Ruger M77 and Vertical Stringing

[dak0ta]

Hey,

I have a 1987 Ruger M77 Tang Safety that will shoot a sub-Moa group at 200 meters, but at 100 meters, it strings a 5 shot group into a 4.5'' group. I am completely confused by this. I'm shooting factory Federal Vital Shok 165 gr ammo with the Sierra GameKing bullet.

I shot this sub-MOA 200 meter group back in August:

Yesterday, at 100 it strung bullets vertically at 4.5'' group. I then asked my friend to shoot it and he also got 2 shots very high at 100 meters. Then he shot 3 shots at 200 meters, and the rifle printed the first shot almost right under the bulls-eye by an inch, and his 2nd shot was horizontally strung 2'' to the left. The 3rd shot missed the target.

So I'm wondering if this is a rifle or ammo problem. We thought that perhaps the ammo is loaded to a higher velocity and performs better at longer range. Any ideas? The rifle hadn't been shot since last August, and it was cleaned and stored until yesterday.

 

[crazysccrmd]

Assuming you fired at the same point of aim that looks like a 4" group, not sub-MOA. Make sure the scope mounts, rings, etc are tight, maybe try a different scope, use other brands and weight of ammo, etc.

 

[notaglockfanboy]

Umm, that is not a sub moa group. I would check mounts, rings, and action screws and if it has been glass bedded, check for anything between the action and bedding. If it is shooting less than 2" at 200, then it is likely it would be shooting less than 1" at 100, if you are doing your part.

 

[dak0ta]

I'm only counting shots 4-6 as the group at 200 meters.

 

[witchhunter]

I am not understanding this, a rifle does not shoot better at a farther range. The BEST it can do is twice as big at twice the distance. If you shoot a 1 MOA group at 100, the best you can hope for is 2 MOA at 200. Try shooting an aggregate (5 each - 5 shot groups)and you will see how good or bad your groups are. One group does not define a rifle's accuracy. Not trying to be rude, just spouting math.

 

[crazysccrmd]

I'm only counting shots 4-6 as the group at 200 meters.

That's really not how it works. You can't pick and choose what shots you're going to count as a group and which you leave out. If that was the case everyone would have a sub-MOA rifle - shoot a box of 20rds and pick the ones closest to count.

Most importantly, your M77 is a fine hunting rifle and has hunting rifle accuracy which is to be expected. Any one of those shots would've killed a deer at 200yds. If you use it for hunting and not target match shooting don't get caught up in the tiny group craze.

 

[dak0ta]

You're right it's good enough for hunting. Just couldn't really explain what was happening at 100 meters from 2 different shooters. I know how to shoot, as I shot a 1/2 MOA group at 100 meters with a different rifle (needed to confirm that it wasn't my marksmanship).

I'm just wondering if it's worth trying to trouble shoot this rifle. My first instinct was to make some handloads and try other brands of ammo/bullet weights after making sure the action screws, scope mounts, rings are all tight. I don't really want to free-float or bed anything right off the bat.

 

[stiab]

That's really not how it works.

Actually that is how it works, soon as I saw the target I knew only #'s 4, 5, and 6 counted. All the others (except the labeled flyer) were for sight in purposes. You are not required to walk down range and put up new paper after you have made you scope adjustments. He sighted in, then shot a 1.5" 3-shot group at 200 yards, simple as that.

Open the floorplate and make sure the diagonal screw is tight.

 

[dak0ta]

Alright boys, did the math and measurements for the 100 meter target. Maybe you guys can help me out. The 1/2 MoA group at the Point of Aim is from a McMillan BR .308 Win rifle, but ignore that.

 

[redbullitt]

That lower group should help reduce doubt in the shooter at least lol.

Maybe we should dig into the optic setup a bit? Whats the optic and mounting situation? Hows the cheek weld etc? Sandbags or bipod?

You mentioned the rifle was cleaned and stored. That is a red flag for me any time i go out to shoot. I ignore all the shots until the rifle settles in. Cleaning it or oiling the bore can really mess with POI consistency.

 

[dak0ta]

Optic is a Bushnell 3-9x32. I just went over all the screws on the rifle. All action screws were tight. The scope bases could be tightened 1.5-2 turns on both the front and rear mount. The scope ring screws could all be turned about a 1/4 turn each. The crown looks fine.

I clean the bore after each range session. I do not oil it though, leave it dry. Fire one fouling shot before group.

 

[Andrew Leigh]

The Ruger may be a great rifle but not even a Ruger can deny the laws of physics.

Dak0ta, at 100 your aiming point is more defined, the winds barely will have an effect so all things being equal it is easier to shoot at 100 yards. Clearly you can shoot if that was your group with the McMillan. The Ruger does not understand if it is shooting at 100 or 500 yards so the rifle will not arbitrarily shoot poorly as closer ranges.

A loose stock also does not understand range neither does a loose scope so all these are factors I would find unlikely.

I am only left with that you may have a scope with an adjustable objective that is set for 200 or more yards and you have forgotten to set it when coming back to the 100 mark. So parallax may be your problem.

Oh and on the McMillan group .... I see some white target between the 3 shots and the 2 shots, little disappointing not to see one big hole .

 

[dak0ta]

Just had to rub it in eh?

Yeah I was annoyed at myself for those last 2 shots that printed to the right. I need to practice more.

The scope is one of the Bushnell 3-9x32s that came with the rifle. I zeroed the 200m at 9x, but was shooting at 100m using 4x. There is no parallax adjustment. Is this the problem?

 

[crazysccrmd]

Between those two targets it looks like the rifle is doing what it should. A 2.8" 100yd group becoming a 4" group at 200yds is not uncommon. If the 100yd group showed a clearly defined tight cluster and then you fired a 200yd open group like pictured I would question it. Since that isn't the case I'd assume the combination of that ammo/rifle/shooter is about 2 MOA. My suggestion is still to try other brands and weights or work up some hand loads for it since you checked out the mechanical aspects of the rifle.

 

[dak0ta]

For hand loading, should I pick a bullet weight that suits the rifling twist rate? I want to use the 165 gr as it sits nicely between 150 and 170, and can take Whitetail and Mule Deer. I was thinking of using some Nosler Ballistic Tips.

 

[Andrew Leigh]

I am not sure that you are comparing apples with apples.

Firstly on the parallax, as you have no setting on the scope the scope is generally pre-set to be parallax free at 100 yards, at 200 you will not notice a difference, in any event parallax is insignificant with scopes having a max of 9X magnification.

To do this test correctly you need to clean your barrel well, shoot 3 fouling rounds and with the scope set at 9X, and keep it there, shoot a 5 shot group at 100 and then 200m allowing cooling time between shots. Do not discount any shots as flyers etc.

Dialing back to 4X altered your sight picture and reduced the aiming resolution which may account for the problem.

What is confusing is I have never seen a vertically strung group in descending order? I am assuming the shooting rest etc. did not change between groups? There are many reasons for vertical stringing but then this would be magnified at 200yards which it is not, on the contrary you are laterally stringing at 200.

Are you touching the barrel when shooting?

 

[dak0ta]

I'm going to hope and see that tightening the mounts and scope rings will fix the issue

 

[Andrew Leigh]

Not a bad idea but why would they be loose at only 100m and not 200m?

 

[dak0ta]

I think the 9x at 200m and 4x at 100m could be it? Will also try some Rem 150 gr Core-Lokts that I have.

 

[southern_grudge]

The biggest issue with a ruger m77 is the angled locking lug. I think the factory called for something like 90 inch pounds which is really about as tight as you can get a screw with a screw driver. That's what my money is on.