Norma MRP temp sensitivity test

[Ridgerunner665]

And it was a major disappointment...

280 Ackley (24" barrel), 160 Nosler Accubond, 60 grains of MRP, lit with a CCI BR2...


66 degrees...3,003 fps...rounds fired a few months ago
85 degrees...3,058 fps...fired today, same everything (powder, primers, brass, etc.)...ejector marks and stiff extraction.

2.9 fps per degree....completely unacceptable!!!

 

[ntg]

Heard it claim that it's the same as RL22 and RL22 isn't know for temp stability.

 

[Ridgerunner665]

Heard it claim that it's the same as RL22 and RL22 isn't know for temp stability.

I now believe it is true...

 

[jrsolocam]

I shoot lot of MRP, in 240 Wby, 6.5x284 , 7wsm, and 300 Dakota. The newer lots are better than the older ones. I read that they improved it quite a bit in 2013...Never had a problem with it. what are you shooting and what's the variance compared to the Hodgon Extreme powders?

 

[Ridgerunner665]

I shoot lot of MRP, in 240 Wby, 6.5x284 , 7wsm, and 300 Dakota. The newer lots are better than the older ones. I read that they improved it quite a bit in 2013...Never had a problem with it. what are you shooting and what's the variance compared to the Hodgon Extreme powders?

This is a new lot (2014)....

H4350 in a 30-06 doesn't vary at all... Haven't tried it in the 280 Ackley

 

[jonthomps]

Interesting. Manufactures need to work on making their powders less temp sensitive. Thanks for sharing.

 

[Marine sniper]

Not saying your results are inaccurate: but to how much trouble did you go through to ensure your baselines are accurate?

For example:

When I do testing like you did I will set up my chronograph the day I am going to test / expose the rifle and ammo to the temps to be tested in long enough to take effect / level the rifle barrel and chronograph, etc. I want EVERYTHING except the temperature to be as consistent as possible.

It is usually pretty easy to get at least 20+ degree temp swings in a day. I will set everything up and shoot early in the morning; then come back later in the day to test further. For the later in the day shooting I will leave the rifle and ammo somewhere where temps are representative to the testing I am trying to do. When I am at my ranch in Idaho I can leave the chronograph and bench set up and simply put the rifle back on the bench and shoot at the exact same target I had shot at earlier.

Some guys don't take into account (particularly with closely spaced together skysceens) how much a slight degree of change in chronograph set up can effect apparent velocities.

As a source of additional data this type of testing is usually done at 1000 yards- then I can track chronograph data and actual bullet impacts. After gathering all the data you can get a true representation (1* = X MOA)

 

[Ridgerunner665]

Not saying your results are inaccurate: but to how much trouble did you go through to ensure your baselines are accurate?

For example:

When I do testing like you did I will set up my chronograph the day I am going to test / expose the rifle and ammo to the temps to be tested in long enough to take effect / level the rifle barrel and chronograph, etc. I want EVERYTHING except the temperature to be as consistent as possible.

It is usually pretty easy to get at least 20+ degree temp swings in a day. I will set everything up and shoot early in the morning; then come back later in the day to test further. For the later in the day shooting I will leave the rifle and ammo somewhere where temps are representative to the testing I am trying to do. When I am at my ranch in Idaho I can leave the chronograph and bench set up and simply put the rifle back on the bench and shoot at the exact same target I had shot at earlier.

Some guys don't take into account (particularly with closely spaced together skysceens) how much a slight degree of change in chronograph set up can effect apparent velocities.

As a source of additional data this type of testing is usually done at 1000 yards- then I can track chronograph data and actual bullet impacts. After gathering all the data you can get a true representation (1* = X MOA)

For both phases of the test...everything was out in the open (outside) for the entire day...everything was at the ambient air temperature.

Chrono setup and use...I always take the time to ensure I'm shooting straight through and across, I'm well aware of what even a slight angle will do to the numbers.


The baseline data is as good as it can be outside of a dedicated lab and much more expensive equipment.

 

[Marine sniper]

Sounds like you did your homework.