Merry Christmas to Me !!!

[Hobbyman2007]

Those new 25gr pellets are real winners in both my BT65 and the K550. So good I bought an extra 5 tins of the same batch. Urrious to try the 34’s but their out of stock except in the US.

[rsterne]

I have had no luck with the 34 gr. in .22 cal.... they have been spiralling past 50 yards.... You need a really powerful PCP to use them, of course....

Bob

[OldFart56]

Bob,

I have just taken delivery of a new Chief. I have read through this post several times and you provide lots of valuable information for those of us that are considering doing our own tune. As someone without access to machine shop tools, which of the steps you went through might I attempt, having a drill press, Dremel, files, sandpapers? I have already cleaned up and adjusted the trigger to my liking, although I didn't put in the second stage plunger as you did. Looking to get a decent shot count in the low to mid 900fps with JSB Heavies. Any advice would be appreciated. Also, does anyone have experience shooting Polymags through their Chief, and if so how do they shoot? Or opinions on the best pellet for pest control with the Chief.

Brian

[rsterne]

With your limited tools, I would drill the exhaust and barrel ports out to 5/32" (0.156"), making sure they line up correctly when assembled.... If you have to, use your Dremel to move the holes over BEFORE you drill them out.... If you have any "number drills", you can go to a # 19 drill (0.166"), or if you are feeling adventurous to 11/64" (0.172")…. Don't go larger than that, or you may damage the pellets when loading them.... If you go larger than 5/32", you should really enlarge the throat of the valve as well, but drilling that out without a lathe is tricky.... You can do it if you have a set of number drills and go ONE size at a time, using your drill press to insure you drill it out concentric to the existing throat.... If you go all the way to 11/64" porting, you should drill the throat out to 7/32" (0.219") to match the flow area of the ports....

It would be a good idea to enlarge the hole through the gauge port to at least the equivalent of a 7/32" hole, and larger won't hurt.... You will have to do a lot of this with a Dremel, because if you simply drill the offset hole out too large, you will run into the O-ring seat for the gauge.... Read over the mods I did to the gauge port and the front of the valve on Page 2 of this thread carefully, and make sure you understand before hogging out the gauge block.... Drill the front of the valve out to at least 1/4", and countersink it, and the back of the gauge port, to ease the flow between them....

If you stay with the 2000 psi fill, which I would recommend, you don't have to replace the valve screws.... Don't bother with milling out the barrel , receiver and valve for a plastic transfer port, just go with the bigger holes, and rely on the O-rings to seal it.... You may need to replace the transfer port with a piece of icemaker tubing with an ID to match your ports.... I would find that first, and measure it, before you start hogging out the ports.... no sense drilling them bigger than the ID of the TP you have....

I would try and reduce the OD of the poppet a bit, it will make it easier to open.... You can mount it in your drill press and file or sand it down.... Make sure you leave enough material to seal with whatever size throat you use.... About a 1/32" overlap for the seat should work OK....

Check for damage on the hammer like I found.... Do your trigger work, and reassemble the gun and test it and report back....

Bob

[wesb2007]

Thanks as well Bob from all the rest of us guys with limited tools and skills. This sounds very doable! Sure wish I had a drill press though!

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[rsterne]

You can enlarge holes and keep them pretty straight with a hand drill if you use number drills and go up just one size at a time.... The quality of your finished product will depend on how good your "calibrated eyeball" is....

Bob

[wesb2007]

That's my worry! =$

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[OldFart56]

Bob,

Thanks for all your advice. Borrowed (permanently) some ice-maker tubing with 5/32" ID and 1/4" OD from my kind neighbor, so will go with 5/32 ports. Do I need to enlarge any areas to the tubing OD as well? I will certainly post the results.

Brian

[rsterne]

I can't remember about the hole in the tube, I think it is already large enough, if not you will have to drill it out.... You can also drill out the bottom of the receiver, file a flat on the bottom of the barrel, and then seat the TP tubing directly against it.... however if you do, you will have to drill a hole in the bottom of the barrel to access the phillips head screw that holds the receiver in place under it (see page 2).... If the TP tube seats against the barrel, you must install the barrel into the receiver and THAN bolt it down to the tube, compressing the TP tube to get a seal....

Since the top of the valve is curved, you may want to file it flat for the TP to seal against.... otherwise you will have to curve the bottom of the TP tube.... The same goes at the top, against the barrel, file it flat, or you need a curved end on the TP.... You may find if you measure carefully that the ice-maker tubing is a bit over 5/32" ID.... IIRC, 0.162-0.166" ?.... If so, you can use a number drill for all the ports to match that.... If you decide not to drill the receiver for the TP, then it is concave and the top of the valve is convex.... You may be able to use a very thin slice of ice-maker tubing for the TP and let it curve by itself, the way the rubber one does.... Alternately, you may be able to use the TP seal from a Crosman 22XX, I know that works on a QB, and the ID is again about 0.166".... If that will work, that would be easier than the tubing.... What is the ID on the stock Chief TP seal?.... Looking at the photo on page 2, it may be large enough to use as is....

ACTUALLY, FORGET ALL THE ABOVE.... I JUST MEASURED THE STOCK CHIEF TP SEAL, AND IT IS .166" ID.... USE THAT IN THE STOCK WAY, AND JUST DRILL THE VALVE, RECEIVER AND BARREL PORT TO THE SAME ID....

Bob

[OldFart56]

Bob,

Thanks for taking the time to investigate that. Makes the process much simpler. So I will search out a #19 drill. Thanks again.

Brian

[rsterne]

Yeah, just drill the valve exhaust port, receiver and barrel port out to 5/32" (making sure the all line up) and then to 0.166".... Drill the valve throat out to 7/32".... Round off the bottom of the exhaust port to blend it into the valve throat.... Maybe sand the OD of the poppet a bit to make it easier to open.... You should get a nice increase in performance.... Don't forget to open up the inlet of the valve and the gauge block to at least 7/32" ID....

Once you assemble the gun, crank the hammer spring preload to the maximum, fire a couple of shot, back it out a turn and repeat until you get a drop in velocity.... Go a turn at a time until you are down 100 fps or more.... Plot out that information, or just report it here and we will know all about what to do to tune it....

Bob

[OldFart56]

I will do that. I just shot the Chief for the first time, all stock except for the trigger cleaned up. I'm hoping the chrono is acting up. The velocity was bouncing erratically, from 620 to 890fps, using Crossman Premier Domed 14.3's, thru three 2000-1200psi sessions. No high to low slope like yours. The velocities were also higher overall (but still erratic) with the hammer tension spring backed all the way out CCW!!! Am I confused as to which way CW or CCW increases velocity?

Brian

[wesb2007]

Sounds like it needs some major polishing inside or something!

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[rsterne]

Clockwise increases velocity, CCW reduces it.... If you are using your Chrony inside, you need TWO light sources, one over each diffuser.... and they must NOT flicker.... No fluorescents, either incandescent or LEDs running on DC.... Some LEDs pulse because they are running on poorly regulated DC, and those cause problems too....

Bob

[lleader]

I just shot the Chief for the first time, all stock except for the trigger cleaned up. I'm hoping the chrono is acting up. The velocity was bouncing erratically, from 620 to 890fps,..Brian

Any possibility it may be dieseling? I think you would notice that though - louder on the fast shots and smelly.