H4350 hotter than normal?

[Greyfox]

H4350 is my most used powder, my go-to in my competition rifles(260, 6.5CM, 6.5x47). This powder has proven very consistent with my loads, and very close to published data. My most recent purchase within the last month or so of a 10#x10 case produces velocities and actual shooting data that is equivalent to my prior lots going back at least a few years. I test new lots of powder with my Magnetospeed and a ladder test. I am generally suspect of results generated by optical chronographs. In the OP's case, I would try to confirm his velocities. I expect that if there was a change in the performance of H4350, I would have heard about it from buddies that, like myself, use a lot of H4350. I had read a while back that some shooters experienced a "hotter" performance of H4350, but I believe this pre-dates the "Extreme" formulation.

 

[woodnut]

I used to be a "speed freak". more is better. whoowhoo. Not any more. I did notice your 63.0 gr load was slower than the 62.5 load. But they were also at the short 5' chrono reading. I'm glad to see you go down to 61.8 gr. You can always compensate with the scope for any drops at distance, so don't worry about being ultra fast. That big bullet will geterdun at any speed!

 

[dibbs]

New powder lot, new lot of brass, two things have "potentially" changed substantially with your load. I am guessing you need to re-develop your load with the new components and as others have recommended move your chronograph out a bit. A number of years back I had a new "fast" lot of Reloder 22, as I recall I had to drop my pet load approximately 1.5 grains.
I have had pretty consistent lot to lot results with H4350, but take this into consideration when I break into a new keg.

 

[RogerPA]

Please back your chrono out to 15'.
Also, I've owned about at least six Mcgowen barrels, two of which has exhibited massive pressure/velocity increases in sub -freezing temps using the exact same lot# components .

I'm not entirely blaming the Mcgowen barrel but these two scenarios had Mcgowen barrels involved. One was with Retumbo the other with RL33.

Regarding "tbrice23"'s comment on massive increases in pressure/velocity in sub-freezing temps: I've been searching for a reference to this observation! Just this week, while shooting the exact batch of loads created and tested this past fall in 50 degree temps, I decided to fire a few rounds in the 4 degree temps. The rifle is a Christensen 26 Nosler, with 72.0 grains of Retumbo, Federal 215M primer, and 130 gr. Berger VLD hunting bullet. I'll spare you the intimate details, but the bottom line is a modest load that in the fall shot under 1/2" moa without a hint of pressure issues, in the 4 degree temps is a load that's hard to open the bolt on, and has two bright extractor rings printed on the headstamp. (I even pulled a couple of rounds just to make sure nothing funky happened. Every load was exactly 72.0 grains, and every bullet pulled weighed 130 grains.). I'm familiar with excessive heat causing pressure variations, but not so much with cold. Is this a common occurrence that doesn't get much press? Or perhaps a phenomenon related to certain barrels and/or powder? Thank you for sharing whatever experience you've gained in this regard.

 

[243winxb]

https://www.thehighroad.org/index.p...imer-temp-sensitivity-testing-results.830366/

Temperature testing link.

 

[Predator 22]

https://www.thehighroad.org/index.p...imer-temp-sensitivity-testing-results.830366/

Temperature testing link.

Didn't seem like a very controlled test. I'm definitely not buying the 300+ fps difference with 4831. It was probably due to using a old optical crono.

 

[theodoreh]

I think my H4350 is normal.

It is the heavier norma case, design of the bullet, copper fouling and possibly other factors involved.

 

[243winxb]

the 300+ fps difference with 4831.

I would like to see it tested with a magnum primer.

 

[Predator 22]

I would like to see it tested with a magnum primer.

Shouldn't need a mag primer though. Especially with the case capacity of the '06 family and a single base powder. I would be willing to bet that it's not the powder.