1/31/2020
It’s finished. The last piece came in today, it was the adapter that goes between the handgun and arm brace and allows the use of the arm brace. The manufacturer had 2 runs of 50, then this run of 100. I bought adapter #102.
For those who don’t know, what’s an arm brace? It’s a sort of stock that wraps around the arm so that folks who don’t have full use of their arms can still use handguns. But not strapped to the arm it can be shouldered and used as a sort of stock. Totally legal at this time and because it’s still a handgun there is no $200 tax to turn it into a short barreled rifle. I write “at this time” because it’s an ATF determination and those can change. If it does change I’ll just pay the $200 to SBR it. It’s too handy to ever give up. But at this time I have no intention of SBRing it. That too can change if I find that it’ll work in Steel Challenge better than what I’m presently shooting. This is a feather and swings very fast.
The point of the gun as pictured with the arm brace was a very lightweight handgun with better hit potential than a handgun normally gives. When I first saw a CP33 I thought, “What a fantastic arm braced gun this would be.”, clearly I wasn’t alone in thinking that. The target for the gun being rabid animals when the wife and I go on our walks. Over the years I’ve killed a half a dozen or more. I can’t run, only stand my ground, so I’m going to carry something and this beats a stick or harsh words. Yes, I have other guns I can use in this role, but nothing as feather light as this with the same hit potential (as good as I am with a handgun). It’s a .22 but holds 33 rounds in the mag’. .22 isn’t known to be a wonderful round for animals up to coyote size, but many of them launched as fast as possible, and I can launch them very fast with accuracy, will do the job. With the can in place it can be exceedingly quiet. With the right ammo there are air rifles that are significantly louder. I did contact CCI to find out what they would suggest for fox and coyote and was told their regular CCI Min-Mag HP ammo. I was told that it performed quite nicely in gel out of a handgun.
The arm brace folds to the left side for storage and it can be fired with it folded, but why would anyone want to? It’s my first arm braced handgun and I thought maybe it would be too short but I don’t find that to be so. It could actually be a little shorter to be perfect for me. One benefit to being of small stature.
Weight w/o the K configured can or any ammo load is 2# 13 oz and the short K configured can is another 10 oz. . Slung it doesn’t even feel as though anything is there. Yeah, it’s a feather on the shoulder or in the hands.
The trigger is quite good and I write that from the perspective of one who is very trigger sensitive, OK, I’m a trigger snob. And in my informal accuracy testing the CP33 it appears to be rifle accurate, very unusual for a handgun, but not surprising for the design of this one. It could easily be used for head shots on squirrel. It’s built with an upper and lower held together with 1 pin. The lower is the serial numbered part and the upper has a rigidly held barrel with a bolt that reciprocates. It’s sort of like a blowback pistol caliber carbine AR15 in operation. The worst part of the design is loading the magazine but there is a mag loader that really speeds the chore up as long as one is using round nose bullets.
The red dot is a Holosun 507c and mounted like that the open sights are still usable if one can get the eye down far enough to use them. With the arm brace folded or the gun not shouldered that works but not with it shouldered. It doesn’t come with a cover but they are available 3D printed.
http://amaroktactical.com/at3d-optic-cover-for-holosun-507c-508t-407c/
The sling could be on there using hardware, but I find the para cord to work fine, is silent (I like silent a lot!), and is lightweight.
Many online reviewers mention that the magazines don’t drop free and that it has a heel release. They’re correct they don’t drop free and it does have a heel release. But unlike those other reviewers I don’t see either as a negative. I have to ask myself, what is the mission of the gun? If it’s a self defense gun for 2 legged animals then yes, those qualities might be a negative. But I don’t see it as that at all. I see it as a competition gun where rapid recharging isn’t required and as a hunting gun where it’s also not required. Too, if one is carrying it in the puckerbrush an easily hit mag’ release coupled with a drop free magazine is a liability. IMO it has exactly what it needs to fulfill it’s role. I have a mag’ heel release on another gun and it too doesn’t have a role where a rapid mag’ change was never in it’s future.
2/1/2020
I apologize in advance for any out of focus pix and there are some here.
I sighted in the Holosun 507C today, again from a lousy shooting position hunched over the side of the truck. It’s still too cold to spend any time at a bench to do it right. Again, I’m impressed at what I saw for accuracy of the gun when I did my part. I was only really getting it close to being sighted in at 25 yards and some 3 round groups had all bullets touching. I think when I finally get around to testing the guns accuracy I’m going to need to put a scope on it to remove myself from the equation as much as possible and only test the gun. Ammo was bulk packaged Federal Auto Match. Temperature was in the mid 30s and the air was still.
Here is the gun set up as discussed here.
Sarge called it’s accuracy “rifle like” and I would agree from what I’m seeing yet again with my less than wonderful shooting position.
I started the shooting session with one in the chamber and a full mag of 33 in the magazine. Others have shown in their online reviews that chambering a round from a full mag is difficult, and it is if done by the charging handle. But chambering the first round from a less than full mag’, then inserting a full mag’ results in no problem with chambering the top round from a full one. The bolt goes back further than the charging handle can take it or the bolt hits the buffer and rebounds with more velocity. Whatever the reason it just works. This is the 2nd time I tested this with success. Yes, my CP33 also has problems loading the top round of a full mag’ using the charging handle. The solution is let the action of the gun load the top round from a full mag’. At the end of the sighting in I had 18 rounds left in the mag and rather than doing a mag dump decided to just leave them in it for whatever comes next.
That “problem” with not loading the top round is part of the design that allows the gun to reliably cycle CCI Quiet 710 fps ammo and also ammo with lots more power. The 710 fps ammo requires a lubed bolt and the brass just “drools” out of the action when it’s ejected, the action cycles and bolt comes back far enough to pick up a new round. If the recoil springs were stronger they wouldn’t work for the 710fps butterfly fart ammo. Too, with stronger springs the overhang beyond the grip wouldn’t be needed but then you’d have the same .22 handgun everyone else thinking inside the box makes. I call this design a long recoiling blowback action. I have no idea what KelTec calls it. But KelTec thought outside the box as they are known to and came up with this gun that has a huge latitude in what it will run reliably. That’s pretty much an unknown for a semi-auto. I know of no one who has mentioned that facet of the gun yet.
The more I shoot this gun the more I like it. I especially like it set up with an arm brace. It’s a feather when slung.
The Rehv Arms brace adapter is a nice unit and there is no slop between the gun and adapter. The SB Tactical brace is nicely made but you won’t be butt stroking anyone with it. It’s a minimalist brace and therefore lightweight yet gives a decent cheek weld. It too has no slop in it and the pair of parts works wonderfully together. The tolerances between the adapter and brace junction are tight and that’s exactly what you want. It can be a bit snug when assembling, but that’ll only happen once. After assembly the brace folds to the left side for storage or transportation.
I doubt that I’m going to change the configuration in a permanent way, I might slap a scope on it for accuracy testing but that will come off right after. So let’s figure out cost. I have $500 in the gun with state tax, the sight cost $225, the UTG riser mount I had on hand and I don’t know what it cost me but it wasn’t a lot; I’m allowing $15 for it. The brace adapter cost $72 from Rehv Arms and the brace was $139 (I shopped around and wasn’t in a hurry, it’s made by SB Tactical and is their 1913 rail model). I’m not adding in the HK 3 lug adapter since not everyone will want or need one. So I get $950. The components will cost more if you don’t shop around. I potentially saved a hundred or more dollars by not being in a hurry and shopping around. The hardest part to find was the Rehv adapter, the only source for it is Rehv Arms and I had to wait for the 3rd production run. They had 2 previous runs of 50 units each and this run was 100 units. I got #2 of this production run. 
I wasted no time in placing my order once I knew they were once again available. Once parts are in hand assembly isn’t at all difficult. One wants the brace in the lowest position to give required clearance for the charging handle. That also lowers the line of bore lessening muzzle flip of the mouse cartridge, but it also requires the sight to be on a riser*. Would a 1/3 cowitness mount work if one had a sight with one? I’m pretty sure it would.
HK pattern 3 lug adapter that makes can attachment extremely fast. The problem is that no .22 specific cans use it. I use it for my Dead Air Ghost-M can.
Not figured into cost is the cover for the 507C (it doesn’t come with one) that I got from Amarok Tactical. I think it was less than $15.
*I did watch a youtube video that had a sight mounted low on the rail with a brace. I don’t remember it actually being fired. I don’t understand how they could get their eye in place without having their cheekbones surgically removed. Maybe if they used a “ghetto hold” that sight placement would work.
I did put a TandemKross “CornerStone” Thumb Ledge (for right handed folks) on the left side of the gun, and that isn’t in the price above. It’s an extended safety and as the name implies is a ledge for the thumb. It also makes the safety much easier and faster to wipe off. I wish TandemKross had one for the left hand also, but they don’t. (at this time? I didn’t inquire if they ever will.) I might like to add a lefty thumb ledge at some time but it’s not a must. I can still access the safety for the left hand as it is, just not as easily if a ledge was there. I chose the red anodized thumb ledge since it’s a safety and I thought red to be appropriate, but it’s also available in black.
At this time is there anything I would do differently on mine? The answer to that is no unless it’s already been mentioned. I might play a bit with slinging it or maybe moving the sight a bit, but I’m fairly certain that it’s set up the way I want it and better than the way I envisioned it when I first fondled it as a stripped down handgun at the LGS. It just took me some time to find the right components and frankly some components I that hadn’t thought of.
Unless someone has questions or I left something out I think this will be the last update until I have accuracy results in a few months. I might add some additional pix if required between now and then.
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I also could have used any number of firearms I already own (and I have). The CMR30 will definitely not do what this will do for precisely the reasons you stated and the reasons I already gave in the thread though I didn’t run down the list of firearms that wouldn’t do the job. I more concentrated on the one that would do what I wanted done. It just made sense to me to do it that way.