Scratches from pilot bushing

M

Martin64

Guest
I used a 60 degree piloted centre drill to finish the crown a barrel, and upon close examination, I am getting copper deposits on the area the bushing was. It appears the pilot bushing lightly scratched the lands. What did I do wrong, and should I lop off 3/4" of the barrel? I will never try that again.
 
How much did you cut off the muzzle end before you crowned it? Could the scratches have been there before it ever saw the reamer pilot?
Regards,
Ron
 
I cut off 1" but after that I probably used up close to another 1/2" after all work was done, experimenting around on the lathe with different profiles for the crown, trying the piloted centre drill to finish the edge of the rifling, removing that failed "experiment" and finally getting it the way I wanted it to look. Its around 29" now. I want it as long as possible for shooting 155gr SMK's at 1000 yards. I'm not sure if I'm making a big deal out of nothing, but I want to do the best job I can on my rifle.
 
Martin64,

Unless the scratches are really bad, like you can catch the fuzz off a q-tip, I would not worry about them.

Have used the piloted 60 degree reamer for many bbls used for 1K shooting and they all will shoot much better than I can hold.

As long as the crown is concentric with the bore and nice sharp edges, go with it.

Bob
 
How about some 1200

I would give some 1200 grit compound on a patch a try and/ or JB paste. Go EASY.
 
bob3700 said:
Martin64,

Unless the scratches are really bad, like you can catch the fuzz off a q-tip, I would not worry about them.

Have used the piloted 60 degree reamer for many bbls used for 1K shooting and they all will shoot much better than I can hold.

As long as the crown is concentric with the bore and nice sharp edges, go with it.

Bob
Click to expand...


I agree with Bob!

Also, most barrels leave their heaviest copper fouling deposits within the last inch of the muzzle which is commonly believed to be atomized copper coming out suspension with the drop of bore pressure as the bullet exits the muzzle, so what you are seeing at the muzzle may have nothing to do with the pilot bushing and can be confirmed by a good bore scoping.
 
I would coat the reamer with Vipers Venom ,works every time for me... No marks no scratch.
 
Martin64 said:
I used a 60 degree piloted centre drill to finish the crown a barrel, and upon close examination, I am getting copper deposits on the area the bushing was. It appears the pilot bushing lightly scratched the lands. What did I do wrong, and should I lop off 3/4" of the barrel? I will never try that again.
Click to expand...

I'm not sure one is connected with the other. In fact all you say you see is copper. Polish with a tight fitting patch with Flitz, JB or Iosso bore cleaner and shoot it.

Dave
 
One theory is that throat reamer marks are to blame for copper fouling near the muzzle, from vaporized copper. JB polish the throat, and do the breakin clean-shoot routine for about 10-15 shots. One well known gunsmith claims to do breakin by putting JB on the bullets of the first 5 rounds, and this does the throat polish. Never tried this, myself, but sounds reasonable.
 
I think the leading and trailing edge of the pilots are the cause of those 'light' scratches that sometimes appear in the bores. I made a little 'spinner' device that I polish/radius the edges of the bushings and no longer get any marks on top of the lands. I always thought a pilot with the profile of a football would be best for axial alignment issues, but that may be overthinking things.
 
Over the years I've had to work on finished barrels between centers for a variety of reasons. I have brass inserts with short pilots on them for 90 degree and 11 degree crowns, caliber specfic. I lube everything up but from time to time I get scuff marks most likely made by the undersize pilot moving around in the bore. The only reason I can see them is they reflect light back out the muzzle where the new barrel reflects no light, it looks black. A tight patch and a mild abrasive take care of those scuff marks in short order. On the chamber end I don't run snug fitting bushings. A good setup on the barrel and there's no need for a tight fitting bushing. And a Scotchbrite wheel on a grinder is your friend for polishing/breaking edges. I wouldn't be without a 6" grinder set up with a cutoff wheel and Scotchbrite wheel.

Dave
 
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