Home Forums Reloading Big Game Rifles 165 GMX and seating depth

Ok, I picked up a bunch of these on a blem sale earlier in the year and decided to give them a fair shake. I have tried RL17, H4350 and H4831 and just can't get these bullets to group very well at all. With 165gr Accubonds, BT, Sierra HPBT and Hornady Innerlock they all shoot under an inch with anywhere between 57 and 59gr of H4350 at book recommended COL. I have hot nothing better than 2" groups with the GMX, Etip or TSX and am at a loss. I tried loading them .060 off the lands as recommended by Barns and no luck. I loaded them to the COL in the new Hornady book and varied in and out from there with no luck. Any ideas? I would love to shoot these but 2-4" groups at 100yd when other bullets group under 1" just won't cut it.

Are you talking about a .30-06?

Take a look at this thread's first post description by Berger on how to find seating depths for their VLD's. You may find something similar works for you. I recommend doing the seating depth search with a very mild load so your seating depth isn't simply tuning the barrel time to a muzzle deflection swing (barrel vibration) with change in pressure. That can make you oscillate between different apparent "best" spots, none of which is actually better than the other nor even necessarily particularly good. Run something with low recoil to take barrel vibration effects out of the equation as much as you can so you are just looking at seating depth. Then tune the powder charge.

When you have a best seating depth (some guns never show one), then tune the powder charge. Take a look at Dan Newberry's site for a systematic approach to doing that.

Also, the GMX is solid gilding metal. Despite their claim to be fine with conventional loading data, I would consider their start pressure could be a bit higher and that you could be going into higher pressure with them using a load developed for cup and core bullets. Groups getting bigger is one pressure sign. You might try backing off to about 54 grains of H4350 and work up slowly. You can skip over a sweet spot pretty easily sometimes, so I would be moving in .4 grain steps (about .7%) with the 4350.

Interesting contribution, Unclenick. Thank you

I had really poor luck with them also. I tried them in several 30 cal guns without any success. I've tried different powders and seating depths. They just plain aren't an ez win with my guns compared to so many other bullets. And all these guns love TTSX's. Well, I still like hornady products. I'm sure I'll find something that likes the bullet but it will probably be when I'm just about out of them.
Maybe I'm just unlucky...I have seen posts of success with the gmx.

Haven't tried the GMX, but w/ TTSX & ETip in my 257 Weatherby I've had to seat them REALLY short. Much shorter and the bearing surface would be below the case mouth. Loaded cartridges look pretty strange, but give fantastic (ETip honest 1-hole groups at 100 yds) accuracy.

I don't have a COAL gauge for the Roy so I don't know how far off the lands they're seated, but gotta believe they're WAY back... I'm pretty certain they're further than .06". You might just start seating 'em shorter and shorter to see what that does for you?

In my 7mm RM the 150g Barnes TTSX shot great with minimal effort. It was, and probably still is, the easiest load workup I've had to do. I simply placed it 0.050 off the lands as recommended, found an accurate powder weight and was done. I never had to tweak it from there.

The 139g Hornady GMX was more finicky with regards to seating depth. It ended up liking the standard COAL of 3.290" which put it 0.080" off the lands in my rifle. It now shoots quite well, though still not to quite to the level the Barnes.

Maybe I just got lucky with the Barnes. But, in my quite limited experience with the two bullets, the Hornady was a bit more persnickety but still shot great once the right COAL was found.

http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/4617529/2



Check out the following link. Not specific to 180 grain bullets but may be of some insight. I clearly saw better accuracy the further from the lands I went.

My Sako 300 WSM likes the 150 gr. GMX but not much luck trying to get the 165 GMX to shoot.