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December 7 2017 at 5:02 PM
Randall  (Login badgerfarm)

Response to Re: I have one in .25

Running a tethered setup over the chronograph I averaged 870 FPS with JSB 25's, Beeman Kodiak 31.02 gr avg 810, Benjaminn domes avg 830, H&N Field target avg 918 fps. The only pellets that I've checked for accuracy at 50 yards are the JSB 25's, the Beeman 31's, and JSB 34's. The JSB's were the most accurate in both weights with the Beemans an OK second. I've lost the photos of the targets but will get more the next outing. The machine work I did myself with the mill and lathe. Here is a list of the mods.

Bored the pressure gauge block from a 1/8 hole to a 7/16 a 900% increase in area for flow. This made it necessary to teflon tape and o ring the gauge block screw to seal them. The block could benefit from a redesign which I'm thinking about now.

Bored the end cap of the valve to it's max possible diameter without cutting into the threads.

Removed the valve spring since space is very limited in valve body.

Bored the TP holes to .160 from a .070 for better flow.

Machined the delrin limiting block on the valve flush removing the step for move valve travel.

Removed the auto safety set as it was interfering with smooth probe movement.

Polished the probe bore and the probe itself plus lubed with synthetic grease.

Removed the probe detent ball and spring as it interfered with smooth probe movement.

Honed the striker bore and polished the cocking bolts plus lubed with synthetic grease.

Disassembled the trigger group cleaned and polished all surfaces and pivot points. The trigger is now passable.

The last thing is will do is make a new free flowing valve body because of the restrictive interior of the stock valve. I think it might be possible to pick up 75 fps by doing this mod. The interior of the stock valve has almost no free flow space because of the design.

The last mod was to rechamfer the magazine pellet clear plastic front and remove the orings from the mags. These were interfering with smooth chambering of the new pellet. The O ring should be mounted in the barrel for this design but the mods made it workable. As a last touch I added a couple of turns of preload to the mag springs to increase the tension some. It's a whole new feel to it now.

I'm very pleased with the Sentry .25 now after the changes. It has been transformed from a gritty feeling non functioning low power air rifle to a usable platform. It's about what I expected for the price. It's now a matter of trying different weight springs and settings to see what's possible.

Let me know if you have any other questions and I'll try to answer them.

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