Fire Forming Brass

[onelastshot]

Just finished putting together a new build in 6mmAI. I know there have been past discussions in the forum on fire forming brass but I can't locate them. If someone could cover the basics and provide the basic recipe, I'd appreciate it.

 

[ShootDots]

Just finished putting together a new build in 6mmAI. I know there have been past discussions in the forum on fire forming brass but I can't locate them. If someone could cover the basics and provide the basic recipe, I'd appreciate it.

All you have to do is go to the loading manual for a regular 6mmRem and look up a "mid-load". I would get a 100-105gr bullet, seat it WELL into the lands (say 15-20K) and pull the trigger. If you got some H4831, that would be my powder of choice. Look up a load for a 100gr bullet and you will see that about 44.0 will be a "mid-load" >>> neither at the bottom nor at the top. Make sure it is well into the lands so that it fireforms to fill the chamber and keep any headspace problems at bay..

 

[Screamineagle]

When F Fing for my 257 Ackley, I seated a bullet jammed .015" into the lands, with a max charge for STANDARD 257 Roberts. Came out great. I have since ordered a Whidden Hydraulic forming die. I hate fire forming!

 

[Brians356]

I believe if forming with a bullet, a near max charge of one of the faster powders which still produces good velocity in the parent case is best. The faster powders should develop a shorter peak impulse which should pop the case into shape better. You would like the point of the shoulder to be sharp, otherwise it's not fully formed in the first pass.

Having said that, I was not satisfied with results in my 250/3000 AI using bullets, so I switched to "bulletless" with a small charge (10-15 gr) of Bullseye and corn grits filler. I adjusted the charge by trial and error to obtain a sharp shoulder.

Search this forum for "bulletless".

In any method, it's best to use cases not fired more than once, else you should anneal them. I used new unfired 22-250 cases, so they were soft, and finished up with 25-cal necks of decent uniformity. (When you expand necks like that, any neck thickness variation should be reduced slightly as the neck walls get a bit thinner - just my theory.)

 

[onelastshot]

I believe if forming with a bullet, a near max charge of one of the faster powders which still produces good velocity in the parent case is best. The faster powders should develop a shorter peak impulse which should pop the case into shape better. You would like the point of the shoulder to be sharp, otherwise it's not fully formed in the first pass.

Having said that, I was not satisfied with results in my 250/3000 AI using bullets, so I switched to "bulletless" with a small charge (10-15 gr) of Bullseye and corn grits filler. I adjusted the charge by trial and error to obtain a sharp shoulder.

Search this forum for "bulletless".

In any method, it's best to use cases not fired more than once, else you should anneal them. I used new unfired 22-250 cases, so they were soft, and finished up with 25-cal necks of decent uniformity. (When you expand necks like that, any neck thickness variation should be reduced slightly as the neck walls get a bit thinner - just my theory.)

Thanks, I ran a search for "bulletless" and found a Sept. 2014 Post on the subject that covered all the details.
Cream of wheat or corn grits, shotgun powder, toilet paper and some wax for a plug and you're good to go.

 

[Ont0001]

FWIW
Having experienced both fireforming with and without projectiles in a number of wildcats and
"improved" cases, it might be worth seeing if you can "tune" a fireforming load with projectiles.
In a few cases my fireforming load was as accurate and in 1 case even more accurate than the resulting improved case.
You end up with the formed cases either way but one way is just more fun than the other
Regards
Gord

 

[Witchhunter]

I have a load for my .220 Swift AI that just happened to be my load before I changed to an AI. It shoots great and fireforms brass while I am at it. Best of both worlds. All Ackley Improved can utilize factory loads.

 

[fguffey]

I believe if forming with a bullet, a near max charge of one of the faster powders which still produces good velocity in the parent case is best. The faster powders should develop a shorter peak impulse which should pop the case into shape better. You would like the point of the shoulder to be sharp, otherwise it's not fully formed in the first pass.

I agree with Brian356, I form the case first then fire. I have never had to fire a case twice to get details of the chamber. I have had cases shorten as much as .045" from start to finish.

F. Guffey

 

[Ackman]

Look at the 6mm case, it has a lot of taper. Some cases blow out more than others when they become Ackley-ized. Look at the 6mm case, it has lots of taper and gets considerably larger and holds quite a bit more powder. An AI "fireform" load is like finding the best load for any other cartridge, only beginning at a max load for the standard cartridge and go up from there until you find best accuracy. With the 6mmAI a 70gr bullet is perfect, but whichever powder/bullet works when forming brass will also be what you'd use with formed cases. Just remember your "fireform" load is actually a hunting load which also results in a perfectly formed case. It'll be just as accurate as with formed brass, and a whole lot faster. With a 70gr bullet this case (and the .243) likes W760 powder very much. Your "fireform" load will likely be very close to the same charge as with formed brass and might even be the same, that happens sometimes.

"Fireforming" with bulletless loads is an extra step that saves nothing, a waste of time and components.

 

[bigedp51]

Just finished putting together a new build in 6mmAI. I know there have been past discussions in the forum on fire forming brass but I can't locate them. If someone could cover the basics and provide the basic recipe, I'd appreciate it.

At approximately 43,000 cup the peak flame temp is just reaching the melting point of modern barrel steels. Meaning if you keep the chamber pressure well below 43,000 cup you are causing minimum if any barrel wear when shooting bullets. And if you keep the chamber pressure below the elastic limits of the brass the case will not stretch and thin in the base web area.

Below I'm using .312 pistol bullets and Trail Boss powder to fire form my .303 British cases. Using Trail Boss powder you will nearly fill the case with powder, the chamber pressure will be well below the elastic limits of your brass. And no where near the melting point of your barrel steel.

A .303 British case can have as much as .017 head clearance and as you can see below a new case has a long way to fill out the shoulder area.

These lite loads can be shot all day long and have the added benefit of making the Enfields brass butt plate "softer".

Also remember P.O Ackley designed all his "improved" cartridges to be fired at normal chamber pressures and not have any adverse effects on the cartridge case when fired. So test fire a Remington or Federal case that have the softest brass and then check for thinning in the base web area.

A RCBS case mastering gauge tells you much more than a bent paper clip when checking your cases for thinning long before the paper clip tells you anything.