Bolt lug lapping.

[rugerfan.64]

As a diy project,difficulty? Results? Method?

[gunnut69]

To be done correctly the barrel should be removed and device to apply the pressure to the bolt face is screwed into the barrel ring of the action. The abrasive is introduced between the lugs and their seats in the receiver and an up/down motion of the bolt handle provides the lapping action. Dykem on the lugs will provide beginning contact info and as the process procedes is rechecked to follow the percent of contact. 40-60 on both lugs is quite good enough.. If any serious amount of metal is removed the headspace will be altered and so headspace should be checked before the process is initiated.. This also means the necessary tools to adjust the headspace will likely also be necessary. A DIY project? is you're a talented ameture and have access to the tools needed. Just a polish to slick the rifles action MIGHT be doable without altering headspace the trick being the tiny amount of work being done.. I've heard of those doing this without removing the barrel but the are major pitfalls to that. The device used to tension the bolt should NOT use a spring. Most commercial ones do but this replicates the high and low spots that exist at the start. If a rigid tension is used tension to the lugs will only be applied when the lugs are on top of a high spot, just what we are looking to do..

[Silvertp]

Great answer Gunnut...

Ive always wanted to try this myself but figured I'd quickly be over my head if I messed up the headspace.  Now, I am sure I would be.

Silvertp

[gunnut69]

The thing to remember is that for every thousandth removed in the lapping process, a thousandth is added to ther headspace measurement. If the weapon is a bit close to the end of the go guage then problems could easily happen. Resetting headspace is not too hard but requires a lathe and usually a chamber reamer.. A simple polishing can be done usually with little danger but that implies precious little metal removed. 

[torpedoman]

http://www.gswagner.com/      This site has some good info on it and a lot of other things check it out.

[charles p]

I did a Mod 700 this way.  I recall it took about an hour to do it.  I was getting a new Shilen barrel at the same time, so headspace was set by the smith.

[parkergunshop]

On most Mausers the actions, are basically case hardened with at 5-15 thousandth surface case, you can easily remove this case when lapping the bolt in, then the bolt lugs will set back into the receiver a bit with each round fired, leading to excess headspace.  The bolts lugs are generally a bit harder than the receiver  bearing surfaces on these.

Most modern actions are the same hardness due to the steel alloys used and don't have a problem to the same extent.

[parkergunshop]

I should have added that this is not a DIY project.

Do you have headspace guages to check the resulting headspace change or someone who can do it?

Are you willing to pay to have the barrel set back if the bolt closes  on the no go guage?

Also minimum headspace contributes to overall accuracy, this is one of the strengths of the Savage 110 Action and it's barrel lock nut, put a minimum headspace guage in the chamber and screw the barrel up tight and lock down the nut?

Increasing the headspace by lapping the bolt in is counterproductive from an accuracy standpoint, you have 6 of one and a half-dozen of another here.  The gain in uniform lug bearing can be off set.

[rugerfan.64]

Thank you all for the input. So what would I expect to pay to have this done on a ruger m77 hawkeye?

[gunnut69]

First as always why do you want to do this? Dies the rifle have poor lug contact? Have you checked. Checking the lug contact is a fairly simple process. Color the lugs (bearing surfaces, rear) with a permanent majic marker or Dykem (a dye available from industrial supply houses) and insert the bolt into the receiver. Rotate the bolt closed and open several times.  Remove the bolt and check the amount of colorant removed from the rear lug surfaces.. Make certain to clean and degrease the lugs prior to coloring, especially if a marker is used.. If 40-60 percent of both lugs appear to be bearing there is no ral pressing need to work on the rifle.. Jerry's firs trule applies,,'if it ain't broke, don't fix it'..

[rugerfan.64]

First. Yes I have checked the lug engagement. Lower lug 60 % engagement. Upper lug 0% engagement. Fired case chambered or empty chamber makes no diff. I adhere to the if it aint broke dont fix it rule 100% of the time. Not to worry tho,its due for a second trip to the factory for service about the same thing again. The jury is still out on their customer service. If they fix it this time fine,if not I will probably use it to mark a property corner.

[gunnut69]

Sound like a man after my own heart.. Try the test again and apply pressure to the bolt face using a rod (padded) thru the muzzle pressing against a handy wall.  This should elininate the tendancy to tilt the rear of the bolt UP when check the engagement and showing NO contact at all with the top lug. Rugers have not shown a tendancy to produce this type problem and be certain to let The guys in service no what you've done.. They've been great the few times I've had problems with a Ruger.. much different than S&W.

[rugerfan.64]

To late to check it again,besides I've checked it 100 times. Plus the UPS truck just left with it. It seems to me that applying pressure to the bolt face would alter the test results? When a round is chambered it fits the chamber correct? Exerting 0 pressure to the bolt face correct? When I chamber a neck sized case it fits the chamber perfectly so there shouldnt be any back thrust on the bolt. Am I correct in this? Or am I missing something here. Anywhoooo,I sent an email with photos attached and a fired case back with the rifle. We shall see how Ruger Customer service does this time.

[gunnut69]

The fit of a case in the chamber is not what you are measuring. It is the bearing contact between the rear of the locking lugs and the front of the locking lug recesses in the receiver ring. When a case is fired it assumes the shape of the chamber, exactly. Then it contracts slightly, which is what loows it to be extracted. A neck sized case is usually a better fit to the chamber as the exterior dimensions aren't changed by the sizer except for the neck which must be sized to properly hold a bullet. When you raised and lowered the bolt handle there is a tendency to raise the rear of the bolt slightly. This could alter the results slightly..usually on the top lug. Putting pressure on the bolt face eliminates this tendency and gives a more accurate reading.. Let us know how this comes out... 

It just dawned on me that I don't know why this exercise came about? The normal problem causing this line of questioning is a badly out of square case head noticed by a reloader. sometimes bad enough to cause headspace anomolies.. Why were you looking to lap the lugs on this rifle..?

[rugerfan.64]

Well first off it came from the factory with 0 contact on one of the lugs and about 60% on the other. Second and this is the most important part. IT SHOOTS LIKE S***. If it shot well I'd have never checked it. This is probably the last thing I can do to remedy this rifle without sending it to a smithy.

[ardeekay]

This is great !!  I read this, and my brain is just jumping, at first I thought it would be easy to just run a wood hardwood dowel down the barrel, and lapping compound to the rear of the lugs, and lean the thing against the garage wall, (muzz end of the dowel) and start working the bolt handle up and down....  then it hit me.... that dowel would be rubbing on my barrel interior ! causing uneven wear !!  Another "brainstorm".. that I would take a slightly oversized fired brass, lube the foward part of it so it turns freely in the chamber, and use that as pressure when opening and closing the bolt handle, with the lugs doped with lapping compound... it would eventually come to size ( brass is softish) and might have to be replaced with another 'tight' empty cartridge...    what are your thoughts on this..  all I want to attain is contact for  BOTH of the recoil lugs fairly equally...

[parkergunshop]

Here is how to do it right.

Pull the barrel off of the action,   Tools needed, Barrel Vice, Barrel Block to fit the barrel, Action Wrench.

Lap the lugs in,   Tools needed Bolt Lapping set with spring loaded plunger from Brownells.

Prussian Blue to check your lug contact from time to time.

when lugs evenly contact.

Re install the Barrel

Check the Headspace,   No go headspace guage for the chambering.

If the bolt closes on the headspace guage.

The barrel must be set back in the receiver until the bolt will not close on the no go guage.

This is not a Afro Engineering job for the novice.

[parkergunshop]

Had an Interruption,

To continue the previous post.

Once you set the barrel back make sure that the bolt will close on the go guage.

If not you need a finish reamer for the chambering to make the chamber deeper.

And alternatively use the go guage until the headspace is correct, while hand reaming a little at a time.

Try a new unfired case in the chamber as a final check, it should close with little or no effort.

Having a minimum headspace improves accuracy and is easier on the brass and makes the brass last longer.

[gunnut69]

I agree pretty much with Parkergunshop but advise the use of a solid load against the bolt face. A spring loaded pressure device will allow lapping a 'hump' into the abutment areas. The solid device will have to be just tight enough to allow the bolt to lock into battery. The highest contact points will get the most attenetion first, as we would like.. As the bolts motion becomes easier tight the solid pressure device. ventuall a nearly flat surface will result.. Also be very careful to keep all abrasives off the bolt face!