Well about 8 months ago I was looking here on the fire and there was a project 10/22 17M2 that one of the member put up said he just didnt want to mess with it. My hunting partner has ready been a fan of the Mach2. I decided to put one together I ordered a Beyer barrel and Power custom weighted heavy bolt finally got it together. I took it out this AM and took a Box of CCI 17GR and a Box of Hornady 17GR.

Well the first 5 were CCI shot no issue and I loaded 5 Hornady and they grouped better but I was not looking for pin point I was testing function mostly. well I think my next load I felt a spray in my face (no glasses like a balloon head) and the gun is smoking like a old Diesel powerwagon mag blown out . I loaded another group no issue. a group or 2 later it happens again , I started to think about it and it was all CCI there was no issues with the Hornady as a matter of fact I shot the rest of the box to double check. I was very glad I brought both if I only brought the CCI it would have sucked

The pictures show the CCI ammo back by the primer blew out a few the one off the plastic is a round that was never chambered for comparison. The long one was rear blows out and next round chambered into it

The Hornady muzzle Vel 2100
CCI Muzzle Vel 2010

It seems that when you fire the little bit of recoil feels snappier


Anyone have an idea why the CCI maybe an issue?

Hank

That 10/22 is not the correct gas system to run the 17HMR or the smaller HM2. Nuff said.

I don’t know ran 50 Hornady today like clockwork

Not the accuracy I was hoping for yet but no running issues

Hank

From all that I have read, it is monumentally difficult to get those to function correctly. If I had to guess why you are having issues with the CCI, I'd guess has to do with timing of all of the moving parts resulting in out of battery firing. The slight velocity difference could explain it.

“Don’t try this at home”

There are ways to make stuff like this work, the Savage A17 seems to be one, but just hanging weight on an existing blowback bolt system seems like a kludge. I once owned a Kimber M2 1911 conversion, and while it was a pleasant and accurate pistol, it would occasionally produce a case slightly bulged just forward of the rim. Never had one burst. I fiddled with it and found it would allow the hammer to fall with the slide ever-so-slightly out of battery. I decided that was potentially dangerous and traded it off. Currently, I have a .22 mag blowback upper that thus far is working perfectly and shoots very well, but I’m keeping an eye on it. The design has been around for a bit and I’ve heard nothing about problems, so I’m optimistic.

I also have a S&W gas-operated 5.7x28 and a .22 mag that works in a similar fashion is in the pipe (waiting for a bankruptcy to sort out). Those seem like a better way to me. That 5.7 has been flawless, except one incident involving a separated case neck on a reload. I have decided to forgo the reloads for now as the process is very intensive, and I’m apparently not alone.

There has been a lot of discussion about this conversion on RFC and the consensus seems to be that the pressure curve difference between the 17HM2 and 22LR is enough different that the conversions are unreliable from a safety perspective and that it is only a matter of time before the converted rifles will fire out of battery, resulting in blown out rims, damage to the rifle, and often escaping gas and shrapnel injuries to the shooter.

I did a couple of these conversions, one with a GM 96/17 barrel and one with a lined barrel. Both of them worked, but I always kept them spotlessly clean, paying particular attention to removing any unburned powder fouling build up on the back of the barrel and face of the bolt. They were fun, but after reading about all of the "kabooms" on RFC that other people were having, I decided that the risk of injury was more than I felt comfortable with, so I converted those rifles back to 22LR.

I had a 10/22 Magnum to 17HMR conversion between 15 and 20 years ago. I had multiple "kabooms" before getting it to work semi-reliably, wrecking magazines, a stock, and extractor parts. When 10/22 Magnums were discontinued and suddenly became collectable, I converted it back and sold it.

I’ve known some people to put a heavier bolt spring in theirs and it fixed the issue. The most important thing with those 10/22 conversions is to clean it after about 50 rounds. Both of those should help cut down on the blow outs

Possibly, but personally I don’t want anything that fussy, better to go with something else that doesn’t require quite so much “watching”.

The MAP for the M2 is the same as regular .22LR and .22 Mag, so what 260 wrote makes sense. Something like the Savage with its delayed blowback makes more sense, and they aren’t that expensive.

Meanwhile, my BC upper seems reliable so far. Haven’t seen any kaboom reports on those yet either.

I own two 10/22 mach2’s The first one I built I never have had a issue out of it. The second one was blowing the rims and after a little work it shoots CCI flawlessly. So it can be done just be patient and use quality items!

Have a Ruger 77-17M2 with Lilja SS barrel

That thing is lights out on what ever you point it at

Very under rated cartridge

Still running the ole school Eley ammo

My experience with this conversion is that it works well right up until it doesn't. You can add weight to the bolt, install stiffer recoil springs, keep it spotlessly clean, and tune the [bleep] out of it, but regardless of what you do, it will always run on the edge of safety with a cartridge that it wasn't designed for and eventually you'll end up on the wrong side of that edge. Different people have different levels of risk/danger tolerance. so each of us has to decide for ourselves how close to that edge we're comfortable working. My advice is to always wear good quality safety glasses and heavy gloves when you're shooting this conversion.