Temperature sensitivity of IMR4451 ...

[Bobcape]

I've been working on a project to change powders in my .260AI. I'm hooked on the chambering every since I made a wildcat in 1979 while in gunsmith school. At the time I named it .260 Bobcape. I even corresponded with Ackley about the project. I've had 8 or 9 rifles chambered in it since. I have 3 right now. My primary one is on a blueprinted 700, etc. I shot it for 3 years in PRS. It's now on its 4 barrel. This time a Bartlein 25.5".

I have usually used RL17 to get the max velocity but obviously I have to pay the price with temperature sensitivity. H4350 and H4831SC have given slower velocities for me. Now I'm trying out both RL23 and IMR4451. IMR4451 gets me the same velocity as RL17 (within 12fps) and with SD of 6 and ES of 18. I'm liking that a lot. Has anyone tested IMR4451 for temperature sensitivity? What were your results? Thanks.

BTW - both RL23 and IMR4451 were giving poor SDs until near max charges.

My daughter ringing steel.

Current configuration.

RL23 and IMR4451 results.

Bob

 

[codyadams]

My .260 AI has a 29" barrel, I am currently shooting the 156 Berger HBN coated at 2940 fps using 49.0 grains RL-26 and well under max, pressure signs started around 3000 fps. I had 12 fireings on my Lapua brass with similar loads and now have 4 loading on my peterson SRP brass with no signs of wear. But I have heard RL-26 gets finicky and jumps pressure around 80-85 degrees, however in Wyoming I rarely shoot at that temperature. Below that I have tested and seen very little change from 17° to 70°, it was .15 fps per degree.

But, I have heard VV-N565 may be a good stable option, similar burn rate to RL-26 and still high energy, not sure on density if enough vv-n565 would fit, I have to use a drop tube and am right at 100% capacity with 49 grains RL-26, OAL of 2.950" with the 156.

 

[Bobcape]

Thanks codyadams. I bought a couple of pounds of RL26 last summer to give a try. I never used it and a buddy really needed it so I gave it to him. Now he owes me because I can't find RL26 anywhere!

Bob

 

[Bobcape]

I think I'm going to focus on the IMR4451 but would still like input from anyone that has tested temperature sensitivity with either IMR4451 or RL23. Thanks.

Bob

 

[lou400a]

There are few articles stating that IMR 4451 is very temp stable