Why Light Strikes?

[doctorj]

This is really bizarre.

My nightstand gun is a S&W 65 .357 in excellent condition. My standard ammunition for it has been 125 gr UMC SJHP .38 +P for several years. What I have is the old "yellow box" UMC and I've been shooting it off lately, just because it's time to replace.

On one box there were 2 light primer strikes. Then I went out with 2 more boxes. In the first, there were 3 light primer strikes, but the second box was fine. I thought I just had a couple of dud boxes. Yesterday I shot off the last box. There were 2 light primer strikes.

The light strikes are never on the same chamber, and never adjacent chambers. Yesterday there was a light strike on chamber "1" and chamber "4". The peculiar thing was that although these were different chambers, in each case they were the first chamber to be fired after reloading. All the duds fire on the second try, all strikes including the light ones are dead center. The striking does not appear "borderline"-- The light strikes were very light, the others-- including the restrikes-- are hefty dents.

I didn't have any other brand of ammunition to try. If it's the gun, why doesn't it happen more often and/or on the same chambers? If it's the ammo, why both times yesterday did it only happen on the first round of the "load"? Any ideas?

Thanks.

 

[BigG]

Chambers clean?

Rounds in a revo should shake back and forth, otherwise a sticky round can cushion the blow of the firing pin enough to cause a light strike; worse it can jam back against the recoil shield and prevent the cylinder from turning causing revo to be inoperable. HTH

 

[JoeHatley]

You may want to double check that your strain screw hasn't backed out a bit on you.

Good Luck...

Joe

 

[doctorj]

Strain Screw?

How can I tell whether the strain screw has backed off? Don't want to mess with it if it hasn't. If it has, how do I keep it from backing off again? Thanks for the quick response.

dr. j

 

[Brasso]

It sounds like a loose strain screw to me too.

I make it a point to never mess with a strain screw on a new S&W unless I absolutely have to. They always end up backing out once the lok-tite is broken.

Just tighten it all the way (not hard) and then back it out 1 and 1/2 turn. If you want it to stay that way you need to degrease the screw and put lok-tite on it first.

 

[BigG]

Forget backing the strain screw out. It is supposed to be screwed down tight.

 

[115grfmj]

ditto on the strain screw....

My 686 had the same problem. Strain screw was only backed out 3/4 turn.
It should be screwed down tight, and loctited in. Even 1/2 turn is enough to
cause light strikes, and this is from the mouth of S&W Service.

 

[jaybar]

Light strikes/heavy strikes.

Truth be known - all your strikes are probably light. You can't tell how heavy a strike is by viewing the firing pin imprint in a fired primer. When the primer ignites it actually blows back toward the firing pin. Add to this the internal pressure from the burning powder blowing back through the flash hole (tens of thousands of pounds per square inch) further trying to blow the primer out the back and what you get is the primer actually flowing itself around the fully extended firing pin giving the impression (no pun intended) of a very heavy strike by the firing pin. The only way that you can get an idea of what the actual strike looks like is to load a de-activated primer (soak it in WD-40) and then drop the hammer. You'll be surprised at the difference when you compare the strike on the de-activated primer and the apparent heavy strike on a fired primer.

 

[Old Fuff]

The most common causes of light hammer hits are:

1. The mainspring strain screw, located at the bottom/front of the handle has backed out. If so, screw it in so that it's tight.

2. Someone has done a trigger-pull job and either shortened the strain screw, or replaced the mainspring with a lighter one. If so, replace both parts with stock factory ones. (Available from www.brownells.com)

3. There is excessive cylinder end shake (back & forth movement of the cylinder as opposed to rotational movement). If so, have the revolver serviced by either the factory, or a gunsmith who is experienced in working on S&W revolvers.