Bill Calfee
Gun Fool
The bore is damaged
CYA friends:
This old, 4-groove Broughton I'm fooling with has two cases through the bore.......I'll bet a dollar bill that's within a couple bricks either way.
There's no CYankee on Earth that would put two cases through this barrel the way it shoots now.
________________
When I decided to see if I could bring this old Broughton into the modern world of RFBR accuracy, I cleaned the bore and slugged it.
But.........................
I remember that I started a slug in the chamber end, then pushed it gradually toward the muzzle, then stopped the slug with the nose just barely sticking out of the muzzle.
I then turned the barrel around and pushed the slug back toward the breech, to feel the taper release.
And the old barrel felt excellent.....the only bad thing was, it measured .2225" in the grooves at the muzzle.
But it just wallered when I shot it.....
____________________
So today I pulled the barrel to put it back on the shelf.
But then decided to slug it again, very carefully, to see if I'd overlooked something with my initial slugging.
After I cleaned the bore, I put a baggie on the muzzle end, to catch the slug, then started a slug in the chamber end, and gradually pushed it all the way through the bore.....
Uh-oh...................
I felt a check right at the exit of the crown.
I slugged it again, and sure enough, there's a very pronounced check at the muzzle.
I missed this the first time I slugged the bore, since I didn't push the slug all the way through the exit of the crown.
____________________________
This gets even more interesting...
When I measured these slugs, that were pushed all the way through the bore, they still measured a perfect .2225" in the grooves.
So the check at the muzzle was not distorting the slug.
But................
When I looked at the slugs under a loupe, the black oxide of the SK-SSHP bullet was completely gone between two of the land cuts in the slugs.
On this old Broughton, one of the grooves is located exactly at 6:00 at the crown.
When I looked closely at the crown with the loupe it looked technically fine, but, the groove at 6:00 was pitted from the crown back into the bore about 3/16".
CYA friends, this pitting, roughness, was the check I was feeling....
Keep in mind, when you slug a bore, a rough place will sometimes feel exactly the same as a tight place.
This is where measuring comes into play when slugging.
____________________________
So....................
Tomorrow I'm going to cut 1/4" off the muzzle of this old Broughton and re-crown it.
Now..................
I've got a theory as to how that pitted place got in this bore, right at the exit of the crown at 6:00.
When I first took this old Broughton off the shelf, I could see that whomever owned it, cleaned the muzzle with the MD on the barrel, like most folks do.
I had to take some 5-0 steel wool and remove the circular carbon deposit from the face of the crown.
I'll write up the rest of my theory as to how I believe that pitted spot got in the groove at the crown, soon.
Your friend, Bill Calfee
____________________________
PS:
After I re-crown this old Broughton, if it still continues to waller, it will go back on the shelf, for sure.
CYA friends:
This old, 4-groove Broughton I'm fooling with has two cases through the bore.......I'll bet a dollar bill that's within a couple bricks either way.
There's no CYankee on Earth that would put two cases through this barrel the way it shoots now.
________________
When I decided to see if I could bring this old Broughton into the modern world of RFBR accuracy, I cleaned the bore and slugged it.
But.........................
I remember that I started a slug in the chamber end, then pushed it gradually toward the muzzle, then stopped the slug with the nose just barely sticking out of the muzzle.
I then turned the barrel around and pushed the slug back toward the breech, to feel the taper release.
And the old barrel felt excellent.....the only bad thing was, it measured .2225" in the grooves at the muzzle.
But it just wallered when I shot it.....
____________________
So today I pulled the barrel to put it back on the shelf.
But then decided to slug it again, very carefully, to see if I'd overlooked something with my initial slugging.
After I cleaned the bore, I put a baggie on the muzzle end, to catch the slug, then started a slug in the chamber end, and gradually pushed it all the way through the bore.....
Uh-oh...................
I felt a check right at the exit of the crown.
I slugged it again, and sure enough, there's a very pronounced check at the muzzle.
I missed this the first time I slugged the bore, since I didn't push the slug all the way through the exit of the crown.
____________________________
This gets even more interesting...
When I measured these slugs, that were pushed all the way through the bore, they still measured a perfect .2225" in the grooves.
So the check at the muzzle was not distorting the slug.
But................
When I looked at the slugs under a loupe, the black oxide of the SK-SSHP bullet was completely gone between two of the land cuts in the slugs.
On this old Broughton, one of the grooves is located exactly at 6:00 at the crown.
When I looked closely at the crown with the loupe it looked technically fine, but, the groove at 6:00 was pitted from the crown back into the bore about 3/16".
CYA friends, this pitting, roughness, was the check I was feeling....
Keep in mind, when you slug a bore, a rough place will sometimes feel exactly the same as a tight place.
This is where measuring comes into play when slugging.
____________________________
So....................
Tomorrow I'm going to cut 1/4" off the muzzle of this old Broughton and re-crown it.
Now..................
I've got a theory as to how that pitted place got in this bore, right at the exit of the crown at 6:00.
When I first took this old Broughton off the shelf, I could see that whomever owned it, cleaned the muzzle with the MD on the barrel, like most folks do.
I had to take some 5-0 steel wool and remove the circular carbon deposit from the face of the crown.
I'll write up the rest of my theory as to how I believe that pitted spot got in the groove at the crown, soon.
Your friend, Bill Calfee
____________________________
PS:
After I re-crown this old Broughton, if it still continues to waller, it will go back on the shelf, for sure.
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