Modified CO2 cap with a QD Sling Swivel on a Crosman Carbine

I'm always changing configurations with my various Crosman 22XX guns.  Their modular design makes it easy to go from pistol to carbine to rifle and back in a few minutes.  Combined with a few adapters, I've been able to try several interesting combinations.  In the last blog post, I had thrown together a .20 caliber carbine and wanted to use a vertical fore grip from Magpul.   Assembled, it felt pretty good, but there wasn't a spot for a front sling position.  Granted, a single point rear sling worked just fine, but most of these projects come about from trying to solve a unique problem.

A bit of head scratching and I thought a QD front sling socket could be incorporated into to a modified gas tube cap as an inconspicuous attachment point.

Rather than butcher the original cap, 

Started from zero with a piece of 7/8" diameter 12L14.  

Turned the end down to about .8085"

And threaded with a very uncommon 13/16 - 28 die to match the Crosman 22XX gas tube.

The camera angle is bad, but I used a thin parting blade to cut a relief at the end of the thread.

Since I'm using the Crosman mid-length 2250 gas tube, the cap will need an extension to bear against the end of the 12G CO2 cartridge.  Might as well plan ahead for the three different Crosman gas tube lengths--2240, 2250, 2260.

A #3 drill is the correct diameter--

for a 1/4-28 tap.   

More on this later.  

Cut off the excess.

Cleaned up the face.

Drilled 3/8".  This is where several small errors compounded and went slightly sideways.  The tailstock was a bit out of alignment, the drill bit cut a bit oversize, I wasn't paying enough attention and this probably became a version 1 prototype.  

Bored the undercut for the QD swivel.

Some cosmetic clean up.

A piece of sacrificial 1/4-28 in one end and a UTG 1-1/4" QD swivel kinda fits the other.   A bit loose due to the oversized hole.   Tried six or seven QD swivels and had mixed results.   Half pulled right out, and half worked -- with a bit more wobble than I'd hoped, but they do hold securely.  It's not exactly a disaster, but it will limit swapping and might require dedicating a sling.  

Chucking that sacrificial 1/4-28 stud gave enough room to get a knurling tool in there.

Looks pretty good.

OK, back to making the rod.

Piece of 5/16" diameter was turned down and threaded 1/4-28.

A 1/2" carbide bur produced a concaved end.

Some clean up and polishing.

A bit longer than the Crosman cap.

Blackened with G96 paste.

Short set up with a Magpul RVG and sling.

And with the Strike Industries pistol brace.

Gonna work with this for now.  If you have several push button QD swivels and guns, you probably know there isn't 100% guaranteed compatibility.  Too many manufacturers, no hard standard.

I've always used a Magpul QD as the "standard" and done the machining to make that the best fit.  I do wish that the airgun manufacturers would put a bit more thought into how to make their products better interface with some of the other gun "standards' out there.   I think that means making the airguns accept off the shelf AR buffer tubes and stocks, bipods, Picatinny rails rather than dovetails...  Those accessory purchases go further when they fit several platforms and it makes the end user's ability to tailor the gun that much easier.   Or something like that.  

For now, it's functional.  So, maybe it's not a prototype after all.  Now my options have options.  

Thanks for checking in on me.

Just Some Pics of my .20 Caliber Crosman 2050

Apologies.  Not much to report lately.   Some tinkering here and there, but nothing I've found interesting enough to blog about.  

I did swap one of the Crosman 2250s over to .20 caliber.  Didn't take any pics of the conversion.   Just a basic barrel swap--though I did try to make it look like a cohesive assembly.   Converts to a lightweight carbine in about a minute using a Strike Industries pistol brace.  I didn't have a red-dotted carbine, so it fills a niche.  

Quiet and easy to shoot.    What's not to love?

Feinwerkbau 124 Sling Attachment -- Part 2

Picking up where I left off,  I still needed to make that shorter cocking lever rivet and lose those two aluminum washers. 

Pulled the action out of the stock and tapped out the cocking lever rivet.  As a reminder, the aluminum washers had been added to replace the space taken up by the original factory sling swivel.  At the time, those washers let me reuse the original rivet without any further modifications.

In the last post, I waffled around and settled on making a quick scope stop because I couldn't decide how to make the replacement rivet.  Sure, the rivet is a simple project--except I didn't want to pein or mushroom the ends of the new rivet.  Technically, I guess that means I'm actually going to make a pin.  Then, I couldn't decide whether to use a piece of 5mm drill rod and cut grooves for e-clips or turn down part of a larger diameter leaving a head on one side?  Too many options for a guy like me.  Actually none of this was really slowing down the project.  I simply didn't have a grooving tool thin enough for a small e-clip--and I had no experience cutting e-clip grooves.   I got stuck looking at groove specifications and wonder how I'd accurately measure the diameter in that thin slot?  Did I have any e-clips that are suitable?  Then I backed up and wondered if an e-clip was even the right solution for the project?  I did mention my catastrophizing in the last post.

Eventually, I did some research on machining e-clip grooves, figured out how they're supposed to be sized and toleranced, bought a bunch of e-clips, then procrastinated for another week until I could find time to go work in the basement.  About then remembered I still didn't have a grooving tool this small.  

Started anyway.  A piece of scrap 3/8" diameter O-1 tool steel went into the Taig lathe.  Flanged pin design wins.  The deciding factor?  This only requires me to cut one e-clip groove.

Body of the pin needs turned down to about 0.1965"--just barely under 5mm.

Now I needed a groove for this guy.  I believe this is a 4mm e-clip--4mm referring to the OD that it clips over.

I had to grind a tiny grooving tool--0.030" wide from high speed steel.    The width of the Feinwerkbau's base block was 0.590", added about 0.005" to that number, and plunge cut the groove 0 .595" -- 0.596"  from the inside face of the shoulder.

Measuring the diameter was giving me trouble.  Had a hard time getting a repeatable measurement with the caliper in that .030" slot width.   I finally gave up and just used the clip itself as the gage.  Tried to get it to snap into place.  No go.  Took a few more thousandths and tried again.  After a few test fits (and a few mangled clips)  the clip installed and wasn't distorted after removal.  Called that good.

I need to shorten the end a bit more.

Then flipped the pin around and thinned the 3/8" diameter  head down to 0.095" thick.

And there it is.    All this procrastination for this.   Well, this and that little scope stop.

If it was still 1991, Doc Beeman could've sold something like this in his catalog.  "Designed by my wife to upgrade your FWB124 to take modern slings.  Its exquisitely delightful."   That'd be the gist of it.  

Blued the ends that'll be visible.

Almost seated. A wood block smacked it home.

And the e-clip snapped right into place.

 Good clearance with the longer forearm of the stock.

I like that I can now use a "normal" 1.25" sling with standard hardware on my old rifle.  I'm also pleased that it doesn't look like I was involved in any Feinwerkbau gunsmithing shenanigans.  

And just for fun, here's the "delightful" scope stop again from the last blog post.

More soon.