Finding the prefered ammo

[Monkey Medic 83]

I have a R700 .308 varmint 24" (pretty sure 1:12 twist factory barrel). Leupold Mk4 glass, stock pro-x trigger lightened to 4lbs, and a B&C Mk2 stock.

the other day i shot:
SWA 155 OTM, HSM Hornady 168 Amax, and SWA 175 SMK

in the beginning the 175 SMK was making same hole shots at 100yds (best out of the three weights)
168 Amax was shooting about 3" groups
155 about 4"

by the time i shot about 30 rounds rotating the rounds around (3-5 round rotations with no cleaning) over a period of 2-3 hours the 168 was constant at 3" spreads ad the 175 was making 6" spreads, and the 155 was about 8" spread.

any input or suggestions

I just ordered more ammo to do some more testing to find my rifles preferred round. anyone want to go shooting and "help out"

 

[Longshot38]

I'll start by saying that my comments are not intended as an insult. Rather they are supposed to be constructive critisim. So when trying to diagnose such problems it is always productive to start with the shooter. Obviously you were grouping well and are capable of shooting well. But what is your typical time behind a rifle when at the range? Fatigue to cause problems. Next how hot did your barrel get? Heat can do strange things to barrels. Then comes fouling in the barrel. Was the barrel clean when you begin your session? What is the round count on the barrel? The combination of heat, fouling, and a worn barrel can cause all kind of strange things to happen.

 

[Monkey Medic 83]

Round count on the barrel is about 200-250. The rifle was cleaned with standard CLP and brass bore brush a few days earlier. I have not spend an incredible time behind the gun, I'm just starting to get into precision shooting (more of a carbine/medic operator). I'm usually at the range for a couple hours, shoot anywhere from 60-100 rounds then head home. The barrel didn't get very hot. I shot a few rounds, no more than 5, and took a couple minute break, verified my groupings for my zero (just put on a new rail and had the scope releveled).

On a side note, to break in the factory barrel I did use David Tubb TMS rounds.

 

[Longshot38]

My suggestion is to get some bore cleaner that addresses copper fouling (I like Wipe Out). And try giving that bore a good cleaning then see what happens. Given that is a new barrel I would use that as my starting point.

 

[Monkey Medic 83]

Sounds great. Thanks, do you suggest I use the "wipe out" between testing different grain weights?

 

[Barney88PDC]

Sounds like something is loose to me. Check the base screws.

 

[timelinex]

Sounds like something is loose to me. Check the base screws.

+1

Check that nothing is loose. Most other issues will not cause such horrible results.

I'm pretty sure I can take my savage any day of the week, not clean it for thousands of rounds, use random military surplus ammo found in a bucket, and shoot it till the barrel is steaming hot... And it will still produce better groups than 8inches at 100 yards. Surplus rifles with surplus ammo shoot 3 inches at 100 yards... Center fire rounds are just too good not to be at least that accurate(as long as the optic is quality) . Your results are really showing that something is loose or something major is wrong.

 

[Longshot38]

Sounds great. Thanks, do you suggest I use the "wipe out" between testing different grain weights?

No. Just a good once over the bore to ensure that it is clean. No need for any sort of break in procedure. Also take what others have said into consideeration. Both a good cleaning the checking for loose screws are cheap/free starting places.

 

[Longshot38]

Sounds great. Thanks, do you suggest I use the "wipe out" between testing different grain weights?

No. Just a good once over the bore to ensure that it is clean. No need for any sort of break in procedure. Also take what others have said into consideeration. Both a good cleaning the checking for loose screws are cheap/free starting places.

 

[shovelstrokeed]

That rifle should be sub-MOA all day long with almost any ammo, never mind Match ammo.

My first thought is loose mount or broken scope.
Start by checking the scope itself, are the elevation and windage knobs still giving ciicks?
Mount the rifle in something like a Lead Sled and stick a laser bore sighter into the bore. Watch through the scope as you move the turrets through travel. Cross hairs need to move smoothly as you change turret settings.

Are your rings the right size? That scope has a 30mm tube.
Are the screws clamping the scope in the rings tight?
Are the rings tight to the base and is/are the recoil lug in the rings tight in its groove and against the stop. This one catches a lot of people out, particularly if your haven't mounted many scopes.
Check that the base itself is tight Couple of things here. Base screws need both torque and Loctite to keep them in place.
Check that the base doesn't raise off the receiver when one screw is loosened. If that is the case, you may need to bed the base to the action.

To the rifle.

Action screws need to be torqued. Your manual should give you the specification.
Remove the barreled action from the stock and look at the points of contact.
There may be debris in there that is keeping the action from firm contact all around.
Bedding an action is not hard but it is a job for someone competent. I would check with the local shooters for a gunsmith they trust.

I got nothing more other than my Ruger Gunsite Scout is sub-MOA at 200 with the gun at near factory specs. Only thing done to it was to mount a 3.5-10 VX3 in the Ruger rings.
It's a deer killer, not a varmit gun.