Ruger M77
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Welcome to Rugerforum.net. Please go to the welcome member section in the lobby and introduce yourself. I'm going to leave the answer to your question to the Iowegan, since he is our gunsmith. 
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Headspace is the distance between the breach face and the case head. There are three case types that all headspace differently. The rimmed case (ie 30-30 Win) uses the rim of the case to restrict how deep the cartridge will enter the chamber. Belted magnum cases (ie 7mm Rem Mag) use the belt to hold the case from going too far, and rimless cases (typical of most common cartridges such as a 308 Win, 30-'06 Sprg, etc) are a little tricky. They use the tapered shoulder of the case (just behind the straight neck) as a datum point. This means the distance from the datum point to the case head must be the same as the dimensions of the actual chamber with a token amount of "play".
With the first two types, the only way to adjust headspace is to ream the chamber deeper if headspace is to slight, or cut the barrel back then ream the chamber to specs and screw the barrel in.
With conventional rimless calibers, the process is similar but usually not needed unless headspace is way off. Most gunsmiths like to see about .005" of headspace in all rifles. Lets say your gun has .002" of headspace. This means some factory ammo may not allow the bolt to seat without pushing it very hard. Accuracy or case life won't be an issue but you may have to find ammo that will chamber normally. If your headspace is too much (let's say .010") case heads will separate, case bodies may split, and accuracy will suffer.
The simple fix for rimless chambers is to reload. In a tight headspace guns, you may have to grind a bit off the shell holder to get the case pushed into the sizer die far enough. With excessive headspace, you can buy new brass and shoot a very mild "fire form" load. The case will stretch to fit the chamber without splitting or head separation. When sizing, back the sizer die out to get the proper shoulder set back.
So the real answer is: It depends on the cartridge and weather you have sights or not. You wouldn't want to screw the barrel in a quarter turn and have the sights at 9 o'clock. Besides, the lock lugs have to line up so at a minimum, you have to screw the barrel in one full turn. As I recall, each turn is about .014" so unless the gun is way off, you will end up cutting the barrel back and reaming the chamber. In all cases with Mod 77s, a good gunsmith or a trip back to the factory is required. It's way more than just tightening the barrel a little.
Could you explain why you think your headspace needs to be adjusted? What cartridge is your 77 chambered in? Are you getting head seperation or split cases?
With the first two types, the only way to adjust headspace is to ream the chamber deeper if headspace is to slight, or cut the barrel back then ream the chamber to specs and screw the barrel in.
With conventional rimless calibers, the process is similar but usually not needed unless headspace is way off. Most gunsmiths like to see about .005" of headspace in all rifles. Lets say your gun has .002" of headspace. This means some factory ammo may not allow the bolt to seat without pushing it very hard. Accuracy or case life won't be an issue but you may have to find ammo that will chamber normally. If your headspace is too much (let's say .010") case heads will separate, case bodies may split, and accuracy will suffer.
The simple fix for rimless chambers is to reload. In a tight headspace guns, you may have to grind a bit off the shell holder to get the case pushed into the sizer die far enough. With excessive headspace, you can buy new brass and shoot a very mild "fire form" load. The case will stretch to fit the chamber without splitting or head separation. When sizing, back the sizer die out to get the proper shoulder set back.
So the real answer is: It depends on the cartridge and weather you have sights or not. You wouldn't want to screw the barrel in a quarter turn and have the sights at 9 o'clock. Besides, the lock lugs have to line up so at a minimum, you have to screw the barrel in one full turn. As I recall, each turn is about .014" so unless the gun is way off, you will end up cutting the barrel back and reaming the chamber. In all cases with Mod 77s, a good gunsmith or a trip back to the factory is required. It's way more than just tightening the barrel a little.
Could you explain why you think your headspace needs to be adjusted? What cartridge is your 77 chambered in? Are you getting head seperation or split cases?
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17,226 Posts
Got this email from Bodine 40 "I HAD MY ORG. BOLT STOLEN AND I BOUGHT ONE AT A GUN SHOW FOR THAT GUN AND ITS
HARD TO CLOSE THE BOLT. THANKS JEFF"
This would be more of a lock lug issue than a headspace problem. What I would do is "smoke" the front bolt lugs with a magic marker, seat the bolt, then remove it. Look for "witness marks" where the lugs made contact with the internal lugs. Likely you will have to remove a little metal from the rear of the bolt lugs. This should be done a few file strokes at a time until the bolt seats properly.
Actually you are lucky to find a slightly oversized bolt. My luck is to find one that does the floppy chicken. Not a safe situation.
HARD TO CLOSE THE BOLT. THANKS JEFF"
This would be more of a lock lug issue than a headspace problem. What I would do is "smoke" the front bolt lugs with a magic marker, seat the bolt, then remove it. Look for "witness marks" where the lugs made contact with the internal lugs. Likely you will have to remove a little metal from the rear of the bolt lugs. This should be done a few file strokes at a time until the bolt seats properly.
Actually you are lucky to find a slightly oversized bolt. My luck is to find one that does the floppy chicken. Not a safe situation.
I have a Ruger 77 bolt that essentially is brand new. I bought a .22-250 varmint probably 30 years ago. It shot so bad I sent it back to Ruger, but somehow forgot to send the bolt. They worked on the gun and sent it back with a new bolt! I have no use for it. If anyone does, it's theirs.
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17,226 Posts
sheepdog, Sometimes bolts will interchange in other gun, depending on how much material was removed from the lugs when factory fitted. In Bodine 40's case, the tighter bolt should be able to be fitted in his gun. It doesn't always work out this way. Also, the bolt face is made for a "family" of cartridges. Any short action case such as a 308 Win, 243 Win, 22-250, 7mm-08, etc will work. Cases such as 223 Rem would not interchange with a 22-250 bolt.
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rman, I'm new here but have been on the "other Rugerforum " for several years. The email is disabled for me here but I'd like to take you up on your offer for the extra bolt.
If you say OK we can figure out how to communicate. Thanks, OldRugerMan
If you say OK we can figure out how to communicate. Thanks, OldRugerMan
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269 Posts
That's an old thread (back in 2006) you responded to. I'd be surprised if that bolt were still around. Never know however!!
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