Groups opened up and I can't figure out why

[Daze]

I was shooting fine for months and suddenly groups are twice as big, but it changed nothing, what causes accuracy to randomly get worse?

 

[URIT]

There are many reasons for shot groups to open up. One is boredom with your shooting routine and targets. Others are more physical oriented like hand and wrist fatigue or wandering eyes as you press the shot.

Oops, I didn't realize this was posted for rifle/shotgun and not handguns.

 

[Alan]

I was shooting fine for months and suddenly groups are twice as big, but it changed nothing, what causes accuracy to randomly get worse?

Check your screws first. Rifles love loosening things right when your confidence peaks

 

[Native_Tarheel]

As Alan says, check your screws. I was once shooting rifles with a friend at 300 yards. He was shooting a 5.56 AR with a scope, but was all over the target, while I was shooting a new Savage bolt .308 with a scope and was consistently within a 3 MOA group. As my friend went to shoot another string, his scope almost fell off his rifle. One of his ring screws was found on the bench!

 

[Leo King]

Always check your screws first. I once wasted two trips to the range blaming myself, only to find my scope ring was loose the whole time.

 

[PapaGeorgio]

If it’s a wood stock, the wood can change your accuracy by swelling in humidity or shrinking in extra dry conditions. But yes, check your scope mount screws. The scope could also be squeezed too tight by mounts being torqued too much. That could make scope adjustments show up way late.

 

[I_am_Bulletproof]

Check your crown first, then the points where your cleaning rod contacts the barrel. Both have caused me problems before and those looked like shooter errors at first.