Gentlemen,
I have been observing this phenomenon in two rifles now and am wondering what gives. The rifles are a Winchester 70 FWT Stainless in 6.5x55 with a used Leupold 6x42, about 300 rounds through it, and the second rifle is a nearly new Remington 700 SPS DM in 7mm-08 with a 3-9x40 Bushnell on it. Good guns and good scopes. I handload for both, and both have given groups of well under an inch with preferred loads. Here is the question. Is it normal for a rifle to throw the odd group, ie, normally shoot under an inch, and then for no explainable reason open up to 2 inches? I was sighting in the 6.5x55 the other day after changing scopes, and the first group was nice and tight, under an inch. I adjusted the scope, and did another three shots, giving the barrel time to cool between groups. The second group had two shots close, then I adjusted the scope again and shot the third shot. Instead of being about an inch above where I had aimed, the next shot was two inches high and about the same wide of the intended point of impact. The next was a bit lower, but two inches to the left of intended impact. The ammunition was just loaded, I weigh every charge, and the bullets were Hornadys that I had grouped well with before, so I do not understand what the issue is. Any suggestions as to why this is happening. Neither gun has been cleaned between the shooting of the good groups or the wide groups so that is one less variable.
Thanks for the help.
Regards,
Graham

M70,

the second group was not really a group but a bunch of succeeding shots with scope adjustments in between.

Both the Leupold and the Bushnell do not have precise enough adjustments to guarantee 100% accurate sight adjustment. Its more a trial and error game. (BTW, this applies also to much more expensive scopes.) This is especially true if you approach the limits of the adjustment array. The reticles are spring mounted and will render unproportional movement per click as the springs approach their max. tension/slack.

Furthermore, the reticle may need a shot or two to settle in its final position after adjustment.

Thanks. I wondered if that was the case with the Leupold, but that still doesn't explain the 7mm-08's problem. I had not adjusted the scope at all on that one, and it still was not as consistent as the first two groups showed that it could be. Thanks for the idea,
Regards,
Graham

I don't want to piss anyone off but why are you firing #3 shot groups and not #5 shot groups ?.

Also as stated previously groups are without sight adjustment in between , IMO any way .

I had always been taught to shoot # 3-5 shot groups then average for weapons true accuracy .

Did I not pay attention or miss some thing ?.

Shoot Straight Know Your Target . ...

You fire 3 shot test groups for economy. If you are making scope adjustments, you need to make a “scope jarring shot†to make sure the reticules are settled in and then fire your 3 shot test group.

Dr. K,
I normally shoot three shot groups during my load development, and if a group shows promise, as in under an inch, I will load 5 or more of that load and test it that way. This gun had previously shot 5 shots under .75" and I had just fired a three shot group to find where it was hitting. I assure you that it was well under an inch, even though I did not measure it.
I do not measure groups with sight adjustments inbetween, usually, but I was confused as to why the gun would shot very well with the first three shots, and then the next three were all over the map, even with the scope adjustment, and allowing time for the barrel to cool. I tested it again this evening, and it was where it should be after I tweaked it a little more. I was just wondering why the gun would shoot well with one group and then spread the same load all over even with time to let the barrel cool.

You're probably right about the average of the groups being the test for the rifle's accuracy. I have other guns that are consistently sub MOA at 100, with a couple of loads.
Thanks for the help.
Regards,
Graham

Except when using Swarovski scopes, whose dual counter springs have proven reliable in click value over the years, I made it a habit of tapping the turret with a screwdriver's handle whenever I make an adjustment. The slight jarring has the same effect as the "settling shot" suggested by MickinColo.

Andre,
I always do that,too. After an adjustment and before the shot, I will bump the scope tube infront and behind the turret several times with the heel of my hand. Thanks for the tip.
Regards,
Graham

I didn’t have a lot of time to respond to this post last night.

M70 and Andre are right about tapping the turret. The tapping with the plastic end of a screwdriver works better because the hard plastic gives better shock than the palm of the hand, but be gentle.

However there are scopes out there that are not so great (we don’t need too name names here, if you been shooting for a while you know them) that need tapping and a shot to settle them in.

quote:

Originally posted by MickinColo:
... there are scopes out there that are not so great (we don’t need too name names here, if you been shooting for a while you know them) that need tapping and a shot to settle them in.

... and a kick in the "objective" before getting rid of them

LOL Andre.

With lots of shooting I see group variations by +100% and - 50%.

1 moa average, the worst group ever 2", the best group ever .5"

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With less shooting I see group variation by + 50% - 25%

1 moa average, the worst ever 1.5", the best ever .75"

[or in the case of some old military rifles, 4 moa average, the worst ever 6", the best ever 3"]

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I have a target from a Rem 610 old single shot 22LR with 6 bullseyes at 50 yards. Most groups on the target are .75 ~ 1.0", but one 5 shot group is 0.18". Usually the errors add up to make a bigger group, not a smaller one

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What does it all mean?
If I had a 1" gun and shot 300 rounds, I would expect some 2" groups and some .5" groups.

And shooting when the wind is above 3 mph does not count.


My 610 got a group several standard deviations to the left.

Listen to Tek and Dr. K. This is another case where gun writers wrote about things of which they had minimal to no knowledge. Yeras ago they shot 5 shot groups and reported accuracy. They found it looked better in print if they shot 3 shot groups and threw out flyers "because I kenw I pulled that one."

If you really want to know what your rifle/load combo will do, then shoot five, five shot groups at 100. Use wind flags, good rests, and a good bench. Do not throw anything out. This will tell you what your rifle will really do. One five shot group after shooting 3 shot groups will not tell you anything.

I confess to now mostly shooting 3 shot groups these days. It is faster and easier on me physically. I have some limitations and have had to make adjustments to how I do a lot of things. I shoot 3 shot groups, but I do not get surprised when I see a lot of variation in group size. It is the nature of the beast with smaller sample sizes, regardless of whatever BS in is a gun magazine this month.