Need advice with cratered primers vs pressure issues

[strangwn]

I need some advice about cratered primers and pressure. Am developing a load for a Weatherby Vanguard .270 Win using Hornady V-max 110 gr, IMR4831, CCI 200 standard LR primers, and once-fired/partially FL sized RP cases. Shot yesterday one each 58 gr, 59 gr, 60 gr. The 58 gr showed no external evidence of excess pressure. The 59 gr showed only a tiny bit of primer cratering, no flattening, no resistance to bolt lift. The 60 gr showed a little more cratering, but otherwise was same as 59. The cratering in both cases can be felt when dragging a pointed awl across the ridge.

My policy has always been to stop short of any cratering, but in this case most of my data sources list 60 gr as max. Also, all my sources used standard LR primers as opposed to magnum LR.

Any advice about how to proceed will be appreciated.

Bill

[felix]

Using your gun we have to assume the so-called factory load is at average max pressure. Fire three rounds and measure the expansion of the cases at the base. That value would indicate the average pressure desired as max. Because multiple firings of the SAME cases will expand the cases further at the same pressure, allow no more than an expansion of +0.0005 max above that new case averaged value. Those cases have a belt, right? If so, then find the location along the case where expansion did indeed took place from the value of an unfired case, and use that location for all future measurements. In other words, cratering does not mean too much other than the primer apparatus needs work. ... felix

Your gun is a straight up 270, upon re-reading your post. No belt to worry about. ... felix

[sledgehammer001]

FWIW, I've had older rifles "crater" due to a wallowed out firing pin hole in the bolt. One Mauser I had was just measurably larger than spec, but still primer craters. Something to bare in mind.....
Jon