Fire forming 6.5 Grendel cases with Trail Boss

[Joe S.]

So I ended up with a bolt action 6.5 Grendel... my first in that caliber... in the middle of a pandemic and presidential election induced ammo and components shortage. I was able to secure 100 7.62x39 Starline cases, which takes large rifle primers. I traded into a set of Grendel dies and have sized all the brass. The next step is fire forming. I was lucky enough to be given 100 cast bullets so the plan is to fire form the brass with 7 gr of Trail Boss powder and these cast bullets. I have a LOT more large pistol primers than large rifle primers. I dont see why i couldn't use LPP to ignite the 7 gr of Trail Boss adequately enough to achieve my goal of a fire formed case. I am not after accuracy on this excercise, just a puffed case.

Am I right? Or missing the mark?



L to R: 1) Factory resized 6.5 Grendel case, 2) sized, fire formed, and resized 7.62 x 39 case, 3) sized but pre-fire formed 7.62 x 39 case.

[Joe S.]

So I tried one round with a magnum pistol primer It seated a little deeper into the primer pocket, but the striker did ignite it. For some reason the shoulder didn’t form as well as with rifle primers, so I decided not to chance it. I have a few hundred mag rifle primers and don’t ever load magnums, so i tried one of those as well. It seemed to do the trick just fine so that is what I loaded up all my fire form loads with.

Not sure if you can see the dimple in the shoulder on the one on the right but it is there.


Ready for a fun little plinking session.

[bigbrowndog]

Joe after sizing 7.62x39 down to 6.5G, I do not use a fireforming load per se, I load 95gr VMax bullets with a normal 120gr. bullet load and go shoot stuff like coyotes or jackrabbits. Then load as normal, so technically not a fireforming load but I guess it is.

Trapr

[Joe S.]

Thanks! I’ll keep that in mind next time. Those cast bullets do not do well loading from an AR mag in my American Predator. They were accurate enough (about 3” shooting fast at 50 yards with elbows resting on my bench), they just dont load that well.

And i guess you dont get much cheaper practice than that. $9/100 bullets, a pack of primers, and 700 grains of Trail Boss.

[medicdave]

Been forming 7/30 Waters from 30/30 the last few days. I'm using 6.5 grains of Bullseye, then filling the case with cream of wheat to the case mouth, then adding a piece of tissue to hold the cream of wheat in. My little guy does the honor of pulling the trigger and loves the magic of putting one shaped case in and taking another out of the contender.

[Lee Martin]

Here's something to consider: fire-form your brass with hefty loads of the powder you'd normally shoot in the cartridge. Reduced loads are hit or miss. You want stout pressure to form the shoulder and drive the case-head back hard (on the bolt or standing breech). I've worked with dozens of wildcats and always go this route. Case splitting isn't normally a problem with virgin brass. It is however with old work hardened hulls.

Speaking of the Grendal, my .30 Stingray is formed on it. I expand to .30, turn the necks, jam the bullet hard into the lands, and fill the case with 32.5 grs of LT-30 (formed it'll hold 34.3 grs). The shoulder improves to 40 degrees and is moved ahead another 0.040". I've formed 600 to date and haven't lost one yet.



-Lee
www.singleactions.com
"Chasing perfection five shots at a time"

[Joe S.]

Good to know Lee. Split cases is why I didn’t go with a normal load. I think that trail boss dod the trick but I’ll definitely try your way next time I end up with 7.62x39 brass.

Dave, i like the part about your little one enjoying seeing the dofferent shapes. I feel much the same way. Ha!

[zeus]

As long as the bullet is tight in the lands, split cases aren’t usually a concern. The problem lies when people don’t do that and allow the case head to go back first versus the shoulder. Ends up with a weak point ahead of the case head.

I load my load stout with all fireforms and hunt with them. I have found typically FF loads are extremely accurate and so by shooting deer pigs etc, I wasn’t wasting powder along the way.

[Joe S.]

Good to know.

[paulh]

When sizing the 7.62x39 down to 6.5 do the necks need to be turned or reamed?

[Joe S.]

Nope. At least I didn’t do it and they seem to be working fine.

[bamagreg]

Feb 5, 2021 9:43:29 GMT -5 medicdave said:

Been forming 7/30 Waters from 30/30 the last few days. I'm using 6.5 grains of Bullseye, then filling the case with cream of wheat to the case mouth, then adding a piece of tissue to hold the cream of wheat in. My little guy does the honor of pulling the trigger and loves the magic of putting one shaped case in and taking another out of the contender.

I just saw a video on Youtube of a guy using this technique to make 375 Winchester cases out of 30-30 brass.