How much might groups open with loose scope mount?

[WillaminaOR]

So, I'm a dingbat today. I've got a new to me upper, in 300 blackout. I got a new Warne mount. I mounted a cheap but reliable scope in the mount. Then popped it on top of the upper. Forgot to torque the nuts that clamp the mount onto the upper.

I was trying to sight it in, results weren't very good. Finally figured out I'd forgotten to torque the nuts down and they were loose, tightened them as tight I could with my fingers, just about finished sighting it in with much better results. Still not quite as good a group as I'd hoped for though. Anybody have any experience with having rings or mounts finger tight and then tightening them, groups shrink? How much does a scope have to shift for groups to open up?

Thanks,
Bryan

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[DieselScout]

Depends on the yardage and how loose. If the mount was loose while shooting or only finger tight, I would throw out my results and start over because frankly they mean nothing.

 

[ron]

In my experience a rifle will not group with loose mounts.
Consider barrel breakin not getting the best groups to start
out with. Also you need to find what load the rifle will group
the best with. Bullet selection can make a big difference. I
know nothing about 300 Blackout round. I am referring to
experience with the AR and 5.56 caliber.

 

[Sgt Nambu]

Seriously, if the scope is shifting, just start over!
Take a look on utube, there can be much more involved in mounting a scope than stickin' her on and torquing her down!
Good luck with your new rifle!

 

[WillaminaOR]

The barrel is broken in. It's a used barrel. I'm trying to evaluate accuracy to decide if I want to keep it and sell my current one.

The group shown is at 100 long paces, the squares are about 1/2", so even then accuracy is not terrible, it's just not great. It was fair when I started, then the mount loosened up and it went to pot. I figured out what I'd done and finger tightened the nuts and started getting something resembling groups again. I'm mostly just wondering if someone has had a rail mount and a similar snafu and seen their groups tighten up when it was properly torqued. Or, it didn't seem to move just finger torqued, but I'm sure it could have been, so I'm wondering if someone knows how much of an imperceptible shift would open a group by 1/2"-1"?

Thanks,
Bryan

 

[Member 5605]

That looks reasonable for i assume factory loads?
Also let's count the scope too. Your crosshairs cover how much real estate at 100 yards? That difference could be the error in shooting. For the sake of shooting I'll exclude the flyer. Everyone has one of those.

Recoil is low on those anyway. I've seen my own firearm shoot a 2' pattern with a loose scope mount.

What you have going for you is the grouping. If it was random and sporadic then I'd be concerned; as it sits nope.

 

[WillaminaOR]

Those are hand loads, not loaded specifically for that gun though. 125gr Hornady SST over a near max charge of Enforcer and a CCI 450 primer I think.

In my other gun, they group right about, maybe just over an inch.

My other upper has a 4140CM CMMG barrel I believe, this is an AR Stoner lightweight stainless. It's a bit fancier, more expensive barrel. I like the light weight and less worry about corrosion. If it groups as well or hopefully better than the CMMG, the CMMG will be for sale.

Bryan

 

[oknow]

Seriously, if the scope is shifting, just start over!
Take a look on utube, there can be much more involved in mounting a scope than stickin' her on and torquing her down!
Good luck with your new rifle!

Like lining up the rings so they are straight in line with each other.

 

[rick benjamin]

http://www.brownells.com/gunsmith-t.../sinclair-scope-alignment-tool-prod36960.aspx
http://www.brownells.com/gunsmith-t...nclair-scope-ring-lapping-kits-prod36022.aspx

 

[WillaminaOR]

I know it's still possible that the rings could be out of alignment, but it's a one piece Warne x-skel mount, unless it's bent they should line up.

What wasn't properly torqued was the two nuts that clamp the mount to the rail.

Bryan

 

[twowheels]

POI shift for certain. You get POI shifts just changing torque. You slung ammo, you didn't sight in your rifle.

 

[Member 38843]

I had something similar happen. New mount on my AR wanted to go out to 100yds. damn thing came loose after 7 rounds. the spread was the entire 11x17 page.

 

[2506]

The barrel is broken in. It's a used barrel. I'm trying to evaluate accuracy to decide if I want to keep it and sell my current one.

The group shown is at 100 long paces, the squares are about 1/2", so even then accuracy is not terrible, it's just not great. It was fair when I started, then the mount loosened up and it went to pot. I figured out what I'd done and finger tightened the nuts and started getting something resembling groups again. I'm mostly just wondering if someone has had a rail mount and a similar snafu and seen their groups tighten up when it was properly torqued. Or, it didn't seem to move just finger torqued, but I'm sure it could have been, so I'm wondering if someone knows how much of an imperceptible shift would open a group by 1/2"-1"?

Thanks,
Bryan

I'd say you have WAY too many variables going on to evaluate the barrel's accuracy. Scope, mount, rings, not to mention ammo... Eliminate all those things, or at least make them consistent, then shoot for accuracy testing.

 

[jdaddy15911]

It's crazy to think about but minute of angle can change things dramatically. If your sight is 1/4" off at 10 yards, it will be 2 1/2 inches off at 100 yards, and 12 1/2 inches off at 500 yards. For this to be the case, your scope only needs to be .025 inches out of alignment on the rifle. That is about the thickness of a piece of paper.

 

[pakrat57]

.025 inches out of alignment on the rifle. That is about the thickness of a piece of paper.

Actually, a piece of standard printer paper is only about .004.

 

[jdaddy15911]

Actually, a piece of standard printer paper is only about .004.

Oh, that's right. Sorry, I forgot this is a firearms forum. I know how unacceptable inaccuracy data is here.

 

[DieselScout]

Geez in the 11 months since this was posted you'd hope the OP would have figured it out by now.

 

[Goosebrown]

I dud not tighten the pic rail to my rifle and was getting about 2moa dispersion right and left. Took me a long time to figure out

 

[jdaddy15911]

On the flip side, my son hit a shotgun shell dead center with a Ruger 10/22 at 50 yards on his first shot. After the shot we realized the scope mount had loosened, and the scope slid back until it was only hanging on with one claw.

 

[Member 5605]

.020" is 20" approx at 100 yards

Therefore:
.010" = 10" at 100 yards.
.005" = 5" at 100 yards.
.001" = 1" at 100 yards.

As per Leupold when I asked about a 20 MOA scope mount. Their response was the first line. Raise rear by .020" to get 20MOA at 100y.