Gun or Scope creep?

[HarryToolips]

After checking my gun earlier this year, I thought it was sighted in well, and I know it was last year at least. Been doing a lot of longer range shots lately, and several werent hitting the target or were off to the right, always to the right..so tested it tonight and sure enough it was out. Not just out, but a whopping 3" out at a 100 yards.

Yes I check the tightness of my scope rings and base regularly, and clean my gun using a quality one-piece rod pushing it from the action out to the muzzle end only, never back and forth. I clean it every 20 to 30 rounds. I've put a 1000 + rounds through this .30-06...

Any ideas as to why it would be out from last year so badly?

[Pioneerman]

Was it still a tight group but 3" out or all over?

[HarryToolips]

No it was tight, I moved it 3" to the left and it was a tight group at bullseye..also makes sense since all my shots at longer range were all to the right..

[375shooter]

If your rifle has a wood stock, specially if it has forend pressure, could have warped slightly due to humidity changes since your last sight in. This slight warpage can change the barrel harmonics, causing the shots to go to a different point of impact. With my wood stocked rifles I make sure every square inch of area is properly sealed with gun stock finish to minimize warpage. I also be sure to shoot my rifle at the range before a hunt to verify that it's still sighted in.

[oscar makonka]

Are you shooting the exact same ammo as before? If you change the ammo it will often change where your rifle hits.

[HarryToolips]

If your rifle has a wood stock, specially if it has forend pressure, could have warped slightly due to humidity changes since your last sight in. This slight warpage can change the barrel harmonics, causing the shots to go to a different point of impact. With my wood stocked rifles I make sure every square inch of area is properly sealed with gun stock finish to minimize warpage. I also be sure to shoot my rifle at the range before a hunt to verify that it's still sighted in.
Very good info, but it's not a wood stock..good to know though..

[HarryToolips]

Are you shooting the exact same ammo as before? If you change the ammo it will often change where your rifle hits.
Always been shooting Remington Core-lokt..I have however changed from 180 grain to 150 grain bullets..but would bullet weight really change bullet trajectory like that???

[Lucky77_]

Absolutely bullet weight will change POI. I have a .375 with a synthetic stock that consistently changes with bullet weight. Zero with 270 gr.= 6" low 6" right with 300 gr. and vs/vr.

[j270wsm]

A change in bullet weight or increase in velocity can change your point of impact.

[Steeleco]

The fact that your groups seem tight despite the weight change is a good thing too, that's not always the case with most guns.

[250 sav]

[QUOTE=HarryToolips;1657854]Always been shooting Remington Core-lokt..I have however changed from 180 grain to 150 grain bullets..but would bullet weight really change bullet trajectory like that???[/QUOTE

I've seen a change in bullet weight change poi in 30 06 of 11" ( Any change in ammo make, bullet weight etc requires a recheck of zero)

[HarryToolips]

Ya but a change in bullet weight making a change in left/right impact?? Sure of course it would affect drop but affecting left/right doesn't make sense to me...

[Steeleco]

The change in weight chances the barrel harmonics. If you bought a same weight offering in a different make, it will shoot different too. If the 150's are to be your "go too" bullets, simply adjust the wind-age and have at er!!

[250 sav]

Ya but a change in bullet weight making a change in left/right impact?? Sure of course it would affect drop but affecting left/right doesn't make sense to me...

The facts do not always make sense, but they do remain facts.

[HarryToolips]

Just got back from blastin, adjusted it to where it needed to be for 150 grainers..tried 180 grainers again as well, seemed to not group as well although that could have been shooting fatigue..

[Brew]

Ya but a change in bullet weight making a change in left/right impact?? Sure of course it would affect drop but affecting left/right doesn't make sense to me...
I was shooting a 300 rum the other day. Sighted in for 200 gr lrx bullets. Then tried a group with 215gr bergers and they where not even on the same target but a nice tight group the right and low. It's all barrel harmonics.