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.45 ACP rim dimensions and moon clip flatness


wheelie
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I'm having a recurring problem with misfires in my 625. I've reamed the chambers as they were undersize from the factory, tuned the action and installed an Apex long firing pin. Generally the primers look like they are well hit and the gun has plenty of mainspring tension - it hits hard. I had a Wolf spring in it that was much lighter but swapped back to a slightly bent factory spring trying to cure this problem. If anything its way heavy for a pure target gun. But occasionally, I'll have a misfire - maybe 1 out of 150 rounds. A second hit works most times to set the round off, and a second hit single action always does so. I'm seating primers flat and fully and paying strict attention to my reloading practices. (way better ammo than any revolver should ever need) But I really hate a gun thats not 100%. This thing has me talking to myself.

What I'm down to now is the brass rim dimensions and flatness of the clips.

Brass:

I measured my brass and found that Remington was the thinest case mouth and selected that as my standard for a looser fit in the chambers. I am wondering though, if RP brass in general, or my batch of it, is not consistent in the rim extractor cut. The rounds are loose in the clips as they should be but I wonder if there is not some interaction between the clips, brass and chambered rounds that is sometimes putting a round in a bind or cushioning the strike in some way. Any thoughts on brass? What have you found best and worst in .45 brass in your 625? Does it matter?

Clips:

I have a batch of 100 new Ranch Products clips and about another 40-50 used clips. I'm checking them for flatness on a granite surface plate. About half of the new ones are not prefectly flat. Today, I'm culling out by feel any clip that rocks even slightly, checked from both sides. What is the flatness tolerance for these clips? Any tips on straightening clips?

Any and all suggestions appreciated.

Thanks.

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Keep in mind, the firing pin mark on a fired round is no indication of firing pin strike because upon ignition the case will set back and deepen the dent. That said, if it isn't the hammer/firing pin strike causing your misfires, I don't have an immediate answer.

Dwight

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Welcome to the madness, I hope you enjoy your stay!

You appear to be a logical thinker, that will help.

High primers are usually your first stop. You've addressed that in your comment but don't slacken your diligence.

That brings me to what I think the cause will be. The hammer assemblies on these guns walk back and forth on the hammer stud from the factory. There will be arc shaped scratches on the side of the hammer that you can see; probably on the left side.

You've got just enough spring in your gun to run most of the time, but when the hammer drags just a bit more occasionally, it will rob enough momentum from the hammer that you get a light strike.

The hammer assembly must be centered in the frame and kept there, usually with shims. You may have to narrow the factory hammer so shims will fit (like with a stone) and you may need to smooth and even the inside of the frame.

Or just do like S&W and put the regular truck springs back it it so it doesn't matter if all the internal parts drag on each other or not. :)

Edited by Waltermitty
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The main causes of misfires on these guns is: Cylinder endshake, firing pin too short, hammer fall too light, bent moon clips, primers not fully seated, cylinder out of time causing off center firing pin hits. Other things like too much headspace or too thin rims on brass are much less common.

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Good information from the others.

The problem probably has nothing to do with your brass or moonclips. For the past 25 years I have been running my various .45 revolvers with the same bucket of old mixed brass (much of it picked up off the range) and plain Ranch Products moonclips that I have accumulated. I don't do anything special to maintain or check any of this stuff. If the loaded moons go in my cylinder and allow the cylinder to turn normally, they will work 100% in all my guns.

I am wondering if you might be overseating your primers, as Matt suggested. If you can see the little anvils in the center of the primers after squeezing them, you might be seating them too deeply.

Are the FP hits fairly well centered on the primers?

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Thanks to all who have replied.

Rather than putting in a bunch of quotes, I'll just dive in, in no particular order.

I'm seating primers carefully with an old RCBS bench tool and can feel the primer bottom out. The tool has excellent feel and I'm not crushing them, but they are fully at the bottom of the pocket. Pockets are clean. All I'd have to do is turn the case necks and I could claim benchrest rifle quality ammo with a straight face. I've been loading metallic ammo for literally 40 years and bazillions of rounds but this gun is not acting in a reasonable fashion.

Hits are well centered on the primers. The 99.5 percent that go off have great big impressions from the Apex long firing pin. Its knocking the *&^% of of them. The ones that don't fire have a light strike - really light - and look like they shouldn't have fired.

Gun came with zero endshake and would lock up when the least bit dirty. Firing pin bushing stood .006 proud of recoil shield. I fixed both - gave it .002 end shake and stoned the firing pin bushing to flush with the recoil shield. The Apex long FP is plenty long (almost too long).

This gun is pain in the ass. As I wrote already, I had to ream the chambers as they were smaller than SAAMI standard. The gun barely worked with factory ammo. Would not chamber a reload with a .452 bullet. And the firing pin bushing - how the heck did that get out the door? This is the first one of the detached firing pin guns I've had and while most of it looks good and fits nice S&W seems to have made an epic fail on these guns.

I'm shooting with my perfectly flat clips tomorrow and keeping my fingers crossed.

Any more suggestions, just keep 'em coming.

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Whoops - left out the hammer sliding around in the gun.

I may order some washers and see about that.

Do I need to take out the (personally offensive and absolutely foolish) safety trinkets? Or just leave then in?

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Whoops - left out the hammer sliding around in the gun.

I may order some washers and see about that.

Do I need to take out the (personally offensive and absolutely foolish) safety trinkets? Or just leave then in?

I still have mine...in a drawer around here somewhere. ;)

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You know those super light looking strikes? That's what happens when there's not quite enough mainspring energy to pop the primer.

You know those nice deep dents you see on the ones that fired? That's what happens when the primer is driven backward from the primer pocket against the recoil shield while the firing pin is still extended forward, just before the primer is pushed back into its pocket by the case being pressed back against the recoil shield. (I'm merely expanding on what Dwight pointed out in his post above.)

In other words, totally normal situation. Means nothing.

You just need a little more mainspring tension. Just a little. Bend the mainspring a tiny bit straighter, or use a strain screw that is a tiny bit longer. That's it. That will solve the problem.

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You know those super light looking strikes? That's what happens when there's not quite enough mainspring energy to pop the primer.

You know those nice deep dents you see on the ones that fired? That's what happens when the primer is driven backward from the primer pocket against the recoil shield while the firing pin is still extended forward, just before the primer is pushed back into its pocket by the case being pressed back against the recoil shield. (I'm merely expanding on what Dwight pointed out in his post above.)

In other words, totally normal situation. Means nothing.

You just need a little more mainspring tension. Just a little. Bend the mainspring a tiny bit straighter, or use a strain screw that is a tiny bit longer. That's it. That will solve the problem.

To back up Mike, while there's an obvious Too LIGHT! where I get 2 out of 6 not firing, there's also a "too light, barely" where it's 2 out of a hundred. It's a fine point, and usually the difference of a mere 1/4 turn of the strain screw. Give it that turn, and if you still have failures, I have to point back at the ammo. While I respect that you are a meticulous reloader, you may not be a heavy-handed reloader, which is what primers want for fiddly revolvers. If you still have failures, caliper 200 primers and discard anything below .006 or over .012. If you still have a problem, investigate deeper.

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Firing pin bushing stood .006 proud of recoil shield. I fixed both - gave it .002 end shake and stoned the firing pin bushing to flush with the recoil shield.

And the firing pin bushing - how the heck did that get out the door?

All the guns I have worked on with the frame mounted firing pin have what I call a domed firing pin bushing they are supposed to stand a little tall. There was nothing wrong with yours(before you filed it down). You have now created .006 extra clearance between recoil shield and cylinder. This domed bushing is a great idea IMO as it supports the back of the case and primer when in the firing position but allows for a little extra clearance for the rest of cases as they index into position.(Less drag)

Is this your problem? Maybe - maybe not but if you have a fully loaded clip in gun and it is all the way back against recoil shield when the hammer falls the hammer has to push the clip loaded with 230 grain bullets forward .006 more than before to seat clip against cylinder and fire. This uses some of the energy of the hammer fall.

The Apex firing pins are made to have a longer notch for more freerun at the primer(speed) but if the firing pin has to push everything forward an extra .006 you lose some of this .

If the clip happens to be seated against the cylinder than the gun should fire normally. But if it is back against the recoil shield you might have problems setting off the primer giving you a random firing problem.

I'm sure that IF this is part of the problem you can make up for it by increasing the mainspring tension.

Good luck and keep us posted with what you find.

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So, I went down to bend the spring and whadya know - the strain screw has backed out. This after I loctited it a couple of months ago. Now its got another big dose of loctite. I'll watch it.

After all the going around with this gun I about melted down last week when it misfired again after thinking I had it cured. Now it seems to be just the strain screw backing out. I hope so, because I'll look stupid but the gun will be fixed.

About the firing pin bushing -- This gun would hang a cartridge on the firing pin bushing every couple of cylinder fulls, worse when it got dirty and just enough to throw me off. Just a momentary grab and catch trigger pull. That's why I stoned it down. I don't think it has anything to do with the misfiring. I understand what you are saying about it but its a darn poor design to think that you can smoothly drag 6 cartridges over that kind of hump. And yes, it does have .006 more headspace than it did. I measured before I stated cutting and it has no more than several other older guns I have. Do all the "firing pin in the frame" guns have this hump? (other calibers)?

Thanks again to everyone for all the help.

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So, I went down to bend the spring and whadya know - the strain screw has backed out. This after I loctited it a couple of months ago. Now its got another big dose of loctite. I'll watch it.

After all the going around with this gun I about melted down last week when it misfired again after thinking I had it cured. Now it seems to be just the strain screw backing out. I hope so, because I'll look stupid but the gun will be fixed.

About the firing pin bushing -- This gun would hang a cartridge on the firing pin bushing every couple of cylinder fulls, worse when it got dirty and just enough to throw me off. Just a momentary grab and catch trigger pull. That's why I stoned it down. I don't think it has anything to do with the misfiring. I understand what you are saying about it but its a darn poor design to think that you can smoothly drag 6 cartridges over that kind of hump. And yes, it does have .006 more headspace than it did. I measured before I stated cutting and it has no more than several other older guns I have. Do all the "firing pin in the frame" guns have this hump? (other calibers)?

Thanks again to everyone for all the help.

If you still have a problem with the strain screw backing out, you can do what bullseye and PPC shooters do, drill and tap a hole from the bottom of the grip to the strain screw hole, after setting the strain screw, drop in a lead shotgun pellet, and then a set screw to anchor the strain screw.

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So, I went down to bend the spring and whadya know - the strain screw has backed out. This after I loctited it a couple of months ago. Now its got another big dose of loctite. I'll watch it.

After all the going around with this gun I about melted down last week when it misfired again after thinking I had it cured. Now it seems to be just the strain screw backing out. I hope so, because I'll look stupid but the gun will be fixed.

About the firing pin bushing -- This gun would hang a cartridge on the firing pin bushing every couple of cylinder fulls, worse when it got dirty and just enough to throw me off. Just a momentary grab and catch trigger pull. That's why I stoned it down. I don't think it has anything to do with the misfiring. I understand what you are saying about it but its a darn poor design to think that you can smoothly drag 6 cartridges over that kind of hump. And yes, it does have .006 more headspace than it did. I measured before I stated cutting and it has no more than several other older guns I have. Do all the "firing pin in the frame" guns have this hump? (other calibers)?

Thanks again to everyone for all the help.

Hope the strain screw solves the problem for you.

As for the firing pin bushing just curious how you could tell that the cartridge was hanging up on the firing pin bushing? Maybe some other problem causing it to hang up?

As for it causing the misfires, I don't know what kind of trigger you are seeking but if you are after a sub 6 pound trigger then I'm going to say that it will be a problem. If you are ok with 7 to 8 pounds probably not. You added .008 clearance with endshake and pin bushing being filed down. That is a big deal when getting the last few ounces out of a trigger and being 100% reliable.

As for comparing clearance with older guns that is apples and oranges if you are comparing Hammer mounted firing pin to frame mounted firing pin. While it is the same basic principle the dynamics are quite a bit different. Hell the difference between two guns that have the same style firing pin can be be a headache. Every gun is it's own when working on them.

As for it being a poor design I stated in the other post that I think it is a slick idea. Hundreds of these guns with the domed firing pin bushing are being used in competition every weekend and thousands of them are being shot at the range with no problems.

I learned a long time ago to never say ALL because someone will shoot you down everytime. I will say that every frame mounted firing pin gun I have worked on be it K,L,N frame has had the domed firing pin. To be truthfull I don't even pay that close attention any more to the bushing. I just run a finger over it to make sure that it doesn't have a sharp edge on the edge of bushing(Never have found one that did).

Every gun is a learning experience even after you have done lots of them. You just have to turn frustrating into fun. :)

Don't take this as criticizing your work just trying to help(Hey I'm learning stuff here all the time-this post included)

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It was the simple fix. No problems at all today. I have lots of blue loctite on the screw now.

The "domed" firing pin bushing in my gun was not domed it just protruded with a fairly sharp edge. The gun worked fine after cutting the bushing flat and was lots smoother. I guess I could see that if done right this elevated bushing could help with smooth function but mine did not. This might have been related to the tight chambers and bushing together. I worked both at the same time. (reamed chambers and stoned bushing flush) Maybe a combination of a little snugness of the six cartridges in tight chambers and then having to be drug past a raised bushing caused the almost ratchet like feel I was getting. 4-5 cylinder fulls and it would start catching. Now the gun runs free and easy and no change in trigger pull when the gun is hot and dirty. It was way too tight as it came and probably was the reason it got traded in before I bought it. Wouldn't shoot a box of factory ammo without cleaning.

All my prior experience has been with old style guns from years ago, prior to full moons and frame mount pins. I never saw any of this with half moons or otherwise and I did lots of revolver work when I was in the business.

I'm going to look at the hammer shims idea. The hammer in this thing is a bit wobbly side to side and does have big rub marks on it. Shims should cut the drag down a bit and get a little harder hit for the same spring tension. I don't have a suitable pull gage, just a spring scale type that goes to 6 pounds, made for single action type pull. 6 pounds won't pull it through.

Feel free to give any answer you want - I asked for help and I thank you all for it. And this is not an argument forum, its a discussion forum. Just go ahead and write what you're thinking and we might all learn something.

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