Hand lapping a barrel

[padaro]

I don't really understand why this is something to brag about when talking gunsmithing.

It's mentioned a lot that barrels are hand lapped when looking at custom stuff. Surely a machine does it faster and more precise than a person ever can.

Personally I have no experience with such things, but I mean like a mill is crafting things to a thousandth of an inch, no person can be so precise.

Doing it manually has to be more imprecise.

What's the fuss over hand happing a barrel then?

[Chronos]

Every metal working process produces minute flaws and stresses in the steel. It doesn't matter whether it's a factory mass produced barrel or a custom target barrel. The difference is when you pay for a match grade target barrel you expect it to shoot its best straight out of the box, to achieve this barrel manufacturers machine their bores slightly smaller than required then use a cast lead slug and a lapping compound to achieve a finished bore that's as smooth as possible. These barrels foul less and shoot more accurately.

Bore scope pics would show the difference better than a description could.

That's not to say factory hunting rifle barrels can't shoot accurately but they're more likely to have a longer "run in" period and possible a shorter life

Chronos

[Apollo]

"Chronos" has mentioned part of it but there is a lot more to the art of "hand lapping a barrel" and the difference it makes in the final accuracy, plus why the cost.

Laying material down that is raised during the production process, to run the direction of a bullet travel. Polishing out the irregularities of chambering a barrel and putting that mirror finish on the bore are all part of a custom barrel that may shoot 1/4 MOA but that's pretty bad, getting it down to 1/8th and even better accuracy is the art and in my view part of treating and expensive custom barrel during it's early run in stage.

As "Chronos" knows shooting my Custom Stolle and he has shot it himself to produce 1/4" group at 200 Yards but....it has done better. It's actually shot, not in my hands, but a 0.089" shot group at 200 yards, very experienced target shooter.... that's a Custom Grade Hand Lapped Target Barrel.

You are looking at not far off these days of $1,000 for a Custom Match Grade Barrel, chambered.....!!!!

[Jack V]

More to the point the reason they say hand lapping is because a machine can't feel . Hand lapping is done by feel not actual measurements . Having said that I do believe that some barrel makers do in fact do some machine lapping and then finish up by hand.
The lapping is only to smooth it up and remove burrs not change the basic bore dimensions . During the process you can get a feel for how good the bore is , how straight it is and which end should be the muzzle .

[mausermate]

I have just taken delivery of a new TSE barrel and took the option of paying the extra bucks and having it lapped. I have not taken the option before, I generally spend a significant amount of time, carefully running in a barrel which IMO does the same job.
I am hoping the lapping will reduce the run in time dramatically.
I suppose we will see what happens.

[Chronos]

More to the point the reason they say hand lapping is because a machine can't feel . Hand lapping is done by feel not actual measurements . Having said that I do believe that some barrel makers do in fact do some machine lapping and then finish up by hand.
The lapping is only to smooth it up and remove burrs not change the basic bore dimensions . During the process you can get a feel for how good the bore is , how straight it is and which end should be the muzzle .

Directly from the Lilja barrels website, note the hi lighted section

Chronos

A. The hand lapping process, that all of our barrels undergo, ensures that you will receive a rifle barrel that has the very best and most desirable type of internal finish that we can provide. The lapping operation brings the final internal dimensions up to size and also improves the finish. No production barrels are hand lapped, only the finest custom barrels receive this very important operation. And it is partly for this reason that hand lapped barrels cost more than lower grade production barrels.

In practice, a lap is cast around a rod placed inside the barrel. The profile of the rifling is cast into the lap ensuring a very precise fit with that individual barrel. The lap is then "charged" with lapping compound, oiled, and pushed and pulled repeatedly through the length of the barrel. The lap is "recharged" and oiled many times and several new laps will be cast before the lapping procedure is completed. The man doing the lapping judges when the barrel is finished by a very experienced feel for the job, inspecting the internal finish as it develops with a full length borescope, and by measuring the diameters of the lands and grooves.

We have, over the years, developed a process that we feel gives us the very best finish and uniformity of diameters the full length of the barrel, that we can obtain. And the proof is, in our opinion, in the very minimal amount of bullet jacket fouling that our barrels produce, and in their outstanding accuracy.

Our process completely eliminates all tooling marks from the inside of the barrel. And very importantly the resulting finish runs parallel with the rifling.

It is for these reasons that we discourage anyone from submitting their new Lilja rifle barrel to any subsequent internal finishing operation.

[Jack V]

Dan Lilja has a reputation for good barrels he also has a reputation for stretching the truth a little bit . The lapping process should not be carried so far that it makes the bore bigger in any real measurable way . You just want to polish out the burrs and any possible tight spots but if it's got feelable tight spots it's not a match grade blank anyway , in my book . Button rifling has less burrs to deal with than cut rifling process but more stress . Most target barrels are made a bit on the small side to start with . A good run in process does a fair job of removing any burrs also. Remember that stuff from Lilja is advertising .

[Chronos]

Yep, advertising their product by explaining why they do what they do. I'll take their word for it.

There's no possible way to lap anything without removing good metal as well as burrs and machining marks , we may be talking in the ten thousandths of an inch but that is measurable.

Just my opinion, and dan lilja's

Chronos

[Jack V]

It all depends on how much lapping you do . You could keep going and lap the rifling right out. The whole point is you don't want to go too far and they don't either.
So the notion that they bring the barrel UPTO final dimensions is crap. They start out undersize anyway and they stop lapping when it feels right and the bore scope image looks good and what ever size that is , is what it is sold at . It's such a small difference in each barrel that for practical purposes it's not measured after that .
Have you ever seen barrels sold as .30755 . The reason Lilja says that they lap to bring the barrel to the "right "dimensions is to for stall the customers question . Will the lapping process ruin the precision of the manufactured size ? It just makes the customer happier to believe that the lapping is the last precision process and the dimensions are then perfect . When we all know that everything ever made has production tolerances and variations no matter how small they may be . In the case of good barrels very small indeed .

[lapp]

and which end should be the muzzle .

Never heard that point raised before.

Why might one end be better than the other?

[Jack V]

There you go . Generally one end of the parallel blank will be a bit tighter than the other . Usually they cut off a section at the start of the buttoning as it takes a few inches to stabilise the twist . This usually means that the far end will be the muzzle but during lapping you can feel which end is tighter and smoother than the other and you should lapp more at the chamber end than the muzzle to preserve that tightening as it goes towards the muzzle.
The stamps on the barrel at the end indicate the chamber end but it's not always 100% right as far as fit goes but some people like to have the bullet go the same direction as the button travelled in the bore . If you receive a profiled barrel blank then the muzzle end is already set and you have no choice anyway.

[becks]

The stamps on the barrel at the end indicate the chamber end but it's not always 100% right as far as fit goes but some people like to have the bullet go the same direction as the button travelled in the bore.

To go with the direction of burs or flaws in the barrel?

[Jack V]

Yes I believe that is the thinking .

[chacka]

Gotta say that strikes me as one of those 'makes sense in theory but bugger all difference in reality' kind of practices.

The same bullets going down the same barrel regardless of direction. If anyone had a test both ways I'd be keen to be proven wrong, I'm just not seeing it really.

[disko]

I guess a few burs wear smooth breaking the barrel in soon enough either way too.

[Jack V]

I can't see it making any difference really but who knows. It would take a lot of testing to prove anything.

I think a good smooth well made barrel that has tight tolerances is going to shoot about the same from either end, all else being equal.

[chacka]

I think a good smooth well made barrel that has tight tolerances is going to shoot about the same from either end, all else being equal.

That's my thinking as well.

Just my 2c but I've always thought it was odd some people get so focused on negating every last little insignificant bur or blemish on bullets and barrels...... Only slam the bullet down the barrel at 3,000fps where the rifling and fouling batter the jacket to hell anyway

[Chronos]

Chacka,

Perhaps if you had invested tens of thousands of dollars and thousands of dollars in competing at the highest level you'd be careful to ensure every possible chance that each shot you fire goes exactly where its supposed to.

We're not talking about hunting rifles here, even extreme long range hunters have a large target zone to hit but when the blokes either side of you are trying to beat you by .001" at 200y you'd better cover your ass and make sure everything's perfect. These guys will recrown their barrels by 1/2"-1" every few hundred rounds because of the "sandblasting" effect they say ruins groups and causes flyers.

It's what allows the people at the pointy end to do this



Chronos

[1290]

I would like to add to this discussion, but I'm afraid the post would be so long that no one would actually read it.....

All I'll say is that I think Chronos and Apollo are BROTHERS......Else why would you refer to Chronos in quotation marks? Mr Apollo...(or Mrs, I'm assuming both male gender of course)

[Chronos]

lmfao. Maybe were the same person ? Except were more that 20 years apart in age and live 300 km apart.

I've been invited to shoot at Apollos property a few times, some of my load development was done there and we share an interest in accurate rifles , though his tend to cost a fair bit more than mine. What's wrong with that ?

Chronos

[1290]

Wrong? its great! what made me suss was you also naming your dog after him, or him assuming the name of your dog, that also ok!

I'm watching to at the moment, if you turn to your left - I'm the bloke waving frantically!!

[Chronos]

Haha I see you.....put you're pants back on

No worries

Chronos

[chacka]

I would like to add to this discussion, but I'm afraid the post would be so long that no one would actually read it....

I'm game for it.

Post away...

[1290]

Haha I see you.....put you're pants back on.....

You first

You know what theyve said about clothes in the workplace!....

[Norton]

They're optional?