Re: US-869 Burn Rate Question
James is right on on where Hodgdons says their new powder ranks in burn rate but remember, I believe this is in testing the big 50 BMG, not conventional small bore rounds.
Powders take on a totally different personality when used in situations other then their original designed purpose which for US869 is for use in the 50 BMG. That is its purpose. Yes they offer data for many conventional small bore rounds but to my knowledge, all their burn rate and temp change sensitivity testing was performed on the 50 BMG test platform.
I also do not like burn rate charts either, to fixed and it seems every one is different, sometimes dramatically different.
In my experience I would say the the burn rate of US869 has ranged from very slightly slower then Retumbo to slightly faster then the old H-870 and H-50BMG. I have yet to find a lot of US869 which when loaded in conventional bore rifles produces a burn rate as slow as these two powders but they may be out there.
As far as the temp change stablility, again, in a 50 BMG this powder may perform as advertised but in convention bore rifles, you better develope your loads in warmer temps if you even intend to shoot in these temps.
Its a good powder but I think it has been a bit misunderstood mainly because of the claims of Hodgdon. Most are not using this powder in the 50 BMG but they are taking the advertisments of Hodgdon as fact over a wide range of chambering choices and this simply has not been the case in my experience.
TO be honest, this powder seems to perform extremely similiar to the old H-870 and WC-872 but faster in burn rate then either of these two powders. I will say it is slightly cleaner burning then WC872 but when both are loaded to top working pressures, not a big difference. That is the trick with these powders, they have a pretty narrow pressure window where then burn relatively clean. That is on the top 10% of the pressure range in my experience. THey really like 65,000 psi or slightly more to burn clean. Only problem is that there are not to many chamberings out there that have the right ballance of case capacity to bore diameter and bullet weight to make this possible, I know if a few that do though!! [img]/ubbthreads/images/graemlins/grin.gif[/img]
Good Shooting. just my 2 cents!!!
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