Home Forums Hunting & Shooting Gunsmithing Lug Lapping Question

ok, on the Remington 700 i have sitting here, the bolt doesnt close very smoothly. i would like to lap the lugs, but my only question is this...

can i lap them by simply applying a little lapping compound to the rear of the lugs, and just go to town working the bolt handle up and down?

i know i need to check the surface contact by marking it with a permanent marker or some Dykem...

i just want a smoother bolt operation.

thanks in advance.

Whatever you do, go slowly. You can lap enough to enlarge headspace in which case you've worked yourself into a relatively expensive repair.

Have you tried cleaning and relubing the bolt, cocking piece, and engagement surfaces? How is the bolt lift not smooth? Just heavy, or does it bear or drag in particular places?

There are easier ways to get a smoother bolt lift than lug lapping.

actually, there is no barrel on it right now, and there is also no real problem with bolt lift.

the issue is with the bolt close. its "sticky" and "lurchy" not smooth. also, it is well oiled as that was my first thought. and clean, since Kend cleaned the crap out of it to coat it.

It may not be the bolt lugs causing your problem it may be the cocking piece on the firing pin and sears. Does it have this problem when the firing pin is cocked and ready to fire or when re-cocking with the bolt life. You can try some grease on the back of the lugs and see if this helps. Lapping really should be done when barreling, but if you do don't get all carried away and it may be a good idea to check with a no go gauge when done because some factory rifle are put together with head-space set at the max from the go. The difference between a No Go and Go gauge is only 0.004 inch's.

If it is sticking on closing that might be a problem with the cocking piece rather than the lugs. Is it binding when you're pushing the bolt forward or when you're rotating the bolt handle down?

Either way, I'd just have your 'smith lap it when installing the barrel. That way all the parts work well together.

Unless you sleeve the rear end of the bolt, lapping really doesn't benefit the action. You said it was just coated, would check to make sure all camming surfaces are clean

when you pull the bolt up after firing the cocking piece rides over a beveled edge on the bolt and it can be sharp so polishing this will sometimes smooth this out, plus you can put some grease on the cocking piece also and it can make the bolt opening and closer easier. Look at the cocking piece and you will see what I'm talking about. If this happening with a round in the chamber and not happening when unloaded the extractor could have a burr on it.

Pull the firing pin and see if it is better. I have seen some horrible feeling j locs.

i believe that this rifle was made in the late 70s. IIRC that is.

Honestly, that's the last thing you should be doing. If the lugs on the bolt or the lug abuttments in the reciever have serious gouges or galling, take it to an accuracy 'smith that knows what he's doing. The proper way to resurface the lugs/abuttments is by cutting, not hand lapping.

When doing it the way you describe you intend to, there's no way to insure the mating surface will be 90 degrees to the long axis of the bolt. If you do it with a trigger in place, the trigger raises the rear of the bolt as it's closed due to the clearance between the bolt body and the reciever. If you take the trigger out, how will you center the bolt in the reciever? It will be loose in the reciever and your lapping may again result in out of square lugs.

I've seen a couple of 700's that have been messed up by doing this..it can open up more problems that you can imagine. I've also very carefully fixed a couple with badly galled reciever lugs using this method, but have been darn careful when doing it. In both cases, I removed the trigger and firing pin (obviously) and centered the bolt in the reciever by sliding two .003 thick blade style feeler guages in from the rear....one on top of the bolt and the other on the bottom in the rear reciever bore and used some thinned down valve lapping compound, followed by some 400 gr. compound. I only did 10-12 'up and downs' and held the bolt face back against the lugs with a wooden 5/16" dowel rod clamped in a vise....being darn careful not to let the bolt get up on the mechanical cam angle on the back of the reciever and come back.

Not doubting your enthusiasm....you just need to understand all of what's involved and be darn careful.

FWIW. -Al

very informative Al.

i have a small amount more info than i did yesterday. i took the rifle out, (i call it a rifle, but it is just an action with a barrel hand tightened to the receiver, and a stock) and worked the bolt up and down. during the time the bolt lugs are in contact with the receiver lugs, it is quite smooth, whether lifting from a fired spring, or and unfired spring. there is a small catch at the top when closing the bolt. i personally believe that this is simply the bevel on the bolt lugs engaging the receiver lug cutouts, but it is so "lurchy" i want to smooth this part out.

do you have a recommended bit of advice for this issue?

Unscrew the firing pin from the bolt. If you don't have the tool, a shoe lace or piece of wire will work. Often the spring will twist up and feel all kinds of wrong as it rubs in the bolt. This will take but 1 minute of your life, but tell you a lot about isolating the issue.

Then go for it! And when you get done [bleep] up the lugs you'll have another issue that needs to be fixed, along with the cocking piece as three others have suggested...

With the barrel out, you should be able to SEE any gauling on both the lugs AND the lug abutment AND bolt camming surfaces, and if it is as old as you say it could just be worn at the camming surfaces or the shroud threads dinged or worn.

Lug "LAPPING" implies actual metal removal with a fairly large size grits in the lapping compound like 180-240 to rapidly take down burrs and machining marks. Then the use of smaller and smaller grit sizes to POLISH the lapping marks out and to put a smoother surface.

Lapping can take reduce the thickness of surface hardening so you need care when doing it.

Lapping "can" change headspace, but from my experience that is just scare talk...done right you don't take off more than maybe 0.002" and POLISHING hardly changes dimensions at all.

Everytime I buy a new or used rifle I check the lug contact surfaces and about 90% of the time in a new rifle one lug is "higher" and basically takes the full load for a few microseconds until it deforms slightly or takes ALL the load ALL the time untill it gets "worn" in.

Most of the older rifles, depending on how much they've been shot and how old they are "most of the time" have nearly 100% contact and only require a small amount of lapping with 320-400 grit to finishe the process...if I bother at all..and MANY old rifles have more headspace than new and that "excess headspace" can be adjusted out buy setting up your sizer die correctly.

My "sage advice" is put a small amount of 400 grit on the firing screw surfaces of the shroud and screw it in and out for a "while" which many times will smooth out any rough spots...you can feel them very easily, then clean very well and look for slightly dull spots in/on the threads...the dull spots are where the grit has cut down rough areas. You can leave it that way and "wear" in by use or change to maye 800 grit and polish a bit. This might reduce your "thumps and bumps" or at least let you know it wasn't the problem.

You can also check the camming surface on the bolt for any dings, burrs or grooces in some cases and polish.

Alternatively just send it to a smith to be "Blueprinted"...the lugs and lug abutments get squared to each other and to the bore centerling and the threads get squared to the centerling at the same time, along with the raceways polished up also...plus a bush job will make the bolt much less floppy...

You can do all or a few of the various excellent suggestions and work through "the problem" also. Diagnosing gun problems long range is like asking the doctor WHY you have a belly ache and giving him only ONE symptom...pretty much usless...especially if your description is a bit nebulous.

Basically depends on how much "fancy" you want, how much accuracy you are willing to pay for etc. Hardly needed in a basic hunter unless you plan on stretching out the range or going for a high dollar hunt trophy.

This game is like Golf...you can buy a bag of sticks for a C note and have all the fun you can stand or reach deep, advance the level of you equipment, work hard and reduce your scores considerably.

Sometimes a hard bolt lift can be corrected by just grinding off a small amount from the front action screw which my be contacting the bolt when tightened in the stock. This is the first thing i check if the bolt is hard to close or open.

Remember the Doctor's Rule, Marty.

"First, do no harm!"

I would be damn sure I had my brain around the situation before I cut ANY metal from a critical surface, and your lug interface is about as critical as it gets.

Would it help to say that at roughly twice your age, I know exactly the itch you are feeling, but have learned the hard way that that itch is saying "Slow down!", rather than the "Speed Up!" that it feels like? It's a sneaky bastid, that itch.

I'd look at virtually everything else, before I lapped lugs for that reason. As others (who know vastly more than myself) are saying.

Good luck to you- I do applaud your gumption, seriously!

I'm in no hurry. i was just asking. i dont want to screw up my only left handed rifle. just thought that it might help as i did it with my Mauser 98 and it helped tremendously. much smoother operation after i lapped it with some valve lapping compound.

install the action into a stock and then try the bolt - it will make a big difference in leverage and working the bolt. your 700 may not have the anti bolt bind feature that involves a slot on the bottom of the right locking lug which will ride in a corresponding groove on the right hand receiver rail and this may be why you have bolt bind. Clean the coating off all the engaging surfaces. Polish the bolt body, lube the cocking cam and bolt plug (bolt sleeve) with lubriplate - same stuff used for M1 Garand lubrication. This should help. Good luck with it. Mel

I predict you'll have that action BLUEPRINTED (by your own hands) in 10 years... you've got the bug and the inclination to learn the skills and buy the tools. Very cool.

I've got the lathe, but it's a money-maker doing other things at the moment, and the tooling to really set up a lathe for chambering multiple calibers is eye-watering... grin...

The machine is a 12x36" Logan, 1 HP, weighs about 1000 lbs. Preliminarily, the spindle appears to run true enough to chamber, at least without a load on it, and within my ability to measure. And it came with spiders (it was a gunsmith's lathe), but that's all the further I've gotten.

Come play on it sometime! I'm generating lots of scrap we can cut up <g>.

There's some great info here in these posts. My son's Ruger .308 had a rough catch cocking the rifle. I pulled the firing pin assembly and the roughness was gone. I took a magnifying glass and looked the threads on the firing pin assembly and saw two slightly buggered threads like the assmbly had been dropped. I took my needle files out and slowly corrected the threads and it's smooth now.