Pressure?

ColColt · Jun 13, 2014

Some time back I bought a box of Hornady's SST 130 gr ammo for the 270Winchester at a friends suggestion. That was the first box of factory ammo I've bought in years but, h e swore by it's accuracy. I had two 270's the day I tried them out. One a current FN Model 70 and the other a pre-64 Model 70. The pre-64 showed, to me, signs of pressure having the primer flattened.

I wrote Hornady about it and they told me that wasn't pressure and upheld their ammo as being used in all manner of rifles. I think otherwise. Stated velocity on the box indicates 3200 fps. That's a bit more than any other ammo available. Usually, velocity for that caliber and bullet weight runs 3050-3100. What do you think?

http://s180.photobucket.com/user/ColCol ... 9.jpg.html

Ridgerunner665 · Jun 13, 2014

The older rifle likely has a rougher bore than the hammer forged FN barrel...I seriously doubt there is enough pressure to be worried about....flat primers aren't a very good indicator anyway, improper headspace can also cause flat primers...I don't think I've ever fired a factory loaded 270 round that didn't flatten the primer...in several rifles.

SJB358 · Jun 13, 2014

Same here, flattened primers indicate pressure but I've seen mild loads flatten primers as well. If all other parts of the psi check were okay, I'd be okay with em.

DrMike · Jun 13, 2014

Hornady was most likely correct that what you observed wasn't pressure. While it is true that flattened primers can be indicative of excessive pressure, they can occur from a variety of benign situations.

Ridge_Runner · Jun 13, 2014

flattened primers can be a sign of excessive pressure, but have you ever had a more than slightly flattened primer that was not accompanied by at least one other sign such as ejector wipes, casehead expansion, sticky bolt lift, etc.
a sierra tech once told me that if your using soft cupped primers like fed. then ignore flattened primers until there is another sign present.
RR

ColColt · Jun 13, 2014

I don't know. Seems odd that from the same ammo two different looking primers. There was no hard bolt lift and I wouldn't have expected that from a factory round. Hornady has upped the velocity on their Superformance ammo. I haven't seen any other factory rounds with 3200 fps for that bullet weight. You can tell it when you fire one of them versus 60 gr of H4831-a distinct difference. It felt more like a stiff 150 gr load rather than the 130.

I've never had any problem with the four 270's I've had flattening a primer until this one. Of course, 99% of what I shoot are reloads.