IMR 4350 Temperature variance?

[5RWill]

Running 105gr VLDs out of our youth model .243 @ 2700fps, over 40grs of IMR 4350. Finally loaded some more and went out to check my zero and make sure everything had been retained since last winter.

1st shot at 100yds was a tad high, thought it might have been me. Then at 200yds with 6/10ths of a mil elevation (i thought i was missing) they were scraping the top of a 8" circle. And at 5/10ths it's a little high above center, POA. So i'm wondering about the temperature sensitivity of IMR 4350.

 

[turbo54]

Re: IMR 4350 Temperature variance?

I don't have any data for the temp sensitivity, but can guaran-damn-tee you it's not what's causing a .5 or .6mrad POI shift @ 200 yards.

Any reason you don't run H4350 instead?

 

[majohnson2]

Re: IMR 4350 Temperature variance?

I have read someplace that IMR 4350 was a powder not a temp sensitive powder.

 

[5RWill]

Re: IMR 4350 Temperature variance?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">I don't have any data for the temp sensitivity, but can guaran-damn-tee you it's not what's causing a .5 or .6mrad POI shift @ 200 yards.

Any reason you don't run H4350 instead?</div></div>

I didn't mean a .5 Mrad shift in POI i was just listing the elevation i had dialed. Usually it's .5mrads for a 200yd shot it's shooting a tad high from POA at .5mrads elevation. I had generally dialed .6 because that's what the ballistic calculator called for with the given conditions. The shift however isn't much, certainly nowhere near half a Mil as that would've been off the target. Sorry for the confusion. The temperature variance from when i first shot the load is 20 or so degrees. I started shooting this particular load at the end of last winter when it was in the 50s where as it was 80F today.

Could've been me though. This is one rifle i have difficulty shooting due to it's size. Really need to build a full size rifle on the action. Damn thing is so small.

Just don't have any and oddly last time i tried to order some i couldn't find any. Been wanting to shoot H4350 for some time. Though with my .308 varget gives me very consistent results.

 

[Huckleberry75]

Re: IMR 4350 Temperature variance?

IMR4350 does have a bit of temp swing, but am unsure as to how much/degreeF.

 

[5RWill]

Re: IMR 4350 Temperature variance?

Its not a huge shift from my zero just a little high. I'm thinking it's shooting a little faster than we initially chronoed last winter.

 

[MJY65]

Re: IMR 4350 Temperature variance?

I'm not sure about FPS/degree, but a near max load of 4350 that I had worked up one spring locked the bolt on a warm summer day.

 

[mjh30]

Re: IMR 4350 Temperature variance?

IMR 4350 does have some temp sensitivity issues, you are shooting a load that previously was zeroed in 50 degree temp, now you are shooting it in 80 degree temps. You think its shooting a little hotter, well you are probably right.

 

[MALLARD]

Re: IMR 4350 Temperature variance?

i'd say your change in POA/POI has very little to do with the temp sensitivity of imr 4350. I believe the blame falls elsewhere.

 

[Unknown]

Re: IMR 4350 Temperature variance?

IMR4350 is most definitely temperature sensitive. I have a load for my 300 win mag using 68.5 grains, over a Sierra 190 MK. I developed this load during cold winter temperatures running up to 60F tops. Usually, the velocity is 2960 FPS.

When I chronoed the same ammo in 80F summer, it was over 3100 FPS. The first round or two I though something was wrong with the chrono. After 3 rounds, I quit shooting it. I'll save that ammo for winter, and am going to switch to H1000. I also noticed bolt lift was just a touch sticky.

 

[Rob01]

Re: IMR 4350 Temperature variance?

Use <span style="font-weight: bold">H</span>4350. It's one of Hodgdon's Extreme powders and is very temp insensitive.

 

[Rthur]

Re: IMR 4350 Temperature variance?

+1 with Rob

 

[5RWill]

Re: IMR 4350 Temperature variance?

Think i'm going to switch to H4350 before the deer season hits.

 

[ksthomas]

Re: IMR 4350 Temperature variance?

Blackops,

No such thing as a temp insensitive powder; they ALL have some degree of temperature sensitivity. In the case of IMR powders, this has traditionally amounted to about 1.7 fps per degree as a general rule. There's been a lot of focus on this in recent years, and this has given us some less sensitive powders, like the Hodgdon "Extreme" line, and a few others. Double base powders are still the most sensitive to this, and if it's a major consideration, I'd suggest sticking to single based propellants.

From the differences you've described, I'd have to suspect that there's something more than just a temperature variation involved here. A new can? Different lot of the "same" powder? Got to be something else.

 

[5RWill]

Re: IMR 4350 Temperature variance?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kevin Thomas</div><div class="ubbcode-body">Blackops,

No such thing as a temp insensitive powder; they ALL have some degree of temperature sensitivity. In the case of IMR powders, this has traditionally amounted to about 1.7 fps per degree as a general rule. There's been a lot of focus on this in recent years, and this has given us some less sensitive powders, like the Hodgdon "Extreme" line, and a few others. Double base powders are still the most sensitive to this, and if it's a major consideration, I'd suggest sticking to single based propellants.

From the differences you've described, I'd have to suspect that there's something more than just a temperature variation involved here. A new can? Different lot of the "same" powder? Got to be something else. </div></div>

Honestly it's probably me, i can't shoot this rifle it's just too small and doesn't fit me. It is a lot of different powder. Though to reassure i'm going to chrono and shoot a couple more shots. Only fired 5rds because i was going to check my zero and go coyote hunting that night, before the rain came. Want to build a 18.5" rig off of it with a full but it's not mine. Dad loves the fact that it's so small.

 

[5RWill]

Re: IMR 4350 Temperature variance?

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. Maybe lot variance the scope, idk. I can't shoot that little thing, it's shooting sub-MOA it's a deer rifle it will work lol.