7.62 brass conversion

[NightStalker]

I just found a video on converting 7.62x39 to Grendel brass, is this a good idea?

Ive never converted brass to a different caliber just wondering it weakens the brass or if anyone has had any problems doing this.

[tdbru]

NightStalker,
i've done this. back when Grendel brass was difficult for me to get, and 30 Rusky short was available in 5 gallon buckets for free, and i had more time then $. it's a LOT of work to do correctly. you have to do at least 2 neck anneals, neck turning, fireforming. and most 30 Rusky short is LRP not SRP. so your load data needs adjusting too. is it worth it? if you can't get 6.5 Grendel brass or ammo, yes. If you can get 6.5 Grendel brass or ammo. no. unless just for the educational aspect of it or if you just like to tinker, which is fine too. or like me at the time, lots of free 30 Rusky short brass. not lots' of spare $ to buy 6.5 Grendel brass or ammo. enough time and tools already on hand to do the job correctly. my opinion of course. everyone else's may be different.
-tdbru

[Lemonaid]

I have converted some Lapua 7.62x39 to 6.5 Grendel as an experiment, 20 rounds. At first I though it was not worth it as is decreased case capacity, but reviewing my results, the velocity gain from going to a large primer (Fed 210) made up or exceeded for the loss of powder in the case.
This test was in my Ruger (RAP). Some day I will revisit this test to confirm.
In the early posts on the forum the reports were that the primer pockets loosened up after 3x or so reloads so when actual factory Grendel bass was available everyone pretty much abandoned reforming.
As an interesting relating aside, on PrecisionRifleBlog what the pro's use in 6mm Dasher by 5 to 1 they used CCI 450 primers in their loads, so that's another validation for them in the Grendel.

[A5BLASTER]

I just found a video on converting 7.62x39 to Grendel brass, is this a good idea?

Ive never converted brass to a different caliber just wondering it weakens the brass or if anyone has had any problems doing this.

I thought about doing it but the loss in case capacity compared too grendel brass isn't worth it too me.

[LR1955]

This is nothing new. Run a search and find out everything you want to know about sizing and using 7.62 X 39 brass for the Grendel.

You will get the following.

10% loss of brass sizing it down.

Must fireform after sizing down.

Will get two or three more shots before the primer pocket opens up.

Velocities will be lower, no matter what Large Rifle Primer you use.

We did it because there was no Grendel brass available, sometimes for five or six months straight.

With Hornady and other companies making real Grendel brass, using 7.62 X 39 brass is a waste of time and effort.

LR55

[NightStalker]

[LR1955]

NightStalker,
i've done this. back when Grendel brass was difficult for me to get, and 30 Rusky short was available in 5 gallon buckets for free, and i had more time then $. it's a LOT of work to do correctly. you have to do at least 2 neck anneals, neck turning, fireforming. and most 30 Rusky short is LRP not SRP. so your load data needs adjusting too. is it worth it? if you can't get 6.5 Grendel brass or ammo, yes. If you can get 6.5 Grendel brass or ammo. no. unless just for the educational aspect of it or if you just like to tinker, which is fine too. or like me at the time, lots of free 30 Rusky short brass. not lots' of spare $ to buy 6.5 Grendel brass or ammo. enough time and tools already on hand to do the job correctly. my opinion of course. everyone else's may be different.
-tdbru

td:

Never annealed the brass but did have to run an internal neck reamer through the necks after sizing and then after the fireforming. Not sure why but those 7.62 X 39 cases (IMI and Remington) I had that were brand new would get a big donut where the shoulder and neck intersected. So, run a inside reamer through them and take out the donut, then get two more loads before the primer pockets opened up too much for it to be safe.

Guys used the 7.62 X 39 brass for hunting from what I remember because it didn't matter if they lost the brass. Back then real Grendel brass was very hard to find. Alexander would get one or two shipments a year and it would be gone in a week or two.

LR55

[NightStalker]

I might convert some if i run into some 7.62 brass just to learn how to do it. Ya never know it might come in hand at some point

[LR1955]

I might convert some if i run into some 7.62 brass just to learn how to do it. Ya never know it might come in hand at some point

NS:

Nothing to learn really. Run it up into the Grendel sizing die then fireform to blow it out. Two or three more firings and the primer pockets are too loose. Might as well try it to see that it is not a big deal and that it doesn't last long. You may need an internal neck reamer for the donuts but that will be up to you.

LR55

[GregP42]

Not hard to do, but not really worth it anymore. I have about 300+ pieces still, I use them when I am hunting now so I don't care if I loose them.

Greg

[tdbru]

when you neck down, the neck wall thickness increases so you end up needing to do neck turning to restore correct neck thickness. some do inside turning (reaming), others do outside neck turning to get the neck thickness to the correct value. as almost everyone has said, we did this when Grendel brass was hard to get. it's quite time intensive so now that correct brass is more readily available, it just doesn't seem too time efficient to do other than educationally to me anymore.
-tdbru

[LR1955]

when you neck down, the neck wall thickness increases so you end up needing to do neck turning to restore correct neck thickness. some do inside turning (reaming), others do outside neck turning to get the neck thickness to the correct value. as almost everyone has said, we did this when Grendel brass was hard to get. it's quite time intensive so now that correct brass is more readily available, it just doesn't seem too time efficient to do other than educationally to me anymore.
-tdbru

Never had to neck turn one round and I used the tighter of the Grendel Chambers.

I did use a .289 neck sizing collet though because yes, the neck walls are thicker. They still chambered just fine in the tighter match chamber.

In fact, when we had to use the 7.62 X 39 brass, I do not recall anyone neck turning it.

I was the only one who ran an internal reamer through them to take out the donut. I think this gave me one more shot before primers fell out of the primer pockets.

Yes, the brass was thicker. Yes, it probably caused higher pressures. Yes, it worked. But no one really cared if they lost any, either

Not worth the time spent neck turning but may be worth the time to take out the donut.

LR55

[SPECTRE66]

Hi All,
I just posted earlier, in the Reloading section, about fire-forming some brass. I've just completed resizing 4K rounds of Winchester 762X39, to 6.5G.
My question was, with a 123gn bullet over 25.0 gn of WIN 748, will I incur a pressure spike, due to the large rifle primer.
Since some of you have 'more than dabbled' with the 762X39 conversion, and you're still here, I think it's safe to infer I'm on solid footing, regarding fire-forming.

[Lemonaid]

Speer's web data for 120 gold dots start at 25.7 for Win 748. A chronograph will aid in keeping to safe levels. Primer selection also will play it's part. This link is quite good for grading primers from mild to hot.

http://www.sksboards.com/smf/index.php?topic=56422.0

[LR1955]

Hi All,
I just posted earlier, in the Reloading section, about fire-forming some brass. I've just completed resizing 4K rounds of Winchester 762X39, to 6.5G.
My question was, with a 123gn bullet over 25.0 gn of WIN 748, will I incur a pressure spike, due to the large rifle primer.
Since some of you have 'more than dabbled' with the 762X39 conversion, and you're still here, I think it's safe to infer I'm on solid footing, regarding fire-forming.

SP66:

Pressure spike? Who knows?

We had to use less powder because the 7.62 X 39 brass is much thicker than Grendel brass and so had less volume and thus probably produced higher pressures.

After messing with the 7.62 X 39 brass formed to fit the Grendel chamber quite a lot, I found the donuts that appeared in about 80% of the cases after either the fireforming or first shot to be more worrisome when considering pressures. A donut is like a bore obstruction in the brass itself and is a prime cause of blowing primers and other pressure issues. Luckily I had an internal reamer that was small enough not to take off the inside of the neck but big enough to cut through the donuts that appeared in eight or nine of ten pieces of brass.

Not sure how much any of it mattered since no matter what we seemed to do, we only got two or three shots after fireforming before the primers would start to blow or just fall out of the primer pockets.

4K pieces of that stuff ought to last you a while though. My advice is to buy a internal reamer and take out the donuts that will occur.

LR55