Saturday, September 19, 2015

New Trigger Guard for the CP1-M Pistol

My single biggest complaint about the CP1-M pistol centered around the "too small for my finger" trigger guard.   Found some time this week to do something about it.

Started with a chunk of 6061 aluminum. 

At 0.625" thick it was too wide to fit the inletting in the grip. 

 I milled down to ( I think) 0.550".

It was the right size when it just fit into the wood.

Winging it with the layout.  Nothing new there.  There's a bit of stock to hog out.

To get the stock out quickly, I drilled a 1" diameter hole.

Followed by a 7/8" hole.  This removed about 80% of the material.

Scratched some lines to connect the holes and swapped milling vises to one with a different base.  As the guard will have a tapered slot,  I needed the ability to swivel the vise. 

Milled out the web between the holes.

Had some concerns about the guard collapsing and binding the milling cutter as the last of the web was removed.  Went easy on the vise clamping pressure and took lighter cuts to compensate.  Note the metal left at the extreme right for support.  It was later removed with a hacksaw.

Milled a slot in the top of the guard for the trigger blade.  The slot has to be both centered and have the correct clearances to fit around the trigger block.  The sides of this slot block in the trigger pivot pins to prevent them from walking out.

And a relief slot for the sear.

Milled some angles into the guard to lose excess metal and make it marginally less "blocky".

Hand filed the curve at the top to fit into the front of the inletting.


 Test fit. 

Used a transfer punch through this hole to locate the 5mm mounting screw location.

Drilled for the aforementioned screw.   Not shown:  Turned the guard over, lined up the hole again and drilled a counterbore for the head of a M5 SHCS.  (that's a Socket Head Cap Screw)

 More shaping.  Less blocky.

About done.  Here's the counterbore.  Started to deburr the edges.  Needs some sanding and spit and polish.

Obviously, it's not a full wrap guard.

A bit chunky, but it'll work.  Besides, all the metal in the front is hollow for the mounting screw

 Some milling marks.

You can see the trigger housing nested in the oval slot.

After more sanding, blending, edge relief then a light bead blast.

Gave it a shot of black epoxy paint.  It's a pretty close cosmetic match to the anodized breech.

Much, much more comfortable now to shoot.  Instead of being annoyed by the guard, I can focus on the dot alignment.  I see a few areas for improvement (which were ignored while rushing to get it done) that I may revisit--if I can talk myself into stripping the finish.

Thanks for checking in.  More soon. 

Sunday, September 6, 2015

More Misc Sling Attachments

Went off on a sling kick a week ago.  After adding sling attachment points to the short barreled IZH 61, the other 61 was calling.  Then there was the BAM B26-2 with the barrel shroud... Coming on the heels of such a similar post, I'll just kinda gloss over what I did.

Since IZH #1 got the picatinny rail on the underside of the forend, I elected to side mount the second gun.  Milled a bracket from a piece of steel key stock.


Spotted and drilled some clearance holes.

Counterbored for the socket head cap screw heads.

Then angled the sides to make it a bit sleeker.

Knocked off the sharp corners.

And polished it out.

Made a threaded backing plate from a scrap of steel.

Blued it, then drilled a couple holes in the stock and here we are.

Took apart an Outdoor Connection 1-1/4" Super Sling 2 and fed it through.

Rear attachment is identical to the other IZH 61 sling mount.  The side mount doesn't work as well in carry mode, but when using the sling as a shooting aid, it's perfect.

The BAM B26-2  lost the forward barrel band sling stud when I made the shroud.  Don't know why, but I failed to address this at the time. It was just a matter of drilling and tapping a hole in the underside of the shroud for a sling stud.  No pics of the job--it was too easy.

Was concerned about the stud unscrewing.  Given the minimal thread engagement, that would likely result in dropping the rifle before the loose stud was noticed.   A liberal coat of Loctite 680 on the threads should ensure that a blowtorch is now required for removal. 

I really am going to get to that CP1-M trigger guard and the QB77 stock project, and the....

Tuesday, August 4, 2015

Adding A Sling To My IZH 61

Lotta times, I'm just looking for a simple project.  This was one of those days. My IZH SBR project gun seemed like it would be easier to shoot with a sling for additional offhand support.  Problem is, there's really no provision on an IZH 61 to mount anything easily.  That hollow plastic stock, while nice and light, doesn't readily lend itself to sling swivel installation.

Rather than just guess where to put the front sling attachment point, I thought I'd use a piece of picatinny rail to allow fore and aft adjustment.    An $8 Magpul MOE synthetic rail looked like it would be an almost exact match to the IZH's polymer stock.  The fact that it came with threaded backing plates made the choice even easier.

With the stock removed, I fiddled around with where to mount it.  Bottom of the stock or left side?

Bottom of the forend won.  Barely.  A couple pencil marks on the seam showed where to drill. 

Drilled the holes.

This is where is gets tricky.  There's no easy, direct access for the threaded bosses. They'll have to be fished into location and held while I try to catch the thread of each bolt.  Those bolts Magpul included in the rail kit are non-starters for this installation.  The factory applied thread locking compound will make it impossible to spin the bolt fast enough to advance it through the thread.  It'd stick and just spin the backing plate inside the stock.  A couple #10-24 SHCS without any thread goop were used instead.  To get the backing plates into the stock, I superglued each plate to a bicycle spoke.  The Zip Kicker makes the glue dry instantly. 

Here's where I wanted to pull my hair out.  The only access to the interior of the forend is through the trigger inletting.  This was just an exercise in patience and dexterity.   Honestly, it was awful.  The boss had to be lined up with the hole, the bolt pushed through the rail and stock, then rotated to catch the first thread without moving everything out of position.  Twice. 

Eventually, I got to here.  Bolts are tight and the rail nicely centered. 

Doves flew up into the sky and a beam of sunshine lit my workbench. 
Then the light went out because I still needed a rear attachment point.

Thought maybe (yeah, right) a conventional screw stud would work.

Centered up and drilled. 

And it's  hollow, too.  So, no screw stud.  Wouldn't be enough thread contact.

The only access to the interior of the buttstock, at least at the heel, is through this 8mm (about 5/16") hole.

I went through my "weird" fasteners and found a couple of these.  Don't know if I'd call it a t-nut or just a threaded boss?  This has an M5 x 0.8mm metric thread.  It's probably from a bicycle road brake pad.

Shaved the thread down in height slightly until it would push through the 8mm hole.  Then I rattled it around until I could pull it into position and get a bolt to catch the thread.  For some reason, this was easier than the spoke fishing.  Probably had everything to do with the interior shape of the stock funneling the insert down to the hole.  After I caught a couple threads, a few drops of superglue were used to temporarily anchor the insert...

So I can make a sling swivel stud with an M5 threaded shank.  This was starting to not look like a simple project.  Piece of .375"diameter  O-1 tool steel went into a collet and square block.

Found center.

Spotted and through drilled for the sling swivel hole.

Mic'd across the flats of an Uncle Mike's brand stud as a reference number.   0.312"

Chucked a 1/2" end mill, then set a stop so the piece can be relocated in the vise accurately.  The piece is starting at 0.375" diameter. I need to take about 0.032" off each side to make the flats 0.312" apart. 

Math:  (0.375 - 0.312) / 2  =  0.0315" per side.

Touched off, zeroed the depth readout, then slowly milled downward...

Until the readout showed 0.032".

Turned the piece over and repeated the procedure.

0.3115"  Close enough. 

I'd left extra stock so there would be something to chuck in the lathe.  Turned down the end...

And threaded M5 x .8mm.

Trimmed off the excess thread and squared up.

Flipped the piece around.  Faced and beveled the top.

Blued and installed.  Got lucky and it aligned when it was tightened.  Otherwise, it would've needed a shim washer.

Put the action back into the stock and mounted up a sling.   No gaps between the rail and forend.  Aesthetically, these projects are considered a success if they look like I had nothing to do with them. 

The gun is substantially more stable offhand when using a hasty sling.  If I had to do this again, I'd think hard about using rivnuts--either aluminum or the ones specifically for plastic installation.

Thanks for reading.