Peterson pressure 6.5 cm

[Andouille]

You aren't missing anything on the pressure thing....Deeper means more pressure, which means backing off powder more.

I would load 5 or 10 more at 40gr btw with only 1 being spicy and test....or...drop to 39.5gr...or....if you want a bit more gas out of it, N555, RL16 and staball 6.5 are options that are faster for testing.

I agree, a little slow, but not crazy. H4350 has been the best powder for my Tikka 6.5CM, but I've had similar velocities (+/- 25 fps) and respectable accuracy with H100V, Staball 6.5, Superformance, and H4831SC. N555 showed pressure at 2566 fps so I didn't pursue it further.

 

[wind gypsy]

Very interesting- I still don't get how reducing case volume substantially by seating deeper wouldn't affect pressure, much in the same way changing brass volume affects velocity. I'm short on time now but will run GRT in a week or so and plot the results on a similar graph. The caveat is that I'm unsure if GRT will model a jammed bullet, so the output may be more linear in the longer COAL end of the chart.

Why does a jammed bullet have more pressure?

I think with more jump, there's more gas/pressure that escapes around the bullet prior to it obturating to fill the bore. That study with a round nose bullet might have shown a larger jump before hitting min pressure than a modern spitzer, but i'm not positive.

 

[wind gypsy]

I agree, a little slow, but not crazy. H4350 has been the best powder for my Tikka 6.5CM, but I've had similar velocities (+/- 25 fps) and respectable accuracy with H100V, Staball 6.5, Superformance, and H4831SC. N555 showed pressure at 2566 fps so I didn't pursue it further.

N555 didn't seem to be an upgrade on velocity prior to pressure in my 6.5 either.

 

[streamerfish]

N555 didn't seem to be an upgrade on velocity prior to pressure in my 6.5 either.

Yeah...my experience is a bit more but not alot more on N555....Could be a small enough difference to get lost in the noise so to speak.

 

[il_cop]

@Andouille thank you for the write-up, I appreciate it.

In terms of resizing, nothing special:
Lee Ultimate
FL Sizer w/o expander ball
Touch shell holder + 1/4 turn
Lube and size
Sinclair expander mandrel at .262

This is the same setup I've used on my other 6.5 CM but with Lapua LRP brass.
That rifle (savage) was right at 2700 with 143 eldx, 22" barrel, 41 gr RL16
This is my first time using Peterson

 

[pods8 (Rugged Stitching)]

Just as a sanity check question, is all the sizing lube cleaned off your brass?

 

[il_cop]

@pods8 (Rugged Stitching)
I appreciate it. yes