IMR 7828 vs IMR 7828ssc


I recently got a a plb of 7828 ssc and am shooting 1.5 grains less of it to get approximately same ft/s as I did with the regular 7828.Going up any higher was showing start of pressure problems.Company data said the 2 should be no different.I guess this just goes to show why you should start at 90% with all new batches and work your way up.Just thought I would report.

Terminator :  The only reason the powder companies went to the short cut versions on these longer extruded powders was to reduce powder bridging (it flows better) in powder measures.  Theses powders are suppose to have interchangable data.  One thing to keep in mind is during manufacture  different powder lots with their assigned numbers  may have slightly different burn rates and when buying new powder of the same type it is always recommended to back off a little especially at the high end loadings to see how it works unless it's from the same lot.  I do a lot of testing when needed and found that I have powders that are probably 20 yrs old  which are still  in totally good condition that I didn't care for in a specific gun.  Bad thing for me is when ever I decide to use the old powder again and run out I will have to work the load again.  I use a lot of Hodgdons HS-7 in a 10mm auto unfortunately they discontinued it, at least I have enough to last awhile.  That gun just gave me fits to get the load right with  the accuracy, recoil and performance I was looking for. Oh well.   

I'll add my own experience in the 7828 v 7828ssc comparison, but first let me say that I think that's exactly what Terminator was saying, Zonie - working up when switching lots is a serious and real issue.

My experience has been the same across the board with the regular versus the ssc version of 7828.  I've gone through several lot numbers of each and the ssc consistently provides a bit more velocity for the same charge weight.  Sometimes it's almost negligible, around 20-30fps.  But many times, it's been just over 100fps difference.  That's the same charge weight of regular and ssc.  I talked about this with a guy who had some significant testing (lab type testing) experience, and he said the shorter grains would likely, due to increased surface area, be a tad faster than the longer grains.  I'm not sure if that's true, and I've also heard that the shorter should end up slower than the longer due to more coating on the propellant surface, but in my experience, the ssc is always faster.

One of these days when I get a regular, stable job again, I'm going to order up 8lbs of ssc and quit worrying over re-working loads for a while.

Duby : You are absolutely right.  I was explaining for anyone out there why there is 2 different 7828's from the same company.    I would suspect the surface area and for sure the deterent coating would be factors.  We are all on the same page.  The main thing and even the manufacturers recommend starting over when switching  powder lots.


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