Bolt nose recess ?

H

Hal

New member
What tool works best to cut the bolt nose recess on the back of a barrel on a Remington.

I was going to use a boring bar but the ones I have are to big or the angle is wrong.



Thanks
Hal
 
Hal

Grind your own. It takes a lot of clearance in every direction and grinding your own is about the only way I know of to get it. There are ready-made reamers but then you're bound to one diameter and it's better to fit the recess to the bolt nose, especially if you clean up the nose.

Ray
 
I just ground a tool out of a piece of 3/8 shank cemented Carbide. What you are cutting is a counterbore about .700 in diameter and about .150 deep. Remember, it also has to face back to the chamber diameter........jackie
 
Same here. A reground cemented carbide tipped boring tool. You can always run a 5/8" dia. end mill and finish with the boring tool, but I predrill the chamber first and always have enough room for the boring tool to cut the recess.
 
I use a Circle Industries 1/4" carbide boring bar with carbide tin coated inserts made for stainless steel. I think it has a .008" radius on the tip of each point of the triangle. Very seldom do you get to use each of the tips as they are pretty fragile and will usually break before you switch to more than one point. I normally cut the recess at about 1200 rpm taking about .050" per cut turning the compound parallel to the lathe bed feeding in to .130" deep on a Remington counterbore out in diameter to .705" and then finish it up to depth to have .010" clearance on the end of the nose.
 
Thanks

I ground a cutter out of HSS. A tapered long nose shape with a small radius.
It worked.

Hal
 
I use a piloted counter bore tool made for this cut. Just use the chuck in the tail stock and run into the bore the correct depth. I think you can get them from both PT&G and Dave Mansen.
 
I also use the counterbore tool with a pilot. Works real good. Make sure you do the counterbore before you cut the chamber.

Don
 
Do the counterbores come in different sizes? If not, how do you fit a bolt nose that's been trued and is smaller in diameter??

Ray
 
Cheechako said:
Do the counterbores come in different sizes? If not, how do you fit a bolt nose that's been trued and is smaller in diameter??

Ray
Click to expand...

PTG will make nearly any cutting tool they sell in any custom size the customer wants, but this is a simple job with a good boring bar and the boring bar can be used for so many things. I have several very small carbide bars and I use them for counterbores, cone breeches, pre boring chambers, and dozens of other uses. Expensive, but money well spent.

Scott
 
I don't think the bolt should touch the counterbore in the barrel. The counterbore is a safety ring.

Don
 
Absolutely you do not want the bolt nose to touch the counter bore this can cause accuracy and functioning problems. You need some clearance but not too much. The closer the fit the slower the gas will escape if you have a case failure, the larger the clearance the faster the gas will escape causing undue danger... When a primer ruptures the gasses blow out through the firing pin assembly. On Remington style counter bores I like between .007 and 005 clearance form the face of the bolt nose and front face of the locking lugs to their requisite faces of the counter bore with .010 total (.005 each side) clearance around the bolt nose. The counter bore diameter is easy to nail however the counter bore depth is a little tougher because you have to allow for the crush for the receiver and the stretch of the barrel shank. On cone breaches I like the same .007 to .005 clearance. Be advised that if you run your stuff this tight and a bristle falls off a cleaning brush, lands in the counter bore and you don't catch it, the bolt won't close, period.

Individual result may vary,
Nic.
 
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Ray it’s like this… If the bolt nose contacts the breach face and the case length from the head to datum is not exactly perfect then the cartridge floats in the chamber until it is hit by the firing pin. The firing pin drives the case forward until it hits the shoulder datum then it fires… sounds like a real good recipe for accuracy does it not? If the bolt face contacts the breach face and you get some chunk of crud in there it has to crush or swage some barrel material out of the way (the barrel is softer than the bolt) or the bolt won’t close, sounds like real good reliability plan does it not? The bolt has to have some clearance in its raceway in order to move. The firing pin is held back against spring pressure by the cocking piece and the firing pin block. These mating surfaces are at an angle (needs to be that way to work) and this angle when under pressure forces the back of the bolt up. This in turn forces the top, tip of the bolt nose out into harder contact with the breach face, is this just another one of the little accuracy inducing techniques?

So you asked do I have evidence of this? Yes I’ve seen it! Along time ago when the market had balloon head 6PPC brass in it and gunsmiths re-worked Remington actions, the Sako extractor conversion was created. You needed the extractor conversion done to extract the PPC case after you opened up a small bolt face bolt (the standard bolt face was already too big). Being a balloon head case you needed to have as little clearance between the bolt nose face and the requisite face in the breach as possible to produce an absolute minimum or unsupported brass so the case would not rupture. When properly done the extractor was placed back as far as feasible and the nose of the bolt was faced off to reduce the length of the unsupported brass and put the tip of the extractor in the counter bore. With the bolt nose clearance held to a minimum and a proper Sako extractor installation done folks were laughing and all was good in PPC land. Again this was done because folks wanted to shoot the 6PPC, the available brass was not up to the task and custom actions came at a dear price, not because Sako extractors were so “cool”. When people started reading about this stuff in magazines and at the range they had to try it. Sometimes a rifle didn’t shoot well, producing unexplained flyers and the regular culprits were investigated and they having been found innocent, help and answers were sought. I and a couple other gunsmiths I know have found the same thing, bolt nose contact. This took some time to discover because (at lease in my experience) this was not a hard contact issue but rather a slight interference issue. This bolt nose interference issue was probably because of the strong admonitions to “keep it close” and a poor working knowledge (read experience) of receiver crush and barrel shank stretch. When the bolt nose contact was eliminated so were the flyers.

I think that you should try it for yourself. Set up a rifle with the bolt nose contacting the breach face and report back how it worked out.

Been there, done that, wore out the tee shirt,
Nic.
 
WSnyder said:
Some additional thoughts on bolt nose clearance can be found in this thread:

http://benchrest.com/showthread.php?76905-Cone-Bolt
Click to expand...

The older thread discusses some builders that fit the counterbore close (.002-.003) specifically on actions that have been trued and have the threads re cut concentric to the raceway. I think there may be some validity to this. Many Remington actions have the bolt raceway looser at the front right behind the lugs than at the back. There still needs to be some clearance. I like about .003 - .005 front to rear clearance and some guys use a little more.
 
I nhave always just made the Remington Bolt Nose Counter Bore Dimensions like the Factory. If you get too "creative" in this area, it simply leads to problems down the road. Just my opinion......jackie
 
I will explain Nicks position a little differently. Back when they started chambering the 6ppc using standard remington breaching they figured out in a hurry that if they loaded on the warm side they would get a bright ring near the base of the case. With the semi baloon head this was the beginning of a catastrophic occurance! To get around this we had to get about .030 more of the case into the chamber. Whether you coned your bolt or didn't you had no choice other than a sako style extractor. When you took .030 off the bolt nose the rem. ext. wouldn't work any more. It may not have been the safest conversion but it was a hell of a lot safer than not doing it. At one point there quite a few of those conversions out there. I guess we were just lucky!
 
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