Occasional Light strikes

[1911Prof]

I really need some feedback here, as this is bugging the crap out of me.  I have been shooting revolver for about a year with a 929 with an Apex hammer set at about 6.5 lbs.  It had been running fine for a year but just recently I started having the occasional light strikes on Federal primers.  I mean LIGHT, the primers that didn't go bang only had a really light dent.  I figured the spring had worn or the screw had backed out, but I couldn't find anything wrong.  I put a (flattened) spent primer between the tension screw and the spring and the trigger pull went up to about 8 lbs.  At this point I was lighting off Winchester primers, thinking the problem was solved, but low and behold, I had another light strike on a federal primer when practicing.  To my knowledge, the only things are light spring tension or high primers, but my reloading technique hasn't really changed over the last 15 years so for all the sudden to have high primers seems unlikely, I have inspected the rounds and still about 2 out of every hundred don't go off. Do the internals just need a really good cleaning (I haven't stripped it totally down to clean it) 

[practical_man]

Prof

 

a good cleaning never hurts. All manner of gunk can slow down the internals. 

 

I dont have a 929. I have a bunch of S&W revolvers of various vintages. 

 

What you describe sounds to me like excessive endshake, caused by moderate peening of the cylinder yoke (which is never cut square at the factory). Easy to fix. 

 

Could it be your moon clip/ brass combination is mimicking excessive endshake?  Maybe a case of tolerance stacking working against you. 

 

ToolGuy or one of the real experts will be along soon to shine some light in this. 

[Dr. Phil]

I have seen that same problem with a bent moon clip. They usually fire next time you try them? Check your moonclips and see if 1 petal is bent or twisted...

[alecmc]

-primers are not seated at proper depth(.008-.010 below flush)

 

-short / improper firing pin - take out the pin, clean out the channel and make sure the pin return spring isn't gunked up. Use a Apex competition pin or a .495 or longer pin.

 

Bent moon - look into the moon clip checkers from tk custom

 

-exessive end shake - use feeler gauges to measure

 

-loose strain screw

 

- timing issue if hits are off center

 

Edited November 27, 2017 by alecmc

[pete627]

27 minutes ago, Dr. Phil said:

I have seen that same problem with a bent moon clip. They usually fire next time you try them? Check your moonclips and see if 1 petal is bent or twisted...

+1

 http://forums.brianenos.com/topic/248471-moon-clips/?do=findComment&comment=2776536

 

 

[Toolguy]

All of the above. The usual suspects have pretty well been covered.  Endshake or bent moonclip seem the most likely, given the information available. Endshake is normal wear on any revlolver that gets used as intended. I prefer to stretch the crane rather than use shims. The shims wear out fairly soon, then you just have metal debris floating around in there.

[1911Prof]

Thanks guys, I appreciate the expertise.  I am afraid I got into the revolver game too late, there is no one else to ask locally 

[Dr. Phil]

Never too late!

Welcome aboard.

[MWP]

How are you seating your primers? I'd look into that before I started looking at moons or end shake.

[GMM50]

Moon Clips are easy to check.....Stack them like poker chips.  If you see an air gap one is bent.

Don't forget to cut the pile so the top and bottom clips get moved to the middle.

 

Also do you case check each round.  That exposes some issues.

 

Keep us posted

[1911Prof]

Ok, I haven’t had a chance to go to the range yet, but I checked the end shake and it is insignificant.  The moon clips on the other hand might be a problem.  The tk custom moons stack perfectly flat, the speed beez moons are a little warped, I am not sure how bad is bad enough, but it is noticeable 

[Toolguy]

The ones in the bottom picture will act as a buffer to soften the strike of the firing pin. How much is the issue. If you have a full strength factory mainspring, it might still work. With a very lightened competition action, probably not. There are a lot of variables that come into play, and every gun is an individual entity. What works in one, may not work in a seemingly identical one.

[1911Prof]

Interesting,

[practical_man]

Those bent moons will act like a spring to absorb hammer energy before everything is crushed against the cylinder face for ignition. Maybe only on 1 or 2 chambers, depending on how things align. 

 

Ben clips can also cause cylinder dragging or binding. At least they do on my 627, which is a different animal that the 9mm. I learned  He hard way about cheap moon clips and 38 Special. Brass

[Dr. Phil]

Looks like not much but in the practical sense it is probably enough to cause the problem. Easy to straighten tho. I find I have to run through mine a couple times a year and straighten them. Practice clips that is. Match clips are treated more gently and require less straightening...

Sometimes you might feel the bent ones as harder to load. Not always but sometimes. The thicker clips (.035 9mm as opposed to the 38 Special .022) seem to be a lot less prone to bending.

YMMV

[1911Prof]

Well crap, I really thought the moon clips was going to be the bottom line, but I went to the range and even with the flat good moons, it still happened

 

[GMM50]

One step to take in this testing setup is to use factory ammo.  Federal is what I use.  I think Winchester would be OK.

See if you have the same problems with factory ammo.  That will eliminate your reloads.

 

Get you revolver so that it will set off factory ammo. 6.5 might be too lite a pull to start with.

Then  test one thing at a time.  Reloads / Moon Clips / Brass head stamp / etc.

[alecmc]

1 or 2 out of every 100 sounds like a reloading issue to me. 

[practical_man]

1911Prof

 

Isolating these things can be a challenge. It could be ammo, or maybe not. GMM50 gives good advice on starting with consistent factory ammo as a baseline. 

 

Have you checked to see if the light strike is consistently on a single chamber?  If not, it might be worthwhile to number your chambers and track the data a bit. 

 

Light DA pulls require everything to be almost perfect. Crane alignment, ejector rod (unless it floats at the distal end), crane-cylinder interface and endshake...

and of course deep seated primers. Lots of variables. Most easy to correct with hand tools. Sometimes one needs a talented machinist to correct a factory error, especially with how cylinders are cut and chambers are finished 

 

The easy "fix" is to add more energy to the hammer impact on primer. Lighter hammer, stronger spring tension or a combination of both will do it. Often at the expense of that elusive light DA pull we seek. 

 

Please keep us updated ted on your progress. These puzzles are informative and interesting. 

[PatJones]

Double action trigger weight is difficult to measure and is a function of several things that do not influence ignition.

Put your revolver in a vise, hold the trigger fully to the rear, and measure the hammer weight using your trigger pull gauge. That will give us a more useful number to discuss.

[1911onr]

5 hours ago, alecmc said:

1 or 2 out of every 100 sounds like a reloading issue to me. 

Check that your shell plate is tight. 

[1911Prof]

OK, I rechecked the trigger pull from a vise and it is at a repeatable 7 lbs.  The endshake is 8 thousandths which I suspect by itself is not a lot but is still a factor.  I am beginning to believe that the problem is one of stacked tolerences.  Since I am a recovering open shooter, the primers have never been an issue so my reloading technique may have been a little sloppy in that respect.  So I reloaded 100 more carefully (and really leaned on the primers) and all 100 went bang.  I am hopeful, but I will have to shoot a crapload more before I feel comfortable.  If that is dependable I may try to lower the trigger again, but maybe 7 lbs isn't that bad

[alecmc]

.008 of end shake is a tremendous amount.

 

Do you mean your bc gap is 008? 

 

To measure end shake pull and hold  the cylinder to the rear, measure with feeler gauges.

 

Now, push and hold the cylinder forward, measure this gap with feeler gauges

 

Subtract the 2nd measurement from.the first, this is your end shake. 

[revoman]

48 minutes ago, 1911Prof said:

OK, I rechecked the trigger pull from a vise and it is at a repeatable 7 lbs.  The endshake is 8 thousandths which I suspect by itself is not a lot but is still a factor.  I am beginning to believe that the problem is one of stacked tolerences.  Since I am a recovering open shooter, the primers have never been an issue so my reloading technique may have been a little sloppy in that respect.  So I reloaded 100 more carefully (and really leaned on the primers) and all 100 went bang.  I am hopeful, but I will have to shoot a crapload more before I feel comfortable.  If that is dependable I may try to lower the trigger again, but maybe 7 lbs isn't that bad

I think Pat meant to measure the hammer fall weight not the trigger pull.

[1911Prof]

4 hours ago, alecmc said:

.008 of end shake is a tremendous amount.

 

Do you mean your bc gap is 008? 

 

To measure end shake pull and hold  the cylinder to the rear, measure with feeler gauges.

 

Now, push and hold the cylinder forward, measure this gap with feeler gauges

 

Subtract the 2nd measurement from.the first, this is your end shake. 

Geez, that makes more sense.  that makes the endshake more like 3 thousandths. As I may have mentioned earlier, the amount I don't know you could just about squeeze into the grand canyon.  Looking at it that way, is it normal for the forcing cone to be a few thousandths out of flat (one side is closer to the cylinder than the other)?