IMR 4350 temperature sensitivity?

[5RWill]

Running 105gr Hunting VLDs over 40gr of IMR 4350 in our youth model 18.5" .243 @ 2700fps. Makes a hell of a 600yd hunting rig . Anyhow just got around to loading again, we initially zeroed in 50F weather, at the end of last winter. Shot in 80F and my initial shot at 100yds was spot on, but a tad high from POA. Then when dialing 6/10ths of a mil for 200yds shots were scraping the top of the steel, and 5/10ths was high on the steel. I'm not ruling out the fact it could be me. I have a hard time shooting this rifle because its just so small. Wondering if my loads are shooting faster than initially chronoed though. I'll have to chrono to find out for sure.

I've gotten mixed answers on the hide, as well as google results. For the most part since IMR 4350 is not one of hodgdon's extreme powders results are saying it's temperature sensitive.

[Sevens]

I would certainly bet that you are seeing higher velocities and higher pressures on warmer days -- and if the ammo is sitting in the sun for a good bit on a hot day (or left on the seat of a car...), I'd bet it would go even higher.

Hodgdon says that 40.2 grains is a max load for the Hornady A-Max (not the same bullet you used), but if you didn't see a whole bunch of high pressure indicators when you shot the load at 80 degrees, I wouldn't guess that it's a dangerous load...but every rifle is different.

[Dan Newberry]

We had a shooter using a Remington 40x .243 win last Saturday... he had his drop chart marked for 32.5 MOA at 1040 yards... (pretty flat shooting cartridge)... he was using a Hornady 100 grain Spire Point boat-tail, and 40 grains of IMR 4350.

As the day wore on... we experienced a temperature drop of about 15 degrees. When we went back to that target, he needed nearly 34 MOA to center it again.

So it indeed appears (anecdotally anyway) that the IMR 4350 might be a little fussy about the temperature. And I do say "might be" as I've not really tested or proven the issue. Other guys claim over 100 fps of velocity loss from 80ish to freezing... and it could be the case.

Even if the IMR 4350 load did lose around 50 fps (which is what the drop change would have indicated) that doesn't mean it would be a linear drop all the way down the thermometer. We saw temps go from around 75 degrees to around 60 degrees... that's when the difference seemed to pop up. Could have been something else though, so I can't emphatically say it was the powder.

Just adjust your drops to match reality in the temperature you're working in. There are of course more temperature stable powders available, but I'm a fan of the old IMR powders because they're so consistent lot to lot... unlike Hodgdon's "extreme" rated versions.

I haven't shot a lot of IMR 4350 at long range until recently... I use it in my .270 with 150's (52.5 grains) and it works great... but will need to check its behavior at long range next time I get the chance.

Dan

[5RWill]

It's weird that the load even runs in the rifle given the twist is 1:10. Might switch it to H4350 before deer season hits. Seems it's more stable and some are getting more performance out of it in 18-20" .243s. Though lot variance isn't a good thing, we don't shoot this particular rifle enough to worry about it.

[Jimro]

"Temp Sensitive" is like "burn rate" in that it isn't an exact science. The temp sensitivity of a powder depends a lot on the cartridge and load used. A small case like the 243 Win filled to the max with 4350 is going to be different than a 270 Win with a "middle of the road" charge load.

Heck, the Navy chose IMR 4064 for Mk316 ammunition to replace M118LR for SOCOM because in that configuration it is less temp sensitive than Reloader15 in that configuration.

Bottom line, all powders are temp sensitive, some just moreso than others.

Jimro

[5RWill]

Yeah, i've just never seen the effects of it. I will have to chrono to be sure. I run mostly varget through all my .308 based calibers, which is for the most part very stable.

[hooligan1]

I use the IMR 4350 in alot of my rifles and haven't really noticed a big difference in poi, with that being said it's mostly hunting and load developement where I use IMR 4350, .270 win, 30-06. I also use H 4350 in my .270 win with 130 Accubonds, I really can't say I notice the differences that you fellas are commenting on.

Welcome Dan Newberry, I use some of your philosophy.

[5RWill]

Got back home put some scope covers on my VX-R patrol and they were a bit snug. As i was putting the front on the objective lens the scope slid back on the base.. could've been the problem. Shot on paper and it was shooting 5/10ths high at 100yds. So i adjusted and then ran it out to 300yds with success. May have been lot variance maybe the scope, idk. I can't shoot that little thing, it's shooting sub-MOA, it's a deer rifle it will work lol.