Gunsmithing Bolt truing?????

[Mgordon]

Hey Gents, just wanted to get a few ideas from some other gunsmiths out here about truing the bolt lugs and face up on a bolt action, specifically a Remington 700.

Would you agree that the idea of truing the lugs and bolt face should be done so the cuts are concentric to the outer diameter of the bolt body???

The bolt body rests in the bolt raceway via gravity, now were not talking about sleeved bolts, just factory guns. I also understand that the cocking piece and trigger connector contact pushes up the back of the bolt body.

So how do you indicate your bolts in for truing? I'm familiar with a few common practices, but I just dont get that warm and fuzzy about any of them or the process of setting them up.

So if you don't mind, what do you guys do?

 

[JJones75]

Re: Bolt truing?????

indicate off the bolt body so that the bolt in running true in your fixtue , then all cuts are made so that they are square with the bolt body.

I have wondered the same thing , if the sear pushes the back of the bolt up that should make the contact on the top lug light if at all. Best I can figure is that the great pressure of the case trying to get out will overcome the sear pressure and flatten both lugs up so that they are pushing evenly on the action lug embunkments making everything back strait with the trued action and chamber that cut square

 

[Mgordon]

Re: Bolt truing?????

Well, that is a whole different story. I dont even want to think about how high the rear of the body is lifted from the pressure of the cocking piece, or what that is doing to the top lug.

I guess what I'm looking for is someone to agree that if you have the front and the back of the bolt body concentric, then the cuts on the back of the bolt lugs and receiver face will be about as true as possible????

 

[JJones75]

Re: Bolt truing?????

Well if you had setup your reciever and indicated off of a spud in the bolt race way and cut the bolt lug and reciever face true to that , then indicated your bolt in so that it was running true indicted off of the bolt body and cut your bolt lugs and face true to that then you should be having perfect contact.

But like I mentioned , if their is say .003" slop in the bolt to reciever fit at the rear bridge then the bolt "could" rise from the sear spring pressure technicaly causing the top bolt lug to break contact.

These are big ifs though , but I have heard some guy's theory about only bushing the rear of the bolt to prevent this yet allowing plenty of clearance for "dirty work"

 

[BlackOps Tech]

Re: Bolt truing?????

I indicate the bolts in the lathe referencing the bolt body and cut the lugs, face and bolt nose square. Once the face, lug abutments and threads of the receiver are cut true to the bolt raceway, the bolt lugs and face are finish lapped to the receiver. When I machine the counterbore in the breech I allow a maximum of .005" thrust in the bolt, so when headspace is correct, the rear of the bolt will move very little as the lugs are locked up tight. The lugs being properly locked is stronger than the spring pressure against the rear of the bolt.

 

[wnroscoe]

Re: Bolt truing?????

Just dial in the bolt body as close as you can and make your cuts. The sear bar / striker contact are going to deflect the bolt body up in the rear unless you bush the rear of the bolt body. Measure the rear receiver ring / bolt raceway ID and then measure your bolt. The deflection may not be as bad as you'd think.

 

[wnroscoe]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Skunkworks</div><div class="ubbcode-body">The lugs being properly locked is stronger than the spring pressure against the rear of the bolt. </div></div>

When I say bolt deflection, it's a very small amount that I speak of. I doubt you'd ever detect it on the target.

 

[BlackOps Tech]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wnroscoe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Skunkworks</div><div class="ubbcode-body">The lugs being properly locked is stronger than the spring pressure against the rear of the bolt. </div></div>

When I say bolt deflection, it's a very small amount that I speak of. I doubt you'd ever detect it on the target. </div></div>

+1....

 

[Mgordon]

Re: Bolt truing?????

Yeah, I'm sure I'm on the same page as everybody else for the most part, but I guess there are too many variables that are not worth controlling at this degree. I feel like there is still lots to be desired with this design.

 

[BlackOps Tech]

Re: Bolt truing?????

Exactly....That's why I finish lap everything together so the mating surfaces are as exact as possible....Although I may not really need to finish lap, it does help to remove the variables....

 

[300sniper]

Re: Bolt truing?????

riddle me this, when there is pressure rearward on the bolt lugs during firing, is there still upward pressure on the bolt from the sear?

in my opinion, dialing the bolt body in with an indicator at two places is the best bet. i dial the bolt body in to better than two tenths but think that is way over kill since there is a large amount of slop between the bolt body and receiver. spending a few extra minutes on dialing it in is worth it to me just knowing i did the best i could. will the difference show on a target between a bolt trued to better than two tenths and one trued to better than one thousandth when there is 5 thousandths slop between the bolt body and receiver? i'm not sure.

 

[Keith Johns]

Re: Bolt truing?????

Like 300 just said, the way I've gathered would be best to do it, would be to indicate two places on the bolt body. If the two indicators read less than .0005" run out, the bolt is pretty damn true right?

And as far as lapping the lugs, why do that if you've already trued it in a lathe? I've never liked the idea of lapping. I dont know as much as you guys about it but it just seems un needed after truing the lugs to the bolt body, and the lug recesses to the raceway(well the face, but the face would be trued to the raceways before)

When I bother my instructor about truing actions to this degree, he laughs. He still helps me, but says it's un needed. I disagree with him

 

[BlackOps Tech]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">riddle me this, when there is pressure rearward on the bolt lugs during firing, is there still upward pressure on the bolt from the sear?

in my opinion, dialing the bolt body in with an indicator at two places is the best bet. i dial the bolt body in to better than two tenths but think that is way over kill since there is a large amount of slop between the bolt body and receiver. spending a few extra minutes on dialing it in is worth it to me just knowing i did the best i could. will the difference show on a target between a bolt trued to better than two tenths and one trued to better than one thousandth when there is 5 thousandths slop between the bolt body and receiver? i'm not sure. </div></div>


I also use two indicators to dial the bolt body in and when I'm finished, the bolt is dialed in to at least .0001" or better. When the lugs are locked truly square to the lug abutments and headspacing is properly set, any upward movement at the rear of the bolt will be minimal to non-existant even without bushing the bolt body. Bushing the bolt body eliminates this variable completely (I know I'm speaking to the choir here Robert). After all the time involved in doing this I truly believe it makes a difference downrange....

 

[Keith Johns]

Re: Bolt truing?????

How are you guys indicating to within one tenth? Or even two tenths? There are variations in the steel larger than .0001"

 

[BlackOps Tech]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">Like 300 just said, the way I've gathered would be best to do it, would be to indicate two places on the bolt body. If the two indicators read less than .0005" run out, the bolt is pretty damn true right?

And as far as lapping the lugs, why do that if you've already trued it in a lathe? I've never liked the idea of lapping. I dont know as much as you guys about it but it just seems un needed after truing the lugs to the bolt body, and the lug recesses to the raceway(well the face, but the face would be trued to the raceways before)

When I bother my instructor about truing actions to this degree, he laughs. He still helps me, but says it's un needed. I disagree with him </div></div>

Remember that when you true the lugs you're referencing the bolt body, not the bolt race way. The lug abutments are trued to the bolt raceway, so why not finish lap the lugs to the lug abutments referencing the bolt raceway?

 

[Keith Johns]

Re: Bolt truing?????

I know the bolt isnt the same size as the ID of the receiver(raceway), but I try to set that fact aside when thinking about this.

I know the bolt is pushed upward when cocked, but in the time the pin drops, and pressure builds in the case, do you think the rear of the bolt is still up? I think the it lowers when fired. Makes sense to me that the pressure would center it, as long as everything is true.

Doesnt that last bit of lapping, bring it back away from "true" or 90 degrees from bore centerline

 

[Keith Johns]

Re: Bolt truing?????

If the bolt was the same saze as the raceway, would you still lap the lugs?
If they were the same size, how much contact do you think you'd have without lapping? If the truing went well, shouldnt contact be near 100% of what it can be?

It just seems like lapping is used to remove imperfections that can be removed, or should be removed, in other ways.

And again, I'm just asking here. I dont have the experience you guys have, and I value what you guys say. So please dont feel like I'm questioning ya. Just learning

Oh and do you check contact by using a layout fluid or anything? Or do you just prefer to always lap?

Thanks

 

[wnroscoe]

Re: Bolt truing?????

AZ

When lapping bolt lugs to the receiver lug abutments there's a fixture that screws into the receiver and holds positive pressure against the bolt face/nose. This keeps everything tight and inline.

 

[BlackOps Tech]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">I know the bolt isnt the same size as the ID of the receiver(raceway), but I try to set that fact aside when thinking about this.

I know the bolt is pushed upward when cocked, but in the time the pin drops, and pressure builds in the case, do you think the rear of the bolt is still up? I think the it lowers when fired. Makes sense to me that the pressure would center it, as long as everything is true.

Doesnt that last bit of lapping, bring it back away from "true" or 90 degrees from bore centerline </div></div>

When you get a chance, cock a 700 WITHOUT A ROUND IN THE CHAMBER and squeeze the trigger. You'll see a significant amount of movement at the rear of the bolt because there is no rearward pressure on the lugs. At the range do this again and see if there is any perceptible movement (I missed the "during firing" in 300's response a few minutes ago). During firing, with all things being correct, the amount of movement (if any) should be hard to see.

As far as lapping, do you think if you make truing cuts referencing two different datums that those two surfaces would be square to each other? They'll be close, but finish lapping is just that....I can shoot you a few pics of what my lugs and abutments look like after truing and finish lapping....

 

[Keith Johns]

Re: Bolt truing?????

Well I was assuming the rear of the bolt falls down, into true, when no longer being held up by pressure. And is infact, being pushed straight back by 50,000psi.
I know the body, and raceways is two different referance points, but shouldnt they line up perpandicular to eachother when the rifle is fired, IF everything is somehow true.

If the above were true, there'd be no reason to lap. Right?

And when you lap it, What do you use for pressure on the lugs? I've seen a few different methods.

When the rifle is fired, is it in the same position it was when lapped?


Sorry for all the questions

Thanks

 

[RADcustom]

Re: Bolt truing?????

Finish lapping also lessens the likelihood of the lugs galling.

 

[Keith Johns]

Re: Bolt truing?????

That I can see. How much are you removing when you finish lap? over .0005?
If its a few tenths, then lapping makes sense. But if it's a thou or near that, I dunno.

 

[BlackOps Tech]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">Well I was assuming the rear of the bolt falls down, into true, when no longer being held up by pressure. And is infact, being pushed straight back by 50,000psi.

If the above were true, there'd be no reason to lap. Right? </div></div>

If the surfaces aren't perfectly square, the more movement you're going to have. Try this: Make truing cuts on the lugs referencing the bolt body and true the lug abutments referencing the raceway. Afterwards, paint the bolt lugs with blue Dykem (or a Sharpie), screw your lapping tool into the receiver (to provide rearward pressure on the bolt) and work the bolt handle a few times. Remove the bolt and you're likely to see striations in the Dykem indicating there are small portions of the lug not truly contacting the abutments. I finish lap to remove these striations. I don't solely depend on lapping to take the place of precision machining.

 

[BlackOps Tech]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">That I can see. How much are you removing when you finish lap? over .0005?
If its a few tenths, then lapping makes sense. But if it's a thou or near that, I dunno. </div></div>

It's a few tenths at the most....

 

[Keith Johns]

Re: Bolt truing?????

Ah. That changes things in my head. When I thought of lapping I thought of removing way more(like a thou or two.
Dont some people just lap instead of truing? As sort of a short cut.

 

[RADcustom]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">That I can see. How much are you removing when you finish lap? over .0005?
If its a few tenths, then lapping makes sense. But if it's a thou or near that, I dunno. </div></div>

If that. 320 grit only changes the finish and smooths the surfaces that would occur during firing.

 

[wnroscoe]

Re: Bolt truing?????

Lapping is like a final surface finish, no more or less.

 

[BlackOps Tech]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">So your removing a very small amount by finish lapping right? like 5 tenths or less? </div></div>

Very minimal amount....I depend on finish lapping as more of a polishing, not to remove copius amounts of material....

 

[Keith Johns]

Re: Bolt truing?????

K. If I think of it as polsihing, it sounds a lot better to me.

Lapping makes me think of some material removal. Dunno why

Thanks by the way.

Oh and about the bolt rise in the back again, does it fall at all when firing?

 

[RADcustom]

Re: Bolt truing?????

Same thing they do to barrels after rifling.

 

[RADcustom]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">K. If I think of it as polsihing, it sounds a lot better to me.

Lapping makes me think of some material removal. Dunno why

Thanks by the way.

</div></div>
It all depends on the grit of the compound.

 

[BlackOps Tech]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RADcustom</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">K. If I think of it as polsihing, it sounds a lot better to me.

Lapping makes me think of some material removal. Dunno why

Thanks by the way.

Oh and about the bolt rise in the back again, does it fall at all when firing? </div></div>
It all depends on the grit of the compound. </div></div>

Very good point RAD....I use 800 grit for finish lapping....

 

[RADcustom]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">
Oh and about the bolt rise in the back again, does it fall at all when firing? </div></div>

No, the force of the case head pushing against the face centers the bolt body square with the lugs.

 

[Keith Johns]

Re: Bolt truing?????

Thats done with compound and what? Lead comes to mind

 

[Keith Johns]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RADcustom</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">
Oh and about the bolt rise in the back again, does it fall at all when firing? </div></div>

No, the force of the case head pushing against the face centers the bolt body square with the lugs. </div></div>

Thats exactly my point though. If the lugs are square, wont the bolt sort of center out in the raceway? Why would it remain upward

and is why I was saying, I try to get that upward pressure out of my head when thinking about this, because it wont be up anymore when the weapon is fired.

 

[RADcustom]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Skunkworks</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RADcustom</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">K. If I think of it as polsihing, it sounds a lot better to me.

Lapping makes me think of some material removal. Dunno why

Thanks by the way.

Oh and about the bolt rise in the back again, does it fall at all when firing? </div></div>
It all depends on the grit of the compound. </div></div>

Very good point RAD....I use 800 grit for finish lapping.... </div></div>

It is also worth mentioning to only use aluminum oxide based compound and never silicon oxide.

 

[BlackOps Tech]

Re: Bolt truing?????

It doesn't necessarily move upward when everything is perfectly square and there is case head pressure against the bolt face....

 

[RADcustom]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RADcustom</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">
Oh and about the bolt rise in the back again, does it fall at all when firing? </div></div>

No, the force of the case head pushing against the face centers the bolt body square with the lugs. </div></div>

Thats exactly my point though. If the lugs are square, wont the bolt sort of center out in the raceway? Why would it remain upward </div></div>

Yes, with a round in the chamber there isn't enough room for it to move upward.

Mike beat me to it.

 

[Keith Johns]

Re: Bolt truing?????

So is it safe to say the upward pressure doesnt effect much?

If not, what can it effect?

 

[RADcustom]

Re: Bolt truing?????

Remember too that the ejector button is pushing against the top lug to counter the sear pressure.

 

[Keith Johns]

Re: Bolt truing?????

Good point. So on firing, there's actually more pressure pushing down the rear of the bolt, than up

 

[RADcustom]

Re: Bolt truing?????

during firing, there is more pressure pushing back than anything else.

 

[BlackOps Tech]

Re: Bolt truing?????

Ideally when the lugs are square against the abutments the rear of the bolt is centered and the bolt is concentric to the bore. This is the heart of accuracy....

 

[Keith Johns]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Skunkworks</div><div class="ubbcode-body">Ideally when the lugs are square against the abutments the rear of the bolt is centered and the bolt is concentric to the bore. This is the heart of accuracy.... </div></div>

Thats what I was thinking the whole time. Problem was, I thought lapping was throwing it off true. Didnt realize it's just barely polishing them


Thanks a lot

 

[300sniper]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RADcustom</div><div class="ubbcode-body">Remember too that the ejector button is pushing against the top lug to counter the sear pressure. </div></div>


in my opinion, the amount of leverage offered at the location of the ejector wouldn't be enough to counter act any upward pressure from the sear. it would have more of a rearward pressure than a downward.

and again, my opinion, i think the ejector and sear pressure are a moot point. even with everything being square, there is still going to be violent bolt movement when the firing pin falls, the upward spring pressure on the bolt is released and the bolt lugs are slammed square against the lug abutments when there is the amount of bolt body to receiver clearance typical of most field/tactical rifles.

 

[BlackOps Tech]

Re: Bolt truing?????

My opinion, when everything is square and locked up, and with firing pin inertia being straight forward, toward an opposing pressure, rearward vertical bolt movement would have to be minimal. The amount of spring pressure from the sear is not a great amount.

 

[Mgordon]

Re: Bolt truing?????

It sucks being on Eastern time, by the time I go to bed I miss all of this good stuff going on!!!

Well, I'm tracking everything you guys have been saying. I would argue that the rearward pressure of the cocking piece is greater than the ejector spring tension. Plus the ejector would have a mechanical disadvantage because of leverage to lower the rear of the bolt.

Anyway, were probably worrying over nothing. There is nothing we can do besides bore out the raceway, sleeve the bolt and/or install an over sized bolt. Plus, it seems that most rifles can shoot the lights out with Remington 700 actions just trued up.

So here is the little fixture I came up with. A hide member actually gave me this fixture, the holes were tapped for coarse threads and its just barely larger than a 700 action, so adjustments are pretty limited and if you have an action that is out pretty bad, there might not be clearance to dial it in. So I put bolts in it, drilled out the center of the bolts and inserted a small Delrin stud. I made a "cock and balls"..lol cut in the fixture to allow my bolt to slide in, and then I screw in an extension in the back of the bolt to allow me to dial it in just like a barrel in a headstock.

I use my (2) .0001" indicators and dial it in. I then make my cuts on the back of the lugs and then the bolt face. It just did not seem like there were any good techniques. I spoke with Greg Tannel at Gre Tan Rifles, and it just seems like his technique is accurate, but a process. You have to have a different setup for the bolt lugs and the bolt face.

With this way I experimented with yesterday, everything seems accurate and the cuts were chatter free. I wanted enough bolt exposed to get a good area to indicate off of, but wanted a supported bolt. Check it out.

 

[Keith Johns]

Re: Bolt truing?????

Nice...

making one of those next week

 

[300sniper]

Re: Bolt truing?????

great idea on the fixture

edit: i have the material but just have not gotten around to it yet. i plan on making a direct d1-4 spindle mount action/bolt truing jig that is safer and more rigid than this setup.

one more thing i have found this setup to also be handy for was precision threading muzzles on short barrels, such as a 12" 10/22 barrel for a suppressor. it works the same way as doing a barrel though the headstock.

 

[Mgordon]

Re: Bolt truing?????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">great idea on the fixture

edit: i have the material but just have not gotten around to it yet. i plan on making a direct d1-4 spindle mount action/bolt truing jig that is safer and more rigid than this setup.

one more thin i have found this setup to also be handy for was precision threading muzzles on short barrels, such as a 12" 10/22 barrel for a suppressor. it works the same way as doing a barrel though the headstock. </div></div>

300Sniper....we must be twin brothers separated at birth!!! haha

I'm glad others are thinking on the same page and I'm not just crazy!