Home Forums Hunting & Shooting Long Range Hunting IMR4350 Vs. H4350

Ref: 6.5 CM
I've noticed that most people loading for the 6.5 CM use H4350 powder, and I have worked up a very accurate load for my 6.5 CM using H4350. I also noticed that Nosler in their Version 9 reloading manual list IMR4350 as their most accurate load, over H4350.
I have 5+ lbs of IMR4350 and have used it successfully loading for my 30-06 and I fall in the category that if it ain't broke, don't fix it. Before I burn up a few primers/IMR4350 & bullets I thought I would ask if any of you might have already been there, done that and have the T-Shirt on this matter? Your experience and opinions will be greatly appreciated - Thank you,

BTW - I live in Florida and it is always hot! So, I have heard that IMR4350 is temperature sensitive; however, in 30+ yrs of using it in my 30-06 I have not ecperienced any problems.

My 6.5 Creedmoor shoots great groups with IMR4350. This is with 140 grain class bullets. I haven't deliberately tested for temperature sensitivity.

I haven't used it myself as I have a good stash of IMR4451 and H4350, but my cousin uses it without an issue in his Creed.

Temp sensitivity comes into play with temp fluctuations. If your AO is "always hot!", then the only time you'd bother to worry about it is if/when you travel to somewhere not "always hot!". Even then, given your scenario, the only concern would be a slightly lower POI from your "always hot!" Zero. Simply work your load up within safe pressures for your shooting conditions and rock on.

IMR4350 and H4350 are close, but powders should never be considered interchangeable. H being one place slower than IMR on the burn chart. Work up safely whenever changing a component.

Edit to add: IMR4451 is another "close" powder and I used it a lot in my 243 PRS rifle when H4350 got really scarce, but the Enduron line of powders is discontinued, so when the existing stock runs out it's gone.

I use the IMR version with 120 Barnes in 6.5 Creeds and a 6.5mm-06. Great groups out of both. Loading for 3 Creeds, great in all of them.

My CM likes H4350 the best with 120 Sierra and 129 Hornaday SST's the Sierra's will group 3 shots under a dime in a Tikka rifle

Testing IMR against Hodgdon under identical equipment and conditions, 14# M70, Krieger, Berger Hybrids, Hornady match brass, Fed 210M's...I couldn't see any marked difference in 10 shot group sizes...H4350 gave a little bit more velocity, IMR 4350 gave less extreme spread. Only 20 shots for record and only one lot number of powder. Good enough for me...but to really tell I should have fired a lot more shots for record.

I load IMR with 129gr AB in a 260 Rem with great accuracy, but also load H4350 with 130-139 gr berger, Atip and scenar with great results too. Half dozen of one...

IMR4350 is somewhat more temp-sensitive than H4350, but it won't make any difference at temperatures from around 25 to 80. Just about any modern rifle powder won't be affected by temperatures in that range.

Also, temp-sensitivity depends on other things, such as load density (a little charge-compression usually helps) and primer. As an example a load I used for years in my first .375 H&H was 81 grains of IMR4350 with a 300-grain bullet--which was pretty compressed. Velocity didn't vary much at all from zero Fahrenheit to 80 degrees. But have also seen IMR4350 handloads vary over 100 fps in the same temperature range with loads that weren't compressed--and around 100 fps is where variations in point-of-impact can occur.

All of this is explained in greater detail in Chapter 10 in my Big Book of Gun Gack II, "Temperature and Rifle Powder." This also includes the temp-test results of a number of handloads in cartridges from the .17 Hornady Hornet to the .375 H&H.

This has been my experience with IMR 4350 as well. No issues with it whatsoever, but then again I fall into that 25-80 degrees category 90 percent of the time.

Panhandle,

How old are you?
Under 45, use H4350
Over 55, use IMR-4350
In between, use either.

@FLPanhandle

I live in Florida too. I get very good results with both, H4350 and IMR 4350, out of my 260Rem and 257Robts. The IMR 4350 is both faster and gives a bit more accuracy. I develop, load and practice all summer in the Florida heat, then hunt in Wyoming and NY, in teens and 20° temps. All good.

EDIT:
I just noticed this is in the Long Range group. That's not me. Me comment was for my experiences out to 300-350 yards.

I've also used IMR 4451 as a one for one swap for IMR 4350 with pretty much identical results.

Stammstr - LOL!! I turned 84 last July, so IMR4350, eh?

Mule Deer - Interesting - If I understand you correctly, Seasonal changes (temp. swings over time) are of no concern with the IMR4350, rather sudden changes, like 15 deg in the morning and 80 deg. at noon would be of concern? Thank you,

I’m 50 so this explains why I use them both about evenly. 😁

Have done the same thing with around a dozen cartridges, with the same results--though on average 4451 has done a slightly better--and includes a decoppering compound. Luckily, I stocked up before production was "suspended," but am hoping it won't be suspended much longer!

That's just plain funny.

How about those of us who are near 60 yet were using H4350 when it first hit the market when it was made in Scotland?

Brown jug for me. Love imr 4350. Shoot it in about everything. Favorite is a 6.5-06 and a 140 or a 30-06 and a 165.