Surgeon PSR .338 lapua magnum

[sacuster]

I'm trying to develop a load for this rifle. All the books use a c.o.l. of 3.681", my rifle uses the CIP mags which allows me to run a col of 3.765", I'm currently loading to 3.750" because of feed issues. I'm using berger 300gr hybrids. I have measured to the lands by making a cartridge long and seating it a few thousandths at a time until the bolt drops with no resistance, the col is 3.894". So that gives me .144" jump to the lands from the mag and .213" jump from the book col to the lands. This seems extremely far to me, but I'm new to this. Any thoughts would be great.

 

[Chandalar]

You may want to just barley size a fired case and seat a bullet long the neck tension should be just enough to hold the bullet in the case with out getting stuck in the lands, single load it into your chamber and close the bolt slowly. Open the action and slowly allow the Over All cartridge to come out with out hitting or hard rubbing the side of the action as the bolt is pulled back. Check the overall length to the ogive. Pull the bullet out .100 and do it again to check for consistency. Measure again and see if its the same as the first. That is your true overall length. Start your loads .100 off the lands and at lowest charge weight for safety and then increase your length to find the sweet spot. Be careful of developing pressure. record everything so that you have a clear picture of what you are doing. You may find that your best groups are from longer overall cartridges, and may have to be single loaded. If you are set on using the magazine and the 300 grain Bergers, give a quick call to Surgeon and ask them what their OA load was for the CIP mags and the PSR chamber. All the best!

 

[sacuster]

Thanks for your reply. That's essentially what I did to find my lands. The base to ogive measurement is 3.043"( if my memory serves, I don't have my book in front of me.) I was going to load to 3.003" as my non repeater rounds. Something I have noticed is loading to the mag length I'm getting as good if not better muzzle velocities as stated in the manuals. I figured with more space I would need more powder to get the same velocities? I did contact surgeon and they sent me a print, but the there was a note on the print stating that from the 3.681" col is a .082 jump to the lands, which doesn't correspond with any of my measurements?