Dynamic .25 cal PCP - First Impressions and Observtions

[nervoustrigger]

Well fellas, I'm just tickled pink by how this .25 cal is shooting.  I dialed in a few clicks of windage yesterday to fine tune the 43 yard zero (after greasing the house fly) and then put it away.  Today after work I wanted to check for any signs of regulator creep or zero shift and it just sent the first pellet right through the center of the aspirin-sized red bullseye.  Next shot clipped the red.  That was the last two pellets in the magazine so I decided to stop while there was a big smile on my face.  Accounting for the windage adjustment, that's sub-MoA for 6 shots at 43 yards with the buttstock shouldered, not on bags.  This thing is sweet.

[Gertrude]

Jason,
 That's sure to put a smile on your face.

These guns do show a LOT of potential. I feel they are kind of a budget "diamonds in the rough" that benefit greatly with a little knowledgeable and experienced tinkering. So far, I have been focusing on the unfortunate QC issues, and have not spent any real time tuning or tinkering yet. Hopefully we have identified all of the problem areas, and can get them coming out of the box soon with similar performance. I'm looking very forward to seeing what your 'smithing skills will produce.
 What are your current velocities and shot counts looking like ?

[nervoustrigger]

Ron, I haven’t run a full string since the rebuild but I’ll get that for you as soon as we get a break in the rain from this tropical storm.
 
At this point I can only say that by using the shorter spring and adjusting to the knee, efficiency is much better than stock but nothing great.  Limiting factors are the small plenum and a middling barrel length (approx. 17”) so I’m probably going to keep it around the 45fpe level.  I may see about fashioning an SSG but seeing how it’s stacking JSB heavies right now, I’m probably going to let this ride for a while.
 
For the guys that are hungry for power, what you could do is bypass the regulator and see what it cranks out with the full 3000psi on the valve.  The OEM hammer spring looks like it’s plenty strong enough to knock it open, and of course it’s possible to dial in some preload by tightening the cap behind it.

[nervoustrigger]

Wolverine reminded me of something that I wanted to mention about a leaking poppet after the rebuild.  There’s a brass bushing threaded into the valve body that guides the valve stem.  When I reinstalled it, I applied threadlocker and snugged it up (threadlocker is anaerobic so being tight helps it cure more quickly).
 
Unfortunately, the poppet then leaked badly when I tried to fill it.  So I took it apart to burnish the poppet against the valve seat with a slurry of J-B bore paste and polishing compound.  After spinning the parts together for a few seconds, I inspected the valve seat and sure enough, there was a polished crescent appearing instead of a uniform circle.  It occurred to me that the brass bushing might have canted ever so slightly when it bottomed out (tightened), whereby holding the valve stem at a slight angle and preventing the poppet from seating fully.  So I backed it off a quarter turn and tried again.  Very quickly a nice polished circle appeared.  Once reassembled, it sealed perfectly from zero pressure with a hand pump.
 
I then set it aside overnight to allow the threadlocker to cure.  The point being, if I had fired it right away, quite possibly the blast of air would have blown the liquid threadlocker right out of the threads and then the bushing would be apt to back out over time.
 
Tl;dr  Don’t bottom out the brass bushing in the valve body.  Apply threadlocker, thread it in until snug and then back off ¼ turn.  Then install the poppet, valve spring, and cap…what that does is it presses the poppet against the valve seat and aligns the bushing to the valve stem while the threadlocker cures.

[Wayne52]

Wolverine reminded me of something that I wanted to mention about a leaking poppet after the rebuild.  There’s a brass bushing threaded into the valve body that guides the valve stem.  When I reinstalled it, I applied threadlocker and snugged it up (threadlocker is anaerobic so being tight helps it cure more quickly).
 
Unfortunately, the poppet then leaked badly when I tried to fill it.  So I took it apart to burnish the poppet against the valve seat with a slurry of J-B bore paste and polishing compound.  After spinning the parts together for a few seconds, I inspected the valve seat and sure enough, there was a polished crescent appearing instead of a uniform circle.  It occurred to me that the brass bushing might have canted ever so slightly when it bottomed out (tightened), whereby holding the valve stem at a slight angle and preventing the poppet from seating fully.  So I backed it off a quarter turn and tried again.  Very quickly a nice polished circle appeared.  Once reassembled, it sealed perfectly from zero pressure with a hand pump.
 
I then set it aside overnight to allow the threadlocker to cure.  The point being, if I had fired it right away, quite possibly the blast of air would have blown the liquid threadlocker right out of the threads and then the bushing would be apt to back out over time.
 
Tl;dr  Don’t bottom out the brass bushing in the valve body.  Apply threadlocker, thread it in until snug and then back off ¼ turn.  Then install the poppet, valve spring, and cap…what that does is it presses the poppet against the valve seat and aligns the bushing to the valve stem while the threadlocker cures.

I'm kinda wondering about that on my .22 because it is leaking very slow and I figure it's by the poppet, just found that out this morning when I was going to head to the state land with it, I did fill it and brought along my tank too but I really wouldn't needed the tank if I'd just gone hunting rather than shooting at some targets too.

[Gertrude]

Wolverine reminded me of something that I wanted to mention about a leaking poppet after the rebuild.  There’s a brass bushing threaded into the valve body that guides the valve stem.  When I reinstalled it, I applied threadlocker and snugged it up (threadlocker is anaerobic so being tight helps it cure more quickly).
 
Unfortunately, the poppet then leaked badly when I tried to fill it.  So I took it apart to burnish the poppet against the valve seat with a slurry of J-B bore paste and polishing compound.  After spinning the parts together for a few seconds, I inspected the valve seat and sure enough, there was a polished crescent appearing instead of a uniform circle.  It occurred to me that the brass bushing might have canted ever so slightly when it bottomed out (tightened), whereby holding the valve stem at a slight angle and preventing the poppet from seating fully.  So I backed it off a quarter turn and tried again.  Very quickly a nice polished circle appeared.  Once reassembled, it sealed perfectly from zero pressure with a hand pump.
 
I then set it aside overnight to allow the threadlocker to cure.  The point being, if I had fired it right away, quite possibly the blast of air would have blown the liquid threadlocker right out of the threads and then the bushing would be apt to back out over time.
 
Tl;dr  Don’t bottom out the brass bushing in the valve body.  Apply threadlocker, thread it in until snug and then back off ¼ turn.  Then install the poppet, valve spring, and cap…what that does is it presses the poppet against the valve seat and aligns the bushing to the valve stem while the threadlocker cures.

Excellent info.

Another thing to be aware of is that some guns brass bushing will go in farther than others. We have 2 guns that the brass bushing can thread in so far that they will actually begin covering/blocking the exhaust port of the valve.
So as advice to others out there who are reading this, when you are installing the brass fitting, be sure to watch the port, and back out the fitting to the edge of the port.

[nervoustrigger]

Well, sunshine smiled upon me after work this evening so I set up the chronograph and ran a string with the .25 cal.

It gave 31 shots inside of a 4% ES with an average energy just shy of 45fpe.  Or 28 shots inside of a 2% ES.  I'm a bit disappointed at the efficiency, even given the caveats in my previous post...so it must've been really bad out of the box.  Still, 31 shots is about 20 more than I've ever needed for a long gray squirrel hunt and the accuracy is there in spades so I'm just gonna enjoy this for a while.

Gotta say the regulator is working splendidly.  It was 1fps away from having 26 shots inside of 1%...and this was with a 50/50 split of MK I and MK II pellets!

[Wayne52]

Jason your 25 is working great IMO !!!

[Wolverineshooter]

Great strings.

[Bob Pratl]

Looks great and well worth your efforts in tuning up your DAR25. I hoping that mine look as good.
Are using the stock hammer spring and what was the final spring adjustment?

[Wayne52]

Right now I have my .25 set for 1 clip, the cast 34.5 grain pellets I'm shooting shoot extremely well out of this gun at 900fps. It's no problem getting a dime size group with them at 40 yards

 FPS                                                                 FPS
1.   900.8             34.58g     62.32fpe            6.   914.7            34.66g     64.40fpe
2.   910.2             34.42g     63.33fpe            7.   899.2            34.48g     61.92fpe
3.   914.4             34.64g     64.32fpe            8.   872.4            34.66g     58.58fpe
4.   918.4             34.42g     64.48fpe            9.   895.4            34.52g     61.46fpe
5.   900.4             34.62g     62.33fpe            10. 891.3            34.32g     60.55fpe

[Bob Pratl]

Right now I have my .25 set for 1 clip, the cast 34.5 grain pellets I'm shooting shoot extremely well out of this gun at 900fps. It's no problem getting a dime size group with them at 40 yards

 FPS                                                                 FPS
1.   900.8             34.58g     62.32fpe            6.   914.7            34.66g     64.40fpe
2.   910.2             34.42g     63.33fpe            7.   899.2            34.48g     61.92fpe
3.   914.4             34.64g     64.32fpe            8.   872.4            34.66g     58.58fpe
4.   918.4             34.42g     64.48fpe            9.   895.4            34.52g     61.46fpe
5.   900.4             34.62g     62.33fpe            10. 891.3            34.32g     60.55fpe

Wayne, very, very nice for 60+ fpe. What is your hammer spring settings?

[Rat Sniper (AKA: PaulT58)]

Right now I have my .25 set for 1 clip, the cast 34.5 grain pellets I'm shooting shoot extremely well out of this gun at 900fps. It's no problem getting a dime size group with them at 40 yards

 FPS                                                                 FPS
1.   900.8             34.58g     62.32fpe            6.   914.7            34.66g     64.40fpe
2.   910.2             34.42g     63.33fpe            7.   899.2            34.48g     61.92fpe
3.   914.4             34.64g     64.32fpe            8.   872.4            34.66g     58.58fpe
4.   918.4             34.42g     64.48fpe            9.   895.4            34.52g     61.46fpe
5.   900.4             34.62g     62.33fpe            10. 891.3            34.32g     60.55fpe

Wayne:  Looks like you are well prepared for that coyote!  Awesome results!  I've got my .25 holding air, just waiting on some tall 30mm rings so I can mount the scope.  That magazine for the .25 is huge!

[Wolverineshooter]

Wayne, Great strings for the power.

[Wolverineshooter]

Have you seen https://www.gatewaytoairguns.org/GTA/index.php?topic=147936.0?

I am wondering if the DAR can do the same with heavier pellets.

[Lastdog]

Nervioustrigger,Wayne 52,  can both or one of you give me a step by step of how to tune my dar 25 to get these numbers? Should get mine or a replacement back in a week (according to aim) and want to set it up for urban coyotes. I am on 80 acres but surrounded by houses so can’t use firearms. I have read about your tunes on some of your posts but would be great to see a post with all in one. I am fairly new to air rifles so if you could use the k.i.s.s. Method it would be great help for me. Thanks

[Rat Sniper (AKA: PaulT58)]

Nervioustrigger,Wayne 52,  can both or one of you give me a step by step of how to tune my dar 25 to get these numbers? Should get mine or a replacement back in a week (according to aim) and want to set it up for urban coyotes. I am on 80 acres but surrounded by houses so can’t use firearms. I have read about your tunes on some of your posts but would be great to see a post with all in one. I am fairly new to air rifles so if you could use the k.i.s.s. Method it would be great help for me. Thanks

+1!  A tuning thread specific to the DAR25 would be awesome!

[Bob Pratl]

Nervioustrigger,Wayne 52,  can both or one of you give me a step by step of how to tune my dar 25 to get these numbers? Should get mine or a replacement back in a week (according to aim) and want to set it up for urban coyotes. I am on 80 acres but surrounded by houses so can’t use firearms. I have read about your tunes on some of your posts but would be great to see a post with all in one. I am fairly new to air rifles so if you could use the k.i.s.s. Method it would be great help for me. Thanks

+1!  A tuning thread specific to the DAR25 would be awesome!

+2 on tune data and procedures.

[Wolverineshooter]

Nervioustrigger,Wayne 52,  can both or one of you give me a step by step of how to tune my dar 25 to get these numbers? Should get mine or a replacement back in a week (according to aim) and want to set it up for urban coyotes. I am on 80 acres but surrounded by houses so can’t use firearms. I have read about your tunes on some of your posts but would be great to see a post with all in one. I am fairly new to air rifles so if you could use the k.i.s.s. Method it would be great help for me. Thanks

+1!  A tuning thread specific to the DAR25 would be awesome!

+2 on tune data and procedures.

+3

[Nvreloader]

Jason

That spread sheet is outstanding,
Very simple to understand and see your results etc.

By any chance is this spread sheet available to us uninformed pellet shooters?

When you say, scale them manually, you can move the required boxes to fit your computer?
Sorry for the dumb questions, I am not tech savvy.

Tia,
Don