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gqjohno
03-07-2015, 07:26 PM
I am new here and have been advised you fellas are the ones to ask

I have a CZ 527, 7.62x39. I want to improve the case to squeeze a bit more velocity and was going to run a PPC reamer 0.150" deeper into the chamber to keep same COL & neck length, but gain the straight walls and better shoulder angle.

After discussing this with blokes on the campfire it seems the better option is the 30 Major or Gremlin, I think they are the same.

But this is a .308 and I want to keep to .310 and use the 123grn Hornady SST. I believe this case will get me closer to 2,500fps.

So how best to go about this, do I just get the smith to use the 30 Major reamer and neck ream for for the .310 or get a reamer made, cost is a factor now i'm retired.

Appreciate any tips

John

Dusty Stevens
03-08-2015, 12:00 AM
I would set the barrel back and use one of the 30ppc variants. Dont just run a reamer in deeper- set it back to eliminate all of the old leade and chamber. If your gunsmith is any good he can line the writing up to look factory

mwezell
03-08-2015, 11:53 AM
I am new here and have been advised you fellas are the ones to ask

I have a CZ 527, 7.62x39. I want to improve the case to squeeze a bit more velocity and was going to run a PPC reamer 0.150" deeper into the chamber to keep same COL & neck length, but gain the straight walls and better shoulder angle.

After discussing this with blokes on the campfire it seems the better option is the 30 Major or Gremlin, I think they are the same.

But this is a .308 and I want to keep to .310 and use the 123grn Hornady SST. I believe this case will get me closer to 2,500fps.

So how best to go about this, do I just get the smith to use the 30 Major reamer and neck ream for for the .310 or get a reamer made, cost is a factor now i'm retired.

Appreciate any tips

John

Hi John,
You have a decision to make, as I see it. First, I agree with Dusty in that it would be best to set back, if only for the fresh throat. Herein lies part of the decision. Not only is it a good idea, but the x39, while does have less capacity than the 30 Major, is several thou longer at the datum. So, setting it back is pretty much necessary in this case....unless, you choose some other method of headspacing, such as a false shoulder. Then you get into die issues.
You said you were on a budget, so I'm bringing these things up. It's not that it can't be done, but these things change the overall cost.

That said, I don't agree with him about using a 30PPC variant. I simply don't see the appeal. The Grendel brass being top quality and available being the most important reasons, but so is case capacity. The 30 Major could be viewed as a 30PPC variant, I suppose, but one that is .070 longer and requires no forming of brass..just neck it up and shoot.

Also, you're underestimating velocities, IMHO. In my bench rifles, I've been able to get well over 3,000 fps from the 30 Major. Brass life is good if dies are a good fit relative to the chamber and if velocities are kept at or just under 3,000 with 110-125 grain bullets. Granted, that's in a custom actioned bench rifle. You're max may be considerably less, but I still think well more than the 2,500fps you mention. I have an AR15 specific reamer that I use for gas guns. Max velocities from an AR15 with an 18" barrel are around 2,650fps..the gun being the limiting factor.

Even if you do a x39 Improved, you run into the same issues with needing to set the barrel back to do the job properly. This, in itself, can pose problems for some smiths, being a metric thread. Some have worked around that by using a near fit 20tpi thread.

Bottom line I guess, is speed costs money...How fast do you want to go?--Mike

Dusty Stevens
03-08-2015, 02:21 PM
I was counting a grendel as a variant. Anything with the 7.62x39 bolt face and lapua brass

jackie schmidt
03-08-2015, 02:43 PM
That CZ barrel is in all likely hood hammer forged, and can have a significant RC hardness on all of the surfaces, including the chamber walls.

And if you have ever chucked up one of these hammer forged barrels, just finding two spots that run true can be a challenge.

A gunsmith might ask you to supply your own reamer, (probably carbide),and make no guarantees.

Gene Beggs
03-08-2015, 03:01 PM
This may not be what you want to hear but here it is; the truth.

Leave that little CZ alone. Keep it clean and original. If it's not what you want, sell it or trade it for something else. Bastardizing a fine firearm is always a mistake.

Hope you'll take this advice and save yourself lots of money and frustration.

My opinion, for what it's worth.

Gene Beggs

Greyfox
03-08-2015, 03:17 PM
This may not be what you want to hear but here it is; the truth.

Leave that little CZ alone. Keep it clean and original. If it's not what you want, sell it or trade it for something else. Bastardizing a fine firearm is always a mistake.

Hope you'll take this advice and save yourself lots of money and frustration.

My opinion, for what it's worth.

Gene Beggs

Damn good advice!

Rick

gqjohno
03-08-2015, 06:45 PM
I thank you for all the help and advice, maybe I got a little carried away with all ive read about the 30 major. It just seems to me its screaming out to be chambered in short action CZs as a hunting round.

Gene, that is exactly the advice ive been given down here, I use the 123grn SST only, the rifle shoots 3/4" group 3 shot one hole. You really can't ask for any more in a short barrel carbine. Its just the i'm showing an average of 2,240 fps with 27grn of RL-7 I would have liked to be up around the 2,500 fps.

The other advice ive had is find another cheap CZ, buy a pac nor barrel and have Mike or someone else chamber it for the 30 major. Wish I could afford that.

I think after taking onboard what you fellas have said I think i'll leave the little rifle as is and try and find another powder to get a bit more velocity

Thanks
John

mwezell
03-08-2015, 07:05 PM
I thank you for all the help and advice, maybe I got a little carried away with all ive read about the 30 major. It just seems to me its screaming out to be chambered in short action CZs as a hunting round.

Gene, that is exactly the advice ive been given down here, I use the 123grn SST only, the rifle shoots 3/4" group 3 shot one hole. You really can't ask for any more in a short barrel carbine. Its just the i'm showing an average of 2,240 fps with 27grn of RL-7 I would have liked to be up around the 2,500 fps.

The other advice ive had is find another cheap CZ, buy a pac nor barrel and have Mike or someone else chamber it for the 30 major. Wish I could afford that.

I think after taking onboard what you fellas have said I think i'll leave the little rifle as is and try and find another powder to get a bit more velocity

Thanks
John

I'm not sure, but again, the rifle will probably be the MOST limiting factor, along with brass.
The x39 is certainly capable of more speed than that if the gun and brass can handle the pressures. Most data for the x39 is based on sks or ak service rifle pressure limits. I'm not saying to jump in with both feet and get yourself hurt, but I think the cz will take considerably more pressure than the sks type service rifles can stand, therefore, with the right powders, I think you can find more speed than what you are seeing. I'm assuming you're using published loads for the x39, which limits it to 45,000psi.

You're on your own when loading hotter than published data, so if you're not 100% competent at recognizing pressure issues, seek help from someone that is, locally to you and proceed with caution.

gqjohno
03-08-2015, 08:31 PM
Mike

Thanks again, i'm slightly over the Hornady manual at 27grn of RL 7, but absolutely no sign of presure. Vhit N-120 might be worth a try I think.

Unfortunately down here in Australia we don't get the Accurate Arms line of powder, would love to use 1680 in my 19 badger and in this x39

John

mwezell
03-08-2015, 10:21 PM
You should be able to see great improvement with the rl-7 and h-4198 well before you run out of room. 120 is pretty fast and very hard to find or afford here.

M Casselton
03-12-2015, 05:29 PM
Give that a try. 1680 is fantastic but really designed to manipulate the actions in the x39. Wish I could trade the two jugs of 2200 I have for 1680 for use in my 17 hornet. If you were here in the states, bob green would be the guy to take the project on. I do have to say that if I had the gun, I'd be torn between keeping it original and making it something like a 6 or 30 PPC
All of my other CZ 527 rifles remain as built except for trigger adjustment. I'm almost afraid to bed them, they shoot so well...

gqjohno
03-14-2015, 09:44 PM
I am going to try some different powders and boost the RL-7. I have no presure signs at 27.0grn A friend ran some nombers on top shot and came up with what he reckons should ork safely 28.5grn RL-7 + 2498 fps presure at 55,000 PSI I will work up carefully and see how I get on

John