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All Springer/NP/PCP Air Gun Discussion General > German AirGun Gate

Standard deviatio 95 fps

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Fran49829:
My HW30 began shooting erratically and has a sd of 95 fps over 10 rounds ( 520 to 615).  I pulled the main spring and it looks fine.  The lockup seems good.  Any ideas?
Fran

eeler1:
Thats an extreme spread all right.  So, not the spring.  Was there a pattern to the fps?  Like started at 615 and dropped continuously to 520?  I suspect the piston seal is the culprit, in any case.

Yogi:
As mentioned, check the piston seal.  Then check the breech seal.  Put a piece of TP over the barrel lock-up and see if it moves.
Otherwise, inconsistent lubrication. :-\

-Y

FWIW-always check your stock screws.

Mark 611:
Let's ask a few questions first, did you buy the gun new? if so, how many shots have you put through it? and lastly has the gun ever been opened up? 8)

MDriskill:
What you describe is "extreme deviation" of the velocity over the shot string. "Standard deviation" is a different bit of mathematical chicanery that analyzes consistency over the string.

Now - with my annoying trivial pedantry out of the way - the usual suspects have been well covered above. But I would also ask what pellets you are using (any gun likes some better than others of course). An odd spike from a diesel, odd drop from a peewee pellets, etc., are not unusual; but if it's gone from "mostly high" to "mostly low" then yeah something is off.

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