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

Hey Kevin, If you used the "same cases", I'd suspect you might have had a bit of "Headspace" with the initial shots. Cases are made a bit small to be able to fit all chambers. Then after they were shot, they stretched slightly to fill the chamber and achieve the proper Headspace.

You always want to Seat the Primer with enough force so the Anvil is touching the bottom of the Primer Pocket, but not so hard as to "crack" the Priming Pellet. It is easy to "feel" it Seat properly if you are using one of the hand-held Primer Seaters.

And for absolutely sure you want the Primer Seated below the Casehead. You can check this by setting the case on a flat surface like a table top. If it wobbles, the Primer probably needs a bit more Seating.
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Look back through this Board about Partial-Full Length Resizing(P-FLR) and you will see how to prevent creating excess Headspace with your Full Length Resizing Die.

Thanks Hotcore.

I will pursue the excessive headspace question. I've also developed a better feel for the hand priming tool and am getting better at seating "just below" flush.

Hey Kevin, When I have new, unfired cases, I generally spend one loading by Fire-Forming the case.

I use the cheapest bullets I can find for that caliber and Seat the bullet so it is about 0.010" Into-the-Lands on a bolt action. And I typically use a "fast for cartridge" powder so the Pressure Peak occurs quickly.

If the cheap bullets won't reach the Lands, reverse them and they will. They generally don't shoot accurately for me reversed, but good enough to do some Off Hand practice.

Then to the P-FLR for resizing so the case is held in the chamber with a very slight "crush fit" which eliminates the Headspace issue entirely.

I noticed on the Gunsmith Board someone mentioned you might have a weak firing pin spring or the actual tip of the firing pin might be a bit short. If Fire Forming does not totally correct the problem, then I would agree with them.

Best of luck to you.

A light pin hit can very easily affect accuracy. I had the same problem with a Stolle actioned 30X47 and cured 90% of the trouble with a trigger hanger with a bit more pin fall. Pin protrusion should be between .055 and .060. This is not a factor of the hanger, but can be measured with a depth mick. with the pin released to the fired position.