I had an issue with H4350 availability but had a ton of IMR-4350 on hand. I searched and searched fot 6XC load data with 105+gr bullets but found exactly nothing. So I looked at 6CM and 6x47L data and burn speed, bulk density and energy content and made an educated guess. My guess worked better than I’d hoped.
The load below was safe in my rifle. Your mileage may vary. Start at least 2 grains lower and work up.
Case: Norma LRP
Bullet: 115gr DTAC
Primer: Federal 210
MV: 3050 avg
Barrel: 25.5″ Columbia River Arms 3-land polygonal
I see the question asked constantly about IMR-4350 vs H4350. Nobody ever has the answer for IMR4350, they just say, “go get H4350.” but that’s both glib and unhelpful. With an identical load of H4350 I get 2980fps with similar SD’s and an identical POI. Group size with both powders was identical, 5 shots into half an inch, 10 shots into 3/4″ from a bench.
Yes, H4350 is more temp stable but sometimes you just have to run what you brung. I personally think IMR-4350 might be a better choice for those that shoot in relatively stable environmental conditions (so most of us). Velocity is higher without any more sign of pressure than H4350 (I’m sure there is a little more but not enough to say grace over).
If you can’t figure out how much of a particular powder to use, sometimes you just have to use your head and a little judgement about your head’s abilities to make good judgements and, when appropriate, give it a go. I know that will run afoul of the sensibilities of a lot of people but you have to understand that modern BOLT ACTION guns are so ridiculously strong that you’re unlikely to damage the gun itself with a small error in burn rate, energy content or charge weight. Semi-automatic platforms are very different and you can damage them substantially with a lot less of an error. In modern bolt aaction rifles it’s when the errors in burn rate, energy density or charge weight get really big that things come unglued suddenly. The line between safe and actually dangerous for a bolt action rifle is a lot wider than most people think. The line between within the pressure limits of brass cases is much narrower but that’s mitigated by all the safety elements designed in to rifles like gas venting ports.
Now you have the information anyway. IMR-4350 is a great powder choice for 6XC and other fast 6mm’s like 6x47L and 6CM with bullets from mid-weight to heavy for caliber. Don’t let the me too’s on web forums cock block you from reaching your goal. If you like. IMR4350, it’ll work just fine. In a case with ~40gr powder capacity, you should come down 2 grains from your H4350 load and work up.
As always with my load data, this is information not advice. You are responsible for your actions and your safety. I provided data as an EXAMPLE of what can/will happen. It’s not a prediction or your results and you should exercise reasonable amounts of caution.