Lug lapping

[Eric in NC]

So aren't the bolt heads just surface hardened? And if you lap them, wont it make the mating surface soft?

[1jonzmith]

So aren't the bolt heads just surface hardened? And if you lap them, wont it make the mating surface soft?

Eric, Can SS alloy be surface hardened? I don't know. Is that the proceedure, surface hardening, that Savage employs? When I finally get to talk to the engineers I will answer with what they say.

Till then,


John

[1jonzmith]

I guess I need a more stable platform to measure my bolt and action. The difference in depth of the ramps from my Trued action rim to the ramps varies between 6 thou to 1 thou. I don't trust what I am doing and I will get help from my Smith to get real numbers. It seems that there is variance between the bolt lug thickness and from the front of the lug, the center and the rear. The ramps look to be uneven. A lot of stuff sure needs to jump into even contact when that puppy lights off. Not my thoughts.

Maybe Monday....we will see,

John

[nsaqam]

C'mon guys, it's folly to think that a Savage doesn't benefit as much as any other rifle from having everything in perfect perpendicularity to an axis drawn through the centerline of the bore.
Sure the bolthead floats a bit, but the boltface doesn't in relation to the bolthead. If the bolthead is tipped due to uneven lug abutments then the boltface, which is what really matters, is also tipped out of perpendicularity to the bore C/L.
The exact same procedures done to a 700, barrel threads recut, lug abutments trued, mating surfaces of the lugs trued, and boltface trued, will benefit the Savage as well.
Savage makes it easy to cut the small shank threads to the large shank size and still be able to utilize prefit barrels if that's what you wish to use. The Savage is also just as easy as the 700 to chuck up in a lathe with zero runout.

For most hunting rifles the benefits of such a treatment are dubious on the Savage or the 700 but there can be no question that everything in perfect perpendicularity would be the ideal situation.

[1jonzmith]

For most hunting rifles the benefits of such a treatment are dubious on the Savage or the 700 but there can be no question that everything in perfect perpendicularity would be the ideal situation.

Pretty much, it's you and me, Bro. I think there should be no question either. The biggest problem for me is that the "heavies" around here have lined up squarely against the idea. With all due respect to those with the many years of experience, I will wait for "Savich", silly or otherwise, to clear the air.

Thanks for your thoughts,


John

[cgeorgemo]

Okay I'm confused about something fundamental in the firing process I believe.
Doesn't the firing pin just jam the cartridge forward against the shoulder when it releases until the case gets stopped by the shoulder and then the pin dents the primer down to the anvil?
At the point it's forward motion is stopped by the shoulder the round fires.
The pressure pins the case against the wall of the chamber and the brass starts flowing backwards toward the bolt face and forwards lengthening the neck.
The pressure against the sides of the chamber is what is holding the case in place and only part of it is moving rearward as flowing brass.
Since the case is being held against the chamber wall by the pressure of firing at this point, the bullet is going to exit the barrel before that pressure drops enough for the bolt head to be actually holding the case again instead of just stopping the rearward flow of the brass?
What I guess I'm asking is this... Aren't the bolt head/lugs supporting the rear of the case again after the bullet has already started down and out the barrel?

[cgeorgemo]

Here is a link explaining some of my thinking. It might even be where I originally read about pressure in the chamber/barrel upon firing. I don't know it has been years since I first read what I'm asking about above.
http://www.ar15barrels.com/prod/operation.shtml

[Eric in NC]

Doesn't the firing pin just jam the cartridge forward against the shoulder when it releases until the case gets stopped by the shoulder and then the pin dents the primer down to the anvil?

Not when the extractor is holding the rim against the bolt face. Saw a guy fire a 308 in a 30-06 M1 Garand - nothing holding the case but the extractor (no way it reached the shoulder of the chamber - came out almost straight walled).

[cgeorgemo]

I can wiggle my cases against the bolt head even hooked under the extractor....
And of course the .308 would need to be held by the extractor there's no way it's going to reach the shoulder in a 30-06 chamber.

[Gmac5]

In response to lapping lugs ,do what floats your boat ,just be careful if you switch barrels and bolt heads .
Ive seen ownets lap lugs only to find out the orig bolt lugs were not equal to start ,which lapped rec and lugs equally then switched cartridge and and had only one lug touching. Min and max specs can stack and cause problems unforseen down the road . As the receiver im refering to was never trued and i got it after the fact ,it is possible it left the factory that way ,but the customer insists he had even contact on both bolt heads until he lapped?
GAry

[Gmac5]

It is possible to shoot 308 in 30-06 chamber( I DO NOT RECOMEND IT) ,the 308 dia at sholder ,side wall junction is larger than 30-06 chamber at 308 lenght check your reload books or chamber specs
Gary

[fgw_in_fla]

How about a little hypothetical inquiry to the mix?

If the bolt face / head was not square & true to the centerline & chamber and all that, what effect would it have on brass over the longer term?

Whenever I dress a case & have it chucked up in the drill, hit the trigger & it spins on sort of an elipse - the head is rotating & the case mouth is spinning on a 3/4 inch circle - I wonder if the chamber had anything to do with it.
Especially when I get into 5 or 6 firings where I'm finding many cases the same. 1 or 2 firings - OK. the more use, the worse they are.

Would this be related to anything regarding the bolt head / face to chamber relationship?

Whatcha think ??? ??? ???

Frank in Fla

[Gmac5]

Yes you could have a problem ,but more likely its the way you are spinning the case
You need a more precise case spinner ( trimmer)
And if your bolt face isnt square it can cause harder bolt lift than if everything was true.
Gary

[nsaqam]

If your boltface is not perpendicular to the bore axis you may see what you're experiencing after one firing but five or six firings would not be likely to increase it as it is unlikely that the case is entering the chamber the same way every time.

[1jonzmith]

Novice opinion here....if the bolt face isn't true then the brass will fireform to the irregularity and the brass will come out out of true. You repeat this process and you will have "worked" the brass back and forth. If the stroke is big enuff or you do it a lot then the brass would be weakened. The dreaded "light line" that creeps in around the bolt brass head(?), the one that heralds imminent head separation, could that be related or make things worse and shorten brass life? Lots of stories out there about short brass life, like three firings, and others get 15 or 20 reloads.

Gmac..... you seem to have a handler on this..... I sure don't speak with any authority.

Thanks John

[1jonzmith]

The bold bodies, and bolt heads are not hard chromed. The bolt bodies are a carbon steel in the white, that have been heat treated, (And are harder than the hubs of heck.) and the bolt bodies are made from stainless.

OK! According to Savage Customer Service, Engineering Department doesn't talk to customers, The bolt bodies and bolt heads have never been chromed....ever. Their words. Both the bolt body and heads are made from the same alloy steel....didn't have the number as that is "engineering's" purview. The dept that I can't talk to!!!! BUT, neither the bolt bodies or heads are stainless in the NON stainless version of the action. HUMMMMMM! Didn't think to ask whether the bolt body is SS in the SS action but I suspect it isn't. But, to say that bolt bodies are stainless without a qualification would seem to be "not entirely correct". At any rate, I am working with what Savage told me and that is also subject to "what I heard the man say". In my self defense, I am not entirely without skill at listening.

Thanks All,

John

[sharpshooter]

You'll probably never get a straight answer even from an engineer. Here's what I know for a fact:
The bolt heads are made from special profiled stock, 41L40 and heat treated to 35-42 Rc.
The bolt bodies are made from 1020 tubing and carbo-nitrided (case hardened)to a depth of .012-.015" @ 50 Rc.

[ellobo]

After reading all the posts about lapping lugs I see that all the posts seem to be saying 'What if?" this or that. I have come to the conclusion we have a solution desperately in need of a problem.

El Lobo

[82boy]

After reading all the posts about lapping lugs I see that all the posts seem to be saying 'What if?" this or that. I have come to the conclusion we have a solution desperately in need of a problem.
El Lobo

Very well said.

[1jonzmith]

After reading all the posts about lapping lugs I see that all the posts seem to be saying 'What if?" this or that. I have come to the conclusion we have a solution desperately in need of a problem.
El Lobo

Very well said.

+1

SS,

Thank you. I had a knife made from D2 alloy. When it was finished and delivered I was delighted at the craftsmanship. Beautiful! Then I dropped it on my hearth stone and the tip "BENT". WTF? Had it tested and it came in RC40. That is the untempered/hardened workable D2. It came back RC60+....harder than a file's RC58. But it is brittle for anything but tool steel or a special profiled knife.

Heat treating is a MUST and it is also difficult and time consuming to do right. I am surprised that they are only getting RC 50 on the bolt nitriding. My bolt has scratches in the side from dragging on the SS action. That doesn't seem that that would be possible buy little of this makes any final sense from my perspective. I had been considering having my action nitrided after I make sure the ramps are actually both depressed equally from the mouth/front of the action.

Thaqnks for taking the time to get into this. I know you are busy.

John