I have all the parts to put together an extended range fun gun in 338 Norma IMP. After reading a little more and seeing the popularity of the 300 version as well as the cost of 338 bullets, I'm second guessing my decision to go 338.
Intentions are to build this as a repeater for out to a mile maybe more. My thoughts were like an ELR PRS match rifle even though I'll probably never shoot matches with it.
Action is a BAT HR set up to run the longest cartridges it can. Plan on sticking to the Norma case to be able to mag feed it without having to seat the bullets deep in the case. If I were to single feed, might go with the Lapua but that's not what I want to do right now.
Any advice on one over the other? What twist and bullet in a 30?
If you don't have a copy of QL and some practice using it, the metric that gives the strongest indication of ballistic potential is the ratio of the case volume to the bore area. To a large degree, the performance of a given cartridge can be approximated in another caliber by adjusting the case size. That metric is also a solid first cut at barrel life.
With everything else held constant, moving from 338 to 30 caliber picks up more performance than can be had from improving the case. Figure cashing out about 1/3 to 1/2 the barrel life moving from 338 to 30 with the same case. From the 30 caliber perspective, the 338 barrel lasts half again to twice as long. My take on the MRAD sniper rifle cartridge selection is the user replaceable barrel made the 300 Norma feasible for military sniping use. It wasn't going to last a full deployment otherwise. The 338 barrel is provided because they were heading that direction with the SAW and the 300 just was just too hard on barrels for full auto use.
What the actual barrel life is depends on how you shoot and your retirement criteria. Using the metric, a 338 Norma will have approximately the barrel life of a 7 saum, 6.5 PRC, or 6 CM. In 30 caliber, it splits the difference between 300 WSM and 300 WM. A 300 Norma will be closer to a 338 Lapua Improved or 7/300 WM.
The short version of that is whatever savings there will be in bullets, it'll be more than offset in barrel costs.
The relationship between the 338 Norma and 338 Lapua is a lot like 308 and 30/06. Yea, there is a drop in performance but it's just not all that. Another perspective is the remaining case volume in a 338 Lapua with a 300 grain bullet loaded to fit in a CIP (3.75" COAL) magazine is about the same as a 338 Norma Improved with the same bullet at the same length.
The 338 Norma is overkill for recreational shooting at 1500 yards. If you want one, build it. If you want to Improve it, do it. Just get it out of your system. Depending on how you're wired, a few hundred rounds into it you may realize that the 7 saum guys are doing it the cheap way. Another thing that may fade with time for that type of shooting is the desire to mag feed.
If you do the 30, I run 1:8 for everything ELR from 300WM to 300 Lapua Improved. 1:9 works well up to 230 grain bullets. Again, that's a first cut. Elevation makes a significant difference. With the 300 Norma, everything from the 215 hybrids to 250 Atips have worked well for somebody. I have a 24" 300WM R700 with the 24" factory 1:10 5R barrel on it. Out to a mile, it's hit percentage is awkwardly close to dedicated ELR rifles on a steel IPSC using 215 Hybrids.