Diagnosing timing/firing pin depth on SP101?

[MatthewVanitas]

A couple friends who shot my SP101 opined that it "spits lead out the sides" more than it should. I realize that a certain amount of material will exit the cylinder gap, but how do I know how much is too much? We were firing cheap Win FMJ rounds, so it would be shaved copper flying out if anything. Accuracy is consistent; do I need to have a smith check the timing or forcing cone, or are my friends just not used to being spit on by revolvers? Personally, I haven't noticed any problem.

On a similar note, a pretty gun-savvy acquaintance pointed out that the primers on fired rounds from said SP101 have _really_ deep firing pin marks. On looking at said primers, I agreed, and noticed the primers seemed "blackened" more than would be explained by carbon in the works. How deep is too deep, and what symptoms will I notice if I cause "pierced primers", or other woes due to a hyperactive firing pin?

I don't know much about mechanical affairs, but I'm slowly learning...

 

[tomthel]

Some thoughts

Spitting could be due to too wide a barrel/cylinder gap or the cylinder not being lined up with the barrel. The first could be checked with a feeler gauge and the second with a range rod. Rugers generally seem to have a tight barrel/cylinder gap. Anything over about .007-.008" would be excessive.

Firing pin protrusion can be measured. Bowen maintains .055" is ideal. Most all Rugers seem to have less than this ideal. A number of gunsmiths offer a modification to increase this protrusion .005-.010" (e.g. Stroh, Bowen). I guess one could slip by from the factory with too much protrusion but would think this would be unusual. Really hot ammo could give the same visual results on the primers I would think such as cratering and smudges.

 

[Nick96]

Mine spits a little too. Like every other revolver I've used. The gap in mine is pretty close. .357 may spit more due to the increased pressures. If it's shooting accuratly, I wouldn't worry about it too much. It's not going to blow up on you or anything. Actually a little loose isn't all a bad thing. Especially in stainless steel revolvers, cylinder binding can be a concern.

 

[Jim March]

Here's one set of instructions for checking the timing and gap:

http://www.thefiringline.com/forums/showthread.php?s=&threadid=57816

If the firing pin really IS too deep, mild filing with a knife sharpening stone or something oughta work?