Need Help: Velocity Issues

[Bill Steele]

To me, it seems maybe a few different things are going on. Clearly temp will raise pressure/velocity, but it seems that may not explain the big variance in your results.

Perhaps the chrony also had errors

To me, if you are not seeing any major pressure signs, I would not worry about it.

I agree that you need to shoot longer strings to get reliable velocity data.

Good luck, have fun.

[Bmars06]

Yea, I definitely think it's a temperature issue. I'm not too sure about the chrony issues. The Load 1 (WXR) results are within expectation and I'm under the belief that WXR is a more resistant powder to heat.

However, the other powders seem to put about a larger velocity difference and therefore I think that's a powder sensitivity issue and not really a chrony issue. If it was a chrony issue, I would think that the WXR would have a large differentiation, like the other powders.

I read on a different forum that it seems like if you work up a load below 85 degrees ferenheit, that the velocity/pressure can change considerably once it hits 85 degrees and higher. It seems like 85 degrees is a tipping point for some powders from the results I've seem from other people.

[Bill Steele]

Yea, I definitely think it's a temperature issue. I'm not too sure about the chrony issues. The Load 1 (WXR) results are within expectation and I'm under the belief that WXR is a more resistant powder to heat.

However, the other powders seem to put about a larger velocity difference and therefore I think that's a powder sensitivity issue and not really a chrony issue. If it was a chrony issue, I would think that the WXR would have a large differentiation, like the other powders.

I read on a different forum that it seems like if you work up a load below 85 degrees ferenheit, that the velocity/pressure can change considerably once it hits 85 degrees and higher. It seems like 85 degrees is a tipping point for some powders from the results I've seem from other people.

You may be right about the different powders. I know some in the Hodgdon Extreme line are very temp stable. I understand WXR is similar (if not identical) to Reloader 22 which I read is pretty temp stable.

Not sure about the 85degree tipping point thing, sounds like one of those anecdotal rules of thumb with no basi in fact, but what do I know. What I do know is Ball 2 is temp sensitive and max loads have to be reduced as the sun climbs in the sky.

As far as the crony, I am still scratching my head on how you could have gone so far up in velocity and not started seeing things like flat primers, flow and sticky bolt life. If the Day 2 velocity is right, you have a very fast barrel.

For me, the pressure signs are the main determinant in my drawing the line.

Maybe shoot a few more strings on warm days?

Good luck.

[Bmars06]

What I think I might do is keep the loads that I have for cooler days but if the temp is at 80 or above I'll drop the charge a few grains to compensate for the increased pressure and velocity to hopefully keep the velocity at the point where I want it.

When I was trying to find the right charge I shot a lot more shots on Day One to figure out that information. As such, I have a rough idea as to what each charge will put out velocity wise. With that information, I can probably guestimate what a reasonabel charge would be in warmer weather and then test that.

If I was pushing max loads in 60 degree weather, I should definitely need to back off the charge a little bit in warmer weather, regardless of chrono... just seems logical...