I spent a few hours at the range today with my 300 Weatherby. This has always been a fairly accurate rifle but i don't know what the problem was today. At 100 yards i had 5 shot groups around 1 inch consistently. The velocity was 3120 - 3128 fps and everything looked good. Wheni moved it out to 200 yards i could never get better than a 5 inch group. I didn't even try further out than that. All shots were off a bench with a solid rest. There was no breeze but it was pushing 95 out. Knowing that it can't be me because I'm perfect (that's what my wife says anyway ), what other varibles do i need to be looking at?

Sounds like a scope mount problem to me. Admittedly it is a coincidence that it happened when you moved from 100 to 200 yard range. Heavy recoiling rifles like the 300 Weatherby can break loose scope mounts or damage them.

By any chance are you using Talley Lightweights? I know several that have had problems with them, myself included.

Check your parallax. Some scopes will produce great groups at 100 but have the crosshairs crawling all over the place at 200 or farther. The opposite is also true, I see scopes that produce groups at 200 that aren't much bigger than their 100 yard efforts all the time. Since you mentioned temperature, how hot did you get your barrel? A weatherby that shoots great 5 shot groups is the exception.

It could be that the scope picked that instant to pack it in, or come loose, but you should be able to confirm that with a screw driver and 100 yard re-testing. Check your action screws while you're at it, it doesn't cost anything.

Has the load produced good results at 200 and out before? If I had a dollar for every bughole load that fell apart at longer distances I could buy a couple new rifles. It should be worth 5 bucks for every shooter that is left shaking his head and saying things like "I wouldn't have believed it" or "never saw that before". Its more common at ranges longer than 200, but can happen there too.

scope parallax is set at 100yds that's why I buy scopes that have the adjustment feature.
they cost more but you got a weatherby so a few hundred bucks shouldn't be a problem.

I'm reluctant to bring this subject up since there is far too much said, written, and obsessed over twist rate. However, if your rifle is an original German Weatherby it will have a 1-12" twist rate, which is a bit on the slow side for certain 180 grain bullets (which is what it sounds like you're using). This is especially true if the bullet is a monometal, a tipped bullet, or a special sharp-ogived long range bullet, all of which are somewhat longer than the 1-12" twist was designed for.

It is typical when a bullet is fired from a barrel which is marginal for its required twist that the bullet will be fairly stable for some distance, then as it loses velocity will become unstable. This can manifest itself in fairly good groups at a closer range and fairly poor groups at a more distant range. If this is the case, then the bullet will eventually lose all stability and yaw/tumble to the point that it no longer groups at all.

If your problem is twist, then you might find that your 300 yard groups are even worse. The cure is to change to a shorter bullet.

Slow twist might or might not be the culprit, but a sudden scope failure would be unusual, and the difference in parallax at 100 and 200 yards would not introduce enough error to account for the size of the groups. Besides, if your eye placement is the same for each shot there can be no parallax error.

Eveyone has a theory, but I don't buy parallax or twist rate as causing your problem. Brian Litz covers these issues nicely.

Bullet stability increases as the bullet slows down, not the reverse. Besides, bullet stability - unless wildly off - does not effect group size. A less than perfectly stabilized bullet will still print small groups.

Poor bullet stability will decrease ballistic coefficient, similar the increased air resistence of a wobbly pass thrown by the quarterback, compared to the efficient penetration of a perfect spiral.

Parallax is a potential problem for close shooting, if you don't compensate for it. And Brian Litz believes that's why some folks shoot MOA groups at 200 yds but 2 MOA groups at 100 yds. Nonetheless, if you have a focus adjustment on you scope, use it. The sight picture should be in perfect focus and your eye centered, wherein parallax is essentially eliminated.

Finally, I ask what's going on at your range. Range conditions can vary with distance down range.

Is the wind gusty, possibly more so between 100 and 200 yds. Some ranges show variable wind conditions at various points. Also, the wind and terrain will affect mirage, which can open your groups. Possibly, range conditions are quite different between 0 to 100 yds and then from 100 to 200 yds.

PS: IMO, all shooters, who desire maximum accuracy from short to long distance, should read Brian Litz's books..."Applied Ballistics for Long-range Shooting" and "Modern Advancements in Long Rang Shooting". Brian Litz has got his shit together and has become World famous for good reason. The books are very well written and backed by experimental data. Brian Litz is not a bull shitter.

95 degrees is about the right temperature for mirage to become a factor. No wind causes mirage to boil instead of running one direction or the other, but any stray breeze can have its effect magnified by the resulting change in mirage. Admittedly, 200 yards is a little close for mirage to be a factor, but I have seen it to happen.

Remember, mirage has the effect of displacing your aiming point, so no matter how well you hold, you may be aiming at different points from shot to shot.

The best way I have found in dealing with it is shooting every shot with identical conditions. The best way to establish that is to set your spotting scope slightly out of focus, which makes mirage easier to observe. Watch through the scope until you identify the prevailing condition, and then get your shot off as soon as possible, then get back into the scope to see if conditions have changed. Better yet, have someone coach you by looking through the scope and telling you if there is a change in conditions while you are aiming. This is routine in high power team matches.

quote:

Originally posted by xausa:
95 degrees is about the right temperature for mirage to become a factor. No wind causes mirage to boil instead of running one direction or the other, but any stray breeze can have its effect magnified by the resulting change in mirage. Admittedly, 200 yards is a little close for mirage to be a factor, but I have seen it to happen.

Remember, mirage has the effect of displacing your aiming point, so no matter how well you hold, you may be aiming at different points from shot to shot.

The best way I have found in dealing with it is shooting every shot with identical conditions. The best way to establish that is to set your spotting scope slightly out of focus, which makes mirage easier to observe. Watch through the scope until you identify the prevailing condition, and then get your shot off as soon as possible, then get back into the scope to see if conditions have changed. Better yet, have someone coach you by looking through the scope and telling you if there is a change in conditions while you are aiming. This is routine in high power team matches.

I'm a benchrest rifle shooter (our goal is to print 0.1 MOA groups, and you're likely to lose the match if you print 0.2 MOA or above groups) - the above is good advice from xausa.

Thanks for all the advice, this is great. I very rarely go to the range when its that hot so I'm going to get out early one day this week and see if its better. Also sounds like I need to go book shopping. Thanks for the help everyone.

quote:

Originally posted by Ackley Improved User:
Bullet stability increases as the bullet slows down, not the reverse. Besides, bullet stability - unless wildly off - does not effect group size.

I think you misread the dynamics of bullet stability. It is true that at longer ranges bullets often "settle down" and shoot tighter groups than their 100 yard performance would indicate. However, this is not due to their becoming "more stable" due to velocity loss, but rather somewhat the opposite: Internal imbalances can be magnified at higher velocities (and rotational speed), causing some dispersion from the center of the group. As the bullet slows these imbalances can "settle down", allowing the bullet to continue on a path that is narrower than the expected "cone of fire". Or at least that's the way the theory goes. Since wind is a big factor and is almost always present in longer range shooting it is impossible for most casual shooters to say, but I'm often surprised at how many of my rifles tend to shoot a tighter MOA at 300 yards than at 100 yards.

On the other hand, a bullet which is unstable due to lack of rotational velocity (too slow twist) will begin to yaw. This yaw increases with time/distance. At some point along its path a yawing bullet will lose all stability and diverge completely from the expected cone of fire, resulting in much less accuracy downrange than uprange. I've had bullets strike a 100 yard target in partial yaw as evidenced by the oblong holes they made (a long 100 grainer in a 1-12" .244 Rem), but five shots still fell into a 2" group. Those same bullets were totally unpredictable at 200 yards.

I'm not saying that slow twist is River Jordan's problem (it could be simply overheating a light barrel with magnum loads in very hot weather, or any of a number of other problems.) But this is one of the few instances in which twist might be suspect. If he would specify what bullets he is using and whether his rifle is one of the older Weatherbys with the slower twist then we might have a better clue.

When did you clean your rifle last? How well?

River: Was your rifle a Light Weight by any chance?

If its shooting and inch at 100 and 5 inches at 200 then you need to change bullets, your bullet is stabilizing at 100 but starting to yaw beyond that..I personally prefer the 200 gr. Nosler partition in any 300 magnum..

I'm pretty sure that's your problem, but you failed to mention what bullet and what load your using..That could change opinnions also.

The rifle is a standard Mark V, not a lightweight and the bullets are 180 gr Barnes TTSX's.

I have a load for my 30.06 using Barnes 180 gn TTSX. MV 2850 fps from a 24 inch barrel. At 100 yds shoots sub 1 moa, and slightly more than moa at 200, 300, 400 yds, on the range over a bench. Having exhausted my current batch of projectiles I purchased more, but a different batch. Result: 100 yds, slightly to the left of aimpoint and slightly more than moa. 200 yds, 3 - 4 inches left and 3 moa. 300 yds - same as 200 yds and hardly any drop. 400 yds, 15 inch drop with one shot so far left it missed the target, moa....?? Now I'm trying to find more of the same batch that shot much better. Not saying this is the problem for you, just suggesting another possibility perhaps....