I ran into a glitch I have never had before. I loaded 7mm Mag with 160 grain Accubonds. Coming out of muzzle at 2940 fps. Dead accurate out to 250 yards. Velocity doing well. Group size blows up at 300-350 yards. 6 to 8". Same gun, different bullet (competitors bullet, sorry) touching shots out to 500 yards. The barrel twist is 1:9 1/2. I see the load data has 9" twist. Would that make so much of a difference? I have been loading a long time, and many calibers/bullets/powders. I have never had a bullet do this.
unstable 160 gr accubonds 7MM mag
- Thread starter BAUFDER
- Start date
- Nov 4, 2004
- 25,160
- 8,409
What is your load?
I'm thinking that you might be on the edge for stability and you may be able to increase your speed to get past this issue.
JD338
I'm thinking that you might be on the edge for stability and you may be able to increase your speed to get past this issue.
JD338
salmonchaser
Handloader
- Dec 13, 2013
- 4,974
- 4,911
Yep, had that happen to a buddies rifle
RL338
Handloader
- Mar 23, 2017
- 3,272
- 5,289
What is the group size at 250 yds? A good load that falls apart in 50 yds just doesn’t make sense.
What is the other bullet , is it lighter or heavier? A 9 1/2:1 should be fine unless at sea level or lower. Are the holes oblong or nice and round , that will tell you about being stable?
If you’re dialing between the ranges given a suspect scope could also cause your issue.
salmonchaser
Handloader
- Dec 13, 2013
- 4,974
- 4,911
I loaded some in my buddies rifle for elk season. Good groups at 100. But then he couldn’t hit the 8 inch plate at 400. Put up a big sheet of paper, group was about 18” with some key holing.
Charlie-NY
Handloader
- Mar 11, 2005
- 1,418
- 845
Test the twist for yourself. Claimed twist can be off a bit or incorrect all together. My 9 twist Savage is actually an 8.5" twist.
I haven't ever seen a 9.5 twist become unstable with a 160 AccuBond at any elevation. Not saying it isn't possible, but if you're shooting well at 250 it's likely a paralax, scope, or other issue.
Fully agree with you RL.
Ridgerunner665
Handloader
- Oct 28, 2008
- 2,516
- 298
I run the 160 AB at that same speed from a 24 inch 9 twist barrel and get great accuracy out to 800 yards... thats all the scope adjustment I have (Zeiss HD5)... been using this load for several years, it has never failed me in my 280 AI.
- Thread starter
- #10
The group size is above 6 -8" at 300 yards. The bullet I used was 175 gr berger elite hunter. That held groups out to 500 yards. My son shot a moose with it last week. Not the scope. New mounts, new Leopold scope, all tight. the 9 1/2 " twist was actual measured twist. It doesn't make sense. I gave up on them. I was running out of time with the hunt coming up. I may play with them more this winter when I have time.
- Thread starter
- #11
The 9 1/2" twist was measured on the gun. I too have seen inaccurate twist claims.
Guy Miner
Master Loader
- Apr 6, 2006
- 17,746
- 5,815
A head-scratcher for sure. Usually the 160 - 168 gr bullets work GREAT from a standard 7mm Remington Magnum...
Please - if you do some more testing of this, keep us informed about your results. I don't understand why that is happening for you. Can be difficult to diagnose in an online conversation too.
Best of luck with it! Regards, Guy
RL338
Handloader
- Mar 23, 2017
- 3,272
- 5,289
A very true statement , this one is a head scratcher for sure with the ABs
