6.5CM/fast powder question

Pickle Rick · Tuesday at 8:18 PM

I have a 20” 6.5CM that I want to run 123’s in. I’m getting great velocity with Staball Match and IMR 4895. My question is, will the velocity drop be less significant per barrel inch with relatively fast powder? For example, I’m getting 2870 fps with 40.5gr Staball and 2828fos with 39.2gr 4895. Thats a lot faster than I expected. No sticky bolt, some primer cratering but I’m using small rifle primers.

Doom · Wednesday at 9:11 AM

You are comparing two different types of powder. StaBall is a double based powder and H4895 is a single based powder. Generally the double based powders are higher energy and give a higher velocity for similar peak pressures. Staball is also slower so that also tends to increase the velocity. As for changes in velocity per inch of barrel length, that is difficult to say because of all of the noise associated with trying to test, but in general I would say that the difference in this case would be insignificant.

diggler1833 · Wednesday at 9:22 AM

I am getting almost the same velocity out of a 22" 'Salvage' in 6.5CM (2,815 ish) with about a half grain less IMR 4895 and a 120gr bullet for comparison. I am using a LRP though.

I think your velocity is in the right ballpark, and as long as you're getting the accuracy you want that you should have zero worries otherwise.

FWIW, I did take my load testing up to Nosler's max published load (39.5) in Starline brass - which is notoriously thick with less case capacity - and still didn't get any swipes smears, or flattening of the primers.

Pickle Rick · Wednesday at 6:44 PM

Doom said:
You are comparing two different types of powder. StaBall is a double based powder and H4895 is a single based powder. Generally the double based powders are higher energy and give a higher velocity for similar peak pressures. Staball is also slower so that also tends to increase the velocity. As for changes in velocity per inch of barrel length, that is difficult to say because of all of the noise associated with trying to test, but in general I would say that the difference in this case would be insignificant.

Yes, I know the difference between single and double based powders and that Staball is slower than 4895.

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