What is the common powder to use while fireforming AI cases? How much powder is a starting point?
243AI Fireforming
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lancetkenyon
Well-Known Member
H4350. Find a good fire forming load and go have fun.
I was banging steel out to 1400 with my .260AI while forming brass.
I was banging steel out to 1400 with my .260AI while forming brass.
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sierracharlie338
Well-Known Member
I didn't have as much luck as @lancetkenyon when fire forming my 257AI but ended up getting there.
Find a solid powder charge and seat your bullets close to the lands and you should get some nice shoulders.
Find a solid powder charge and seat your bullets close to the lands and you should get some nice shoulders.
Let me throw a wrench onto my post. Which powder should I use if I was to use the C.O.W. method to fireform?
codyadams
Well-Known Member
Red dot is a good option. Just look at some of the faster pistol powders if using the COW method.
I've been a life time wildcat and AI man. Never never jammed bullets into the lands. Never wasted precious barrel life doing something as dumb as pistol powder
Lot's of the rifles I've owned are limited barrel life. So I have never messed around with fire forming shells to be reloaded later. I take the parent case and use the exact same load that the AI that I have perfected. If it is a first time without load data. Just look up the parent case reloading data and look at the max load. Logic tells you that the case volume of the 243AI in your case is going to have a bigger volume. So you start out at a grain or two over the max 243 from the reloading tables. Then go use them.
I'm a 243 man and Ram shot Hunter, StaBall 6.5, and Superformance are great powders for 87 on up pills.
I use them paper and hunting. Generally I have found that something below max pressure and acceptable case life is the most accurate loads. Or I will drop to some even number like 3200 fps for ease of ballistic calculations. Summer time I shoot bullets out of cooler and winter out of a warm inner pocket. So I don't have to worry about temp sensitive powders. Even my hunting rifles are often single shots because of the long AOL. with throated rifles. Actually I've never needed a second shot big game hunting.
They are perfect fire formed cases
Lot's of the rifles I've owned are limited barrel life. So I have never messed around with fire forming shells to be reloaded later. I take the parent case and use the exact same load that the AI that I have perfected. If it is a first time without load data. Just look up the parent case reloading data and look at the max load. Logic tells you that the case volume of the 243AI in your case is going to have a bigger volume. So you start out at a grain or two over the max 243 from the reloading tables. Then go use them.
I'm a 243 man and Ram shot Hunter, StaBall 6.5, and Superformance are great powders for 87 on up pills.
I use them paper and hunting. Generally I have found that something below max pressure and acceptable case life is the most accurate loads. Or I will drop to some even number like 3200 fps for ease of ballistic calculations. Summer time I shoot bullets out of cooler and winter out of a warm inner pocket. So I don't have to worry about temp sensitive powders. Even my hunting rifles are often single shots because of the long AOL. with throated rifles. Actually I've never needed a second shot big game hunting.
They are perfect fire formed cases
QuietTexan
Well-Known Member
COW forming works great in many cases, specifically if you're drastically shortening neck length - 6 BR to 6 Dasher is an example, +0.080" increase in headspace. My opinion is that it's not necessary in this one particular design because if you spend an extra half hour running a mandrel and setting up your sizing die correctly from the start you get better fit cases after one actual firing than you do from the COW forming shot.
For 243 AI specifically, I use a .2550 mandrel (LE Wilson .257 'new' mandrel) to neck up the case, then fit the case into the rifle using a 6mm bushing neck die to where the bolt was putting more crush on the case than the base AI design does. I ran full-house 243 Win loads for firing forming, and fired one case 15 times without case head sep, losing the primer pocket, or trimming. Stacked five shots in a row on a 1-moa gong at 1200 yards with the un-tuned fire forming load. I used Magnum because I had a lot of it and it's sufficiently slow for my rifle. H4831/H4831SC works well in general in fast twist barrels with heavier bullets. H4350 is probably on the fast side for bullet weights over 100gn because you'll have a lower case fill ratio and for fireforming I want the highest fill rate I can get, but if this is a slow twist barrel for varmint bullets it would work fine.
The advantage of the false shoulder method is the case seals better in the chamber and there was a measurable improvement in consistency of the formed shoulder over jammed/un-shouldered forming loads. No carbon shooting on the case, no carbon at all past the false shoulder, and calipers don't lie. 3150FPS out of the gate with 105 Bergers
But I shoot loooong barrels, not pencil stubs.
Sheridan Engineering slotted 243WIN gauge to show the neck crush fit in a 243 chamber. In theory a correctly set-up AI chamber would pivot around the neck/shoulder junction, but the false shoulder removes any tolerance stacking and gives you a consistent crush on every case regardless of the virgin brass measurements.
For 243 AI specifically, I use a .2550 mandrel (LE Wilson .257 'new' mandrel) to neck up the case, then fit the case into the rifle using a 6mm bushing neck die to where the bolt was putting more crush on the case than the base AI design does. I ran full-house 243 Win loads for firing forming, and fired one case 15 times without case head sep, losing the primer pocket, or trimming. Stacked five shots in a row on a 1-moa gong at 1200 yards with the un-tuned fire forming load. I used Magnum because I had a lot of it and it's sufficiently slow for my rifle. H4831/H4831SC works well in general in fast twist barrels with heavier bullets. H4350 is probably on the fast side for bullet weights over 100gn because you'll have a lower case fill ratio and for fireforming I want the highest fill rate I can get, but if this is a slow twist barrel for varmint bullets it would work fine.
The advantage of the false shoulder method is the case seals better in the chamber and there was a measurable improvement in consistency of the formed shoulder over jammed/un-shouldered forming loads. No carbon shooting on the case, no carbon at all past the false shoulder, and calipers don't lie. 3150FPS out of the gate with 105 Bergers
But I shoot loooong barrels, not pencil stubs.Sheridan Engineering slotted 243WIN gauge to show the neck crush fit in a 243 chamber. In theory a correctly set-up AI chamber would pivot around the neck/shoulder junction, but the false shoulder removes any tolerance stacking and gives you a consistent crush on every case regardless of the virgin brass measurements.
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I've dabbled with Magnum and R-26. I've only got a 9 1/8 twist 26 inches long. So my limitation is 105 or 107
The poster didn't say what he was doing, But starting at .020 of the lands and using existing 243AI load data is a good place to start with fire forming. The beauty of AI's is that even down loaded they can exceed the FPS of the parent case
The poster didn't say what he was doing, But starting at .020 of the lands and using existing 243AI load data is a good place to start with fire forming. The beauty of AI's is that even down loaded they can exceed the FPS of the parent case
Tidus56
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I couldn't figure out the false shoulder way of doing it when I first started shooting my 243 AI. So like @lancetkenyon i just load up a 243 load and go shoot. I use my 243 AI for blowing up prairie dogs so my use may be different than yours but I have been pleased with accuracy during forming. Just my 2 pennies.
I use green dot when fireforming with COW.
This rifle will be used for 60-80 gr. bullets. We all know about powder availability...So, I will be putting all my trust in H-414, WIN 760, H-4350, and possibly H-4895.
Tidus56
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What are you using it for primarily? Not that it matters for FF but just curious what you'll be shooting it for.
I've fire formed hundreds just shooting full house 243 loads at prairie dogs.
