My target rifle project

[Finn]

I've been working on building a multi purpose target gun mainly for training 3 position and 10 meter shooting. I started designing the prototype somewhere around march 2017. I wanted  to test many ideas, and from the beginning it was somewhat clear that this should be primarily a precision paper puncher, not a power tool.
 Early April I had the first sketches of the gun and I started working in the garage. First thing to make was the basic frame. In principle its a simple piece of aluminium, but there is so many places to screw it up. First night in garage I managed to drill two holes, so not very much. Second night in I machined five threads and that was all I had time to do in three hours. Threading with CNC lathe is fairly trivial task but making sure the part is absolutely straight and centered takes time.
Next weekend I had time to do some milling, last two photos show the trigger group slot milled and pin holes are also drilled. In the last picture you can see the brass regulator housing.

I noticed its 1:30 am already and my dayjob starts at 7am so maybe I post some more info and photos tomorrow.

[Wayne52]

Very cool

[Finn]

Must be, its desingned in sub zero climate conditions.

Here are some pictures of the design, its pretty conventional PCP target gun action.
   In the first picture the action is in resting state after firing. Trigger functions are set with M3 grub screws, foremost screw adjusts second stage pull weight, second one is sear engagement, third screw is first stage travel, fourth screw just behind trigger blade is overtravel adjustor and final screw behind the trigger is first stage pull weight.
 Trigger has small instrument ball bearings for smooth and reliable function when pull weight is set to minimum value (close to 20 grams or 0,7 ounces). Yellow part is brass regulator housing and above that can be seen five belleville springs and aluminium piston. Regulator is set by M5 grub screw from below. Stock will be attached between the frame an UIT rail and to the rear mounting block with 3 M5 screws.
That lever above the hammer is for dry firing mode, detent spring is hidden in these pictures. Cocking levers are pretty self explanatory, small external lever above the trigger is sear reset lever. Most designs have resetting built into the hammer itself but i couldn't fit it into the available length thus the external setup. Sear would work without resetting when 2nd stage pullweight is fairly light, but heavier setting locks the sear down after firing.

I have made these parts already but don't yet have any properly good photos of them. Material is CrNiMoV4 and contact surfaces are hardfaced with stellite 6 superalloy since it seems to have lower friction and it resists corrosion and wear.

I will post another update as soon as I have good pics to show.

[Rob M]

pretty conventional , I think I saw a worm gear in there 

[Finn]

I think you have mistaken the splineshaft for worm gear. Splines are there to give possibility of changing the cocking lever from right to left and index it in 10 different positions (to clear the scope rings for example).

[Rob M]

very cool, excellent planning, ill be following the thread for sure !

[Horatio]

You guys that know machining impress me.

...when this baby hits 88mph...

[Finn]

Couple more design pics. Frame sits inside carbon fiber stock, and furniture is attached to aluminium rails. Grip is rail mounted and has balljoint to allow for adjustment in any direction. Front stock moves back and forth, I also want vertical adjustment and horizoltal tilt but I have no idea so far how to make it fit (any good ideas anyone?).   Barrel is 16mm choked LW .177, it's hidden inside the aluminium shroud. Steel muzzle piece is threaded on the barrel and in turn stretces it against he shroud for added rigidity. Normal rail mounted globe sight with inserts, air cylinder is hydraulic pipe and uses hatsan type fill probe.
Rearview shows adjustable aluminium buttplate and cheekrest. Cheekrest can be moved in any direction and it tilts in two directions. Buttplate has length of pull, height, rotation and tilt adjustments. Buttplate curvature can be also be adjusted.
Rear sight and cocking lever are missing from the pictures, I haven't had time to design the rearsight yet, maybe this weekend.

[Finn]

Heres a few stock parts, most of em completely unfinished but still look something like the design.

[Rob M]

everything looks incredible..

[Finn]

Thank you.
 I'm always too busy while making something, never enough time to take a few good photos, I did however take a few bad quality phone camera photos of the stock making process.
 First pic shows some of the plywood plug parts, small hobby bandsaw was really handy tool for this.
 
In the second pic, all the parts are together and mold fence is glued on with hot snot, after that the whole thing was carefully sealed and waxed.

Next thing was to laminate fiberglass on the plug. When it was cured, I removed the fence (pic 3), waxed the fence surface and laminated the other side. Once fully cured, I trimmed the perimeter and separated the two halves. After couple of hours of cleaning an waxing the mold was ready for use. I used combination of different carbon and glass fabrics to laminate the stock itself, I did this one half at a time and used a vacuum bag to hold the laminate in place while curing.

Once the parts were partially cured, I removed the mold from vacuum and trimmed the excess with box cutter blade. Then I bolted the two halves back together and laminated narrow strips of carbon to all the seams.

 It really was quite a circus to laminate the parts together from few narrow openings with a long stick with gloves all sticky from the resin and full of long gluey carbon strings, but it turned out just fine in the end.

[Rob M]

wow, lots of work.. nice job on the vacuum seetup

[Finn]

Not so productive day today. I did some quick backyard testing however and measured a velocity of few shots. I had somewhere around 140 bar in the gun and set the target at 10 meters (33 feet).
 First shot went way low and second one just under that, so I adjusted the sights. Now it was on target but sounded really weak, I decided to measure the velocity and it was just touching 280 fps. Something wasn't feeling right and I pondered if the dry fire mechanism was jamming the hammer and causing low velocities and went on to remove that part to test the theory.
 It turned out to be the hardest ever part to remove because there was some garbage jammed between the frame and the small plunger and it wouldn't just freely fall out. However I finally got the part out and tested the velocity and it was pretty much the same, I was sure that there was something going on with the regulator although I had adjusted it correctly. Turned the regulator setscrew and it was all loosey goosey when there should be considerable resistance in pressurized gun. Turned the setscrew where it just touches + half a turn and tested the speed again. This time it was definitely better 492 fps but still lacking, so another quarter turn tighter and it goes up to 660 fps. I wanted to have some velocity strings, but chrono said: nope its too dark, please try again another day.
    I managed to shoot 25 shots at paper targets, three targets have five shots each shot standing from 10 meters and the last target has 10 shots from 30 meters. I didn't have any bench available so I shot the 30 meter target from knee position.
It seems like an easy gun to shoot but the regulator thing has to be investigated, maybe one of the springs is broken or the screw needs to be locktited.

[Rob M]

holy cow, is that the completed gun in the pic?

[Finn]

It is not absolutely complete but it works, many parts are to be made and so far only few pieces have been anodized.  All the alu colored parts need polishing and anodizing. Stock and grips also need much thicker clearcoat so it can be properly polished.
  Rear sight parts have to designed and machined etc. and front stock adjustments need thinking, recoil absorber is also WIP,

Hard time deciding what colors to use for all the alu parts, opinions anyone?

[JMJ in NC]

Gorgeous. I'd go with blue for the aluminum parts.

JMJ

[Rob M]

same , 2nd vote for blue

[HappyHunter]

Wow...you have some serious talent, Sir!

From planning, to making chips, to final assembly...beautifully executed all around!

Vote #3 for blue anodizing...would tie in nicely with your grips 

[Finn]

Ok heres a few renderings of those color schemes, I got the grip color looking almost right. I think it would be a bit boring if all the alu parts are dyed blue. I had this idea of adding gold or magenta colored highlights. Let me know what you think or if you have an artist inside you, suggest something. I really want to get it right the first time, I'm absolutely sure that if I don't, I'll probably stick with the ugliness rather than machine a bunch of new parts.

[uglymike]

Red, grey, and maybe a little gold somewhere for an accent.