Still getting misfires with Model 18 after reaming

[max503]

I reamed the cylinders, then installed a Woulff factory replacement spring (not reduced power). I cleaned and lubed the innards. Mainspring tension screw is fully seated.
I checked end shake per the Larry Potterfield Youtube video. It measures .006.

What's my next move? Is there a way to measure firing pin protrusion? I don't think this gun has been fired much. It was made in 1958 and it's in like-new condition.

It averages 1-2 misfires per cylinder-full. The second hit sets them off.

 

[BE Mike]

What different kinds of .22's ammo are you testing?

 

[THE PILGRIM]

Take out the new spring, put the Factory back in.
That’s the change you made that has the most to do with ignition.

 

[elpac3]

I would check the ammo. .22 rimfires have had a history of misfires due to priming mix not getting spun into the rim properly. A number of years back I had a batch of .22 from a large, well known US manufacturer that was consistently giving a 10% misfire rate

 

[murphydog]

Honing/reaming the cylinder bores tends to help with sticky extraction, not misfires.

It sounds you have done a thorough job of going through other causes besides the firing pin. Putting the old mainspring back in and trying several other different types of .22 LR should let you know if that is the problem.

 

[H Richard]

When the chambers were reamed, who did it, and did they go a little too far into the chamber seat? If so, you might need a longer firing pin.

 

[cmansguns]

reaming issues possibly

You may know all of this, but if not then check it out. When reaming did you leave the extractor star in place and ream together with the cylinder? If not then the rim of the ammo might be "tilting" in battery causing the firing pin to "strike" as surface farther away.

Also after finish reaming where the face of the recess reamer has just "kiss-cut" the charge hole and extractor star, this area needs to be cleaned of angel dust and any oily residue very, very meticulously.

Again...if you did it right, then it is some other issue for sure and I agree...go back to factory spring and see if it goes away. Easiest to try, that's for sure.

 

[Hair Trigger]

I think the issue you're having is cartridge setback. When you fire the gun, recoil, or what there is of it on a .22 causes the other rounds in the cylinder to move back against the recoil shield. It's only a millimeter or so, but it is enough that when you fire the next chamber, part of the energy of the firing pin goes to pushing the cartridge back into the chamber, leaving too little energy to hit the rim hard enough to crush it enough to fire. I have the same issue with my M48-4. I think a longer firing pin may help, or having a gunsmith peen the edge of the rim recess on either the cylinder or extractor star so the seated round won't back up without being pushed out with the extractor. It would only take a very small spot to accomplish it, using a punch.

Mine has had this done by a previous owner and on three of the chambers I never have the misfire, but the other three weren't done quite as well so I still have issues. The gun never misfires on the first shot, and the cylinder lockup is very tight, no forward or backward movement at all, and when open the end shake is so little you can barely measure it.

Arrow points to what I'm talking about.

 

[stansdds]

I reamed the cylinders, then installed a Woulff factory replacement spring (not reduced power). I cleaned and lubed the innards. Mainspring tension screw is fully seated.
I checked end shake per the Larry Potterfield Youtube video. It measures .006.

What's my next move? Is there a way to measure firing pin protrusion? I don't think this gun has been fired much. It was made in 1958 and it's in like-new condition.

It averages 1-2 misfires per cylinder-full. The second hit sets them off.

0.006" end shake sounds like a lot for a rimfire. That would be a lot for a centerfire revolver too! Ideal end shake is only 0.001-0.002". I'd say you need to install cylinder yoke shims to reduce that end shake.

 

[Protocall_Design]

I think the issue you're having is cartridge setback. When you fire the gun, recoil, or what there is of it on a .22 causes the other rounds in the cylinder to move back against the recoil shield. It's only a millimeter or so, but it is enough that when you fire the next chamber, part of the energy of the firing pin goes to pushing the cartridge back into the chamber, leaving too little energy to hit the rim hard enough to crush it enough to fire. I have the same issue with my M48-4. I think a longer firing pin may help, or having a gunsmith peen the edge of the rim recess on either the cylinder or extractor star so the seated round won't back up without being pushed out with the extractor. It would only take a very small spot to accomplish it, using a punch.

Mine has had this done by a previous owner and on three of the chambers I never have the misfire, but the other three weren't done quite as well so I still have issues. The gun never misfires on the first shot, and the cylinder lockup is very tight, no forward or backward movement at all, and when open the end shake is so little you can barely measure it.

Arrow points to what I'm talking about.

The peening that is shown in the picture is from the firing pin striking the cylinder when a chamber was not aligned with the barrel. Peening the cylinder is not the answer.

 

[gmarshall99]

I think Wolfsprings also sells extra power mainsprings. For a few dollars it may solve your issue.

 

[max503]

I think Wolfsprings also sells extra power mainsprings. For a few dollars it may solve your issue.

They list an extra-long strain screw, but I didn't see an extra power spring. I'll give them a call.

As soon as the weather breaks I'll try some different ammo. Been using Aguila SV and Mini-mags. Both have misfires.

 

[max503]

You may know all of this, but if not then check it out. When reaming did you leave the extractor star in place and ream together with the cylinder? If not then the rim of the ammo might be "tilting" in battery causing the firing pin to "strike" as surface farther away.

Also after finish reaming where the face of the recess reamer has just "kiss-cut" the charge hole and extractor star, this area needs to be cleaned of angel dust and any oily residue very, very meticulously.

Again...if you did it right, then it is some other issue for sure and I agree...go back to factory spring and see if it goes away. Easiest to try, that's for sure.

I reamed the cylinders with the star in place, stopping when the step on the reamer was below flush with the end of the cylinder, but before it contacted the star itself.

 

[Hair Trigger]

The peening that is shown in the picture is from the firing pin striking the cylinder when a chamber was not aligned with the barrel. Peening the cylinder is not the answer.

You know, until you said that I couldn't understand why there were similar marks away from the chambers. It's obvious now, and thanks for pointing it out. After I read your comment I tried to duplicate the out-of-time situation it would require and it was extremely difficult to do, makes me wonder how that happens "naturally". At any rate, three of the strikes were along the fine edge of the recess and make a tiny indent that peened the edge. Those are the only chambers I don't have issues with misfires, and I have been trying to figure it out almost since I bought the revolver (used).

In keeping with the subject here, of max503's issue, would a longer firing pin be the best solution?

 

[armorer951]

The rear gauge, or "headspace" is critical, especially on rimfire frames. Can you use a feeler gauge and check the gauge or space at the rear of the cylinder, between the cylinder and the breachface? Correct gauge here would be .008" - .010".

As someone previously suggested, you may need to correct an excess here by using shims on the end of the yoke barrel. Adding shims will move the cylinder back, and correct any excessive headspace found. Cylinder shims are available from Triggershims.com........


S&W K L N Revolver Shim Kits


Carter

 

[Alk8944]

If you installed a Wolff "Power rib" mainspring and didn't use an extra length strain screw that is probably the problem. Wolff doesn't tell you ) (last I looked) that their power rib spring MUST have a longer than standard strain screw!

You may have other issues, but this is a big one.

 

[ken158]

Take out the new spring, put the Factory back in.
That’s the change you made that has the most to do with ignition.

Sometimes you gotta face the fact that the factory installed a spring that would fire a rimfire cartridge no matter the brand. Now, use fancy spring in a centerfire gun instead and you should be good. Keep your strain screw tight and if someone has filed the tip of the screw, replace it.

 

[Nightowl]

The very first process is to make sure the gun is withing factory specs! If you do have .006 endshake, fix that first. Make sure everything else is with specs, too, including fixing the throw by that is causing the firing pin dents. Once the gun is in spec, inspect the firing pin for damage. Replace that aftermarket spring with the original or a new factory one. (my favorite mainsprings are made by Smith & Wesson, thank you very much). Then test fire. Misfires with .22 ammo are very common, so ammo could also be a part of the culprit. You might try some .22 match ammo from Ely or other high quality match brand to check gun reliability. I have several .22 pistols and seldom get 100 % out of any of them with the bulk .22 ammo of today!

 

[Timb1]

Maybe a broken firing pin. The problem is that sometimes the two pieces line up correctly fore a good impact on the rim and other times they don’t and that’s when the miss fire happens.

 

[-BTM-]

[ QUOTE=Hair Trigger;142174831]I think the issue you're having is cartridge setback. When you fire the gun, recoil, or what there is of it on a .22 causes the other rounds in the cylinder to move back against the recoil shield. It's only a millimeter or so, but it is enough that when you fire the next chamber, part of the energy of the firing pin goes to pushing the cartridge back into the chamber, leaving too little energy to hit the rim hard enough to crush it enough to fire. I have the same issue with my M48-4. I think a longer firing pin may help, or having a gunsmith peen the edge of the rim recess on either the cylinder or extractor star so the seated round won't back up without being pushed out with the extractor. It would only take a very small spot to accomplish it, using a punch.

Mine has had this done by a previous owner and on three of the chambers I never have the misfire, but the other three weren't done quite as well so I still have issues. The gun never misfires on the first shot, and the cylinder lockup is very tight, no forward or backward movement at all, and when open the end shake is so little you can barely measure it.

Arrow points to what I'm talking about.[/QUOTE]

I would think the opposite reaction would happen, the rounds would pulled forward. Also, that doesn’t look like intentional peening to me. Never heard of such a thing.