7.62x39 Seating Depth

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Potashminer

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So, this cartridge is a new one for me - I went through the commotion to determine that a COAL (Bolt face to bullet ogive hard on the lands) gets me 2.250" in this previously owned Savage rifle that I recently acquired, but have never yet fired. The first shocker to me, was the detachable magazine will accept much longer rounds than that!!

So, backing off 0.030" for some "jump" to the lands, results in perhaps .100" seating depth - I wonder if that is correct? - strikes me as maybe "hanging on by toe nails" compared to 30-06, 7x57 and other rounds that I reload for. Then I measured the case neck - there is not even a "caliber" worth of neck on the case - so must be going off an entirely different concept than I have been used to using - 1. Loaded rounds must fit into the magazine. 2. At least "some" bullet jump to the lands - do not want hard contact. 3. Seat bullet about a "caliber" deep.

I must admit to not finding just a whole bunch on Internet about reloading for 7.62x39 with soft point expanding bullets for hunting purposes - as if most that is written / discussed seems to be about lowest cost, Full Metal Jacket for "blasting away" ammo for various semi-auto rifles. Does the 7.62x39 go with a very shallow bullet seating depth - at least with 123 grain bullets?
 
You have a barrel with a long throat, so with short and/or "pointy" bullets you'll either seat shallow with a small jump like you did, or seat deep and have lots of "jump" before the bullet engages with the rifling. Either can be quite accurate.

Two problems can arise:

1. there isn't enough "grip" on the bullet; and
2. there is a point where the bullet is completely out of the cartridge neck and not yet engaged with the rifling, in "limbo" so to speak. This can cause hangfires - not good.

It look like #2 won't happen in your rifle with that bullet, but 0.100" is quite minimal. The "rule" that bullets must be seated at least one bullet diameter deep in the neck, is a "guideline" - if it was a rule, it's one I've broken several times.

That said, if the combination you described works for you, it ain't broke, if not, your alternatives are to use bullets that are longer (and usually heavier) and/or with a more round-nosed profile.
 
Thanks, Andy - you are correct - to paraphrase from your last paragraph, "if it works, it ain't broke". And that is to be determined by firing the thing - does it feed, fire, and send bullets "close enough" to each other, for my needs?

I found some AA2230 powder, some Barry's Plated .310" 123 grain bullets - and various S&B previously fired brass - so is what I want to try to "make work". Is many other loadings and components that could be used, but these are the items that I have on hand - to be seen, if I can make them "work". I was a bit concerned that I was making some sort of "gross error", since the combination of brass and bullet seemed to result in such short (to me) bullet seating depth. I will be trimming all cases to attempt to get similar seating "grip", then I plan to use a Lee FCD to crimp the case mouths - something I do not normally do for bolt action rifles - this 7.62x39 seems to be "different" than other case designs.
 
I shoot Hornady Interlock SP 123g and Hornady sst 123g. With my CZ 527, I seat both the Interlock sp and the sst bullets 0.020 from the lands (Base to Ogive). The sst gives me 0.5" 3 shot groups consistently at 100 yards. The Interlock sp shoots 0.5-1.5" groups, not as consistent as the sst.

The sst seating makes the overall length of the cartridge longer than the max length specified in manuals. The Interlocks are within the max.

For Barnes ttsx bullets, i seat them at 0.075" from the lands, and get 1.25" groups.

I experimented with CFE-BLK, Reloader 7, H4198 and IMR 4198, and at the end settled on CFE-BLK.
 
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