Torque?

[RiverRider]

Here's a question for you guys who've had more calibers than I have...

I have decided I like the 75-grain V-Max in my .25-06, and I am testing loads that yield about 3700 fps. I usually have gone with heavier bullets in '06-based cartridges but decided on a different route with the 25. I've had .22 centerfires that produce velocities matching and exceeding that, but the rifles are heavier and I shoot 50-grain bullets in my centerfire .22s.

I've been dealing with a bit of frustration in getting consistent accuracy with my .25-06. I'll see trends that point me one direction or another but results have been rather inconsistent. The other day I shot again and here are the results.

The charge was held constant with these loads, I was varying seating depth in .003-inch increments. I love the .34-inch group, but I've seen groups like this with different rifles where the performance could not be repeated. Another thing that bugs me is the idea that so little difference in seating depth produced such drastic differences in accuracy. But is that what's really happening?

In examining these results, one thing that stood out to me was that the second and third loads wanted to print right where the fourth load put all three shots.

I am beginning to wonder if my rifle has been torquing on the rest. Like I said, I've shot plenty of high-velocity ammo, but nothing as heavy as 75 grains and always in rifles that were heavier. Maybe a little adjustment in bench technique is called for with this rifle.

I know someone is likely to ask what rest I am using. It is the Caldwell "Full Length." I like it a lot.

Any thoughts or ideas welcome!

 

[FOTIS]

Make 9 of the .34" group. Change nothing and go shoot 3 3 shot groups

 

[DrMike]

Make 9 of the .34" group. Change nothing and go shoot 3 3 shot groups

+1

 

[RiverRider]

I guess that's a big "negatory" on the torque idea then?
:wink:

I figured I would HAVE to try that load again, and that has already been logged into my loading plan. I did want to know if anyone has examined the torque theory, though.

Thanks, my buds.

 

[FOTIS]

I do not understand. Where would the torque come from? Which part of the stock action would be torqued?

 

[RiverRider]

The torque would originate from the rifling imparting spin on the bullet as it accelerates down the bore. If the barrel wants to spin the bullet clockwise, then the bullet wants to impart CCW torque on the rifle.

In getting familiar with this particular rifle, I have tried managing it in different ways on the shooting rest. If allowed to recoil with minimal grip, it definitely wants to twist. I am pretty sure I've shot other rifles allowing them to nearly "free" recoil, and my memory may not be serving me correctly but I do not recall a rifle that wants to torque like this one does. That's why I brought up the bullet weight and the velocity. I've shot rounds of higher velocity, but always 50-grain bullets and in heavy-barreled rifles. My .25-06 is a Model 70 Classic, so it's not very heavy by comparison.

Hopefully that makes my muddy thoughts and my question a little more clear.

 

[Ridge_Runner]

I've ran some pretty heavy bullets pretty darn fast and never had a problem with torque. 7mm 120's at 3700, 160's at 3575.
RR

 

[FOTIS]

Same here RR.

 

[Mortis]

RiverRunner..... the only way you might get 'torque' on the barrel from bullet spin is in shooting a bullet heavier then the rifling twist will handle. And I certainly doubt that Model 70 is unable to handle 75 grainers.

My Ruger 77 in 257 Bob hates bullets under 100 grains.

I agree with Fotis's comments...... go with it.

If unsatisfied, only answer is change bullet and/or powder combination.

 

[Ridge_Runner]

try shooting with sandbags, lean into the rifle and put a few pounds of foreward pressure against the buttstock see if that changes anything.
RR

 

[nvbroncrider]

Make 9 of the .34" group. Change nothing and go shoot 3 3 shot groups

Agreed looks like it closed up there and then started opening back up as you gained jump.

 

[Oldtrader3]

The torque of the bullet leaving the rifling takes effect when the bullet has flow a distance through the atmoshere and rotational torque causes the bullet to runout into the direction of the rifling twist. Maybe an inch in 300 yards or so.

Bench handling technque and use of sandbags and/or rest pretty well negates any small torque residual in the barrel which might affect groups for torque at shorter ranges. Because leaving the barrel is a pretty small torque quoitent not large enough to effect group size at shorter (100 yard) ranges..

 

[Dr. Vette]

Here's a question for you guys who've had more calibers than I have...

I have decided I like the 75-grain V-Max in my .25-06,

Any thoughts or ideas welcome!

Unfortunately, it appears that your rifle doesn't like the 75-grain V-Max. :shock:

This looks like what I just went through with the 160 Accubonds in our 7mm Wby. Various powders and charges later I then tried Bergers with no luck and then swapped to Barnes TTSX. It's now a lazer and shoots like a different rifle.

The more reading I do the more I tend to think along the lines of rifles not doing well with certain bullets more than not doing well with certain powders. I'd change the bullet first.

 

[RiverRider]

You may be right about the bullet. I will shoot the load that have me the .34" group again and if it doesn't show an acceptable amount of consistency, I might give the 85-grain BT another look. If that doesn't work, maybe a Berger or Sierra or something.

I know I have to pay particular attention to how I manage the rifle on the rest. It seems that several of my rifles seem to have different preferences. I may try out a speed lock firing pin before it's all said and done. This rifle has teased me from the get-go.

 

[Mountain Goat]

I had a 25-06 that just hated the 85gr NBT. Once I went to the 75gr V-max all groups closed up considerably, not as fast as 3700fps though. My M7 .243 absolutely refuses to shoot 100gr bullets of any make, regardless of powder used. I dropped to the 70gr TNT for grins. It shot great, so that told me something about the heavier bullets. I stepped up to the 90gr Hot Core, shot great as well. I never did go to one of the 95 grain Noslers in that rifle to see the results. My point being, like others have mentioned, sometimes a rifle just doesn't like certain bullets, with weight not being the only exception. I'd try that load again or just move on to another bullet.

 

[Wincheringen]

I have yet to get a bullet lighter than 90 grains to shoot well in any of my 25/06s. I really only have one rifle that will even shoot a 90 grain bullet well and it is the 90 grain Barnes solid. I have acceptable accuracy with either of the 90 grain Sierras but the 100 grain NBTs do better and thats what counts for me.

 

[Oldtrader3]

I use the 75 gr BT in my .257 Roberts and it works exceptionally well at 3495 fps.