From what I've seen over the past 40 years it's a crap shoot of 4350 lot #s. The only other powder with such wide swings I've seen is a particular late 80s lot of IMR4320, & H380. In fairness, the H380 could have been temp related. I stopped using it years ago after a locked bolt on a groundhog hunt in July with ammo that was shot well in May.
Right before the covid madness I got 2 different lots of H4350 about a month apart. All else exactly the same there was 250 fps difference between them in my 22-250 Ackley. There were slightly less but still gross differences in 7x57, 338-06 ackley, & 358 Norma quite often fired the same day with the exact same components the 2 lots of powder being the only difference.
The 8#er metal can of IMR4350 I got about 35 years ago was, & still is, closer to the faster of the 2 recent lots of the newer H as the big can empties. A brand new jug of IMR4350 was closer to the slower lot of recent H. Throw in AA4350 which in the lot I had was about equal to IMR4831, or the SW 4350 which was a tad slower yet. IMR4451 was mostly a wash, pressuring out at lower speeds with less accuracy, but could still be useful somewhere I hope as I got 8#s of the stuff.
There is still a bit of the original "Newly Manufactured" H4350 before it was cut short in the closet & a small, but treasured supply of Scot 4351 that's earmarked for my 22-250 Ackley still in the closet too. These 2 perform similarly gr for gr vs velocity & accuracy, but dont bulk the same. Isn't this fun? It's a disease, I tell ya.
Edit... The loading manuals are nothing more than guides. Their start loads are mostly safe places to start. Their max loads may or may not be your max load. Your stuff isn't the same as their stuff, so you probably wont get the same results. Some times it may be close, sometimes not. Like I said... a crapshoot.
Last edited by 358WCF; 07/21/22.
