Gunsmithing Galled Bolt Lug

[MontanaMarine]

Rem 700 308Win. Several thousand rounds through it.

I was shooting this recently and bolt closing felt a little wierd, opening after the shot felt really stiff and 'bumpy'.

I pulled the bolt and saw this galling on the left lug. I deadlined the rifle. Sprayed out the lug recesses with carb cleaner, all kinds of carbon and gunk came out of there. Makes me think some small hard bit of debris might have gotten caught up between the lug and it's bearing surface in the lug recess of the receiver.

Anyway, I need to get her back up and running. Was wondering if some lapping compound and a bunch of hand cycles are in order, or does it need to be taken apart and refaced, re-headspaced, etc.

After a good cleaning and fresh grease, it runs generally smooth, but with a noticeable 'bump' when closing the bolt.

The side that galled has always beared more solid than the other side.

Thanks in advance for any opinions, recomendations, and advice.

 

[Force_Multiplier]

Re: Galled Bolt Lug

how close is it to needing a new barrel?

if it's over 1/2 way there, and it sounds like it might be, I'd have it trued and a rebarrel done.

if it was fairly fresh, I'd hand lap it to smooth it out and run it a while...

almost looks like a tiny bit of the lug, just at the bottom broke off and got caught

P.S. if it's already had work and a good barrel, maybe just the lugs cleaned up and a barrel set back

 

[MontanaMarine]

Re: Galled Bolt Lug

It's the factory Rem barrel, and it does have some mileage, probably 4-5K rounds. Being a 308, that's probably about half used up.

I figured if it needs to go to the 'smith, I'd put on a new tube while it is already there and pulled apart.

 

[Force_Multiplier]

Re: Galled Bolt Lug

sounds about right to me MM... that was the impression I was getting... send her in

but it's not gonna be unsafe to just lap it a little, if you want to keep popping primers w/ her, and I doubt you notice much difference after that vs before all this

 

[turbo54]

Re: Galled Bolt Lug

First, stop shooting the rifle until this has been addressed, or you'll cause more damage.

It doesn't look that bad.

If you have a few tools, and/or know someone, this can easily be repaired pretty nicely until the action gets reworked at your next barrel change.

Fasten the bolt, nose down,on a flat surface such as a surface plate.

Build up a stack of jo-blocks (or similar) to build a "perch" to sand/grind/lap the lug surface LIGHTLY.

You're only looking to remove the highspots, NOT retouch the entire lug surface. This won't take much.

I've done this before. After stoning, the galling was almost totally imperceptible, it DIDN'T gall anymore, and the rifle shill performed as well as it ever had.

 

[BK7saum]

Re: Galled Bolt Lug

+1. A fine stone to knock off the high spots and your back in business

 

[jrm850]

Re: Galled Bolt Lug

I would get a look at the mating surface inside the action just to make sure you don't have any stress risers on that lower lug.

 

[MontanaMarine]

Re: Galled Bolt Lug

Well I took a fine stone to it, and very carefully smoothed off the protruding metal. Greased it up and it's running as smooth as ever.

Haven't shot it yet, so will have to see if zero has been affected.


Thanks for all the wisdom.

 

[2156SMK]

Re: Galled Bolt Lug

I have run into this in the middle of a match.
My solution was to take my knife sharpening stone and knock off the high spots on the lug.
That's the easy part since you can get right to them.
Then I went and got some lapping compound and I lapped just the lug with the galling.
Then I flushed everything out real good and re-greased it.
No more problems for thousands of rounds after that.

The key is to never let your lugs get so dry that they gall...

 

[MontanaMarine]

Re: Galled Bolt Lug

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2156SMK</div><div class="ubbcode-body">....The key is to never let your lugs get so dry that they gall... </div></div>

Yep. I'm usually very diligent about that. I normally only neck-size my handloads so they are already a snug fit.

 

[MontanaMarine]

Re: Galled Bolt Lug

A little follow up.

Took this rifle out for a re-zero today, it's shooting fine. Two three-shot groups at 100 with a known accuracy load. 155gr Scenar, 38.0gr RL7, 2.81" oal.

 

[LRI]

Re: Galled Bolt Lug

While the lugs certainly do need some attention I would also take a moment to look at the helical ramp on the back of the bolt that resets the fire control when you lift the bolt out of battery.

The bolt lugs don't really have a load applied to them when rotating out of battery. Galling is oftentimes the product of a case that might have needed a touch more shoulder bump, FL resize, etc. The pressure exerted against the lugs as it closes leads to the chewing on the surfaces.

The cocking piece however sees load every time you cycle the bolt. It can create a groove along the ramp that makes lifting the bolt feel horrible. If there's a groove/shiny line the easy way to fix it is to burnish/polish the ramp on a soft felt wheel. Then use a high shear load grease. (like Tri Flow for instance)

As for the bolt lug, a medium grit stone will knock off the wart. Just be careful not to get carried away. The lug surface wants to be flat. A stone can/will create a draft angle if you get heavy handed. This may make it look pretty, but it'll just start the problem over again in a big hurry. Surface area to spread the load generated by closing the bolt is what your after.

Hope this helps.

C.

 

[MontanaMarine]

Re: Galled Bolt Lug

Thanks for that info, it all makes sense.