IZH 46M velocity after reseal.

[buellm2]

I chrono tested today after replacing the piston seal.  I did not replace any other seals.   405 fps plus or minus 6 fps with 7.9 CPHP.     460 FPS  + or - 5 fps with  7.0 Meisterkugeln.  It was pretty cold on my deck (mid 30s).   Is that an acceptable velocity? 

[Frank in Fairfield]

Looks perfect:

[buellm2]

Interesting that the average velocity differential between the two guns when shooting the RWS 7.0 WC and Meister 7.0 WC varies  less than 1%.   With the 7.9 CPHP there's a 5% difference.

[Frank in Fairfield]

The 7.9 is very tight in my IZH46 and IZH 60..

[MDriskill]

The thing I have found with CPHP's is that the heads tend to be a bit bigger than most pellets, and the skirts a bit smaller. Thus you get this weird situation where the feel very tight when you load 'em, but actually may not be sealing that well.

A typical ".177" pellet measures .176 to .178 at the head (just enough to contact the rifling lands), and .182 to .184 at the skirt (seals the bore and grabs the rifling grooves). CPHP's measure about .180 on both ends, which when combined with the hard lead compound, can lead to puzzling velocity numbers.

CAVEAT: The last Crosman pellets I measured were pretty old! But I suspect they haven't changed much.