January 22nd, 2020

TECH TIP — Check Barrel Tightness If POI Shifts Erratically

loose barrel vortex scope optics point of impact change fix

Are you seeing unpredictable changes in Point of Impact on your target? Think you may have a scope issue? Well maybe not — when was the last time you checked your BARREL?

Yes scopes do fail, and scope bases/rings do get loose. But sometimes problems with erratic POI shifts are caused by a LOOSE BARREL. This issue came up recently in our Shooter’s Forum. One member complained that his zero was shifting from day to day — by as much as two inches at 100 yards. He was convinced he had a scope problem, based on erratic POI:

“I think my scope loses 1 to 3 MOA per day. When I shot my rifle Monday it was dead on. On Tuesday it was 1″ low. Then on Wednesday it was 1 or 2″ lower. I don’t get it. — the elevation knob never touched. Scope will track and return to zero that day perfect. Yes EVERYTHING has been checked, nothing loose. What is the chance the erector tube spring has gone south? For the record this is a Vortex GE. Never had a bad scope, but this has me wondering”. — LB

On Forum member told LB to send the scope right back to the manufacturer. Two other members suggested mounting the scope on a different rifle to test. Good advice. That’s generally a smart strategy before you conclude a scope has gone bad…

Could Problem Be the Scope Base?
Two Forum members, ExPiper and Dickn52, suggested checking the scope base, recounting their past experiences with troublesome bases. This was intelligent — anyone with a POI problem should check all the optics attachments:

“Went crazy one day chasing my impacts on a 100-yard target. Shots would group fine for three then go nuts for 4-5. I cranked and un-cranked for about an hour. Then I reached up and the base wobbled on the rifle. Removed scope, tightened base screws and back in business.” — Dickn52

“Years ago I had a problem [where] shots were climbing with almost every shot. I was blaming the scope. However, when removing the scope I noticed that the 20 MOA base was cracked and getting wider with every shot. Needless to say I replaced the base and the problem was solved. — ExPiper

Eureka Moment — The problem was the BARREL, not the Scope

There were many helpful suggestions, but member PirateAmmo steered LB to the real problem — a loose BARREL: “We had a problem on a home-built AR-platform rifle once, barrel was loose a tad…”

Member Snert chimed in: “Yep — I had a PPC that suddenly went 19″ low. Picked up gun off bench by barrel and felt a wiggle. I tightened the barrel and the POI went 19 inches up”.

Problem Solved — Barrel Tightened up and POI Back to Normal
The gentleman with the POI problem took the advice of PirateAmmo and checked his barrel. BINGO! Low and behold, the barrel WAS loose.

LB posted: “Barrel loose by about 2%, checked it twice before and didn’t find it the first two times”.

After LB re-tightened his barrel, his rifle started shooting normally again. No more shooting low by 1-2 inches. Problem solved. The fix didn’t cost a penny and now LB doesn’t have to send a perfectly good optic back to the manufacturer.

Lesson learned? Check ALL the variables before you assume a scope has gone bad. Along with the barrel, also check your action screw tension, and of course the scope base and rings.

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