Lads and Lassie's,
Having problems reloading for my CZ carbine. Some reloads won't chamber, others show just a slight dimple in the primer and won't always fire. Don't want to develop a flinch.
S&B factory ammo chambers a bit hard, but always goes off. Also shows that the rifle is very accurate, so I'd like to shoot it more.
Question: where does the cartridge headspace? Shoulder, case mouth?? I'm having a tough time trying to figure out which case OAL is proper as well.
I've tried chambering unloaded cases, but I'm always wondering if neck expansion after loading a bullet alters that method as well.
Is there an "absolute" standard for the dimensions of this round? I'd be able to start from there.
Tried seating the bullets to different lengths, and unless it's waaay out there, it doesn't seem to be the problem - ergo, I think it must be the cases.
Currently trying to load Winchester new, unprimed brass - but I'm still not sure to what length it should be trimmed.
Any and all advise is appreciated.

Mike

Si vis pacem, parabellum!

quote:

Originally posted by Michael A. Glass:
Lads and Lassie's,
Having problems reloading for my CZ carbine. Some reloads won't chamber, others show just a slight dimple in the primer and won't always fire. Don't want to develop a flinch.
S&B factory ammo chambers a bit hard, but always goes off. Also shows that the rifle is very accurate, so I'd like to shoot it more.
Question: where does the cartridge headspace? Shoulder, case mouth?? I'm having a tough time trying to figure out which case OAL is proper as well.
I've tried chambering unloaded cases, but I'm always wondering if neck expansion after loading a bullet alters that method as well.
Is there an "absolute" standard for the dimensions of this round? I'd be able to start from there.
Tried seating the bullets to different lengths, and unless it's waaay out there, it doesn't seem to be the problem - ergo, I think it must be the cases.
Currently trying to load Winchester new, unprimed brass - but I'm still not sure to what length it should be trimmed.
Any and all advise is appreciated.

Mike

Si vis pacem, parabellum!

Mike,

The 7.62 X 39 m/m headspaces on the shoulder of the cartridge. I once owned a Ruger MK II-77 chambered for the 7.62 X 39 m/m round had found it necessary (when using .308" bullets) to only neck size my cases or there would be a headspace issue, like misfirings. By neck sizing the cases and using .308" bullets this solved the problem. If you are using the standard .310" 7.62 bullets that weigh 123 grains then you should have no problems with your reloads. They can either be neck sized or full length sized. Also you might want to check the adjustments on your sizing die. One more thing, try Full length sizing your cases as if you are going to reload with .308" bullets and fire a primed (not loaded) case in your rifle. If the primer backs out this try another case that has been neck sized to see if it does the same. I know that the Ruger Rifles had a long throat and this might be true of the CZ models also. Hope this helps!

the maximum case length is 1.525 and the trim to length is 1.520

Your easiest bet is to buy a cartridge gauge and USE IT. I had the same rifle and had the same problem as you. The problem lies with your reloading dies. According to my case gauge it was possible to push the shoulder back over .020"! too far if I wasn't careful resizing.

I tried to figure out the cause of this for years and only did so after buying the aforementioned gauge. I had always mistakenly blamed either cci primers or the rifle

Thanks for the info.
Question - can you set a regular RCBS die to "neck size" only??? Or do I have to buy a special die?? Never really ran into this problem before.
What about fire forming?? Might that help as well?
Again, thanks for the info.
Mike
Si vis pacem, parabellum

quote:

Question - can you set a regular RCBS die to "neck size" only???

Yes! you just don't screw the die in against the shellholder.

This is supposed to be the "Accurate Reloading" forum, yet I find that many folks do not understand one of the fundamentals of reloading dies: They are NOT designed to simply be screwed down hard agaist the shell holder head. Doing so will frequently create excessive headspace (depending on the depth of your reloading dies, the thickness of your shell holder, and the cut of your chamber.) This practice will also overwork your brass and cause case head cracks or separations.

Only screw the die into the press far enough that the resized case easily re-enters the chamber. Any more is creating a situation where there is more headspace than is desirable. Sometimes, if the die is deep, the shellholder lips are too thick, or the chamber is short, you must run the die all the way down; I have even had circumstance where I had to grind some thickness off of the shell holder in order to get the case to resize enough.

All of that notwithstanding: Michael Glass, if you are using surplus military ammunition, it is frequently difficult to set off with a sporter firing pin. The military primers have a thicker/harder cup than commercial primers, and military rifles have a heavier firing pin fall. If your problem is with reloaded rounds, then start with your reloading die .05" off of the shell holder and adjust it downward incrementally until the resized brass enters the chamber with acceptable resistance. This will ensure that each round is held firmly against the bolt face and that when fired the case stretches minimally.

quote:

This is supposed to be the "Accurate Reloading" forum, yet I find that many folks do not understand one of the fundamentals of reloading dies: They are NOT designed to simply be screwed down hard agaist the shell holder head. Doing so will frequently create excessive headspace (depending on the depth of your reloading dies, the thickness of your shell holder, and the cut of your chamber.) This practice will also overwork your brass and cause case head cracks or separations.

While completely true you also know as well as I do that there's also about a 1/2 kagillion threads out there where people who DON'T cam their presses over against the shellholder at the top of the stroke are left asking if they need small base dies to reload for X rifle.

So as you point out the answer can go both ways depending on the rifle.

quote:

Only screw the die into the press far enough that the resized case easily re-enters the chamber.

this only really works well with a bolt action. I've gotten brass unbelievably stuck attempting use this method on other actions with much less powerful extraction.

IMO there is only one way to correctly set up your FL die. That is to use a gauge like the Stoney Point Head and Shoulder Gauge. Measure your fired brass and set your dies accordingly.

Sure you can do it the touchy feely way. Adjusting the die in or out until you have the slightest "crush fit" then adjusting the die in or out just a tad for no crush fit or more crush fit. The problem with this method is that it is not consistent. The only way to be sure that this method is "dead nuts" is to chamber each and every piece of resized brass. Pain in the ass. Much easier to check the head to shoulder length with a gauge instead of the chamber.

And NO, you cannot truely neck size with an FL die. Oh, there are those out there that say you can, but in reality it is not possible. At some point the case body will come in contact with the FL die. At what point this happens depends on things like chamber dimention, case design/amount of taper and number of firings. If you want to neck size purchase a neck die.

quote:

Originally posted by Michael A. Glass:
Lads and Lassie's,
Having problems reloading for my CZ carbine. Some reloads won't chamber, others show just a slight dimple in the primer and won't always fire.

Any and all advise is appreciated.
Mike

Si vis pacem, parabellum!

Mike,
Have just gone through exactly the same problem with the 458AccRel ... die was pushing the shoulder way too far back. Serves me right for reloading in a hurry.

Does your CZ use a 0.308" or 0.311" bore? If its the smaller, many dies come with both expanders and you can probably use the 0.311" expander to open cases enough to create a bit of a false neck to headspace on.

Neck sizing with a FL die is a hit/miss affair. I tried it with my 8mmRemMag and the die was squeezing the shoulder enough to increase case length. Seriously ... just buy a neck sizing die and avoid the hassles.

The 7.62x39 is one case where headspace dimensions vary especially in ex-mil ammunition. There's a definite spec but the ex-mil brass can be quite different. Headspace was an issue in some target rifles that were built in Australia in 7.62x39 to use the cheap ex-mil ammunition available awhile back.
Cheers...
Con

Again,
Thanks for all your helpful advise. I'll incorporate it into my reloading practices.
BTW, I try to avoid "crunching" the brass - I (hopefully) do not "force" anything in the reloading process. I do set the dies to less than full length but a tad more than just neck-size.
I should have mentioned that I'm using new Win brass and CCI primers. I'll try trimming to 1.520 and see if it helps.
Haven't slugged the bore on the CZ, but I use 308 bullets exclusively. I've been shooting Sellier and Belloit ammo successfully (and accurately!!!), I'll spec some loaded and once fired ammo to see if anything interesting comes up.
Despite the fact that I've been reloading for years - I always seem to learn something new (as evidenced by my recent quandry). I'm always happy to welcome a new reloader to the community and assist them where I can. Glad this forum is respectful of those who do not possess complete knowledge in this field, but are willing to learn.
Thanks again, and please continue to offer advice to those w/honest questions.
Mike
Si vis pacem, parabellum.

To the best of my knowledge, ALL rimless, bottleneck type rifle cases headspace on the SHOULDER. Since case necks can vary in length significantly based on case trimming, I don't believe it would be very practical to try headspacing them on the case mouth!

I only "partially FL resize" my cases for the CZ 527 in 7.62X39mm, I have had no headspace problems. But my brass was all fired in the same rifle to begin with!

As long as you are seating the primers correctly, sounds like you are setting back the shoulder too far. Bet you are using RCBS dies. My set put the shoulder in another zip code. Take a look at a factory load after sizing yours and you might be able to tell the difference. I had a set of 350 Rem. Mag. dies that gave my cases osteoperosis, looked like a negative wildcat when set to contact position on the shellholder.

It can really be frustrating sometimes. I tell you, this is the best board on the internet. Folks here have patience and about 20 more I.Q. points than any other site. Good luck.