1976 M77 questions for project gun.

Gos · Sep 16, 2014

I've been doing some searching and coming up empty on several websites, so here's to hoping....

I picked up a 1976 Ruger M77 in 30/06, used but not abused as a project gun for the upcoming winter. My thought is to either make it into a three barrel gun with interchangeable barrels, 25/06, 30/06 and the 338/06.
Or, open up the bolt face and make a 338 Dakota out of it.
Problem is, I'm unable to find any information on Ruger bolts. A phone call to the company was not helpful.
What I'm hoping to learn is this.
Can the bolt face be opened up for safe operation with a Jefferies based case? Is there any difference between a standard bolt and a magnum bolt other than the bolt face? Are the actions different in strength? I know they are longer, but are they larger?
Hopefully someone here will already have "been there, done that". I'm just coming up empty on any drawings or real data.
I have a sweet spot for those old tang safety M77's, so I don't want to screw it up, or get someone hurt.
Thanks,
Gos

abarnsley · Sep 20, 2014

Whenever you change the shape of a cartridge from the stock one..

The feed rails in bottom of action need to be modified..

You only get one shot.. Too wide and cartidge feeds too high, hits top edge of chamber..

Instead of messing around with oddball calibers..

Use a standard off the shelf cartridge, near wanted performance level..

Animals do not care when hit with 150 FPS less.. They still die..

I live in.... Big Game country, if I need ammo after a boat turnover, nice knowing local gunshop will have it...

M77's are fine hunting rifles.. Not a ton of aftermarket parts available.. Leave them stock, go hunt, quit messing around..

Opening up bolt face, means increased bolt thrust.. Simple physics..

The Ruger action bedding system SUCKS...

Not even my 10th choice for a switch barrel...

wesg · Sep 23, 2014

Never bothered to look at them close, but it seems to me both my magnum and .308 bolts are both about the same diameter as a M-700. I don't think the bolt lugs are going to care if you open the bolt face up. Same goes for the action profile. Seem to be the same, but I never measured anything. Seems they'd have been screwing themselves royally if they'd designed the things so the stock inletting was different for a standard vs magnum long action.

Bigger drawback to this action for a larger cartridge, IMO, is the 1" barrel thread. Same as a M-70, and they've gone to a fine pitch thread to beef up the barrel shank a bit.

kendog · Sep 23, 2014

abarnsley said:
Opening up bolt face, means increased bolt thrust.. Simple physics.....

Can you explain this? I'm not a physicist.

GGaskill · Sep 23, 2014

Larger bolt face equals more area. Pressure times area equals force.

kendog · Sep 23, 2014

GGaskill said:
Larger bolt face equals more area. Pressure times area equals force.

Smarty Pants.

Thanks!

The Dakota case has the same head size as the 300 H&H case, which is the daddy of a whole lot of belted cases. Would the bolt thrust be withing the design limits of the action, seeing as how it has been chambered in a slew of "magnum" chamberings?

Gos · Sep 23, 2014

wesg said:
Never bothered to look at them close, but it seems to me both my magnum and .308 bolts are both about the same diameter as a M-700. I don't think the bolt lugs are going to care if you open the bolt face up. Same goes for the action profile. Seem to be the same, but I never measured anything. Seems they'd have been screwing themselves royally if they'd designed the things so the stock inletting was different for a standard vs magnum long action.

Bigger drawback to this action for a larger cartridge, IMO, is the 1" barrel thread. Same as a M-70, and they've gone to a fine pitch thread to beef up the barrel shank a bit.

Very sorry to ask an imposing question, but any chance you could measure both bolts and see what the differences are if any? I'm still leaning toward the 338/06 but not committed 100%. The barrel is still in route, so I have time and this is a winter project.
Thanks,
Gos

wesg · Sep 24, 2014

I can measure the magnum bolt easily enough. Not even sure which safe the .308 is buried in, or whether it's in a box in a closet somewhere. Speaking of which, anyone want a .308 flat bolt as new in box? ;-) Assuming I can find it.

Body diameter: .694
Lug diameter: .927
Lug width: .403
Lug length, left: .650
Lug length, right: .395
Bolt face diameter: .540 (but some idiot re-machined this ;-)

Gos · Sep 26, 2014

Very sorry for the delay. Been on 70 hour weeks for the past month. Just about burnt out by the time I get home.
So, your measurements are EXACTLY what I'm looking for. Compaired to my 30/06 bolt:

Body diameter: .694
Lug diameter: .930
Lug width: .402
Lug length, left .652
Lug length, right .400
Bolt face dia: .505

So, the answer is that both the 06 based case bolt and the belted magnum base bolt are the same, except for the bolt face.
Thanks again!

Gos · Dec 16, 2014

Just a quick update:

Cut the barrel threads today, 1-16 but messed up on the timing of the barrel's natural arc to be in the raised position. I'll do some barrel straightening later. Settled on a wildcat, the 338/375 Ruger.
I gave up on the Dakota when it took two weeks just to get someone there to provide me with a cost sheet on brass and dies. Way to expensive for what little gain there is.

I'll post some pictures when it's further along. Waiting for the reamer now.

Gos · Dec 24, 2014

Had some time today, so I dialed in the bolt and opened it up for the new case. Went to .536". Still in need of deburing.

Also, took a couple of photos of the old .270 against the 338-375 Ruger for anyone interested in seeing the match.

tdmidget · Dec 24, 2014

"natural arc"? You mean like "bent"? :skep:

Gos · Dec 25, 2014

tdmidget said:
"natural arc"? You mean like "bent"?

"Bent" is such a strong word.
Every barrel I've ever messed with has a very slight warpage or out of center to the OD in it. I try and finish my barrel threading so that the natural bow of the barrel is in the vertical up position.
I've noticed that the new batch of beaded finish barrels on factory rifles seem to be worse than in years past. Howa and Tikka tend to be some of the straightest and best centered barrels. Others can be quite "interesting" for out of center and out of round.
Once out of the lathe, I'll see what mine looks like and address accordingly.

Gos · Jan 1, 2015

Finished reaming and polishing out the chamber last night. I have .003" worth of headspace room using the 375 Ruger Go Gage. With .0005 worth of finished assembly crush, it will be just fine.

Gos · Jan 4, 2015

Barrel all screwed in tight. Spent some time tonight milling in a much larger barrel groove in the stock. Still have some left to go. Ended up trimming it back to 27.5". Dies ordered today, so perhaps by the end of the week there might be smoke & flame comeing!

Gos · Feb 1, 2015

One day of shooting and load development down.
The two loads I've played with so far, are the Barnes 250 solid and the Hornady 200gr.
I stopped with the 200gr. when I hit 3100fps as it seems to be too fragile and separates on impact.
The 250gr. Solid however was pushed up to 2970 before I could measure .0003 head expansion. I have cycled some cases through for 6 loadings without any issues with that load. It's fast enough for what I was after for a solid.
I've some 225gr. Barnes coppers on the way for putting together a hunting load. Hope to be developing that one by the middle of the week. No external pressure signs exist at any of the loads, as .0003 is not yet a visible amount, or one that affects primer pockets.
So far, it's quite the thumper punching through 18" diameter trees with that solid. Sort of the brush gun from heck.

I settled on a .05 recess on the muzzle, with an 11deg taper. Looks pretty clean that way.

Gos · Feb 7, 2015

I’ve come across something that has surprised me.
When I started out working up the 225gr. Barnes loads, I hit maximum pressure way before what measured out to be maximum pressures for the 250gr. Barns Solid. I’m sure the difference is that the solid is a brass alloy, while the 225gr. are copper. The difference was 80grains for the 250, and only 76grains for the 225. I get the idea that there is different coefficients of friction between the two materials, but in the Barns Loading Manual, there is do differentiation between copper and brass bullets of the same weight.
I’m in need of some sunshine to progress further. Nothing but rain and clouds.

GGaskill · Feb 9, 2015

Maybe try moly coating the copper ones?

sticks · Feb 10, 2015

If the brass solids are 'bore riding' (reduced diameter forward of the driving bands to 'ride' the lands) it's tantamount to having much more free-bore.

A longer 'jump' delays peak pressure, as is prescribed by Wby for all bullets and by Barnes for most of their monolithic fare.

Moly-coating may reduce friction/pressures enough to demand a different powder or workup for each load. (Alternating between coated & non-coated may also add to arguments regarding the worth of using moly at all.)

If you have/use Hornady's COL tool, engage it to determine what distance from bore lands each pill is seated. On the banded solids the bullet may be nearly out of the case by the time the front driving band is able to engrave on the rifling.

gzig5 · Feb 10, 2015

Looks like fun. How's the recoil? Muzzle brake? I'm somewhat new to belted magnums, never had one for 25 years and now I have two in last six months. Recoil isn't as bad as expected with a decent stock design in a 300 WM with 180's. I'm interested in trying something with bigger and smaller holes... Seen some interesting wildcats on the 300/338 Norma case which I think is fatter than the Ruger.

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