Gunsmithing LA Bounty bolt fixture

CS223

CS223

Sergeant
Full Member
Minuteman
Dec 22, 2006
175
1
Alachua, FL
#1
Anyone using one?

LA Bounty Fixture

Thoughts? Opinions?

You'd indicate off the bolt body behind the lugs and adjust the chuck until you were running true.

The issue I see is if the bolt dia. at the rear mics different than the front then the bolt isn't running true to the OD. If it's only off a thou or so, it would be easy to shim.

The plus I see is the bolt face & lugs would be cut true without moving the setup so less chance for error.
 
#2
Re: LA Bounty bolt fixture

Overall I think its a good fixture. I dont like how you have to "assume" that the fixture is running true, plus like you mentioned, the bolt needs to be the same diameter and pretty consistent to get a good set up.

As stated above, its nice to do all of the work with one set up, and its pretty solid so you dont have to worry about chatter or any problems related to the workpiece being unstable.

With that being said, no matter how you true it, if your getting more than a couple thousands of clearance between the action and bolt it does not matter how true and square your bolt is. I say this because you will be sticking you trued bolt in the action and the trigger will push the back of the bolt up, rocking the top lug forward and making your bolt face no longer square when the rifle is locked up ready to fire.

The million dollar question is does it remain this way after the trigger is pulled, ignition happens and pressure builds up? Or does the bolt drop down, level its self off and become more in line?

I dont think either way is best for extreme accuracy.

Mark
 
#3
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: M.Gordon</div><div class="ubbcode-body">Overall I think its a good fixture. I dont like how you have to "assume" that the fixture is running true, plus like you mentioned, the bolt needs to be the same diameter and pretty consistent to get a good set up.

As stated above, its nice to do all of the work with one set up, and its pretty solid so you dont have to worry about chatter or any problems related to the workpiece being unstable.

With that being said, no matter how you true it, if your getting more than a couple thousands of clearance between the action and bolt it does not matter how true and square your bolt is. I say this because you will be sticking you trued bolt in the action and the trigger will push the back of the bolt up, rocking the top lug forward and making your bolt face no longer square when the rifle is locked up ready to fire.

The million dollar question is does it remain this way after the trigger is pulled, ignition happens and pressure builds up? Or does the bolt drop down, level its self off and become more in line?

I dont think either way is best for extreme accuracy.

Mark </div></div>

Yet another benifit of the floating bolt head desgine of Savages
 
#5
Re: LA Bounty bolt fixture

Seen one used. Checked lug contact after and contact was great in an also trued action.

Its quick and simple, but like mentioned, I dont like trusting that it is running true.


EDITED: need to add, Ive seen it do a bad job too now. I dont trust it considering there are others ways. It wont ensure every bolt is running true.

 
#7
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">Seen one used. Checked lug contact after and contact was great in an also trued action.

Its quick and simple, but like mentioned, I dont like trusting that it is running true.

</div></div>

Keith, true an action and bolt then put the trigger in, put Dykem on the back of the bolt lugs and then check it. Make sure you have your lapping tool screwed in the front of the action putting even rearward pressure on the bolt face. Let me know what you come up with.

Mark
 
#8
Re: LA Bounty bolt fixture

and the debate again about lug contact due to bolt body to receiver clearance and the sear pressing up...

my thoughts are that once the firing pin drops, any upward pressure on the rear of the bolt due to the sear is a moot point when 60k+ psi is pushing the bolt lugs against the internal lugs. in my mind, as long as the bolt is true enough that both lugs can make contact at the same time without the bolt body bending against the receiver raceway, you will be fine.


edit: if i remember correctly from back when i drew it up in cad, assuming about .006" of bolt body to receiver clearance, if the rear of the bolt is pushed to one extreme and the front of the bolt the other, there was less than .00015" of gap between the extreme end of one lug.


edit: i just redrew it and came up with .00121" separation at the extreme end of one lug assuming the bolt is pushed up .006" over 5.220" (long action bolt).

 
#9
Re: LA Bounty bolt fixture

Re. Sear pressure. I'm familiar with sleeving a bolt, having a bolt ground by PTG to fit a reamed receiver and Borden bumps. If you're going to go through all that, IMHO just buy a custom action like a Stiller Predator.

A thought crossed my mind along the lines of the Borden bumps, let me run it by ya'll. What about drilling the top of the receiver between the rear optic mounting holes and installing a small brass tipped set screw to act as a "bump" to counter the sear pressure? Should be easy enough to tweak using a little Dykem. I know we're splitting hairs here.
 
#10
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CS223</div><div class="ubbcode-body">A thought crossed my mind along the lines of the Borden bumps, let me run it by ya'll. What about drilling the top of the receiver between the rear optic mounting holes and installing a small brass tipped set screw to act as a "bump" to counter the sear pressure? Should be easy enough to tweak using a little Dykem. I know we're splitting hairs here. </div></div>

I've actualy seen somthing similar done , 4 holes were drilled basicaly at the top 4 corners of the rear and 4 , 8x32 brass screws were put in just far enough to cause a little drag on the bolt after a few hundred cycles its loosened up some and make for a very tight bolt fit.
Personaly it it were bothering me that much I'd just convert the thing to a floating bolt head , ala Savage
 
#11
Re: LA Bounty bolt fixture

The problem with the concept of set screws is that they drag along the length of the bolt when it is cycled. If they are adjusted tight enough to made a difference it would likely be a pain to work the bolt.
 
#12
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CS223</div><div class="ubbcode-body">Re. Sear pressure. I'm familiar with sleeving a bolt, having a bolt ground by PTG to fit a reamed receiver and Borden bumps. If you're going to go through all that, IMHO just buy a custom action like a Stiller Predator. </div></div>

i believe stiller predator and tac series actions by design have similar bolt body to receiver raceway clearance as a factory remington. they are not designed to be benchrest actions, they are designed to be used in the field.
 
#13
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mdesign</div><div class="ubbcode-body">The problem with the concept of set screws is that they drag along the length of the bolt when it is cycled. If they are adjusted tight enough to made a difference it would likely be a pain to work the bolt. </div></div>

Good point.

It's a wonder with all the Rem bolt work that is done, that the Sav style floating bolt head isn't a more popular modification it addresses the extractor issue as well.
 
#14
Re: LA Bounty bolt fixture

Mark, when we did it the bolt was stripped and trigger out. Rearward pressure was applied to the face. Contact was good and even without any lapping... straight out of the machine.
Didnt take long to do either.
My father did it. Maybe he'll chime in or show pics.

But, like you said, I dont like trusting that its running true. Just because THAT fixture worked in THAT lathe, doesnt mean mine would or yours would if we tried it.

I like to be able to adjust the bolt with a double spider fixture like I'm sure most of you do too.
 
#15
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: M.Gordon</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">Seen one used. Checked lug contact after and contact was great in an also trued action.

Its quick and simple, but like mentioned, I dont like trusting that it is running true.

</div></div>

Keith, true an action and bolt then put the trigger in, put Dykem on the back of the bolt lugs and then check it.
Mark </div></div>

Why leave trigger in? Do you want the assebmly in the bolt too? With no round in the chamber, I'd think the bottom lug would make more contact cause of the assembly being in.

When the rifle fires though, I believe that upward pressure is nonexistent. Bolt thrust at 60,000psi will set those lugs no matter what. Esp on larger bolt faces(.532+)
 
#16
Re: LA Bounty bolt fixture

One thing this setup brings to question for me is with the mandrels they use. My understanding is that the Kiff setup and similar systems for dialing in the bore allow for use of 2 seperate bushings for the front and rear ring. With the mandrels that this setup uses, it is a solid rod. if you end up with an action that has a different diameter rear or front ring, then there will be some error induced there.. or am I missing something?

DD
 
#17
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">i believe stiller predator and tac series actions by design have similar bolt body to receiver raceway clearance as a factory remington. they are not designed to be benchrest actions, they are designed to be used in the field. </div></div>

They are not as tight as a benchrest action, but in general are tighter than the Rems. Usually 3 to 4 thousands diameter difference between bolt and hole.
 
#18
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">my thoughts are that once the firing pin drops, any upward pressure on the rear of the bolt due to the sear is a moot point when 60k+ psi is pushing the bolt lugs against the internal lugs. in my mind, as long as the bolt is true enough that both lugs can make contact at the same time without the bolt body bending against the receiver raceway, you will be fine.
</div></div>

Agreed. More critical on a Rem action is the fit of the bolt nose to its mating cut in the back of the barrel, and equally as important, their concentricity to the centerline of the chamber and bore. If this fit is good, the bolt fit in the receiver is nil, and it makes for a more accurate gun overall.

-matt
 
#19
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">
edit: if i remember correctly from back when i drew it up in cad, assuming about .006" of bolt body to receiver clearance, if the rear of the bolt is pushed to one extreme and the front of the bolt the other, there was less than .00015" of gap between the extreme end of one lug.


</div></div>

Close, but you have one too many Zero's in there. I did some tests and so did Greg Tannel a while back (can be seen in his bolt sleeving video) about this very topic.

Like you mentioned, if the front of the bolt was resting on the lower part of the action (which it may with the back of the bolt pushed up) and the back of the bolt raised the front of the lug will walk forward from less than .001 to slightly under .002" depending on how much clearance is around the bolt.

Here is a picture of what I did and here is the results I came up with.



IMG_1113.jpg



With a Remington 700 Long Action bolt.

Back of bolt raised up.... Front top lug advanced forward...

.005 up = .001 forward

.008 up = .0013 forward

.010 up = .0016 forward

.012 up = .0018 forward

Remington Short Action bolt

.005 up = .0007 forward

.008 up = .0011 forward

.010 up = .0013 forward

.012 up = .0015 forward


As you can see from the data with the rear of the bolt body about .008 up the front of the lug goes roughly .001 forward. I know that is not a lot but when you have 60,000 PSI in the chamber pushing back the bolt face, your top lug moves back under that pressure until it contacts the internal lugs of the action while your bottom lug is essentially the pivot point. This is just another variable in the equation that is eliminated by sleeving, grinding bumps or have a tight bolt fit will correct. What makes an action really accurate...keeping the bolt tight and locked up before and during ignition.

I think we all have built actions that shoot really well with just a straight trued action and bolt with plenty of clearance. But when its your job to do it every time, your suggestion for the customer is always going to be to deal with the bolt one way or another to tighten it up.

Give Gordy Gritters, Jim Borden, William Roscoe, Mike Bush or Greg Tannel a call and see what they think. Heck, I bet the GAP Templar has a bolt clearance around or less than .003. They seem to have the formula down for building very accurate rifles for quite some time now and their rifles are all over the world in real life scenarios with out any hitches.

Bottom line, your main accuracy is coming from your barrel, crown, chamber/throat and barrel shoulder junction. Everything else seems to be the icing on the cake and helping deliver the accuracy every time.

Mark
 
#20
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: M.Gordon</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">
edit: if i remember correctly from back when i drew it up in cad, assuming about .006" of bolt body to receiver clearance, if the rear of the bolt is pushed to one extreme and the front of the bolt the other, there was less than .00015" of gap between the extreme end of one lug.


</div></div>

Close, but you have one too many Zero's in there. </div></div>

i think you are right. i started thinking that after i posted but i can't find my drawing or remember the thread i discussed it. it probably was about .0015" i came up with.
 
#21
Re: LA Bounty bolt fixture

It's a similar triangles question (assuming that the bolt lug faces have been cut prependicular to the bolt body).


Mark: In your fixture, where's the indicator touching for the motion in the locking faces? I might be missing something but the trend you showed seems backwards. The long action should show less travel at the lugs than the short action for the same travel change at the rear of the bolt.
 
#22
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body"> I might be missing something but the trend you showed seems backwards. The long action should show less travel at the lugs than the short action for the same travel change at the rear of the bolt. </div></div>

I thought the Long Action would have less movement because of the fact that the bolt is longer in turn causing a lower angle in the leverage. But I will run the test again, but those are the numbers I came up with and I encourage anybody to try to duplicate the results. I tried hard to make sure that I was manipulating the jack and the bolt the same to way to get the most accurate numbers.

I would have to disagree with the notion that the movement forward is closer to .0001. I took the measurements and to my knowledge the way I duplicated the bolt tilt would have been the most accurate way to do so. With the pivot point in the front of the bolt, that would have been the best case scenario for keeping the numbers smaller. But if you move the pivot point towards the rear of the bolt, then the movement forward would just increase.

Bohem, give the experiment a shot, I think you will find that the movement forward is more than the formula's would suggest.

Mark
 
#23
Re: LA Bounty bolt fixture

I'll definitely give it a try. We're on the same page with thinking about the angles on the short and long action, so that was the biggest thing that caught my eye. When I checked into it more with the formulas it started to make me wonder.

I will let you know what happens when I get a chance to do the test.
 
#24
Re: LA Bounty bolt fixture

I figured out the mistake in the formula above. I assumed that it was rotating about the base of the non-contact lug.

It's not, it's rotating about the OD edge of teh contacted lug. In that case the numbers are:


DAR = Distance between aft raceway contact and lug face

DC = Diametral clearance on bolt body to bolt race ways (ID receiver - OD bolt body)

LL = Total Lug length = Lug OD

LC = Lug clearance (the quantity we want to calculate)

(0.5*DC)/DAR = LC/LL

We want to find LC so:

LC = 0.5*DC*LL/DAR

Let's say then that:

DAR = 2.5"
DC = 0.006"
LL = 0.985"

(0.5*0.006)/2.5 = LC/0.985 --> LC = 0.00115


If this was a long action bolt with 3.5" between the lugs and rear raceway contact (again, just a wild guess) then that same calculation comes down to 0.0009" of travel.

That makes a lot more sense. I still can't figure out how you got the long action to move more than the short action though, I'm definitely going to test it and see what happens. Thanks for making me go back and check the formulas.
 
#26
Re: LA Bounty bolt fixture

Yes, it's worth it. You may get away without it, however it's just another thing that adds to the overall package of the receiver. One less issue to worry about, and it will also make the rifle feel better during cycling.
 
#27
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body"> The long action should show less travel at the lugs than the short action for the same travel change at the rear of the bolt. </div></div>

yep. .005" over 5.25" is a shallower angle than .005" over 4.25". there is no way a long action bolt will have more lug separation than a short action as long as the bolt to receiver clearance is the same on both.
 
#28
Re: LA Bounty bolt fixture

i redrew a long action again since i had a bolt sitting here to measure. i was wrong with my first post remembering back to when i drew it a while back. what i came up with this time was .00121" separation at the extreme end of one lug assuming the bolt is pushed up .006" over 5.220" (long action bolt).

edit: i don't have a short action bolt handy to measure but i think they are 7/8" shorter than a long action. if this is true, it looks like there would be .00138" of separation at the extreme end of one lug also assuming the receiver is .006" larger than the bolt body.

 
#29
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JJones75</div><div class="ubbcode-body">OK , so whats the conclusion?

Does it realy justify the cost to have a bolt sleeved or the raceway reamed then bigger bolt installed ? </div></div>

Not in a field or "tactical" rifle. You want to do this sell the Remington and buy a custom.
 
#30
Re: LA Bounty bolt fixture

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JJones75</div><div class="ubbcode-body">OK , so whats the conclusion?

Does it realy justify the cost to have a bolt sleeved or the raceway reamed then bigger bolt installed ? </div></div>

Not in a field or "tactical" rifle. You want to do this sell the Remington and buy a custom. </div></div>

+1 Randy
 
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