throat/neck tolerance question

[eshorebwhntr]

I've got a 7stw that was custom built by gtr. He requests a dummy round when building the gun. I was a novice to long range shooting and reloading at the time and loaded my dummy round with Remington brass. This yielded a case with a .313 neck and that was what my throat was cut to.

Since that time stw brass has been hard to find so I went about fire forming some from norma 300 h&h brass. I've used a .310 neck bushing when I resized before but noticed today when I was reloading the fire formed brass that I had almost no neck tension because the Norma brass is thinner walled than the Remington.

Based on what I've measured the new wall thickness is .010, x2 is .020, +.284 is .304.

So my question is will having a separation of .009-.010 between the neck/throat hurt or effect anything from what I've been use to with the very tight fit?

Thanks in advance for any advice.

 

[Coyboy]

your accuracy shouldn't suffer with new load development, but brass will work harden quicker so you will need to anneal every 2-3 firings to keep necks from splitting.