New Glasses effecting group size???

[lar45]

Hi everybody. I've been working up a new lube recipie and shooting the 454 quite abit and was having a hard time getting any reasonable accuracy.
I was beginning to wonder if I had forgot how to pull a trigger. So I pulled out a 480 SRH that had shot great groups last year.
http://www.lsstuff.com/pics/guns/srh/srh-01.jpg

http://www.lsstuff.com/pics/guns/srh/srh-03.jpg

I sat down at the bench with the same box of ammo I had used last year and shot a terrible group.
I thought maybe my eyes were just getting too old, but then remembered that I had got new glasses last fall just before hunting season.
So I dug out the old glasses and shot a pretty reasonable group.

http://www.lsstuff.com/pics/guns/srh/srh-glasses.jpg
Old glasses on the left, new glasses in the middle, last year with old glasses on the right.

I'm going back to the eye Dr.
Any thoughts on the subject?

[Bird]

Same here. I shoot about double group sizes as compared to 10 to 15 years ago. I always keep some previous accurate loads in reserve to compare to my current shooting abilities. 100 yard target might as well be 1 mile now. Just got new prescription glasses, so will see if that makes a difference.

[243winxb]

I have been taking my old glass to wear when shooting iron sighted handguns. Not perfect but ok for age 77.

[Winger Ed.]

I was beginning to wonder if I had forgot how to pull a trigger.

Looks like you're proof shooting is like riding a bicycle--- you never forget how to do it.

[ShooterAZ]

Sometimes it takes a good bit for you and your eyes to adjust to your new glasses. I'd give it a little time and see what happens. If no improvement, go back and see your Dr.

[Wayne Smith]

Are your new glasses no line bifocals? They are actually trifocals, there is a very small area of transition. If this is in your line of sight it can throw off your shooting.

[dverna]

Doubtful it matters much with a scoped firearm. Put crosshairs on target, squeeze trigger....

[lar45]

Just regular bifocals, not the no line kind.

[TurnipEaterDown]

Most every lens has distortion of one type or another, and the transition zone on a bifocal is one type of feature than can cause image distortion that we don't want.
If the lens itself is shaped to fit a different frame, that also changes the distortion, usually most notable at edge of field.

Correcting vision with glasses is (simplistically) creating beneficial distortion.

Scopes don't fix everything either. Lay your rifle up on a rest, and while looking at the reticle on target, move your head around w/o touching the rifle. Does the reticle appear to move on target? You have experience parallex. This is not as many would think correctable over a range of distance, it is a fixed distance correction. This is one reason eye position is critical for best groups.

Yes, I believe that changing glasses can change groups, or at least group position. I have swapped glasses during a day at the range (to avoid auto darkening pair), and thought 'what is going on' as my shooting suddenly changes. I think that the distortion change between two sets of lenses Can be a lot like putting your face on a different place on the buttstock. Probably isn't anything to do w/ paralex, just making an analogy most shooters are familiar with.
I am not expert on lens design though by any means.

[NSB]

Have you checked the clarity of the reticle with your new glasses? Hold the scope up to the sky and without trying to focus is the reticle sharp and clear? If not, adjust the scope. I don’t think it’s the glasses themselves, it’s that you haven’t adjusted the scope for reticle clarity with your new glasses. Also, make sure you’re looking through the center of the scope and not turning your head up and down between the top lens and the bottom lens.

[45DUDE]

You might try a fold down aperture that clips to your glasses. I group better with 15 year old glasses than my newer ones.

[Alstep]

Parallex is most probably the issue here. Unless the scope is adjustable for parallex for the distance being aimed at, the error can be quite large. Do the parallex test as described by TED in post #9. If the crosshairs move, you've got problems. Then you've got to center the crosshairs in the center of the eyepiece to get consistent results. I've seen some guys rig up a thin cardboard washer with a smaller hole to the eyepiece to center the field of view with the crosshairs. You also have to adjust the eyepiece so the crosshairs are in sharp focus for your vision.

[fredj338]

A proper perscription is pretty important to good shooting, if you cant see, hard to shoot well. The biggest issue is most close perscrips are set up for reading distance, not front sight distance. So I have mine set up for extended arms, front sight> this also works fine for optics. With a scope, you may need to adjust focus a bit for the new perscrip.

[dverna]

My eyesight sucks. That is why I use either a scope or aperture sights when it matters.

The OP is using a scope. I do not understand how glasses are going to affect parallax. I suspect a flinch or a bad scope. Easy to check. Take a buddy with you and have him load the gun. If you have a flinch, it will be apparent. But knowing you are going to look silly if you flinch will force you not to try not to flinch. So if you shoot a good group, it will confirm you have a flinch. If you are not flinching and shoot a poor group, you have a bad scope...it happens.

Hope you have a bad scope....

[243winxb]

Scope eye pieces need to be adjusted for new glasses.