Fire-forming for AI cartridges

[RJinTexas]

Will someone please explain to me why anyone needs or wants to fire-form with COW. All the AI chamberings I've ever owned have shot their fire-forming loads well enough to hunt or even compete with. I've owned the .223ai, .243ai, .244ai, 260ai and 308ai all shot their std parent brass very well and thus provided my fire-formed brass. Isn't that what P.O. had in mind when he developed the process. I've been schooled to believe that a barrel properly chambered for a AI cartridge should just close on factory brass and that bolt should have a little resistance just before it locks up. This is to assure proper head spacing and that the brass will fully form on the first firing. Why waist primers and powder when you can be practicing shooting or killing varmints, am I missing something?

RJ

 

[Elwood]

Cost and barrel life?

For me it's the above, the cost of bullets in the UK is extortionate, the price of Semolina (COW) isn't. I can buy a tub of Unique pistol powder that will last me hundreds of rounds for fire forming, typically 16 grains in a case, as opposed to 48 grains of RL22.
I'm running a hot 6mm in F open with a accurate barrel life of about 1000 rounds, so if I can save myself 50 rounds then that's one match.
In order to use fire forming loads in matches I have to do load development, which I then have to do again with the formed brass, using COW means I only do this once. When I enter a match I'm there to win, I suppose I'd liken it to having a race car and running it on cheap fuel, you will more than likely finish the race but you won't win.

Now that my old barrel has been replaced I'm using it to fire form and practice at the same time.

 

[Minesweeper3433]

I am not 100% sure but I think that when they use COW methods to fire-form they are using calibers that are necking up or down and have to get it close enough out the gate just to chamber. More you move the case around more likely that you have to fire-form using COW or some other method, at least that is how I understand it. Also could just be to save powder and bullets and barrel life on high end barrels. For the same question I don't understand why people use a krieger or bartlien barrels for fire-forming instead of getting an old sporter pull off barrel?

 

[BoydAllen]

I had a friend that fire formed too many Cheetah Mk.I cases in too short of a time, with pistol powder and cream of wheat. He ruined an expensive new barrel. It looked sand blasted inside. Personally, I would stay away from cases that require fire forming for applications that require large numbers of cases, unless I was willing to spring for the cost of having a take off barrel chambered for fire forming.

 

[Jay Christopherson]

Not that I disbelieve you, but how could cream of wheat perform any sort of "sand blasting" on a modern barrel? It's wheat- I can literally crush it to dust between my fingers. Not even similar to sand where you get some material that is hard enough to actually affect steel. When I fireform using the COW method, I do 100 cases at a time and while stinky, the barrel is pristine when done as viewed through a borescope. I won't claim it's not a PITA method though.

I had a friend that fire formed too many Cheetah Mk.I cases in too short of a time, with pistol powder and cream of wheat. He ruined an expensive new barrel. It looked sand blasted inside. Personally, I would stay away from cases that require fire forming for applications that require large numbers of cases, unless I was willing to spring for the cost of having a take off barrel chambered for fire forming.

 

[BoydAllen]

I would surmise that he got the interior of the barrel way too hot, by firing too many rounds in too short of a time. Fast pistol powders generally have a high flame temperature due to their high nitroglycerine content. I was shooting next to him when he did the fire forming, and warned him that he was getting the barrel too hot, and I looked down the barrel afterwords, the damage was easily seen. No, I don't think that the hardness of the COW was the reason for the damage, but rather the misuse of a procedure that might have been OK if the firing had been done at a more reasonable pace, that kept the barrel temperature from getting too high.

 

[expiper]

I fire form with pistol/shotgun powders and NO COW,,!!!!....just put in a 1/4 sq of toilet paper and it works just as good and is easier/faster and noooo stinky mess in the bbl.....as stated above most of the fire forming "B"enchrest shooters are doing is ,,non,,AI....they are doing ppc's and Dashers which are a different animal....like my 280 AImo....not only am I changing 06 brass to 7mm...but I am blowing the shoulder foreward .080 +/- and shortening the neck,,,,there is no ledge at the base of the original neck to palm the bolt closed on!!!!....keep it simple ...Roger

 

[Jay Christopherson]

Ok, yeah, that makes sense.

I will mention that I just hydro-formed 150 cases (Hornady Forming Die) for my 6 Dasher and then went out and shot some @ 600 yards with my full powder load to see if I was going to have a problem with them not being 100% formed. I wouldn't hesitate to shoot them in a match. They easily shot well enough for me to be confident shooting them in match conditions. The hydro forming process is in some ways easier (don't have to leave my garage) than COW, but it's still a PITA. I'd pay Lapua a premium if they would produce Dasher brass. If I counted the time and energy I put into fireforming brass, I definitely be coming out ahead even if Lapua charged extra.

I would surmise that he got the interior of the barrel way too hot, by firing too many rounds in too short of a time. Fast pistol powders generally have a high flame temperature due to their high nitroglycerine content. I was shooting next to him when he did the fire forming, and warned him that he was getting the barrel too hot, and I looked down the barrel afterwords, the damage was easily seen. No, I don't think that the hardness of the COW was the reason for the damage, but rather the misuse of a procedure that might have been OK if the firing had been done at a more reasonable pace, that kept the barrel temperature from getting too high.

 

[RJinTexas]

Folks thanks for your replies, I fully understand the need to fire form cases for cartridges like the dasher and some of the other off the wall wildcats where one has to really make sufficant changes to the brass. I was refering to AI cases where your mostly just blowing out the case slightly and changing the shoulder angle. Most of us have owned and shot the parent case before we get the urge for a AI upgrade. I've always found that the if the load preformed well say in my std 243 or 6mmRem the same load always performed well as a fireform load so therefor no need for load development was needed for fire forming loads. I'd not feel comfortable firing COW down any of my custom barrel. And unless your chambering your own barrels I can't see where it cost efficient to pay to chamber a shot out or factory take off barrel to use as a fire form barrel. But if I was shooting a hot 6mm and only getting 1000 rounds before accuracy started falling off I can see the need for a dedicated fire form barrel.

Regards
RJ