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All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: Earl on June 30, 2019, 01:50:30 AM

Title: What muzzle velocity gives the smallest 10 shot groups for JSB 13.43 gr pellets?
Post by: Earl on June 30, 2019, 01:50:30 AM

I am shooting a .177 Marauder and I can change the muzzle velocity by adjusting the valve screw.
At a power setting of 19.8 ft lbs, the gun shoots most accurately with the JSB 13.43 grain pellets at 815 fps.
For accuracy only, what muzzle velocity should I use for JSB 13.43 grain pellets?
For JSB 10.34 grain pellets?
For JSB 8.44 grain pellets?

Does someone have a suggestion for the settings of the spring, striker and valve to get the smallest groups with the .177 Marauder?
Note: I am interested in accuracy only.  I can probably adjust from 500 to 1000 fps.

Title: Re: What muzzle velocity gives the smallest 10 shot groups for JSB 13.43 gr pellets?
Post by: Doug Wall on June 30, 2019, 07:54:25 AM

I'm not sure that there is any way to predict accuracy for an individual pellet/barrel combo. Best advice that I've seen is to keep the pellets below 900 fps. After that, it's tweaking on your own.

Title: Re: What muzzle velocity gives the smallest 10 shot groups for JSB 13.43 gr pellets?
Post by: Back_Roads on June 30, 2019, 09:06:05 AM

I have my .177 mrod shooting the 13.43 at 910 fps. any lighter pellet is probably too fast, and I would have to lessen the hammer strike to shot .

Title: Re: What muzzle velocity gives the smallest 10 shot groups for JSB 13.43 gr pellets?
Post by: rsterne on June 30, 2019, 12:34:23 PM

There is only one way to determine what YOUR barrel likes for a given pellet, and that is to try it.... I don't shoot over about 960 fps because of efficiency reasons (internal and external)….

Bob