I am making a batch of 1000 rounds loaded with 27.0 grs of Varget in mixed LC brass with CCI primers and winchester bullets. I am testing the load out. So far it is not showing dangerous pressures. I let an AR guy look at the shells and he said that the firing pin was penetrating the primer and hot gasses were venting down the back and torching the pin. He also said it is having light strikes even though it set off every single round. It is a JP trigger and I can turn it up.

I took a look at the pin and it has some burrs on the end of it. It is a DPMS upper. Will replacing the DPMS pin with a bushmaster pin fix the problem or will the problem torch my new pin and is there another way to fix it?

The problem could be any one or two or... of everything.  I used CCI primers that were prone to being peirced.  Could be your seating deapth.  Could be burrs or a sharp pin (not one of those titanium jobs is it?).  Once you peirce one primer the pin could be damaged making the situation more prevalent.  Could be soft or over worked brass that shits the primer.  Could be a bad bolt.

Try shooting through a chronigraph.  That will give a second message about pressure limits.  Do that with an eye to accuracy.  That will give amost as good an idea about whether your pushing the pressure limits.  

Try your loads in some new brass.

If you're sure you're not pushing the pressure limits, I'ld switch the pin then try some different primers and then some different brass.

Look for a shiny ring around the case head.  That's the first sign you're pushing it for that piece of brass.

Assuming the pin is correct in its' dimensions, the brand is irrelevent. Your problem is most likely w/the primers you used. But if the pin you have is buggered up at all, it should be replaced

The only primer I've ever found to be problem free w/the 5.56 round is the Remington 7 1/2, which was specifically designed for the 5.56/.223 used in the AR15.  I too had problems some years back, when I loaded up a batch w/the CCI.

Since I haven't used anything but the Remington for the past 15 years, I really can't say if there is/are other brands out there that will work w/the round. I just stick w/what works

Winchester primers don't work well in my AR's. If the pin is buggered up I would replace it unless you are real handy with a honing stone. Too much one way or the other and it won't work at all or it will make matters worse.

Edit: You could try CCI 41 primers if you can find some. They are military type primers and are harder.

I've seen something similar with my CCI reloads. Once in a while, there will be a dark firing pin imprint, and closer examination will show a small crater at the bottom of the imprint. I can't see light through what I initially thought was a pierced primer, I don't see obvious gas markings on the casehead, so I'm not even sure it's a pierced primer. Even wierder is that I generally only see this on sub-maximum loadings. I mean, .5grs+  down from the max. Yet at much hotter loadings, I just about never see it.

I've seen it maybe 3-5 times in 3k reloads.

Powders I've seen this with include Varget ant IMR 4198, all primers are CCI small rifle.

How are you getting 27grs in a LC case? You must be using ligher bullets or something. I worked up some loads with the Winchester 64gr SP slugs, and above about 26.5, I really had to cram the slug in, because the powder was compressed. Yet my 26.4gr load works fine.

Beats me, but it sounds like what you had.