7.62x39 to 6.5 Grendel Loads

[triggerdog]

Might be too much effort but I have some Lapua brass a resized to 6.5 Grendel, Right now I am shooting 6.5 Hornady Brass with cci br 4 primers and 31.5 grains of Varget using 85 grain Sierra Varminteer bullets, I have about 900 of these. What type powder would be a start for the resized brass with the LRP instead of small, My though was to drop down to 27.5 grains of Varget since that's what I have and with the above combo it shoots much less than MOA

Yes I know just buy 6.5 Grendel Brass but that's not interesting

 

[justpassinthru]

Those bullets are special, wish they'd kept making them.
I can't help with your question because I've never done what you're doing but suspect you're on the right track. What size flashhole does the 7.62x39 have? I wouldn't want to change anything with that.

 

[triggerdog]

Justpassingthru, I dont know the size

 

[Laurie]

It's difficult to predict the effect of the primer / flash-hole size change on a small cartridge like this pair. (Lapua 7.62X39 has the usual 2mm / 0.079" flash-hole, not the 1.5mm / 0.059" PPC, BR, 308 Palma etc size. Note too that unlike Lapua some makes of 6.5G brass have small primers allied to a 2mm flash-hole, just to confuse!)

The standard answer is that assuming all other things remain the same (primarily fireformed case capacity), the large primer / flash-hole will produce a substantial pressure rise and charges should be reduced significantly and worked up again. This certainly applies to larger cased models such as 6.5 Creedmoor and 308 Win. Received wisdom also says that this effect will be more pronounced in a small case like 7.62X39mm / Grendel than in say 308 Win. However, when I tried Hornady and Remington cases in 6.8mm SPC side by side some years I saw no difference at all in either MVs or the size of ES/SD values, very much to my surprise. (Rem SPC brass is LP; Hornady SP; both makes 2mm flash-hole.) The flash-hole difference may make as much if not more change than the primer.

There are two other factors to consider: individual primer model performance and case-head strength / brass life. In tests I did some years back in 308, I found little variance between SR primers in Palma brass but very large performance variances in the large variety in standard Lapua cases. So, choose as mild an LR primer as possible. Then on case strength / life, early 6.5G PPU brass was LP + 2mm, now changed to SP + 2mm. Users of the older variety report poor case life on the 65grendel.com forum due to case-head expansion leading to loose primer pockets. As you already have the spare brass, it's not a great issue, more about returns on your time reforming the cases. (You may need to neck-turn too after the relatively large neck reduction from 30 to 26.)

It's not the first time this sort of conversion has been done. Glen Zediker describes buying cheap 7.62X39mm commercial brass and reforming it to .22PPC for XTC shooting in one of his AR-15 books.

 

[mac86951]

Those bullets are great; and perfect for fire-forming the 7.62x39 into Grendel.


Sorry I don't use varget in my Grendel, but this may help you out. Same 85gr loaded with 29.0gr of h335. So the kicker is case volume is reduced; this was a firm stout load for fire-forming; cci200 was flat, but no other sign if pressure and a nice sharp shoulder was made. From a 20" barrel I was clocking 2800fps, which also would say, mighty hot.

I was using a variety of 762 brass, and if you kept to a starting load that would be better. I don't see that sierra listed varget with the 85; their starting load is 27.2 varget with the 100gr; so around there. A cheap ball powder would make loading the 762x39 cases easier for first firing, and remember when you're done they're not the same as 6.5 Grendel for load data. Still plenty accurate though and hurts far less when one gets tossed into the neverending weeds.

Have you already started the neck-down process? You'll want to check case neck thickness to your chamber if you can; measure o.d. of fired Grendel case and od of resized brass. What's the guideline, 0.001" clearance min?

-Mac

 

[justpassinthru]

Those bullets are great; and perfect for fire-forming the 7.62x39 into Grendel.


Sorry I don't use varget in my Grendel, but this may help you out. Same 85gr loaded with 29.0gr of h335. So the kicker is case volume is reduced; this was a firm stout load for fire-forming; cci200 was flat, but no other sign if pressure and a nice sharp shoulder was made. From a 20" barrel I was clocking 2800fps, which also would say, mighty hot.

I was using a variety of 762 brass, and if you kept to a starting load that would be better. I don't see that sierra listed varget with the 85; their starting load is 27.2 varget with the 100gr; so around there. A cheap ball powder would make loading the 762x39 cases easier for first firing, and remember when you're done they're not the same as 6.5 Grendel for load data. Still plenty accurate though and hurts far less when one gets tossed into the neverending weeds.

Have you already started the neck-down process? You'll want to check case neck thickness to your chamber if you can; measure o.d. of fired Grendel case and od of resized brass. What's the guideline, 0.001" clearance min?

-Mac

For fire forming? The way they shoot in everything I've used them in I certainly wouldn't be fire forming with them. If you have some to get rid of I'll trade you some fire forming bullets and pay some $'s too. I'm down to only 1400, they are NLA and out of stock everywhere I've checked.

 

[justpassinthru]

I have some 335 thanks

I've used Ramshot TAC and N133. Both work very well.

 

[yotehater]

H322 works well for the lighter bullets.

 

[triggerdog]

The new prepped Lapua Brass resized to 6.5 Grendel is .010 neck thickness and the twice fired Hornady is also .010

 

[rockhound78]

I have also re-formed w-w and lapua x39 brass to 6.5g. I drop my fireforming charge about 3gr from what I am using in the 6.5g (benchmark) and use the cheapest bullet I can get near the same weight. I would NOT use those 85gr bullets to fireform, they are unobtanium.

I lucked into some 139gr prvi fmj bullets, so thats what I use if I need to turn some x39 to 6.5g

 

[triggerdog]

1. I have also re-formed w-w and lapua x39 brass to 6.5g. I drop my fireforming charge about 3gr from what I am using in the 6.5g (benchmark) and use the cheapest bullet I can get near the same weight. I would NOT use those 85gr bullets to fireform, they are unobtanium.
   
   I lucked into some 139gr prvi fmj bullets, so thats what I use if I need to turn some x39 to 6.5g

   
   
   
   
2. Good Point on not using the 85 Sierra's , me and a friend bought 25 boxes directly from them

 

[AckleymanII]

If you can find any 7.62x39 brass made by PMC that is new, buy it! This is very tough brass even though it has the large primer pocket. I made many thousands of 22 and 6 PPC cases out of the PMC brass, still shooting the brass. Accuracy is outstanding to say the least for varmints, groups in the 2's easily.

Lot of work on this project, good Winter time project where you are house bound.

 

[triggerdog]

Thanks everyone, i went with 28.5 grains of H 335 and 85 grain Sierra Varminteer Bullets , Lapua Brass resized to 6.5 Grendel , necks .010 same as twice fired Hornady , and Federal Match LRP, Now, only if i could find an indoor range , its about 98 here right now

 

[Lone Hunter]

Thanks everyone, i went with 28.5 grains of H 335 and 85 grain Sierra Varminteer Bullets , Lapua Brass resized to 6.5 Grendel , necks .010 same as twice fired Hornady , and Federal Match LRP, Now, only if i could find an indoor range , its about 98 here right now

That is the same load I use for the 85 gr Sierra except I use a CCI Primer. Shoots extremely well but have yet to hunt with the 85’s. Have used the 123 Hornady’s and Killed a bobcat. DRT.. You will like the Grendel.

 

[triggerdog]

The 85 grain sierra's make the inside of a hogs head look like hamburger meat out of the 6.5 1 in 8 twist

 

[triggerdog]

I went out to the deer woods and fired off 3 rounds and brass looks great with 28.5 grains , also Sierra still have the 85g in stock , i just bought 10 more boxes

 

[mac86951]

I went out to the deer woods and fired off 3 rounds and brass looks great with 28.5 grains , also Sierra still have the 85g in stock , i just bought 10 more boxes

Nice!
I'll grab a few more boxes then. I hear the TNT 90gr shoot well too.

For those who don't understand; fire-forming does not mean less accurate; in fact quite the opposite. The 85gr are way cheaper than 123s though, so they get used.

-Mac

 

[triggerdog]

The Lapua necks grew from .010 to .013 in my chamber

 

[2506]

Sierra has discontinued making the 85gr bullet. Yes the 90 gr Speer TNT is a really accurate bullet but a bit tougher than the Sierra 85 gr. Those that have used the 90 TNT on hogs say they do a great job. Better than many so called "game" bullets that are heaver.

 

[triggerdog]

I have killed plenty hogs with 85g , makes the inside of the head look like hamburger meat