Light primer strikes-Question

My 110 in 270 win really likes barnes vor-tx ammo. Shoots it straighter than anything else, and since I have to use copper in the zone I hunt here in CA I don't mind using it....except for the fact that it's the ONLY round that's ever mis-fired due to light primer strikes. Last year was the first time I'd used it on a hunt and it did it to me, but next round worked and animal went down so I chalked it up to one bad round. Fast forward to yesterday when I was at the range sighting in with my hunting round after working on the rifle the past few months and out of 20 rounds the barnes vort tx misfired 3 times due to light primer strikes. All had a smaller than usual dimple on the primer. The other 17 that went bang had larger dimples on the primer but still smaller than other brands of ammo I had shot.

i also shot 15 low cost lead rounds yesterday with zero issues and have never had this issue except with barnes vor tx. I have hundreds of rounds of other ammo through this rifle and not a single misfire. Looking at the barnes bullets, the primers are set just slightly deeper than some of the other rounds I have (hornady, winchester). They are not flush with the base of the round.... If that makes sense. normally would just write it off and not shoot it except that it shoots so well from this rifle and I have to hunt with copper, so my choices are limited. I have some hornady copper ammo on order just to see if I can switch but would much rather remedy this situation with the barnes.

Now I did compare some spent brass from last year with the brass from yesterday and it appears as if the dimple where the firing pin strikes is a tiny bit less pronounced now than last year, meaning it might be my pin, except that it still shoots every other type of ammo 100% of the time.

Advice, info.....anything is appreciated. I have a hunting trip coming up and want to get this squared away. Thanks

I would start by measuring to the shoulder of a unfired and a fired round. A large difference could indicate shoulders bumped too tar or excess headspace. Sloppy fit could easily cause light primmer strikes.

Headspace has not been changed and is as it was when it left the factory. Is there any was that head spacing can change over time if you don't intentionally change it? Probably a dumb question but I'm just trying to rule out possible issues.

Chambers are specced to be at or over spec. Ammo to be at or under. Some more than others. If the ammo is on the bottom of spec, and the chamber on the high end, you could have excess play. The firring pin would have to push the round to the front of the chamber, wasting alot of fp energy.

If only one brand of ammo acts up, a quick check with a caliper can elliminate the possibility.

A few days ago, a guy had to reset his headspace to his large lot of ammo to make it fire reliably.

I would think a 3/8 drive socket would slide over the bullet(square drive on shoulder) to get a good measurement to the shoulder. To compare.

http://i55.tinypic.com/2ez3ac3.jpgThink diy version of this.

Copy. Makes sense. I will see what I can do.