CharlieDaTuna offers NPSS, NP, CBR, GTX-III, & GRT-III ...



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First let me say thanks for the customers over the past five years.

The reasons I’m getting out of the tuning biz, I want some time for myself. I didn’t do this full time, I have a job, family and hobbies and no time. I might do a few tunes this summer but not right now.

So as I said in the past I’m going to outline the tune for the QB’s Co2 (all) and the Crosman 160’s

 

Next, if you’re not mechanically inclined don’t attempt this tune. Also I don’t take any responsibility for you screwing up your gun. So don’t email me and say, Hey I messed up my (fill in the blank.)

 

Cut the Middle Man and Get your parts direct

 

McMaster Carr       O-rings, springs, Seals, QD's, Seal Material You Name It They have it!

 

Mckinneycorp         4130 and Aluminum DOM Tubing Cut to size, Inexpensive and no minimums

Lother-Walther       Barrels

 

Crosman        Call and get a manual, then order your own parts

 

Numrick        More airgun parts

 

Part Prints       Detailed Drawings to my custom parts ,Plus extras

 

 

 

The Tune

 

Step 1 prep tools seals.

 Step 2 teardown

 Step three Valve bolt barrel

 Step four trigger

 Step five Build up

 

 Hands tools

Steel or brass rod 18” or better 1/2 diameter

6” flat screwdriver

12-14” wide blade screwdriver

#2 Phillips

3mm Allen

Honing stone

 

Seals 2ea 9/16x3/4 size #113 Viton, EPDM, or polyurethane 70 duro or better

(These are for the cap and valve body DO NOT USE BUNA/NITRILE HERE THEY WON’T WORK.)

 

3ea 3/8x1/2 Size #012 Buna (Barrel seals)

 

6” 1/4 OD poly tubing (Breech seal)

 

.22cal bolt seal 1/8x1/4 size #006 Buna

.177 1x3 mm

I use 1/16x3/16 Size #003 after I cut a new groove for the bolt. This will be shown in the steps later.

 

Tear down

This is straight to the point.

Safe to safe and punch out

Remove

Stock nut action

Allen on breech

Rear sight

Barrel band screw

Barrel (twist back and forth)

Phillips in breech Trigger Breech

Hammer pins

Rear caps

Stock stud

Valve screw

Hammer Assembly

From front cap side drive out the valve, don’t worry about the seal it’s going to be replaced anyway

The stock stud nut will come out with it.

Allen in the back of the bolt

Handle

Bolt

 

This is the way I tune them. It’s been tested and proved by 100’s of guns, as said in the beginning; any variation to this process is on you. Basically the tune is a port and Valve job. We’re going to knock most of the sharp corners off and angle the 90deg turns and open the ports. Any 90deg the gas sees, it sees as a restriction. Some of you motor heads just went AH-HA! I see. You see the basic Co2 gun is just a single stroke single piston engine, Piston =Pellet, fuel = Gas. That’s it. Just like a hotrod the more flow the more go and remember the more go the less MPG or in this case shots per charge. With this tune you should expect .22 upwards to 740fps 16fpe .177 800fps 12fpe, 30 good shots depending on Temp and pellet weight. No joke, no jive, just fact!

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Tune

Valve Disassembled

First get rid of the packing and screen, the newer guns don’t use this and it’s is a major restriction.

 

Stem

I angle the stem in the lathe by holding the head from the seal side, turning the compound to 10-12 degrees. Taper the head to about .200-.187” at the point.

Turn it around and break the sharp edge on the seal side, don’t get over zealous. I little goes a long way. Make sure you clean the filings of the seal.

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Brass Base/seat

 

You can open the seat area to #7 drill .201” and with a long 30deg Countersink dress the seat to a smooth angle. The angle isn’t a must but it gives 3-5 fps.

Exit port though most new guns are opened up and angled if you have a older gun ,the port can be open up to .187 no bigger, any bigger and she won’t seal and angled back. Don’t cut the seat on your angle, if you do your done go on home and order another gun.

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Top

Drill .125” .125” from the edge in the slot. Clean up the burr inside.

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Pierce pin

This can be done on a bench grinder, angle back the nose to just blend into the point about 30degs. This is to guide the pin up through the top hole. If you’re bulking the pin can be eliminated completely.

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Replace the body seal and reassemble don’t tighten the valve body. This will be done this the Co2 tube. To make sure every this is hunky dory, press the stem down on a hard surface to compress and open the valve look for the pin to come up with no major binding. If it does tear it down and reassemble.

 

Bolt

Two ways to do this is by hand and machined.

In the lathe part off the tip to just behind the port, Drill #42 drill to .625 deep. Cut the sharp end off the #6 finish nail and dress a lead in. super glue the nail in, Cut off to no longer than .500” dress the probe to a nice radius. The .22 cal is done.

On the .177 your going to open up the o-ring groove to a groove .070” wide x .040 deep. I use a straight pin as a tire iron to get the o-ring on. Have a couple extra they’re a bear to get on.

 

Hand method

Drill the end of the .22 to 5/32”

Drill the end of the .177 to 9/64”

This can be done in a drill press with a vice.

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Barrel

This is the biggest area of restriction; the port is about 3mm diameter way to tiny.

I cut mine in the mill with a .125” end-mill centered in the port .125 to each side, that is to say over all .250” port from o-ring groove to o-ring groove. After that, I make a lead in with a .375 ball nose end-mill; this should just kiss the leading edge of the o-ring grooves.

 

You can open up the port by just drilling

The .22 can be opened up to #16 drill and the .177 to 9/64 then make a lead in with a counter sink. DO NOT GO BIGGER THE THESE HOLES!!! If you do the head of the pellet might drop in the port jam and wad up. The fix, new barrel, or machine a new end and chamber it…Believe me, no fun…..

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Trigger

Stone the mating surfaces of the sear and trigger, I use a spring based on a heavy ballpoint pen spring from a Pilot pen. Oil lightly.

Set the trigger travel now.

 

Breech seal,

Use some poly tubing the type that you use for an ice maker.

You want it from .08” to .100” long and flat. Use a razor blade or X-acto knife. Mark the tube with a sharpie to see your mark.

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Reassemble

With some exceptions

The valve goes in from the cap side, Oil the o-ring with some light oil to help it slide, make sure the port is aligned with the port on the tube, and gently tap it home. Try not to go past the port up the o-ring, if you do more than likely you’ll cut the o-ring and have to start over. With the valve home put the screw in and tighten the valve body use the big flat tip. You want it snug; all you’re doing is seating the o-ring. So don’t get Jethro on it.

Hammer you can add 20-30 fps by shimming the hammer with some #10 washer 5/8 diameter.

This shims up the hammer spring for more wallop. Here’s the catch, it’s a little more difficult to put the breech on. You have to catch the back pin with the bolt compress the spring and drop it down on the front pin all while keeping the breech seal in place. If the front pin jumps out the front bolt notch and you don’t catch it after you put the breech screw in and push the bolt forward she’ll lock right there. Not good if you’ve probed the gun. You can get it off but it’s not healthy for the probe. Also, if you do these, when charging you have to do it this way, or it’ll blow gas. Open the bolt and keep it open, load your carts, twist the cap down till its good tight, back the cap off till she hisses, cock the bolt and fire.

 

 

Well that’s it hope you enjoy the procedure and Pics. See you in the funny papers.

And always remember

 

Springers maybe hot, But Co2 is Cool!!!!

 

Co2une@

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