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2K views 27 replies 5 participants last post by  Vic 3 
#1 ·
I'm new here, and maybe this has been answered. If so, sorry--please point me to the post. I searched and didn't find it. Also, I am NOT a gunsmith, but I'm looking for expert answers.

My M-77 with Hornady Precision Hunter, 162 grain, on a sled, produced a 3 inch group at 100 yds, six inches (if you call that a group) at 200, and was crazy at 250. Last year I had the barrel floated and put in a Timney trigger set at 3lbs. Has a new Leupold 3-9x40, bought last year, professionally mounted. I'm the first owner, babied it all these years. Didn't use it for 20 years while deployed in various places, so it's fired 300 rounds or less. Now back to hunting. Somehow I never noticed its low accuracy before.

Why the HECK is it a 3 inch group at 100yds? I suspect it is a poor barrel design or poorly manufactured. Does anyone know? Has metallurgy and manufacturing advanced in the last 35 years?

I did see an "M-77 accuracy tip" post that describes how to file the mag box so it's a little loose. I'm going to do that. But I'm wondering if current manufacturing quality is much better now and I should just sell this and buy a new one.

Is Gunsmithing the right area to post this?

Thanks for any advice.
 
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#3 ·
I'd try shimming the barrel after you try the mag box mod(if your going to) not all barrels like to be "floated".
 
#5 · (Edited)
First your rifle has a Wilson barrel.........they were hit and miss in the accuracy department.

Are you torqued to 90 IP? This does make a difference. Have you tried to torque tune your rifle? This generally helps. It’s unusual to see a 7Mag NOT shoot heavier bullets due to the rate of twist. I’m fortunate, mine will shoot light or heavy but I had to do some load development.

My buddy uses the same round in his and it’s lights out out to 600yds. I’ve shot them in mine with similar results.

ETA; Hornady didn’t randomly pick the 162gr bullet for their Precision Hunter line, it’s an ideal weight for the caliber.
 
#7 ·
I stand corrected, it is 95 IP...........90 would do the trick though too. As far as the middle and rears screws, throw both those numbers out the window and here's why. When I asked if you had "torque tuned" I was talking about something specific, totally unrelated to torque specs.

Torque tuning is a process that one does as they are shooting their rifle. Lets address the center/front trigger guard screw, that screw need only be tightened enough to hold it in place......nothing more. Now on to the torque tuning part. When you are at the range back the rears screw all the way out, and screw it back in until you feel it bite. Now stop and take a couple of shots, (2 or 3 your choice) and see how they group. The group any better? No? Screw it in a little more and repeat. Repeat this process until the groups tighten up........I have 4 M77's and have done this to each one and they are all sub MOA shooters if I do my part..........My 7 Mag will print .75 MOA.
Yes it's time consuming but it will pay off in the long run.

One more suggestion I have and would do before I went back out would be a good cleaning with some Bore Tech C4 for the carbon and JB Bore Paste for the copper. Barring a bad float job I can't imagine you barrel being shot out at 300 rounds. A buddy had a rifle that started looking like a shotgun test pattern and was about to sell it and told him to give to me and let me see what I could do with it..........turns out it was severely cooper fouled. A heavy dose of C4, Butche's Bore Shine and some JB and it was back on target.

If I didn't make the tuning process clear let me know.
 
#16 ·
Vic, here's a little info on the difference between a G1 and G7 drag profile. This was more than likely compiled by Bryan Litz, he's the chief ballistician at Berger bullets. He was the driving force behind the G7 model. Bryan has at least four books to his credit that I know of, he's a member another forum I'm on, (which is kind of nice), and he's also a member of the 2 mile club. Did I mention he was a rocket scientist for US military? He's the reason that Nosler and other companies lowered their G1 BC's..........He ran the tests and called BS. I don't think there is anyone more knowledgeable when it comes to ballistics than Bryan.

There are more links within the one I posted at the bottom, enjoy.


 
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