Lapped with JB test

[richhymas]

You don't need that extra 50-100 FPS that you are trying to get. Just focus on accuracy. Put a good bullet in the boiler room and the animal will die. May look a bit better in your ballistics calculator, but no animal ran away unharmed because you were 100 FPS slower than the next guy.
You do risk harming your accuracy though. And that will increase the risk of a miss or worse a wounded animal.
Best of luck. Just find the bullet and powder combo that you are happy with in your gun.

 

[mwkelso]

Racing slicks have more traction on dry pavement than treaded tires.
Bullets have more friction or grip on a smooth barrel than a less smooth barrel.
In a chamber the brass is expanding into the crosshatch of the surface of the chamber and prevents slippage.

I was thinking the same thing.
Funny thing with tires too is the difference in width changing traction... Wide tires have less traction than narrow ones because of the weight distribution. The wide tire has fewer PSI of asphalt contact, while a more narrow tire has higher PSI of contact. Hence why the narrow tire has better traction.
@Mram10us - I've never worked on a barrel in any way, shape or form in my life. This question comes purely from speculation: If there are other rifles that you are comparing velocities to, is there a way you could measure the width of the riflings? My thought here, going back to the tire analogy, is that a more narrow rifling would produce more friction against a bullet compared to a rifling that is wider, creating less friction. Maybe there is correlation here?
If any of the experienced smiths could chime in here, I am very curious to know.

 

[ntsqd]

Racing slicks have more traction on dry pavement than treaded tires.
Bullets have more friction or grip on a smooth barrel than a less smooth barrel.
In a chamber the brass is expanding into the crosshatch of the surface of the chamber and prevents slippage.

But a less smooth barrel has all of those tiny obstructions trying to slow down the bullet by gouging off a little more of the jacket. Much like Harry Potter's competitor in the hedge maze where each root was a further impediment to motion.

Conversely the proper technique for stacking two gauge blocks together is to "ring" them together. that is to put the near corner to the far corner and slide them together. Quality gauge blocks assembled this way can not easily be pulled apart. They can be slid apart, but not pulled.

See why I said I could make an argument in both directions?

The more dimples you put on a golf ball the better it flys! That's why the PGA says how many dimples there can be. Dimple a car's finish and it gets better gas milage! Hard to dimple a bullet with out a sabot. Every thing can be an abrasive with time and effort. I would be more worried about the rod and patches than the JB. Too smooth is not good except on ball bearing and races!

Dimples create the boundary layer that I mentioned above. Great for flying thru the air or across the water, but bad for creating a gas-tight seal to drive the projectile with.

 

[Canadian Bushman]

Brass has plenty of grip on polished chambers just like slick tires have lots of grip on DRY smooth concrete.

the problem with either is that just a bit of moisture between those surfaces and most of that grip goes away.

Texture on freeways and tread on tires aint for dry weather traction.

 

[ntsqd]

Brass on steel has a .51 Cf when dry.

Friction - Friction Coefficients and Calculator

Friction theory with calculator and friction coefficients for combinations of materials like ice, aluminum, steel, graphite and many more.

www.engineeringtoolbox.com

 

[keithcandler]

Jb is not lapping compound, and 20 strokes would not be measurable. Bore dimensions have a large effect on velocity, but lapping is not the way to change them, its a way to uniform things. You wont be able to avoid rounding the sharp edges of the lands if you lap too much, and that will cause a loss off accuracy. If its an experiment, go for it. But if the barrel is accurate, Id recommend shooting it a little slower.

I hope you listen to Alex, you do not lap with JB.

I make lapping compounds from 800 Grit to 180 grit For my own use, Al Oxide. 800grit and 600grit Silicone Carbide is used for barrels in really rough shape, or carbon fouled from end to end.

I am not a proponent of fire lapping any barrel that is a fine quality barrel. There is a learning curve with fire lapping and it is an expensive way to go.

 

[ntsqd]

You do not lap a bore with JB, or you should not lap a bore with JB?

 

[gohring3006]

A quick way to gain 50-100 FPS is the proper application of HBN and go a little higher with charge weight.

 

[Dirtrax]

Send your barreled action to Defensive Edge and have them +P throat it. You may gain .002" on your throat but not necessarily. You will gain speed. You may even see an improvement in accuracy.