Because why not! A .22 single shot build

So, I got bored this afternoon, having finished the Chevy truck I had to deal with this morning, my kid down for a nap, and stuck waiting on cutters and materials for all my paying machine jobs. So I decided to do something with the little leftover 5-3/8" chunk of .22 barrel liner from my pack rifle build. I just happened to have a .225 reamer, so I chambered it real quick, then sat down and sketched up a design, as I don't much care to build existing ones, find it boring.

After about a half hour, we had this:



Initially I thought about using two 1/4" pieces of 7075-T651 plate to make halves, but ultimately decided I was better off using a piece of 3/8" 7075 and a 1/8" side plate. Problem is, I don't have any 1/8, and I didn't really feel like sacrificing a piece of 1/4" 7075. But I did have some scrap 3/16" 5052, which is easy enough to turn into 1/8" with a 10" staggered tooth face mill:



Next was hogging the 3/8" piece for the internals. No measurements taken, just photocopied my sketch, cut it out, and traced:



About the time I was finishing that, my kid woke up, so I had to stop here and take care of him until bed time:



But I did get a couple more hours in afterward, which leaves us with a shaped frame, cut for internals, and a roughed out 4140 barrel block, which the barrel will be TIG welded to:









Side plate is attached with three 4-40 stainless flat head socket screws. All the pins for fire control, barrel pivot, catch, etc. will be blind, seated .100" deep in the frame and side plate. The only visible fastener affer grip panels will be the front screw. I haven't decided on grip panels yet, probably carbon fiber like my O/U pistol, or maybe black ABS. But I could change my mind, might incorporate wood for a change

Anyway, got a crazy day with automotive work tomorrow, and a very busy weekend, so not likely to be further progress until next week, but will update as soon as there is one!

Well, the girlfriend wasn't feeling well tonight, so instead of hanging out with her, I kept working. I got done with one of the 304 stainless AR charging handle assemblies I've been contracted to make 2, possibly 4 of for a right hand knob, manual operation only rifle about 9, so I spent another 4 hours on this little guy. Got the barrel block finished, the barrel welded to it, the side plate pin recesses drilled, pins made, and laid the paper parts cutouts in:





It was only 11:30 at that point, so why stop? Went ahead and made the hammer and hammer strut:







After finishing that, I decided to wire the barrel shut and thumb the hammer for a quick test fire. It went fine, but I may find a softer spring; that's a pretty heavy hammer, probably doesn't need the power of an HK USP hammer spring, and it's stiff. This hammer is just cut from mild steel, as I didn't feel like shaving my blocks of D2 or A2 down to 1/4" and wasting a tremendous amount of material. I'll harden it the best I can, and order some 1/4" 0-1 or something to redo it when the sear notches eventually wear. But as it's a single shot, I'm not terribly concerned about that moment when it eventually comes.

How hard would it be to make a .22 cal Rolling Block?

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Not very. This basic layout would work with it, just replace the solid breech block with a rolling one, and do away with the tilting barrel.

I wish I had skills like that.

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Well, the idea behind this design versus my others is that it can be built without a mill and lathe, just basic tools most guys already own. Instead of milling 1/4" deep in 3/8" stock, one would use a piece of 1/4" sandwiched between 1/8" side plates. All the cuts could be made through a piece of 1/4" with drill, hacksaw & files. No reason pins or screws can't run all the way through, I just chose to make them blind. You could even pull it off without any welding by altering the breech block enough to get two pins/screws though it, and making the barrel block in such a way that you can thread a barrel in.

I like to think that's the kind of thing I'd do if I had skills.

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You just gotta try! Truthfully, just about anyone could build a simple design like this and make it work with patience. No, a first time builder isn't gonna throw it together in ~12 hours like I did, but go check out places like weaponsguild.com, and you'll see tons of similar critters (the JACO Derringers are a popular starter) built by guys with only a couple hundred dollars worth of tools in their garage or even apartment bedrooms.

Having said that, this design did expose that I pushed the limits of 7075 aluminum a little too far with such a thin breech block that was not anchored into the off side. First pic is after I spent another 4 hours late last night making and fitting sear, trigger, barrel latch and ejector (spring between trigger and barrel latch omitted for pic because it kept pushing those pieces out trying to have it just sit there):



And this is after firing a dozen rounds:



Doh! It's certainly not a total loss, though, will be milling off the damaged area and making a 304 stainless block that replaces that ear, and seats into the frame and side plate another 1/2" or so down and 0.063" deep. I also need to incorporate a return spring on the ejector so that it needn't be pushed down when inserting a new cartridge to keep the case rim from getting under it.

Did it blow up when you shot it?

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Blow up? No. Just broke away the piece you see pictured above, and bent the side plate a little. Side plate was easily straightened, no damage to any other parts. I had been planning to run a screw through the side plate into the lower portion of that tiny breech block, but tried testing it first, thought it would hold up OK for a few shots. Bad idea (obviously).

This is what sometimes happens, though, when you try to use lighter & weaker materials and push the dimensions ever smaller. The whole pistol weighs just 11.2 ounces, which is pretty dang light for something with no polymer in it's construction, and a more or less full size grip with a 5" barrel.

you will be hard pressed to top that mini AR15 you built.

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Well, I never did get that thing running semi-auto. In fact, I'm still trying to figure out how to get enough bolt weight to stop the case head failures. .17 HM2 is a little more energetic than .22 LR, and about 1 of 3 would rupture the case. I had already added a chunk of carbide to both the rear of the carrier and the buffer, still not enough weight. And, of course, never overcame the hammer spring issue, either. One of these days I'll get back to that one and sort it out, but for now, I'm more interested in doing builds that are useful rather than cool novelties.