Barrel problems

[mauser284]

Barrel Break in is a pipe dream. "Break-In" is the idea of accelerated wear between parts that move and interact with each other like a cam sliding over a lifter or a piston ring traveling up and down the bore of a cylinder.

A given bullet only makes one pass through the bore and is never seen again. The bullet is either lead, copper, bronze or lead jacketed in some form of gilding metal based on some form of copper alloy in modern times. All of those things are softer than modern barrel steel so no wear in at all.

Wear in a barrel is based on heat, pressure and the abrasions from powder. Barrel Break-In is as silly as a sugar pill curing cancer can you say placebo.

A borescope image is used after you have real world data but by itself the surfaces inside do not tell you much outside of how likely it is to foul quickly.

Savages are known for having some insanely rough bores yet traditionally many of the shoot really well and most of them foul quickly too.

The barrel by itself is just one part of the equation. That is why reloading can allow you to make a rifle that shoots marginally into a tack driver at times. If it was just down to the barrel life would be simple! That said baring reloading you do not ever get some magical reduction in group size with the same ammo over time after hitting some magical round count and cleaning. Different ammo can produce differnt result but not a magical round count.

Lapping is not precision machining and is not a precision method of machining either. There is no engineering text book written in the last 50 years that will list lapping with lapping compound as a precision controlled machining process.Also hand lapping can not and will not produce a consistent precision surface. Anyone that does tell you it does is either a liar or ignorant. In fact the allowable clearances and tolerances have to be be fairly large for hand lapping to be acceptable which tells you just how much fudge factor is involved in a product. Lapping is about cost savings and allowable clearances and allowable tolerance stacking. Their is nothing wrong with hand lapping parts so long as it is not being sold as precision machining practice or as a means to a precise manufacturing of a product.

If your mechanic wanted to take your precision machined block no matter if it is a Porsche block or Toyota block and wanted to hand lap the pistons and rings to the cylinder bores with 240grit valve lapping compound or wanted to cast a lead slug in the bore and take lapping compound to it you would never take a vehicle to that mechanic again would you!!!

 

[GerryM]

Its not magic just lapping the barrel with iosso paste The pits and roughness smoothed out . filled in.
It,s still not pretty but it improved quite a b it with kroil and bore paste.

 

[davidjoe]

Up two ^^ on break in. The groups definitely do shrink up and flyers go away after some rounds on a new chamber job. I believe the throat changes rapidly and then stabilizes. All shots are damaging and the rifling down a good barrel’s length can’t be improved from firing bullets through it. If it did improve, something was very wrong with it before the shots, such as a high spot or crown burr. A minority seem fine from shot one, but you don’t know that until they get the same treatment.

 

[jsn]

Several points/questions to the OP:

1) Your original post, photo #1, appears to show heat cracking at the throat only. If that's not heat cracking, I'd like to know what it is.
2) The remainder of the photos in that post show what I would consider advanced wearing away of tooling marks for only 350-400 rounds.
3) Was the chamber cut concentric? There is no freebore or even a taper cut on the lands shown in that first pic. It's not unusual to see an undercut on one side, and an overcut on the other side, on a factory cut chamber for a certain manufacturer. In other words, no taper cut on the two lands on one side, and usually a gross overcut of two lands on the side opposite (assumes a 6 land barrel).

Since you have already decided to get a new barrel, I will assume you are not sending it back to Remington. Since it looks like you're going to replace it.....

4) Can you find someone to run a throating reamer in just enough to cut out that roughness referenced in 1) above, then see how it shoots.
5) If 4) cannot be done cheaply, maybe you could do the JB Bore Paste, or even fire lapping, to remove part of this roughness, then see how it shoots.

If you tell Remington you're running reloads, or do anything with abrasives or a cutter you would probably void the warranty. If you're going to toss the barrel, and you probably won't get all of your tools and parts any sooner than you would get it back from Remington anyway, it would be interesting to see how it might shoot with minor work.