HS-6 vs Unique

logandrut

logandrut

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Forgive a newbie if this has been covered, I have been looking and found nothing comparable.

So I am looking at fireforming more 338 into 458 win and need help with the powder charge. Previously I have used 20 and 25 grains of unique with good success. Unfortunately the Unique powder is not available so I picked up another pound of hs6 as it is usable in my 10 gauge (and also is the closest powder to Unique on the burn rate chart that was available in town).

Does anyone have experience using this powder for fireforming magnum rounds? Does anyone know the math to figure out just how much more hs6 should be used to mimic the performance of unique? Google tells me 10-15 grains of hs6 but I am assuming it was pulling data for smaller cartridges as I was double that much of the faster burning unique. Hoping to get out this weekend and I will update everyone with progress for future fireformers. Any relevant info is appreciated!

*Also reviewing 28 gauge loads which use both powders I listed, it seems to be that you use 15-20 percent more hs6 than unique for similar performance... is this a valid way to estimate?
 
I ended up loading 25 grains of HS6 into 17 cartridges and had a 100% success rate with my fireform recipe. Using unique resulted in 3 cracked necks. So basically I used hs6 interchangeably and had better results. As to if 25 grains is a lot, perhaps it was a bit wasteful but I was with another member who's more experienced than I and that's what we used.
 
logandrut said:
I ended up loading 25 grains of HS6 into 17 cartridges and had a 100% success rate with my fireform recipe. Using unique resulted in 3 cracked necks. So basically I used hs6 interchangeably and had better results. As to if 25 grains is a lot, perhaps it was a bit wasteful but I was with another member who's more experienced than I and that's what we used.
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What did you use for filler? COW?

I made a wild guess the COW might weigh 20gr. Using a 20gr bullet and 25gr of HS6 in a 338 winmag case, Quickload estimates 13K psi peak. The same setup using 25gr Unique estimated 20K psi peak pressure.

I would not have high confidence in the actual pressure estimates, but i suspect that the difference in peak pressure is somewhat representative as a comparison. You had 100% success with the HS6 but experienced some splits with Unique. Was the reason for the split necks with Unique related to higher pressure/more forceful expansion with Unique? "Maybe" Unique would have done less split necks with a lower charge weight? I never considered that before. Maybe some of the split necks I've had while fireforming were caused by too much energy and not the ductility of the brass, which is what I attributed it to.
 
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20 and 25 grains of unique gave similar results although I wasn't as studious in recording results then. I feel that a lesser charge of Unique may result in less than fully formed brass, just a thought however as I don't have any Unique of my own to test with. I was very happy with the HS-6's performance in fireforming however, 5 non annealed nickel plated (the rest annealed), 3 and 3 brass and nickel plated using LRM primers, 3 and 3 again using non magnum primers, all fireformed fully with no cracked necks. So presumably it makes no difference with magnum primers when fireforming.

Another thing I attributed to cracked necks was after the op wad, CoW mid way up neck, I plug with a bar of soap, now when forming with Unique some of the plugs weren't perfectly sealed around the inside of the neck... MAYBE leading to uneven pressure developing? Again, just a guess, but I fixed that issue on my second round of fireforming and all went well. I have 29 more mixed brass/ nickel plated loaded to fireform (exact same recipe) so we'll see how they turn out, if it was beginners luck or the recipe is on point.
 
logandrut said:
Another thing I attributed to cracked necks was after the op wad, CoW mid way up neck, I plug with a bar of soap, now when forming with Unique some of the plugs weren't perfectly sealed around the inside of the neck...
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I wouldn't expect that a bad grease seal on it's own would cause split necks.
 
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