Home Forums Hunting & Shooting Ask The Gunwriters Lapped barrels

I've heard the term "hand lapped barrel", but not really sure I know what it means. What exactly does it mean, and how is it done?
I just replaced the barrel on a new Remington 25/06, that I just couldn't get to shoot. I ordered a Lija barrel and had my gunsmith chamber it and install it. The difference between it and the factory Remington barrel groups is day and night. I,m pretty sure the Lija barrels are "hand lapped"
Thanks,

Yes, Lilja barrels are hand lapped

http://riflebarrels.com/support/faq/#handlapping

Q. What is hand lapping?


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 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. Please see our comments on the BlackStar operation in this section too.

I am no expert but I think they run a lead slug back and forth in the bore to remove tooling marks and smoothen the bore out. Most after market barrels are lapped I believe.

Lapping does remove machine marks and smooths out the barrel.

More importantly if you know what your doing you can fix other issues like rough spots, and tight spots in a barrel.

Of course this is ignoring that barrel makers produce higher quality barrels that factory barrels to begin with.

Hand load will shrink group size

Antelope Sniper speaks of the best way to do this, IMO.

There's other methods, not as effective but sometimes will help somewhat, that is lapping with tight wad and lapping compound. This method will not remove tight spots as well, but it will polish the barrel.

I've done both. Antelope Sniper's method is best, but polishing may help too (but not after the method AS described).

Also, the method of shooting a bullet impregnated with a polish compound may help. It helped tremendously with two of my rifles. Mule Deer has addressed this fire-lapping several times. The bullet can be a cast bullet or a jacketed bullet. This method is the first method I try. (because it is easy)

I believe the comments on Lilja site about comparison of racing slicks on a dragster to a bore that is toooo smooth is correct.
I had a Shaw barrel taper bored and micro pollished by Black Star. I would do the taper bore again in the right circumstance, but the super smooth bore copper fouls quick and heavy. But the gun shoots absolutely great.
jmho
Tim

Some are lapped both before and after rifling.

Pacnor is going to power honing instead of lapping for the pre-rifling step.

http://www.sunnen.com/NewsDetails.aspx?NewsID=108

Interesting article on the honing process..........definitely should make better barrels. (I've had some exposure to production honing on cylinder liners.)

As for lapping, Douglas or someone comparable once said, "Lapping will not make a bad barrel good, but it will surely make a good barrel better".

FWIW

MM

michiganroadkill,

Yep, lapping or coating bores TOO smoothly normally makes them foul more, not less. I visited Lilja's shop some years ago and he'd run quite a few experiments, and I believe recommended lapping compound not finer than 320 grit. The theory is an ultra-smooth bore contacts the bullet more, resulting in more friction, not less, while a little striation from the lapping (which naturally follows the lands and grooves) causes the bullet to ride "on top" of the bore.

Have talked to several other barrelmakers who've come to the same conclusion, including one who made the mistake of lapping some bores with diamond polish. It's also why SMALL tool marks in an unlapped bore often result in very little fouling.

However, I've also found Dyna Bore-Coat usually cures fouling in a super-smooth bore. Dunno why, but it does!

CZ, I believe, hones or laps their barrel blanks before hammer-forging them. That seems to work out pretty well too, and it's probably less labor-intensive than conventional lapping.

Barrels that are to be lapped are drilled and rifled undersized slightly to compensate for any metal removed in the lapping process. Old muzzle loaders were lapped on a regular basis to remove pitting but after this was done several times a larger patch or ball was required. That's why with antique rifles so many have an odd bore size.

RE: Too smooth of a bore. I have remedied this on bores that had been cleaned too much with Flitz or JB bore compound by running a patch with 220 or 320 grit lapping compound down the barrel. This leaves minor longitudinal scratches in the barrel and reduces fowling.