My 6mm AI fireforming results

[Tyler Kemp]

First off, I'm using Winchester brass with some cheap Remington large rifle primers I found. (already have 2 duds in 15...they suck) I am using Unique under toilet paper and a case full of COW up to the neck, then plugging it with paraffin wax.

I started off at 10% of a full case load, only 3 grains. (not sure why only 30 grains Unique fit) Nothing at all happened at 3, at 4.5 I had a slight rounding of the shoulder, but the case wasn't much wider. 5 grains was about the same. I jumped up to 7 grains and it got better, looked like a Weatherby shoulder. Kept getting slightly better until 9 grains when it looked about fully formed. Going to 10 grains didn't do much more. Looks like the only way to get the final sharpening of the shoulder will be to fire with bullets.

 

[Coyboy]

Tyler, I think it would be more productive to just load a real bullet on some suitable powder, and go have some fun. I fireform live loads for my 243ai and 260ai, and both shoot 1/2moa, and run at standard cartrige velocities. I take them out for shots at crows or porkies, or just targets. It's good practice. If you were using somthing with shorter barrel life that consumed gobbs of powder then I would say, go stuff oatmeal!

 

[Tyler Kemp]

I would rather save barrel life and money, as I would need a set of 6mm Rem dies to load with bullets. It's also just 10 grains of powder, I could potentially fireform 700 brass with that.

 

[Iron Worker]

I need to fire form also

Tomorrow I'll be doing the same. Yes those Remington primers suck.I can get I bet 50 grs of WW760 in a case.( Of course with a bullet that would turn my rifle into a bomb) so 10% ? that's 5 grs and that didn't cut it for you. I wonder if I used a magnum primer?

 

[Tyler Kemp]

What is WW760 shaped like? I'm not sure wh only 30 grains of Unique fit, it seems to me the little discs should pack tightly. So I guess I'm actually using 33% of the case capacity. No pressure signs though. I think the headspace is set a little long, with the case in the chamber sometimes the firing pin has to push the case into the chamber all the way, then the second time is fine.

 

[Iron Worker]

Ball powder

Unique is a Flat round flake type powder. Lots of air between flakes.W-W 760 is ball powder.

 

[HoytemanPA]

I think the headspace is set a little long, with the case in the chamber sometimes the firing pin has to push the case into the chamber all the way, then the second time is fine.

And then the third time.

Looks like the only way to get the final sharpening of the shoulder will be to fire with bullets.

If you were to take Cowboys suggestion, Use a bullet to fireform with, seated long to hold everything snug on initial firing, you will end up with a better job the first time around. A pound of unique is about the same price as a used full set of rcbs loading dies. After which you can potentially form 70,000 brass with. Your misfires are coming from the unsupported case slopping around in the chamber, with enough slop sometimes that the firing pin is not long enough to reach. If still insistant on shooting blanks, at least size up a caliber and then partial necksize back down to create a false shoulder to hold your cases back against the bolt.

The words sometimes, and headspace too long can't go in the same sentence. Sometimes, and brass too short, now that works.

Good luck,
Shummy

 

[uncleB]

This is just my opinion but I have fireformed more than my fair share of 6mm AI and 22-250 AI . I have used COW , oatmeal with Unique powder (and others).
I think it is a waste of time, I have never seen a case 100% formed by this method.
The last time I formed 6mm AI cases I bought bulk remington bullets and used some Mil. surplus H4831 powder that I had no other use for, cases were fully formed and ready for load developement.
Headspace should not be an issue whether you seat your bullet into the rifling or not, if your gunsmith chambered your barrel properly there should be about .003" crush fit of virgin brass eliminating headspace problems.
By far the best fireforming method that I have found for my 22-250AI is to have a junk barrel chambered with the same reamer as my new barrel and do all fireforming before a new barrel is installed.
UB

 

[Iron Worker]

Corn meal method is hard on BBLs also

On Bench rest central I was informed of that problem. I don't have a junk BBL so I just finished loading up 50 22-250 with 35 grs of IMR4320 behind 64gr WW PP. I expect poor accuracy,i wonder if that load will harm my BBL

 

[blackco]

Lots of people I talk to who use standard loads to form brass for AIs get GREAT accuracy from those loads. Don't be suprised.

Tyler, you can use your AI dies to load standard rounds for your rifle. They will resize the brass enough for your new chamber and all you are really looking for is neck tention to hold the bullet so you can fireform the brass. No need for new dies.

 

[Tyler Kemp]

Well that's good news. I may just shoot the next 50 brass with bullets then. I'll just keep velocity as low as possible to still get good fireforming.