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I have a 6.5x47 Lapua based on the Small Remington 700 action. One issue with this build is that small rifle primers tend to get pierced and magnum primers were heavily cratered, even on starting loads.

This happens when the gap between the firing pin and firing pin hole is too large, as there is space for the primer to flow into during firing. Primers which are pierced blow a small amount of gas and a small disc of primer metal back through the firing pin hole into the bolt assembly. Not good.

It's possible to remedy this solution by bushing the firing pin hole. This requires the insert of a narrow firing pin hole of diameter 0.062" and to turn down tho OD of the firing pin to 0.060" to produce one thou of clearance either side. The bush also facilitates a sleeve to guide the firing pin through when you pull the trigger.

Needless to say, I now have no more cratering! Neil did a great job fixing this problem and I would highly reccomend him for this work.

Before Bushing

Standard CCI Small Rifle Primers (CCI-400), Pre Bush Magnum Small Rifle Primers (CCI-450), Pre Bush After Bushing

Magnum Small Rifle Primers (CCI-450), Post Bush

Here is a before and after of the same bolt.

Before
After

I used my standard load, here was the best 5 shot group of the day at 100m. Boxes are 1cm x 1cm as my scope is in milrad and like to have one box as one click for zeroing etc.

Have only had good things from trips to Neil's too. He has threaded most of my rifles over the years and done other machining bits for them :)

He's a nice chap, knows his stuff and does good work. Helps that he's quite close to me as well.