Looking for some insight here…I recently purchased a CZ 527 youth carbine chambered in 223. One of the selling points for me was CZ’s literature in which they repeatedly make the claim that this rifle is designed to handle ammunition loaded to 5.56 pressures. This was important to me because this will be a youth deer rifle that I plan to load with Barnes 62gr TTSX, and that extra 150fps from the 5.56 should get us the expansion we need on that bullet out to 300 yards. I’m in Arizona, so that extra 50 yards can make all the difference on a long desert shot.
Looking at the published 5.56 data for this bullet with TAC, it appears that Barnes and Western Powders are not in agreement. The Barnes data has a max charge of 27 gr, and the powder manufacturer lists max at 26.7. I decided to use the more conservative data from Western Powders as my benchmark.
I loaded up a few rounds using a powder charge one grain below the lowest published maximum using CCI 400 primers and once fired Lake City brass. The first two shots had cratered primers and the third shot pierced the primer. I stopped right away. What was strange to me was that none of the primers flattened very much. All of the pressure sign was in the pin strike. I figured this was my fault for not starting with the min load and working up, and decided to reduce the charge even more at my next trip to the range.
The next time out I loaded several rounds 1/3 of the way between min and max. I didn’t get any pierced primers, but all four primers had cratering, they were still not what I would call flat. My buddy has the exact same rifle, and when we tried them in his, the primers looked exactly the same, so I’m not inclined to believe that it is a firing pin issue.
So now I’m starting to think that CZ must just be full of it by saying that the rifle is designed to handle 5.56 pressures, but just to make sure we retrieved 10 rounds of factory M855 from my buddy’s stash. They worked flawlessly. No pressure signs. Pin strike looks perfect. Primer appears as one would expect.
The M855 should have been higher pressure than the handloads, so I don’t know what to think.
My guess is it’s either:
1) Something about how I prepared the LC brass is causing a primer seating issue. I used the reamer on the RCBS casemate.
2) Perhaps the CCI 400 does not handle 5.56 pressures very well? The M855 had a mil-spec primer on it, so could that be the difference? Should I try the load with CCI 41 primers?
3) Maybe TAC is just a whole lot hotter than the data would suggest? I’m also shooting them on days over 100 degrees, but the M855 was fired on the hottest day of them all.
I’d welcome any thoughts.
