I just ordered some RETUMBO and IMR7828SSC. I'm going to try these slow burners in 25-06 AI, 280 AI, 30-06 AI, and 300 WM. Does anyone out there have any experience with these powders? They should be good with over-bore case designs and heavy bullets. Thanks ahead-of-time for any info.

I have shot the Retumbo in several chamberings and it is good. The IMR powder is 7828SC instead of your stated 7838SC. I have not shot it but will be considering it highly for all loads that took the ole IMR7828. You probably know that Hodgden bought out IMR and now does both powders. They had so much success with H4831SC they decided to do the 7828 the same. Good luck and good shooting.

I haven't used either powder, but powders in this burning rate range should be excellent choices, particularly with heavy bullets, for all but your .30-06 AI. Your '06AI will probably not get velocities as optimum as with slightly faster powders. The exception might be if you use an ultra-heavy bullet of 200 or 220 grains.

So, comparatively speaking - how much more of say H4831 SC are you able to get into a case, as compared to the regular 4831?

Just a rough % guess?

I hven't tried Retumbo & do use 7828 in my .260ai, .280 & 7mag. I wan to try 7828sc in my .260ai, it would be easier to get the powder charge I like under that looong 142grSMK. IMR7828 proved to be THE powder for my .280 & 150-175gr bullets. It should be great in your 25-06ai, .280AI & .30-06ai especially w/ heavier bullets.

I've tried to get IMR 7828SC, but it's not yet available, at least where I tried to get it.

I was able to get 2730+ f.p.s. from 200 grain bullets in a 30/06, using 63 grains -- all that will go in the case, yielding a highly compressed load -- of the regular IMR 7828. I'm hoping that this new version will allow maybe 65 grains to go in a 30/06 case.

I'm also hoping that it will give the velocities that people claimed to get 30-50 years ago with the old, surplus, H 4831 in the .270 Winchester, i.e. 3200 f.p.s. with 130 grain bullets, and 3000+ f.p.s. with 140 grain ones.