Does anyone have any experience or reference information on the consistency of shots, point of aim or velocity, due to the effect of a light firing pin strike?

I've been working up some handloads for a Winchester M70 in 308 and have been experiencing rather large spreads in velocity for various charges of Varget and RL15 with 150gr bullets. It's pretty cold in Michigan right now but I was under the impression that both of the powders mentioned shouldn't be too sensitive to temperature.

My first batch of re-loads had a number of shells that failed to fire. I may have seated the primers, Federal 210 Match, a bit too firmly but the firing pin imprint on the failed shots was very slight. The next group of shells loaded I lightened up a bit on seating the primers and had no failures. I've had absolutely zero shots fail to fire with a wide variety of factory loads so I attributed the first failures to the too deep seated primer but started wondering if the light pin strike could effect other characteristics. I've cleaned the bolt body, firing pin, & spring so I know it isn't dragging due to cold temperatures and grease buildup.

Thanks, Kevin

In one word DEVASTATING!
many of the accuracy problems of the Ruger 77 with tang safety can be solved by just a new mainspring.
Have you cleaned your you pin and spring- any excessive oil will slow things down a bit in cold weather.
I have run into M70's with weak mainsprings also.

All powders are to some degree sensitive to temperature .The lower the temperature the lower the pressure and velocity. Seating the primer sensitizes it ,that is pinches the primer compound between primer cap and anvil .Also if the primer isn't seated properly the energy of the firing pin seats the primer instead of igniting it.There must be proper firing pin protrusion [~ .060"] and proper firing pin force.Dirt in the firing pin hole or cheap or too much lube may slow the firing pin.

Could it be a headspace issue?

Bob

Thanks guys for the replys.

As mentioned in my orginal post, I've eliminated a dirty pin, spring or bolt cavity. The gun is a Classic SS that I bought new last year so it hasn't been fired much but still could have a dimension problem with the pin or posssibly head space.

Thanks for the 0.060" dimension, I will check this and look into how to determine whether there is excesssive head space.

Regards, Kevin

I have a Ruger 35 Whelen that had this problem. About every 15 shots the pin would strike the primer but the round would not go off. I had the main spring replaced and also found the pin did not have enough protrusion. Once this was corrected, no problems.

I wasn't hinting that the rifle might have excessive headspace.

IIRC, you only had problems with the reloaded ammo. You *might* be creating too much headspace on your reloads.

Bob

I had a M91 Mauser that blew 2 primers with a starting load of AA2495. It was pretty strange because I was shooting another M91 out of the same batch of ammo with no problems. After the 2nd blown primer I began examining the culprit rifle. This was its first trip to the range after purchase. Finally I dry fired it and got a soft thud. I field stripped the bolt and found it had a ton of cosmoline packed inside the bolt and in the main spring. After cleaning it up it fired normally with no further problems. I later increased the load used about 3 grains with no ill affects.