6.5 Creedmoor and keyhole issue

[9.3 Hunter]

Can't stabilize 150s in a 1:8 twist ..... the ogive, too long + heavy etc

 

[Trevor60]

Your stable in a 1-8 twist according to Berger Stability calculator it has a stability of 1.34 at 0 degree, 2650fps. and 0 altitude (anything over 1.0 is stable)
If the first 50 shot fine i would check your muzzle brake to see if you hit the baffles.
testing
take off the brake and shoot them again
measure the the 123 vs the 150 Sierra occasionally produces skinny for calibre bullets.

Trevor

 

[SigWig]

How are guys shooting factory sako and norma 156gr ammo?

 

[bcsteve]

How are guys shooting factory sako and norma 156gr ammo?

They're round nose and therefore shorter. It's the length that's the issue not the weight.

 

[I Dont Care About You]

I cleaned the barrels both rifles before , a couple of times

Warmer weather the first day? That'd give you a bit more velocity.

 

[Meroh]

They're round nose and therefore shorter. It's the length that's the issue not the weight.

Best answer.

That being said, I understand that precision rifle shooting is a bit different than the type of shooting that I do. Regardless, I find it hard to understand why these rifles are so fussy about ammo.

With 156 gr cheap PPU RNSP 6.5 x 55 loaded to 2300 FPS (+/-) out of a Zastava at 1 in 9, and old M96 with a twist of 1 in 7.87 running about 2400 FPS shoot just fine. with good accuracy out past 200 yards.

Likewise, both twists seem to handle Sierra 85 gr JHP and Sierra 120 gr HPBT Matchkings pushed to the higher end on the reloading charts with tiny groups. 100 yard groups <1 MOA, and often .5 MOA center to center. No miss on groundhogs out to 200+ yards.

I would expect that the CM should perform similarly with similar bullets at similar velocities.