Sunday, December 26, 2021

Yet Another Trigger? A New Trigger for the .25 Caliber QB Project Gun

Guess I'm on a roll.  I liked the way the trigger turned out on the CP1-M last time around.  Since I had a second IZH 61 trigger blade, figured I'd make something similar for a long gun.  Looking at the candidates, the .25 cal QB project gun was volunteered.


Pretty much same deal as the CP1-M.  Need a carrier with a stem to attach the IZH blade.


Pulled the trigger housing.

Removed the cover plate and took out the trigger blade.

A small piece of 1/4" thick 4130 steel.  This is probably a bit easier than it looks.  The only really important dimension is the pivot hole to the sear contact surface.  And there's some grace in that dimension due to how the two arcs intersect.













Traced the outline of the trigger and marked the pivot hole.  Rough cut some of the excess away.





Milled two opposing sides for parallel...














 I could clamp it in the milling machine.  A bit more shaping, then lined up for the pivot hole.  Centered up with a point.










Through drilled with a #31.
















Copying the factory QB trigger, drilled some holes to remove excess weight.




Getting there.


Some milling, some filing.  Little of this, little of that.






The carrier needs a small boss for the trigger spring.





A brass rod was turned down to act as the base for the spring.















Cut off and the head rounded.




X marks the hole location.




I use this ground point all the time to pick up lines/locations.





Spotted and drilled for the spring boss.




Finally, I figured out where I wanted the trigger blade and spotted then drilled for the stem.















Like so.







Just needs some spit and polish




Knocked off the sharp edges then hit it on a brass wire wheel.
















Test fit.  Stoned the sear contact surface. 





Pressed in the tiny brass base for the trigger spring.




Cut a 3mm diameter rod for the trigger stem.  Installed with a light press fit and some Loctite 680 retaining compound.















Test fit---gotta adjust the stem length before the Loctite sets up.













The IZH trigger blade isn't a precision finished part.







Clamped it to a spare 3mm drill shank and sanded out the face and radiused the edges.






























Mine's a bit chunkier.  I'll leave it for now and see if there are any problems. 


Here's that little trigger return spring boss.




Buttoned up.


I'll recheck after getting some shots through, but I set the trigger at about 2 lbs of pull weight.  Dialed in enough sear contact so the rifle will not accidentally fire even when banging the recoil pad against the floor. 




Dunno what's on the menu next.  Don't think it'll be another trigger, but that Belgian Hy-Score desperately needs a blade with more set-back--and that was the reason I snagged that plate of 4130 steel in the first place. 

Merry Christmas and Happy New Year!

Thanks for checking in.  I'll have another post soon.

Thursday, December 23, 2021

A New Trigger For My Mrod Air CP1-M Pistol

The other evening I was kicking around for something to do.  I wasn't actually banished to the basement by my wife, but I can read the room.   Went though a box of airgun pieces/parts and came across a couple discarded trigger blades from my IZH 61 rifles.  Thought about adapting one of the blades to the old CP1-M pistol.








Removed the trigger from said pistol.  






There's an easy tiny project here, I swear.





Cut a little piece of steel and cleaned it up in the milling machine.















I measured the trigger housing itself and milled the block's width a couple thou under size so it wouldn't drag on the sides.

Like so. 



Measured the trigger pivot pin.



 Drilled a couple thousandths oversize.




While still in the vise (and on location) I test fit the pivot pin.   I'm purposefully fitting the new trigger carrier directly to the gun itself rather than match dimensions from the original trigger blade.  Doing it this way because the original trigger had a lot of extra clearance that made it feel sloppy and wiggly. 

At 90 degrees from the pivot hole, I used a 2.5mm drill.

Followed with a M3 x .5mm tap.

3mm set screw test fit.  This will allow for adjusting the sear contact.

Milled away some excess material at the rear of my new trigger carrier.

Now, where to put the stem to hold the blade?   Scratched my head, angled the carrier slightly in the vise and drilled through.

The hole in the IZH blade is nominally about 3mm (0.118").  I went through my number drill bit sizes and picked the snuggest shank size that would still slip through the mounting hole.   A #31 bit--about .120"  gave the closest fit.   Cut the shank with a cut-off wheel in my Dremel tool.

Almost done.

The "stem" still needs cut to length after a quick mock up.

Trimmed and rounded the 3mm set screw.

Broke all the sharp edges on the trigger carrier.  Before starting, I didn't fully appreciate how this was going to be such a miniature project.  Lot of holes in close proximity.



Pressed the stem into the angled hole I drilled through the carrier.  Some Loctite 680 retaining compound pretty much guarantees this is a permanent connection.  Not shown, but just to make certain it doesn't move,  I also staked the pin to the carrier.

Finally, the IZH 61 trigger blade that started this whole project.  It's a bit ragged around the edges.  May need to pretty it up after shooting it for a few days.



That stainless bolt has got to go. 

The new trigger allows adjustment for blade height as well as rotation.  Oh, and sear contact.




And then out of the ether, I also made a new bolt handle.  Just a bit more slender than the original.   Whoops, that's gotta get blued, too.  

OK, so what I got out of this was a trigger that I can easily adjust for position and with the exact sear take up I want.  And unlike the original trigger there's no wigglyness. 

I'm trying to post more.  Check back soon.