Anyone have chronograph readings for a 392PA using an 18.21 gr pellet?

[Don.M]

I have a chart I got off the internet showing FPS/FPE per pump on a 392 using a 14.3 gr Crosman Premier. That gives me a decent baseline for what my rifle is doing, but as we all know, even slightly varying pellet weights and FPS can have a large affect on actual FPE.

Currently, I'm shooting 18.21 gr Crow Magnums. If I use the listed chart, then I'm putting out about 13.05 FPE @ 5 pumps (568fps). Now I know that's wrong, because I got the 568 FPS from the chart which is using a 14.3 gr pellet, a pellet almost 4 full grains lighter than the Crow Magnums which by reason have to be going slower.

What I'm asking is does anyone have any chronograph readings for a 392 with 5 and 8 pumps using an 18.21 gr pellet? I'm looking to get a more accurate idea of how much power my rifle is putting out.

[Habanero69er]

MSPs, like PCPs tend to be more efficient & produce more energy with heavier rounds.
Even though the 18.21g Crow Magnum may be going slower than the 14.3g, it may still have more kinetic energy.
You only need to have a speed of 503fps with the Crow Magnums to produce 10.23fpe, vs 568fps with the 14.3 to produce 10.25fpe.
You're going to have to use a chrony to know exactly what velocities your particular 392 is producing.

[35 shooter]

My 392 is at Mac 1 for some mods right now or i’d run some 18.1 gr. Jsb”s through it at 5 or 6 pumps for you.

Before I sent it off though, I tested crosman 14.3 gr. Domes at 8 and 10 pumps for 630.7 FPS.at 8 pumps and 671.2 FPS. at 10 pumps.
I only shot the 18 gr. Jsb”s at 10 pumps for 626 FPS. and 15.7 ft. Lbs.
The crosman domes at 10 pumps was 14.4 ft. lbs.
The rifle was retaining air at 8 and 10 pumps, so I wasn’t getting full power shots.

[Habanero69er]

Buddy, you're gonna love your 392 after Tim gets done with it. Hopefully, you're getting the full Steroid treatment with the extended billet pump arm. No more retaining air with 10-12 pumps. You're not going to need to pump it as much either since 4-5 Steroided pumps is about what you'd get with 6-8 pumps with the stock 392. 

[35 shooter]

Buddy, you're gonna love your 392 after Tim gets done with it. Hopefully, you're getting the full Steroid treatment with the extended billet pump arm. No more retaining air with 10-12 pumps. You're not going to need to pump it as much either since 4-5 Steroided pumps is about what you'd get with 6-8 pumps with the stock 392.

I ordered the full treatment minus the extended billet arm in the end.
Lol, could’nt bring myself to change the “ looks”
Of the pump arm.
I know it will be harder to pump without it on top end, but that will only be for special purpose use.
Tim has had it about a month and a half now... hopefully i’ll have it back before too much longer.
Can’t wait !

[Habanero69er]

Just forget about & it'll get there faster.   

[Robert 5mm]

Here are some chrono results from my valve modified 392