.243 1:10 twist and 95gr VLD

MXoutdoors

MXoutdoors

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I'm thinking of getting a tikka in .243, but the twist rate is 1:10.
I was just wondering if any of you guys are shooting the berger 95gr VLD bullets through a 1:10 twist and is it stable.
I did some math and I think I need at most a 1:9.7 twist for these bullets.
 
MXoutdoors said:
I'm thinking of getting a tikka in .243, but the twist rate is 1:10.
I was just wondering if any of you guys are shooting the berger 95gr VLD bullets through a 1:10 twist and is it stable.
I did some math and I think I need at most a 1:9.7 twist for these bullets.
Click to expand...

Hi, I wrote to Berger Bullets a week ago and 1 in 10 inch twist rifles should use 6mm 90gr Target bullets or 6mm 87gr Hunting bullets (B.C. is something like 0.410 vs 0.486).

I have a very similar problem as my rifle, a 1 in 9.125 inch Remington VTR: I can't shoot 6mm 105gr Hornady A-Max, Sierra 107 and Berger 115.

Alex
 
I would estimate using the Border Barrel calculator that the 95 grain VLD at 3100 fps in a 10 twist is very likely unstable with a stability factor of 1.03. Unstable is 1.0 or less, while 1.4 is recommended. This is at 59 deg. F. At lower temperatures it will almost certainly be unstable. See the lower graph at this link. The upper graph is recommended twist. The lower is stability factor with a 10 twist.

.243 95gr VLD @ 3100 in 10 twist

You can play around with other temperatures and Berger bullets with these two links. I just use 10 deg. for the boat tail angle.

Twist Calculator
Berger Bullet Data

I believe Savage has barrels with faster twists if you want to shoot the heavy bullets. The Savage is also likely to be more accurate than the Tikka as well. I believe Savage use 9.25 in the .243 which gives a stability factor of 1.2, and probably ok with the 95 VLD, but still short of doing the 105's. Another option is the 6BR in Savage. They make it in a 1 in 8 twist and it can handle all but the 115's.
 
Been shooting 90 and 105 grain bullets out of a 1 in 9.5 barrel for eons. Quit putting so much blind faith in a computer program and work up the load.
 
If it was me, I'd try a few rounds before selling a box of bullets simply because the printing on the side said my twist wasn't quite enough. There are lots of folks shooting 105 amax out of factory 1-9" .243's. I wouldn't buy a rifle in hopes of making a marginal twist work, but I'd sure give it a go if the rifle and bullets were in hand.
 
sunray said:
Been shooting 90 and 105 grain bullets out of a 1 in 9.5 barrel for eons. Quit putting so much blind faith in a computer program and work up the load.
Click to expand...

When you can't keep the bullets on a 8.5"x11" piece of paper at 100 meters, and the computer program says the stability factor is 1.0, you start to put a little faith in the computer code.
 
Ron AKA said:
When you can't keep the bullets on a 8.5"x11" piece of paper at 100 meters, and the computer program says the stability factor is 1.0, you start to put a little faith in the computer code.
Click to expand...

yes, but the other thing about stated twist rates is they are just that- stated. A factory stated 1-9" could be 1-9.3", or 1-8.7", or somehting else....
 
mpwolf said:
yes, but the other thing about stated twist rates is they are just that- stated. A factory stated 1-9" could be 1-9.3", or 1-8.7", or somehting else....
Click to expand...

Yes, it is always worth using a tight fitting bore brush, cleaning rod, and measure what you actually have in the barrel.
 
cam1936 said:
What's easier to stabilize a 105 amax or 95 vld?
Click to expand...

look at the numbers for Berger's bullets:
http://www.bergerbullets.com/Products/Target%20Bullets.html

Clearly Berger 105gr VLD is tougher to stabilize than Berger 95gr VLD but when I contacted them, they stated that 105gr A-Max does stabilize in 1:9" twist.

This is somewhat strange, since Sierra recommends the same barrel twist as Berger for a 107 SMK.

A bullet 95gr 6mm Berger VLD can stabilize in a 1:10" barrel but will suffer a 17% decrease in BC under "normal" conditions. (Applied Ballistic for Long Rang Shooting, 1st Edition, Bryan Litz, p.153.)

Also bullets stabilize better at higher elevation and higher temperature (lower air density), so a bullet might work perfectly in the Rockies in summer and not stabilize in autumn in the Maritimes.

Alex
 
AlexF said:
look at the numbers for Berger's bullets:
http://www.bergerbullets.com/Products/Target%20Bullets.html

Clearly Berger 105gr VLD is tougher to stabilize than Berger 95gr VLD but when I contacted them, they stated that 105gr A-Max does stabilize in 1:9" twist.

This is somewhat strange, since Sierra recommends the same barrel twist as Berger for a 107 SMK.

A bullet 95gr 6mm Berger VLD can stabilize in a 1:10" barrel but will suffer a 17% decrease in BC under "normal" conditions. (Applied Ballistic for Long Rang Shooting, 1st Edition, Bryan Litz, p.153.)

Also bullets stabilize better at higher elevation and higher temperature (lower air density), so a bullet might work perfectly in the Rockies in summer and not stabilize in autumn in the Maritimes.

Alex
Click to expand...

I'd hate to work up a good load in the summer than have them keyhole when hunting coyotes at -30.
 
In my Remington pump 243 (9 twist) I was getting genuine sub moa 5 shots at 100 yards in summer. One very cold winters morning they were printing anywhere all over the target paper. Oh yeah and key holing.
 
A bud has my old Sako .243 with a 10" twist, and I shot the best group of my life at 200 yards with that rifle shooting the 105gr A-Max. It kills coyotes at 670 yards in the winter, too.
 
Jordan Smith said:
A bud has my old Sako .243 with a 10" twist, and I shot the best group of my life at 200 yards with that rifle shooting the 105gr A-Max. It kills coyotes at 670 yards in the winter, too.
Click to expand...

Where does he live?
I'm probably moving from Montreal to Calgary soon and that should probably take care of 1/2 of my bullet stability problems (and 1/2 of my provincial income tax problems also) !

Alex
 
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