Very interesting discussion. I have a batch of RP, Federal and Winchester I loaded a while back and I kept the head stamps separated so I could try them for accuracy. I guess they will also function in a test for misfires. I'll report back! Thanks all.
625-8 Having misfires with reloads
- Thread starter 686forme
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andyo5
Member
Two possibilities: I'ts the gun or it's the brass.
Since you are using mixed headstamp brass, it seems possible that some pieces have deeper primer holes than others. Check visually to see if the problem is restricted to one brand of brass, or if the primer seems deeper in the hole on brass that did not ignite. Since fired primers move in the hole due to pressure, it will be necessary to reseat the spent primers before making this comparison.
Another, even more likely possibility is that the brass which misfires is too short. The 45 ACP round headspaces on the case mouth, not on the rim. Look into the cylinder chambers of your 625, and you will see a ridge in each chamber. The case mouth of each cartridge should rest against that ridge, the same as it does in a 45 automatic. If the case is below specs, some of the energy from the firing pin will be absorbed in movement of the entire case forward until it hits that ridge. So less of the impact goes into the primer. There are specifications for case length which you can use, but also compare the misfired cases to ones which did fire. You will need to resize the fired cases to get a valid comparison.
There are several ways to lighten trigger pull. One is to "adjust" the strain screw by unscrewing it a bit. This is not a reliable method since it can continue to turn during recoil, but that doesn't stop some folks. Check it to see if it is tight. Another method involving the strain screw is to shorten the tip until the desired trigger pull is achieved. This is the method that the factory uses (they are looking for a certain amount of resistance in pounds), and I use it as well to lighten trigger pull past factory specs. If you shorten it too much, you will get unreliable ignition.
A third method is to bend the claw end of the mainspring to de-tension it. This is a sloppy, unreliable, and unrepeatable method but some folks use it anyhow. Compare your mainspring to a new one or one from a known good gun to see if the shape is different.
My S&W revolvers all have very light single action pulls, even as they came from the factory. You barely have to move the trigger before the sear is released. This is normal.
I will not advise you to go out and buy different firing pins or other things until you have sorted through these possibilities. S&W revolvers normally do not need aftermarket parts to function properly.
Since you are using mixed headstamp brass, it seems possible that some pieces have deeper primer holes than others. Check visually to see if the problem is restricted to one brand of brass, or if the primer seems deeper in the hole on brass that did not ignite. Since fired primers move in the hole due to pressure, it will be necessary to reseat the spent primers before making this comparison.
Another, even more likely possibility is that the brass which misfires is too short. The 45 ACP round headspaces on the case mouth, not on the rim. Look into the cylinder chambers of your 625, and you will see a ridge in each chamber. The case mouth of each cartridge should rest against that ridge, the same as it does in a 45 automatic. If the case is below specs, some of the energy from the firing pin will be absorbed in movement of the entire case forward until it hits that ridge. So less of the impact goes into the primer. There are specifications for case length which you can use, but also compare the misfired cases to ones which did fire. You will need to resize the fired cases to get a valid comparison.
There are several ways to lighten trigger pull. One is to "adjust" the strain screw by unscrewing it a bit. This is not a reliable method since it can continue to turn during recoil, but that doesn't stop some folks. Check it to see if it is tight. Another method involving the strain screw is to shorten the tip until the desired trigger pull is achieved. This is the method that the factory uses (they are looking for a certain amount of resistance in pounds), and I use it as well to lighten trigger pull past factory specs. If you shorten it too much, you will get unreliable ignition.
A third method is to bend the claw end of the mainspring to de-tension it. This is a sloppy, unreliable, and unrepeatable method but some folks use it anyhow. Compare your mainspring to a new one or one from a known good gun to see if the shape is different.
My S&W revolvers all have very light single action pulls, even as they came from the factory. You barely have to move the trigger before the sear is released. This is normal.
I will not advise you to go out and buy different firing pins or other things until you have sorted through these possibilities. S&W revolvers normally do not need aftermarket parts to function properly.
Last edited:
Beemer-mark
Member
I have a 625 mountain gun with an action job. Not sure what the trigger pull is but probably 7 lbs, very light. I use CCI large pistol primers (45 colt) and have never had a misfire (in any gun). I'd check the other stuff first.
The more I read in this thread the more I suspect that the OP has a problem with tolerance stack up. The firing pin projection can vary, the thickness of the rims can vary, the flatness and the thickness of the moon clips can vary, the depth of the primer pockets can vary and the sensitivity of the primers and the strength of the hammer fall can vary. I can't measure the last two, but all the rest are pretty simple measurements.
With a set of feeler gages and a pair of calipers you can measure most of these.
What is the firing pin protrusion? Feeler gage set will work with some effort and attention to detail. A transfer gage from Brownells costs as much a cheap pair of calipers but is made to do the job.
Are the moon clips all flat and do they measure the same thickness? Calipers and a known flat surface. A piece of glass window pane works quite well as a poor man's surface plate.
What is the rim thinkness of the brass that fires and that does not fire?
Calipers.
How deep are the primer pockets? Depth stem on calipers.
If you find that one of the variable items varies enough to matter, say you have primer pockets that are .020 deeper than others, or some of your moon clips are bent or vary in thickness then you can start reducing the variables by taking those items out of the picture.
I know that if this were my gun I would order 50 or 100 .45 Auto Rim brass and load them for testing.
If you don't have calipers I am going to commit sacrilige so if you have sensitive feelings stop reading . . . now. . .
You were warned.
Harbor Freight has really inexpensive electronic digital calipers from China. No name, not tolerant of coolant or oil on the glass slide but they do work. Not recommending them although I have been using an 8" pair for some stuff around the house for a month or two. YMMV
With a set of feeler gages and a pair of calipers you can measure most of these.
What is the firing pin protrusion? Feeler gage set will work with some effort and attention to detail. A transfer gage from Brownells costs as much a cheap pair of calipers but is made to do the job.
Are the moon clips all flat and do they measure the same thickness? Calipers and a known flat surface. A piece of glass window pane works quite well as a poor man's surface plate.
What is the rim thinkness of the brass that fires and that does not fire?
Calipers.
How deep are the primer pockets? Depth stem on calipers.
If you find that one of the variable items varies enough to matter, say you have primer pockets that are .020 deeper than others, or some of your moon clips are bent or vary in thickness then you can start reducing the variables by taking those items out of the picture.
I know that if this were my gun I would order 50 or 100 .45 Auto Rim brass and load them for testing.
If you don't have calipers I am going to commit sacrilige so if you have sensitive feelings stop reading . . . now. . .
You were warned.
Harbor Freight has really inexpensive electronic digital calipers from China. No name, not tolerant of coolant or oil on the glass slide but they do work. Not recommending them although I have been using an 8" pair for some stuff around the house for a month or two. YMMV
Ron S,
Not to worry my friend, I have an extensive set of toolmakers tools as that is what I did years ago before I went into engineering so I'm very familiar with tolerance stack up and using calipers. I'll pass on the Chinese stuff and use my Brown & Sharpe's. (I said it was years ago!) I'll do some checking and post what I come up with. I've been thinking about the problem and I believe it is more the combination of mixed brass and moon clips more than the gun. I was looking at some of the empties still in the moon clips and most of the primers have deep marks in them. Now that I have been given some direction I'll have more finite data in the next post. Thanks all for taking the time to reply!
Not to worry my friend, I have an extensive set of toolmakers tools as that is what I did years ago before I went into engineering so I'm very familiar with tolerance stack up and using calipers. I'll pass on the Chinese stuff and use my Brown & Sharpe's. (I said it was years ago!) I'll do some checking and post what I come up with. I've been thinking about the problem and I believe it is more the combination of mixed brass and moon clips more than the gun. I was looking at some of the empties still in the moon clips and most of the primers have deep marks in them. Now that I have been given some direction I'll have more finite data in the next post. Thanks all for taking the time to reply!
There have been several earlier posts about the new frame mounted firing pins being too short on the new guns. You might search those out as they have the measurements for the shorter pins and a recommendation for minimum length.
Mine was misfiring every three rounds or so. I check the strain screw just as you folks said and got a full 2&1/2 turns on that sucker 
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