147 fmj load Testing

[AlcoholicusMaximus]

I have a M1S 10.5" upper and have been testing some Winchester 147gr. fmj's. For the record, the bullets have not shot well for me in any gun, so my focus here is a safe maximum average pressure/velocity. I started out using 16gr of H110, and was averaging right around 1884fps, no pressure signs. Since max load is 17.0gr, I increased charge wt. by .2gr increments for testing. I was really expecting to start seeing flattened primers or ejector gouging, but I got to the 17.0gr load @ 1976fps. with no pressure signs!(so I thought). I have never seen a pierced primer, so the first one got by me, but I caught the second one. Out of ten shots, two pierced primers. I have seen a lot of flattened primers in .223, but never a pierced one. Why would a primer pierce before flattening out?
Leery of the max load with H110, I tried W296 using the same charge wts. mentioned above, & with the max load of 17grs, was only able to achieve an avg. of 1878fps. I have read that the two powders were near identical.

[320pf]

Blown primers are not necessarily a sign of high pressure. This may be the case with your load... especially if the primers of not flattened. Another thing to try is change the brand of primers that you are using. If I remember correctly CCI small rifle mag. primers have the thickest cup. I have an article that I will dig and post the link to.

H110 and W296 are pretty much the same powders. W296 tends to run a bit slower. There can also be a bit of variation between powder lots

320pf

[Rikky Lee]

Pierced primers can also mean the firing pin could benefit from sleeving as it might be a bit sloppy in the bolt face.

I'd also try different primers and then move to 155 SMKs...