Bolt Lift

Years ago

A man by name of phil jones told me to emery your chamber other wise cases will stick like two pieces glass together bill brawand 40 yrs ago
 
bbrawand said:
A man by name of phil jones told me to emery your chamber other wise cases will stick like two pieces glass together bill brawand 40 yrs ago
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Bill, I know Phil Jones in Oz, but he ain't quite that old.
I always do a light lap of my chambers with 320 emery on a wooden dowell.
 
I re cut a lot of cocking cams, I have done it in about every popular Br action. Theres a lot in the geometry of that cam that can really smooth out the lift cycle. However I am usually doing it for a different reason, but not always. If you tell me what action you have, I can tell you if you can improve the cam, probably not. Polishing and lapping are minor things that may help you a little. But the vast majority of bolt lift is cocking cam geometry and spring. In some designs the cocking piece can add a lot of friction as well. The problem with reducing bolt lift is usually you have to do things that may have a negative effect on accuracy like, reducing you firing pin spring force. Or if you reduce the cocking cam helix angle, then you will need cock on close to get your firing pin fall back, not something I would do. Some of the new PRS actions have taken this approach,(shallow cocking cams&low pin fall) they have extremely weak ignition but they sure are easy to cycle. You wont see this catch on in BR.
The action you are referring to I believe is an older CM Bat with a roller cocking piece. Bat used to run a light spring 18-19lb and with that roller, it just wont get any easier to open. However, firing pins, springs, and fall are increasing, and for good reason.
Alex Wheeler
 
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Bolt lift

I currently own the rifle that Charles was using in the video, it opens like butter, by far the smoothest action I own, not sure what Charles did with it to get it that way but the firing spring is around 21-22 lbs. Only time it gets hard lift is when the brass is getting old or someone loaded it a little hot? ;-) Boy can I tell the difference when I work the bolt on my 3L, its one that DS set up too...
 
It might be interesting to catalog all the places that rub when an action is cycled, and look into how the friction could be reduced at those points.

There are some places that are not so obvious. For instance, when you compress a coil spring it has to slide a little around its longitudinal axis. This is the reason for Tubb's two piece striker spring. It eliminates the friction of the ends of the spring rotating against the surfaces that they contact.

If one polished the ends of the spring, and the surfaces that they bear on , and applied a little grease, that little bit would be reduce in applications where a two piece spring is not available.

The angled contact between the cocking piece and the top lever of the trigger causes up force as the striker spring is cocked. Every point of contact that restrains the cocking piece, striker, shroud and bolt from moving up receives that pressure and friction at those points is increased in proportion to the force required to compress the striker spring.

Another place where striker spring pressure increases friction is where the backs of the lugs contact their abutments, both as the closing cams pull the bolt forward, and as the flats of both the bolt and the abutments slide against each other.

In some if not all cases. polishing, a better lubricant, or some sort of surface treatment or coating might significantly reduce friction, and of course there are also modifications of the parts or designs that have that have that potential. Roller cocking pieces come to mind, as does reshaping cocking cams.
 
Keep 'em coming Boyd...... ;)

And who better the embark on the voyage of "interesting to catalog all the places that rub when an action is cycled, and look into how the friction could be reduced at those points." than a certain Boyd Allen?? I know you've a more than passing interest in this subject......

bumps? rings? eccentric bolt?

delrin shrouds?

shimmed flats??

flutes VS smooth?

straight bolt hannle?

deflexed?

reflexed ala XP100?


?????

give a liddle??

LOL!

al
 
I think that we can look at a couple of areas to start. We know that there has been a lot of work done on the outsides of bolts to reduce friction. Beyond durability there is the issue of heat. Some processes are done at temperatures that would modify the heat treat of the bolt, or in the case of a factory Remington bolt, possibly cause a problem with the head to body joint. This is where we pause and solicit comments and experiences. I think that it is better not to try to discuss too many things at the same time. But since I did say a couple of things let's throw in a wild card. What about the inside of the action body. Should some areas be off limits. For example would super slick threads and action face have a destabilizing influence on the barrel to action joint? I am reminded of Harold Vaugn's experiments using different materials in this joint. Pause tape, wait for response....
 
Inside the bolt is a big one.... a couple of the action makers have given me the run-down on that one. I am told it's a 3-6hr job doing it by hand.
 
Boyd Allen said:
Doing exactly what by hand?
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Spinning up a dowel with sandpaper in successive grits, buffing and polishing the interior of the bolt to a mirror finish, then working with the spring as you touched on. I've never done the whole "polish the inside the bolt manually" thing but I remember feeling it would be a multi-hour process. One maker called it "the single biggest thing"
 
I was curious about this 15 - 20 years back, so I colored the whole pin and spring in front of the shroud of my Viper. After a trip to the range, none of it had rubbed off of the spring or the shoulder that it rests against near the front of the pin. On a viper, the pin tip stays in its bore through the entire cock and fire cycle. I had heard of polishing the inside of a bolt before so I wanted to know if that was needed, apparently not....for that bolt. I have never done this on any other action....you?
 
Boyd Allen said:
I was curious about this 15 - 20 years back, so I colored the whole pin and spring in front of the shroud of my Viper. After a trip to the range, none of it had rubbed off of the spring or the shoulder that it rests against near the front of the pin. On a viper, the pin tip stays in its bore through the entire cock and fire cycle. I had heard of polishing the inside of a bolt before so I wanted to know if that was needed, apparently not....for that bolt. I have never done this on any other action....you?
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Great Test!!! wish't I'da' thoughta' that!

Same with my Borden's though. "Captured" the whole stroke.

I have never polished the inside of even a Remington..... I've gotten satisfaction from the outside work.

I maybe will go look through PS, I seem to recall an article on smoothing a bolt action up.
 
Be careful. Some of what was written in the past was like use grinding compound of the shroud threads and other places. It may have smoothed things out, but as you know there are other considerations. One thing that you could set up in your shop to do is done commercially, and was done on the Viper bolts right at the beginning. Here is a link to a business that does it.
http://www.microsurfacecorp.com/ws2...thH0AtVmN-MqwyFUhH0ZqmeLMlDxSAThoCNcAQAvD_BwE
I believe that it is impacted into the surface of a dry clean part at about 120 PSI. Of course I would have a small cabinet with built in gloves similar to what is used for glass beading or sand blasting. I would not want to put that stuff into air that I was breathing as part of an air jet.
Some years back, I had some of the powder that I had gotten for a bullet coating experiment (that I never got around to) and I tried rubbing some into the mating surfaces of an old Hollywood powder measure. the outside of the drum and the main casting bore that it ran in. I had cleaned the surfaces of all powder residue and worked the powder into the metal vigorously with a surplus .30 cal. cleaning patch. Wow! did that make it slick when I put it together. It did not last forever, but then I did not apply it like the process above.
 
bolt lift

For alinwa: You have certainly packed a lot of information into your post #8 above. Thankyou.
You might have raised more questions than you answered: rebuilding the cocking ramp, ball bearings, etc.

I know this is an old thread, but the info is timeless.
 
shooter86314 said:
For alinwa: You have certainly packed a lot of information into your post #8 above. Thankyou.
You might have raised more questions than you answered: rebuilding the cocking ramp, ball bearings, etc.

I know this is an old thread, but the info is timeless.
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thank you for your kind words :)
 
Over time

Greyfox said:
I'm probably exposing myself to criticism here. I enjoyed the video, but was left wondering. That appeared to be a Whidden die which I'm told are very good and are on the spendy side. If one is going to spend big $$ on a die, why wouldn't one get a die that fir the chamber properly? Why would I need another die, such as a ring die to do what the primary size die should have done? Really not trying to be a smartass, but inquiring minds want to know. Since I took Al's advice years ago and started having my reamers ground for "fat butt" chambers, my extraction problems have disappeared. I never have bolt click even with substantial loads. Pretty sure someone will chime in here and straighten me out, so I have my asbestos suit on.

Rick
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Do the cases expand to the size of the oversized butt area in the chamber? Have wondered about that.

Pete
 
Boyd Allen said:
I was curious about this 15 - 20 years back, so I colored the whole pin and spring in front of the shroud of my Viper. After a trip to the range, none of it had rubbed off of the spring or the shoulder that it rests against near the front of the pin. On a viper, the pin tip stays in its bore through the entire cock and fire cycle. I had heard of polishing the inside of a bolt before so I wanted to know if that was needed, apparently not....for that bolt. I have never done this on any other action....you?
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Here’s a couple thoughts/ observations that I think can help, can’t hurt.
On all bolt interior parts…. Pin, spring, bolt interior, I apply Anschutz Ceramic(Keramic) which if one follows directions, leaves no residue, penetrates the metal, and slicks things up nicely. Try some, wipe down bolt body, interior action. You will be impressed how slick things get and how long it lasts……again, nothing to gunk up over time.
Lasty while installing a couple Kip springs on actions I decided to chuck up the pins in the mill, chucking the pin and indicating the body. While I suspect there is not a ton of friction on the pin itself, you’d be amazed how far off some of these things can be, I was startled. On a long pin I got them down to lass than .001” and they were several times that.
The Ceramic, been using a couple years on RFBR actions where ignition is super critical and any drag can kill you.
 
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