Home Forums Hunting & Shooting Hunting Optics 'P.O.I.T.' syndrome

On my work bench now...another one affected by P.O.I.T. syndrome (Point Of Impact & Tracking).

This a well built .30 cal. hunting rig that I'd previously bedded the bases and lapped/bedded the rings on. With the previous scope, it shot honest 1/2" three shot groups with hunting class bullets and a bit of load work. I've spent a bit of time behind the gun so I'm well acquainted with it. It's a good one.

Long story short, a new $1,500 scope and mounts get put on it (by a third party, not me ). Now, it won't/can't hold zero, won't/can't track and shoots patterns...like 4 inch groups.

The post mortem gives some clues. I wonder where I'll start??????

Good shootin' -Al

Wrong bases?
Different shooter?

Bases are correct part numbers for the action. The installation was fumbled and bumbled...no checking for proper contact, etc., etc.

Good shootin'. -Al

Why'd you let someone else mount your scope?

It's not mine.

Faint scuff marks at the edge of the ring base are a giveaway: Base was not securely mounted.

POIT “syndrome” …. Did they do a tracking test before it lost it ?

I understand putting better glass on a rifle - I don’t understand why the new owner wouldn’t have you bed the bases, and lap or bed the rings..


Sounds like Cabelas, Bass Pro or Scheels mounted the scope for them….

Brand of mounts, rings and scope would help.

I'm not saying that improper base fit wasn't the cause of or a contributing factor to the issue; however, I can add that I've pulled a lot of bases off that left marks like that, and the rigs actually shot tight groups while so equiped. IME, Talley LW is about the worst for action to base interface fit, but others can be shotty as well. Just the same, if the bases are screwed tight to the action so that there's no play, and, more importantly, they're properly aligned so that they're not stressing the scope, they still usually group fine. Thus, the first thing I'd do before conclusively blaming anything is independently check the rifle and scope for functionality. New scopes have given me fits before, especially those from a certain brand that has gained a reputation for not tracking too well.

I've also had bases leave marks even though the rifle shot well. This is especially true with the rough, gravel blasted, "matte" finish on some rifles like the one (no prefix M700?) that Al is working on. The rougher finish has a lot more "high points" that mark very easily regardless of how good the bluing/finish may be.

I had a Rem 700 do that, learned the front base had a larger radius than the receiver. It was the correct Leupold base number but it just didn't fit properly. Took me some time and plenty of shooting to figure it out.

Tested the scope at the range today on one of my rifles. A-B-A against the known good scope on my gun and one of my 'iron ball' test scopes that gets used to diagnose scope issues.

The scope is fine. -Al

Paul Mauser brought about the square bridge Mauser what, a hundred years ago?

Why we are using round receivers with ”dinky little 6-48 screws inherited from receiver sights" (Jack O'Connor),
is beyond me.

receivers with integral bases, that's optics mounting evolution if you want it to be........

In 20 more years, I predict that hunting rifles will come with a coupon for brawndo, and chambered only in 6.5 creed:

Don't drag Idiocracy into an discussion that also includes the 6.5 manbun

I found several years ago that bedding the base to the action took away a lot of issues. Lapping rings after bedding the bases took away a lot more.

Going back to what works.

Mount bases have the anodizing removed, cleaned with acetone and bedded to the receiver. The lapping bar aligns the setup and keeps it aligned as the bedding cures. 24 hrs. later, they are removed. Edges will be smoothed with a diamond file and the screw holes lightly radiused with a VLD neck chamfer tool. 100% contact between base and receiver:



A little light oil is all you need on the screw threads. Benelli choke tube oil works well as will a lot of light machine oils. Don't use a creeping oil like Kroil or Marvel Mystery Oil...you want to use something that stays in place:



Lightly snug, then loosen the screws a bit:



Lay the lapping bar in the rings bottoms to align the rings:



Keeping light pressure on the bar, move it forward and back so you can snug the screws. You can just see the back of the bar in this shot. Remove the bar and finish snugging the screws:



Ring lapping and bedding comes next.

Good shootin' -Al

Burris signature rings for the win!

Yes...great product.

But you still have to address the base fit issue. -Al

Al:

Am I reading it correct that you oil the mount screws before turning them into the action?

Yep. -Al

Torque values are calculated with lubed threads.