Canadian Airgun Forum

I have two Streamline .22s. One has a Huma regulator and a 2-1/2" power plenum. The other is original.

Testing both with 14.3 gr Crosman Premier HP:

With Huma regulator and a 2-1/2" power plenum:
MPS FPS FPE
Average 307.17 1007.77 32.05
Deviation 1.36 4.46 0.27

The original before adding the 1" FX Power Plenum:
MPS FPS FPE
Average 291.79 962.91 29.45
Deviation 1.06 3.51 0.21

The original after adding the 1" FX Power Plenum:
MPS FPS FPE
Average 301.41 994.65 31.42
Deviation 0.93 3.07 0.19

I can understand the increase in velocity after the Power Plenum, but what explains the improvement in deviation?

FWIW: I may swap the two Power Plenums between the guns to see what happens. The larger PP is $70.00US, while the 1" PP is only $25.00US, so the less expensive one seemed a better bet as the experiment.

Has anyone any additional thoughts?

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Slavia 618 .177
Webley Senior .22
Jelly SUPER 4.5 mm
Webley Viscount .177
Kral Mega Marine Walnut .22
Artemis PP750 .22
FX Streamline .22 walnut
FX Streamline .22 composite
FX Dynamic 500 .22

The increase in deviation will be detrimental to longer range accuracy.
Appears the FX plenum is best matched for the Streamline and Dreamline, I assume.
Did you also alter the transfer port in size?
My Dreamline is still giving the best (highest) speeds using the medium setting, not the 25/30 setting.
I guess I should also be looking at the standard deviations LOL.

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Best Wishes
Daryl

I haven't tried increasing the transfer port size, because I haven't found any information on the effects for the Streamline configuration I am using. I think that 1,000 fps is about it for the pellets, at least until to do some more work regarding accuracy.

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Slavia 618 .177
Webley Senior .22
Jelly SUPER 4.5 mm
Webley Viscount .177
Kral Mega Marine Walnut .22
Artemis PP750 .22
FX Streamline .22 walnut
FX Streamline .22 composite
FX Dynamic 500 .22

I think the pellets at 1,000fps is a little high (according to U-tubers), but the 22gr. JSB Hybrid or other .22 slugs might like that speed.
That said, my condor does 1/2" at 55yards with JSB Hades at 1,076fps mv, still shooting well and consistently right out to 118yards.

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Best Wishes
Daryl

With lighter pellets at higher speed the wind drift is much noticeable.
If you prefer higher then 950fps to reach out to longer shots you shall consider heavier pellets like the MRD's. But that would need some homework on that gun.
For 15gn Premiers I cannot recommend anything higher then 900 but more into 850's. Slower is better.
These my findings shooting on paper 50 to 70 meters well over 5-7K testing just anything available from 15-18-21 grain.

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FX Impact MK2 PP - heavy modded
Edgun Leshiy2 - heavy modded
and a lot more scopes with great glass