Excellent article. Thank you!
Whenever my handguard comes in, I'll be finished with my 6.5 build. Upon yours and others' recommendations, I also selected the 20" Satern barrel. Picked it up a few months ago when Midway actually had them in stock* and it's been calling to me from the back of the safe ever since. I'm excited that it looks like I'm actually going to finish the rifle in the next week or two, and I can't wait to see what it'll do this Summer. Sadly, the nearest 1000-yd range is a little over 2 hours away, but I expect that it'll be well worth the drive.
If you don't mind, I do want to get your impression of the Wolf/Prvi load and its propensity to be reloaded.
I've got a box of 123 Scenars and the reloading information from AA. If I use once-fired Wolf cases, are the slightly different case dimensions and the large size primers expected to give any issues? Can I still expect ~1/2 MOA accuracy from carefully worked-up handloads, or would I be better off to just use Lapua or Hornady brass right from the get-go? Once a load is developed, can I expect it to transition relatively easily with minor re-working between the Wolf and Lapua or Hornady brass should I ever run into a glut of one or the other?
Also on the subject of reloading, I assume you would recommend sticking to benchrest primers and trimming for every loading? I'd like to use full-length resizing for reliability's sake. Have you tried neck-sizing only and is there a significant difference in accuracy? With my .223 rifles, I use full length resizing, I only trim every other reloading, and those rounds are very accurate in all of my rifles. Can I afford to be as relaxed with the 6.5 Grendel, or is there really a lot of accuracy to be gained by babying the case prep?
Not addressed in the article are POI shifts between ammunition. Obviously, some shift should be expected, but some calibers are worse than others.
Within 300 yards, .223 Rem (for example) seems to shift very minimally in my rifles between 55gr, 62gr, and my 77gr. handloads. Obviously, there's some vertical displacement given the different trajectories.
Some .30 rifles, though, and especially my K31 in 7.5 Swiss, have significant horizontal displacement. The Prvi loads shoot to roughly the same POI as GP11, but my 168SMK handloads generally impact 4-5" to the right at 100 yards. I'm still working on that load, so I hope it closes in a little bit, but the tight groups make me think I'm getting close enough that I simply need to re-zero when I want to shoot the SMKs.
I know that's a long lead-in to the question, but what kind of POI shift should I expect with the GDMR (ignoring for right now the obvious vertical shift associated with varying velocities between loads)?
Lastly, is there any particular advice you might have for the rifle's assembly process? I would assume that everything is the same as for a .223 chambered rifle, and that the standard 40-50 ft-lb torque on the barrel nut is fine, but I just wanted to check since I'm asking questions anyhow.
Oh, and I wasn't able to find any crush washers for the 9/16-24 muzzle threads. I'm planning on using a .308 crush washer and just going slow and careful to keep it centered. Should I try to get a "proper" washer or is it worth it?
Thanks in advance, I know that's a lot to chew through.
* Of note to anyone interested: I just checked and they're back in stock now after 2+ months of being out.