Light Strikes and Blown Primers. What's causing it?

F

freenokia

New member
Hello everyone. I'm having a problem with a revolver I just got back after it had been stolen.

Went out to shoot it Saturday and the problems ensued. First, I got a light strike. Then I rotated the cylinder to fall on the same round again. This time it fired and blew out the primer. Then the next round was a light strike...

I tried different types of ammo and got the same results. All light strikes.

All this after having the local gunsmith check it out and giving it the ok :rolleyes:

Any opinions on what may be causing this? The firing pin is hitting the primer in the middle...
 
Need to be a little more specific. Ammunition used? What do you mean "blown primer?" What kind of revolver, and caliber?

Light strikes usually mean weak mainspring tension. If a S&W revolver, the strain screw in the frontstrap made have backed out.

Also, photos would be a great help.

Bob Wright
 
Well, based on your description...

It may be broken.

Sorry, without a LOT more details, and some really clear photographs, there's not a lot that we can tell you other than that.
 
Most likely a main spring issue, especially if the primer strike is dead center - that is ONE of the indicators of good timing. The other issue may be end-shake which means the cylinder has too much front to back movement on the cylinder pin/ejector rod.
 
Most likely a light mainspring; if it is an S&W the mainspring screw (in the bottom front of the grip) may have been turned out or cut off to "reduce trigger pull".

The light strikes and "pierced" primers go hand in hand. Both result from a too-light mainspring. The "pierced" primers are the result of the firing pin not having enough force to prevent internal pressure from pushing back the firing pin and blowing part of the primer back into the firing pin hole.

Note that the OP uses the correct term, "blown" primers. Those are often erroneously called "pierced" primers in the mistaken belief that they are caused by too heavy a mainspring. Shooters often see a "pierced" primer and react by lightening the mainspring, which causes more "pierced" primers, so they lighten the mainspring still more..... You get the picture.

Jim
 
JamesK,

I've always used the term "pierced primer" when there is indeed a hole through the primer cup. I use the term "blown primer" when the primer falls freely out of the primer pocket, as when the pocket has been enlarged to that extent.

Bob Wright
 
I don't use the term "pierced" for the simple reason that except in a very rare case where the firing pin looks like a needle, the primer is not "pierced" by anything except the gas coming back. Most people who use the term, including some who should know better (Kuhnhausen) believe that an extra strong firing pin spring or excess firing pin protrusion can caused "pierced" primers.

I once ran some tests with a rifle having over 1/4 inch firing pin protrusion (normal is about .06"). It took some manipulation to get the rifle to fire, but the firing pin indent and primer were normal. I also used extra strong springs, and even hit the rear of the firing pin with a hammer. Again, primer appearance was near normal and the primers were not "pierced". I suppose enough force could drive the firing pin into the primer far enough to penetrate the primer cup and the anvil, but no mainspring that could be used in a practical gun can do it.

Jim
 
Just a SWAG, but if the first strike is a light strike, and the second strike sets it off, perhaps it is a light mainspring. Perhaps the second strike, hitting the same divot previously made by the light strike is blanking the primer.

Either way, I would have a qualified gunsmith rectify the situation.
 
Only time I experienced 'pierced' primers (hole in primer cup) was shooting some .45 ACP in my revolver. The 'common' element was these cases had an enlarged flash hole (found in non-toxic greenie ammo). Threw them out out and never had another problem. Oh, it was repeatable too. First time I thought fluke, second time around not.... Tossed.

Light primer strikes is usually a main spring issue.
 
James K said:
The light strikes and "pierced" primers go hand in hand. Both result from a too-light mainspring. The "pierced" primers are the result of the firing pin not having enough force to prevent internal pressure from pushing back the firing pin and blowing part of the primer back into the firing pin hole.
Click to expand...


Very interesting, thanks.

Based on this, then, the "piercing" would look like the "exit" side of a bullet hole, whereas a (theoretical) piercing by a heavy firing pin strike would look like the "entrance" side?
 
MrBorland said:
Based on this, then, the "piercing" would look like the "exit" side of a bullet hole, whereas a (theoretical) piercing by a heavy firing pin strike would look like the "entrance" side?
Click to expand...

Of the primers I have had with holes through the cup were from .44 Magnum rounds. The ejected primer (via the decapping die) looked like a top hat, where the bottom of the primer had flowed back into the small countersunk area around the primer pocket. The recoil plate was imprinted onto this flattened area, and the hole was clean, so far as I could tell, with no indication of direction of piercing. The indentation was slightly less deep than normal rounds. The de-capping did take a normal amount of effort to push it out. The primer pocket of the case was not enlarged enough for the spent primer to drop out.

I hasten to add these were experimental rounds, not normal handloads.

Bob Wright
 
I dealt with blown ("pierced") in normal pressure ammo, where the force blowing a hole in the primer comes mostly from the primer itself, not from the main powder charge. Bit if the pressure from the powder is very high or the flash hole is too big, enough pressure from the main charge can blow back into the primer to push back the firing pin and punch a disc out of the primer.

Mr. Borland, due to the burning of the edges of the "piercing" by the escaping gas, there might not be any appearances of either an entrance hole or exit hole. The hole will often be clean cut, almost like it was burned through with a tiny torch.

Incidentally, that little disc of primer material has to go somewhere, and that is normally back into the firing pin hole in the breechblock. A friend lightened the firing pin spring in his Mauser rifle to the point that he was getting "pierced" primers. Finally, the rifle wouldn't fire at all and it looked like the firing pin didn't even touch the primer. I took the bolt apart and used a thin screwdriver to scrape around inside the bolt body. Sure enough, clumps of mashed up brass discs came out; they were the pieces of primer blown back from those "pierced" primers. Eventually, enough built up in the bolt that they blocked the firing pin.

Another problem is that the hot gas coming back from the primer will eventually erode the firing pin and firing pin hole. Then the "expert" examines the eroded tip of the firing pin and concludes that it caused the "pierced" primers, not realizing that the true situation was the reverse.

Jim
 
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