Imr 7625 - How Does It React To Temp/humidity Changes

[Jack Suber]

I am new to Open and am using 7625 for my son's Open gun. We have a sweet load now that is clocking about 167PF. I starting wondering how IMR 7625 reacts to temp changes. Is this powder very sensitive to climatic changes? I plan to get his PF to around 169 but would that be cutting it close if it gets cold? We shoot in SC and I have been chronoing in 85 - 100 degree weather with humidity. Any feedback would be appreciated.

[Jake Di Vita]

7625 has always been very consistent for me.

[lynn jones]

7625 has always been very consistent for me.

+1

i love the powder.

lynn

[XRe]

My very limited experience, at this point - and what I've been told by other folks with more experience - is that its one of those that can be reverse temperature sensitive (which is a phenomenon I still don't understand...). ie, as temperature decreases, velocity increases given the same charge of powder from the same lot.

I have an 8# jug of it, now, so I'll get to do more definitive experiments on this as the year drags on... It may also depend pretty firmly on your gun and load dynamics, so... Best thing I can tell you is to test it in different conditions with normalized loads (ie, if you switch lots, make sure you find a load that matches the old one in the same conditions...)...

[shred]

I noticed a few PF difference going from cold to hot ammo (gun temperature constant, ammo at 90'F, refrigerator 'F and freezer 'F)

[ipscbob]

I have found it to be relatively stable over temp and humidity exhibiting maybe 1 PF difference over a 30F degree change, morning to afternoon. I no longer use it at all, though, due to the huge variation lot to lot. The variation was so big that I have one batch that only barely makes major with a full 38supercomp case.

[Jack Suber]

Thanks for the feedback, everybody. So far, I have been very pleased with the consistency of the powder, velocity-wise. I am getting very low extreme spreads. I had heard about the inconsistency lot-to-lot. I bought an 8lb keg so I should be OK for a while. When I start a new keg of powder, I chrono anyway so I should catch any variances.

[ipscbob]

Thanks for the feedback, everybody. So far, I have been very pleased with the consistency of the powder, velocity-wise. I am getting very low extreme spreads. I had heard about the inconsistency lot-to-lot. I bought an 8lb keg so I should be OK for a while. When I start a new keg of powder, I chrono anyway so I should catch any variances.

Yup, assuming you can still make major! I have a batch that wont make it unless the case is 100% full. Not enough margin for me. There are so many other choices, why take the chance? My smith had similiar experiences years ago and tried to warn me.

[shred]

Lately 7625 has been pretty consistent for me.. Different lots only need + or - .1 or .2 gr.. now 4756 in the old days.. that was nuts.

[basman]

have been using 7625 in my open gun for the past year. no problems with consistency, over the last 3 lots. in fact my reloading area was in the garage up untill several months ago.

Can't beat the price, working up a 40 limited load now.