that mean that I should load them to a longer COAL?

I was planning to load the Speers to 2.50"

Should I load the Sierras to 2.514" ?

The logic in my mind is that the above lengths would result in the same seating depth of bullets within the brass which should keep pressures equal. Does that make sense?

Thanks!

[piller]

I am not an expert, and this is just an opinion that is worth what you paid for it. Load a dummy round to the longer COAL and check how it cycles. Does it touch the rifling? How is it for fit in the magazine? If it does not touch the rifling and fits the magazine, then load it to the longer COAL without any change in powder, and it should be the same chamber pressure. Touching the rifling will increase pressure. Fitting in the magazine is necessary.

Hopefully someone with more experience will come along soon and help out.

[44shooter]

Theoretically your thoughts are sound that loading the two bullets to the same base depth would yield similar pressure. However things like bearing surface and jacket hardness affect pressure too. I doubt there is much difference in these bullets though but you need to work up loads for both independently. I think it will be fine to use the same setting on your seating die IF your rounds do not jam in the rifling and will fit your magazine.

Are you planning one for varmints and one for game?

[earlmck]

Pressure increases caused by seating depth changes are good to be aware of, especially in pistol cartridges where you can go critical in a hurry. In a bottle-necked rifle cartridge, however, the pressure increase from a .014" seating depth change is relatively minor (unless the change caused a jamming into the rifling which might increase things a bit more). If I play around in "QuickLoad" with that seating depth change in the 250 Savage it shows up as approximately the same as a 0.1 grain change in powder charge in a full-power load.

[FLINT]

Thanks all,

Yes, the other reason for loading them to a slightly different COAL is that from what I've read the Sierra Varminter bullets are less heavily constructed than the Speer Hot-Cor, and while the Speer bullet would be acceptable for Deer, the Sierra may not be. I'll obviously keep the loaded rounds in separate labeled containers, but just in case I can always measure to verify.

I loaded up some of the Speers a couple days ago and 32 grains of 3031 gave an average velocity of 3020 and good accuracy. My rest wasn't very solid so not the best day to really test for groups, but seems like it will work.

BTW, even if I load the Sierras out to 2.514, they should still function fine as the max coal for the 250 savage is 2.515 - but I will definitely test one out before I load a bunch.

one question about checking to see how far off the rifling the bullets are sitting:

I tried googling this but I couldn't find this method suggested anywhere so tell me why this wouldn't work.

What If I took a case that I just fired from this rifle - and pushed a bullet by hand into the neck. I've done this before and the bullet is snug but I can push it in and out by hand. If I leave the bullet sticking a good ways out of the case and then put it in the chamber and close the action slowly and gently, shouldn't that push the bullet into the neck so that when I eject the dummy bullet that coal length is where the bullet touches the rifling? I guess the worst that would happen is that the bullet could 'stick' into the rifling and I'd have to tap it out with a dowel or something but that's not a big deal, but I don't think that would happen since the bullet moves pretty freely within the brass case neck, so there isn't so much pressure there to stick the bullet into the rifling.