Slugging a CZ 527 in 7.62x39 for cast - anyone have a box of .315 round balls?

[colonelhogan44]

I have 7.62x39 dies on order and a lee 312 185gr mold gathering dust from a failed attempt at paper patching 8mm years ago. I'd like to slug the barrel to get a better idea of what I'm playing with. I see some people using 0.315 round balls, but I don't really want to spend $20 on a box to just use one round ball...If you bought a $20 box and have 99 balls laying around, maybe we can work a deal! ;)

[cwtebay]

The best "on the cheap" method I know is to use a 5/16" bit to drill a hole into hard wood, pour your lead into it, split the wood to retrieve the projectile, and hammer it through.

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[rking22]

Egg sinker from the fishing tackle box. Throat is what is most important, and tends to differ. They are pretty good at getting the bore right nowadays.

[colonelhogan44]

Correct me if I'm wrong here, but if you drive a slug through the bore, how would that measure the throat? Isn't the throat always larger than the bore?

[Nobade]

I have one of those CZ rifles. The throat is military style, a big tapered cone. It will shoot anything that can be chambered. Don't worry about sizing your boolits, just load and shoot. BTW, the twist is fast enough to stabilize 250s. It makes a great subsonic shooter with trailboss.

[colonelhogan44]

I have one of those CZ rifles. The throat is military style, a big tapered cone. It will shoot anything that can be chambered. Don't worry about sizing your boolits, just load and shoot. BTW, the twist is fast enough to stabilize 250s. It makes a great subsonic shooter with trailboss.

I was actually planning on loading a bunch of plinkers with red dot, and I have a bunch of powder coated cast 309 bullets on hand from 110gr to 195gr. I'm hoping the bore is somewhat undersize. I'm planning to crimp a plain base gas check on with a 0.311 sizing die and hoping it works well. A 30 caliber at subsonic velocities are so fun, like a glorified 22lr.

[Nobade]

Be careful with that. I tried the same thing and the cases got shorter each time I fired them until they had so much headspace they wouldn't fire.

[colonelhogan44]

Be careful with that. I tried the same thing and the cases got shorter each time I fired them until they had so much headspace they wouldn't fire.

What was the cause of that? I'm planning to neck size only after I run through the 1000 once fired cases I have coming.

[Nobade]

What was the cause of that? I'm planning to neck size only after I run through the 1000 once fired cases I have coming.The primer blast is powerful enough to drive the case forward to let the chamber push the shoulder back, and the light loads don't make enough pressure to push it back against the bolt face. Same thing if you do that in 35rem or 35 whelen or anything with a small shoulder like that.

[colonelhogan44]

Interesting. I've been loading 4.0 gr red dot under a 158gr cast in 300blk recently. I imagine those loads will have the same issue.

[Nobade]

Interesting. I've been loading 4.0 gr red dot under a 158gr cast in 300blk recently. I imagine those loads will have the same issue.Could be the blk case is small enough to boost pressure high enough to avoid that. You'll find out soon enough.

[rking22]

What I was getting at about the throat is to do a pound cast instead of checking the bore only. You are probably going to find the barrel to be .310 to .311. I would still try your bullets, the fast powder just might bump them up enough to shoot well, give them a try. If you PC, you can probably get them big enough, I don’t PC so that is just assumption on my part.The shoulder setback issue needs to be watched, some drill the flash hole larger to help with that. Others have more experience there, I only load really light in rimmed cases mostly. I have tried 2.7 bullseye with a few bullets in my NO1 but not enough to confirm. I would think the case taper on the 7.62x39 might help in that regard if neck sizing only ????

[colonelhogan44]

Could be the blk case is small enough to boost pressure high enough to avoid that. You'll find out soon enough.

We'll see. The first loads only had soot on the neck and appeared to have fireformed completely. For the 7.62x39 the charge weights will be heavier and the velocity higher anyway, so I'll shoot for a load that fully forms the cases and then I'll neck size only.


What I was getting at about the throat is to do a pound cast instead of checking the bore only. You are probably going to find the barrel to be .310 to .311. I would still try your bullets, the fast powder just might bump them up enough to shoot well, give them a try. If you PC, you can probably get them big enough, I don’t PC so that is just assumption on my part.The shoulder setback issue needs to be watched, some drill the flash hole larger to help with that. Others have more experience there, I only load really light in rimmed cases mostly. I have tried 2.7 bullseye with a few bullets in my NO1 but not enough to confirm. I would think the case taper on the 7.62x39 might help in that regard if neck sizing only ????

I'm planning to seat a plain base GC on them with a .311 sizing die. Hopefully that will make them work fine, and the aggressively tapered case will help with the shoulder setback. We shall see.

[Silvercreek Farmer]

You can also open up the flash holes with an appropriate size drill bit to prevent shoulder setback. Do a search to see what size bit people prefer.

[colonelhogan44]

You can also open up the flash holes with an appropriate size drill bit to prevent shoulder setback. Do a search to see what size bit people prefer.

Interesting. I'll probably just make sure the pressures are high enough to fully form the casing. I'm not in a suppressor friendly state, so keeping things low pressure and subsonic is not as important as good accuracy and performance.