Revolver Cylinder chamber alignment

[Koda]

I have a brand new North American Arms PUG 22WMR that heavily blows burnt particles back into my shooting hand and even face (wear safety glasses). I have a similar NAA 22WMR that does not and is actually fun to shoot.
The blowback is bad, I was glad I had safety glasses on but my hand was on its own and is still healing a week later.

I'm not knowledgeable about revolvers at all. Is this normal?

So I was wondering how in the world blowback can occur, where does it come from... I'm aware of cylinder gap blowback at the front of the cylinder and that is not the problem, my guess is this has to come from the breech of the cylinder being fired in order to blow backwards... so inspecting the pistol I look down the cylinder and find the cylinders get smaller at the muzzle end (what is that feature called?) and whats interesting is they do not look concentric with the main part at all. I promptly inspected my other NAA 22WMR cylinder and the two diameters are very concentric (by eye).

Here are some pics of my PUG models cylinder, and my hand injury. Could this misalignment cause this? What is the cause of cylinder blowback?






hand injury


firing grip

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[drstrangelove]

You need to check the timing and bore-chamber alignment. I would RMA it back to manufacturer.

 

[Nutty4Guns]

What he said ^^, timing is off and needs to be corrected.

 

[Koda]

You need to check the timing and bore-chamber alignment. I would RMA it back to manufacturer.

when I shine a light down the barrel the cylinder looks aligned. I dont know a better way to check but it does look aligned.

The misalignment Im seeing is only inside the cylinder. The cylinder seems to have a smaller end on the muzzle end of the cylinder.

Side note , this pistol has been send back twice already for a totally different issue.

 

[VinnieBoomBah]

Take something round and non scratching like a arrow shaft and slide it down the barrel holding it tight against one side, you should not feel it catch when it enters the cylinder. Move the rod around so you are tight against all sides of the barrel to check for cylinder / barrel offset

 

[Koda]

Take something round and non scratching like a arrow shaft and slide it down the barrel holding it tight against one side, you should not feel it catch when it enters the cylinder. Move the rod around so you are tight against all sides of the barrel to check for cylinder / barrel offset

Thats actually an interesting idea, I don't have anything 22cal dia handy though but the tip edge of my aluminum 22cal cleaning rod does not snag the cylinder when its aligned to fire and gently slid along one side of the barrel.

I don't know how to describe this, but I don't suspect its a cylinder to barrel alignment issue. I suspect the issue is entirely inside the cylinder only. There is a smaller diameter in there and I don't know what that feature is called.
A 22WMR is a straight walled crimped round, so the cylinder has to have a smaller diameter on the bullet end. That appears to be not concentric with the part of the cylinder chamber that holds the case. Reference my photos... I think this would cause a gap on one side of the case allowing blowback. I dunno though, im not a gunsmith.

 

[VinnieBoomBah]

What do the fired cases look like?

 

[Koda]

What do the fired cases look like?

I dont see anything unusual, just an average looking spent shell.

 

[VinnieBoomBah]

Looking at the photo with you holding it I am thinking that it has to be blowing back past the hammer. not 100% scientific, but the "cone of damage" doesn't match what you have unless it's coming past the hammer. The frame would protect you hand right by the hammer and the damage *should* be were you actually got cut

 

[CO136]

I'll submit a couple of things here...

As others have mentioned, perhaps a cylinder / bore (timing) alignment issue. Perhaps take some notebook paper, hold it on the left side of the cylinder out a couple of inches and fire a round. Repeat for the right side of the cylinder. Have you got one side chewing up the paper significantly more that the other? I suspect this may be the issue.

Ammo - Are you consistently getting the same issue regardless of ammo?

I have one of these guns. My son does as well. They are a hoot to shoot and we have never experienced the challenges you present. As another suggested, perhaps a trip to the MFG is warranted.

 

[Koda]

Looking at the photo with you holding it I am thinking that it has to be blowing back past the hammer. not 100% scientific, but the "cone of damage" doesn't match what you have unless it's coming past the hammer. The frame would protect you hand right by the hammer and the damage *should* be were you actually got cut
View attachment 1391927

the two most rearward purple lines are the path of the blowback. Its more severe on my trigger finger because more flesh is a but forward where my thumb is tucked downward (you can see just a few specs on my thumbs first knuckle).
The gap at the breech end of the cylinder is pretty tight, its odd to think this would be a problem but my hand stung for several days and is still scarred and I recall occasionally feeling a few speck hit my face. I was at my range so was wearing safety glasses thankfully. Now for the purpose of most any handgun being self defense I would not want to use this and put a granule of powder in my eye, imagine that. Note, my other NAA (different model) does not do this. This PUG model is grounded till I figure this out.

Also, this happens with 3 different brands of ammo so its not ammo related (although the CCI maxi mag was the worst (as well as the most duds)).

 

[Koda]

Ammo - Are you consistently getting the same issue regardless of ammo?

I have tried 3 brands of ammo but perhaps this is worth revisiting. This isn't something one goes into looking for this problem, it happens and then one starts looking for clues where they weren't taking notes. I did test fire a lot that day so maybe another range session is in order but keeping track of ammo brand.
that said, I have a different model of these pistols and intentionally took it to the range today and did not experience any blowback, though I only fired one brand of ammo today.

 

[DLS]

... The cylinder seems to have a smaller end on the muzzle end of the cylinder. ...

You are seeing the chamber mouth. The rearward portion of the chamber is sized to fit the cartridge case. The more forward portion, just past where the cartridge case mouth ends is sized for the bullet, which is a smaller diameter than the cartridge case.

You want the mouth to be a bit smaller than the bullet (about a thousandth) but larger than the forcing cone diameter.

 

[DLS]

The spitting you are experiencing can happen if the cylinder crane is misaligned or warped. While at rest the cylinder mouths can align with the forcing cone, but then flexes during firing creating spalling and blowback.

A trip back to the factory is in order. Yep, again is seems!

 

[Koda]

The spitting you are experiencing can happen if the cylinder crane is misaligned or warped. While at rest the cylinder mouths can align with the forcing cone, but then flexes during firing creating spalling and blowback.

A trip back to the factory is in order. Yep, again is seems!

What is a cylinder crane?

and sadly I suspect I need to send it back. Again. For the third time. At least this time its a totally different reason, the gun didnt even revolve out of the box, and still didnt after they "fixed" it the first time. Now it revolves... and fires, but blows back stuff at me.

 

[Koda]

some web searching I dont think these guns have a cylinder crane.

I think the issue is the cylinder mouth is not aligned with the cylinder chamber.

 

[DLS]

Yep, my mistake. Didn't catch the revolver when I read through the posts.

No crane (the part that swings the cylinder in and out of the frame) on that model.

You can her the same type of issue with a misaligned base pin on that type of revolver. The basepin only needs to out by a tiny fraction to be an issue.

 

[Koda]

You can her the same type of issue with a misaligned base pin on that type of revolver. The basepin only needs to oit by a tiny fraction to be an issue.

It could be, Im learning a lot here as I go.
As I inspect the pistol now I do suspect the cylinder might not be aligned with the barrel... by how much I dont know, nor do I know what an appropriate tolerance is.
I do see the cylinder mouth is not aligned with the cylinder chamber.

The cylinder was replaced entirely on its second trip under warranty.

I bought the pistol in January, and its been shipped back twice and Ive only fired it for the first time 2 weekends ago.

Im not certain how accurate this way is to tell if the cylinder is misaligned?

 

[drstrangelove]

It could be, Im learning a lot here as I go.
As I inspect the pistol now I do suspect the cylinder might not be aligned with the barrel... by how much I dont know, nor do I know what an appropriate tolerance is.
I do see the cylinder mouth is not aligned with the cylinder chamber.

The cylinder was replaced entirely on its second trip under warranty.

I bought the pistol in January, and its been shipped back twice and Ive only fired it for the first time 2 weekends ago.

Im not certain how accurate this way is to tell if the cylinder is misaligned?

View attachment 1391961

That can eventually crack your forcing cone… if it already hasn't.… RMA.

 

[gmerkt]

I think the issue is the cylinder mouth is not aligned with the cylinder chamber.

Your pictures show pretty clearly that the step where the chamber transitions to the bore at the forward end of the cylinder is not concentric. In at least two chambers that I can see. Which will skew the bullet to one side. When the skewed bullet hits the forcing cone, it shaves bullet material which blows out between the cylinder gap.

This is not acceptable. Stop shooting it and send it back to the manufacturer. You don't need to try any more different kinds of ammo. Any revolver that will pepper your hand like that is clearly defective and is causing harm.

It's difficult to understand that this revolver has already been back for warranty work and this defect has escaped notice.