Fire Forming and Powder Selection

[Jim1 AB]

I'm sure I had made the comment that I've been fire forming cases with full throttle load weights. On the low side but nonetheless .... Well I ran out of N165 (Vihtavuori), I was using just to get rid of it and decided to use IMR4350 for the last two loads. I'm using 375 H&H brass with 300 grain Wildcats (junk) to fire form 358 STA cases. 72 grains of powder. Quite a light load. I have published load data for 77 grains of H4350 being max so 72 of IMR4350 should be safe. Well the cases blew out instead of length wise. Ruptured at the shoulder area and neck.

I thought after making the comment that you could fire form with full loads I should "adjust" that comment. Now I'm not sure if I were to using lighter bullets with the IMR 4350 would make a difference or not. I will probably try it and see. Reloading through trial and error is just so much fun. lol

Jim

 

[FOTIS]

I think that is too much of a radical move. From a gently sloping angle to a very pronounced sharp one. I would seriously consider necking up 8mm rem mag cases to 358 cal.

 

[jmad_81]

I think POP might be right. That is what the Nosler book #6 suggests to use when fireforming brass for the 358 STA. I also know that when fire forming brass for the 280 AI they say to use a light load of a fast powder. I use the cheapest bullets I can find.

Good luck.

 

[Jim1 AB]

I don't think it is so much the brass used as it's the method that was the problem. The only brass I have ever used and I'm talking maybe 15 Years is 375 H&H. In the past I've fire formed it with a little bullseye and corn meal. It has only been the last couple of years I've tried Norma/Weatherby 340 Weatherby cases with the full loads. Hell even the loads of N165 (Vihtavuori) are working with the 375 H&H. With that said I will be changing thing a bit because of the case ruptures.
I have the original copy of the Shooting Times that has the article about this cartridge in it. That is where I learnt how to fire form the 375 H&H cases. I believe. I'll check later.

I don't like the idea of the 8mm that is used a lot also. I think the neck brass gets to thin. (opinion) I have never use it though.

 

[Ridge_Runner]

what make of brass? could be a poorly annealed lot of brass.
I use win brass in 270 win to fireform 6.5 gibbs, mostly I lose 2% to a split shoulder, on a couple lots I'll lose 10%.
RR

 

[FOTIS]

BTW quick burning powder works a lot better.