Home Forums Hunting & Shooting Ask The Gunwriters Why would a rifle shoot 1/2 MOA at 100 and 2 MOA at 200 yd???

Am still trying to figure out how that happens, without outside factors being involved.

Quite a few shooters believe bullets "destabilize" as they get farther from the muzzle, but bullets actually become more stable at "normal" ranges as velocity decreases.

According to this article it has the same effect ...

https://www.shootingillustrated.com/articles/2016/3/28/rifle-scope-reticle-cant/

John, didn’t say the bullets destabilized. You have even stated that moving out to the 2-300 increases the error rate. My point has always been that the rifle may not like what the heck he’s feeding it. It may never shoot that bullet and maybe with a little tweak of the load it just might. Did this awhile back with a 700 BDL in 25.06 seeing if a 110 AB would shoot. The sighter was a known load that was used to foul the tube plus I had 6 rounds left over that had to go.
Target 1-5 were all the exact charge just altered the seating depth 5 thou for each except #5 which I altered 10 thou to a jump of 25. All were in the 1-1.5” range @ 100 except 1. Now while all would be minute of deer at 200, reasonably I can expect maybe at best 2.5 to 3” or more @ 200.



I did put one of those 1.5” group loads out to 200 and it looked like this. Still minute of deer, but damn ugly.

bsa,

Bryan Litz has been advertising to pay the expenses of anyone who has one of those "magic rifles" that shoot better at longer ranges for several years now, and has yet to find one. That's because there's no way bullets that start out shooting mediocre groups, whether at 100 or 200 yards, can somehow curve toward the aiming point at longer ranges. Bullets do become more stable as velocity drops, because there's less air pressure on the front end, while the spin-rate stays high, but that doesn't mean they have eyes.

There's also no way to build to build something into a rifle that makes it shoot larger MOA groups at 200 yards than it shoots at 100, as long as the rifling twist adequately stabilizes the bullet in the first place. So something other than the rifle itself has to be causing country boy's problem.

bsa,

Bryan Litz has been advertising to pay the expenses of anyone who has one of those "magic rifles" that shoot better at longer ranges for several years now, and has yet to find one. That's because there's no way bullets that start out shooting mediocre groups, whether at 100 or 200 yards, can somehow curve toward the aiming point at longer ranges. Bullets do become more stable as velocity drops, because there's less air pressure on the front end, while the spin-rate stays high, but that doesn't mean they have eyes.

There's also no way to build to build something into a rifle that makes it shoot larger MOA groups at 200 yards than it shoots at 100, as long as the rifling twist adequately stabilizes the bullet in the first place. So something other than the rifle itself has to be causing country boy's problem.

Or wind--or possibly inconsistent canting of the rifle.

I have seen a lot of people estimate a 5 mph wind at 2-3 mph.

....... I was pointing out that if a rifle groups well with certain loads at 100 yards (which is what country boy says) there's no physical reason the rifle itself will cause groups to open up at 200. So the answer has to lie elsewhere than the rifle itself.

country boy,

Thanks for reminding me of the specifics about the rifle, etc.

Some other people on this thread have also said that the two things they've seen open up groups at longer ranges are wind (especially), and to a certain extent scope parallax--though parallax normally has a far greater effect beyond 200 yards. In fact that was the very first response to your post. Do you know how to check for parallax?

I'm still doubtful about the wind, mostly because I've actually measured wind a lot. Most shooters have very little idea of wind velocity unless they do, and also don't understand how much it can affect bullet drift, even at relatively short ranges.

Combining a little parallax and wind drift can make a considerable difference, even at 200 yards.

You also mentioned that your groups at 200 were scattered side to side, while your brother's were more vertical. Somebody else mentioned a slightly canted reticle as a possibility, but this shouldn't affect group side IF the reticle is aligned with a vertical line on the target the same way for every shot. But if not, at 200 yards, tilting the rifle from shot to shot, even slightly, can make considerable difference. In fact it can make considerable difference even at 100 yards, especially with a relatively high-mounted scope. I have a buddy who was having enormous problems getting a new lightweight rifle to group accurately, and he eventually asked me to help. He'd mounted a scope with a pretty big objective, which required high mounts--and it turned out he was tilting the rifle a little, differently for each shot. I coached him some, and the problem went away.

You've also stated the rifle was rested on sandbags, front and rear. Was the same rest used both at 100 and 200? Did you check to make sure the front sling swivel stud was sufficiently in front of the bag to not bump it during recoil? Did you rest the forend on the same place every time? Some rifles can definitely be affected by forend placement.

Some relatively lightweight rifles can also be affected by the hardness of the front rest. Even sandbags can be compacted hard enough to affect groups after some shooting. With lighter-weight rifles I've found a folded towel over the front rest can make a big difference in group size, as was recently discussed on another thread.

MD, Thanks for all of these suggestions. This is exactly the kind of information and recommendations I've been looking for. I appreciate constructive criticism without treating people like they are an idiot, as I have seen so often by others. I think I would almost rather find out that I'm the culprit than it be a rifle or scope problem......

During my next range trip, I will pay particular attention to the sling studs placement, both front and back. I will also check the wind more closely. I spent a great deal of time checking the original scope (VX5) for parallax and playing with the adjustments, but could not see any problems as it was set. Both scopes have the adjustable ring on the eyepiece.

I truly believe my statement that far more 1/2" groups are fired on the internet than ever fired on the practice range

Can you do this?.....place two targets at 100 and 200 yards distance and one precisely behind the other such that one only has to shoot through paper at 100 yards and therefore can measure the very same (10-shot) group at both ranges.....

This should prove the theory that the MOA is different at different ranges....or possibly disprove it.....I won't speculate!

That one is for focussing the reticle. It is not the one for parallax (which is to say, bringing the target into the same focal plane as the reticle).