Bore diameter
#1
Nontypical Buck
Thread Starter
Join Date: Feb 2003
Location: Body in SE WI, mind in U.P.
Posts: 4,781
Bore diameter
I have to post this due to a recent thread and because on many boards in general, some people confuse bore and groove diameter.
Bore diameter- If you were to use a traditional way of making a rifle barrel, you would use what is called a rifle drill (go figure) to drill a hole through the barrel from end to end. The diameter of this hole would be considered the 'bore' diameter. The easy way to remember this is that you use a drill to 'bore' holes in things.
Groove diameter- After a barrel is bored, rifling is put in by pushing through a button that expands part of the bore, or a cutter is used to remove metal from the inside to produce the rifling. The distance from the deepest part of a groove on one side of a bore to the deepest part of a groove in the other side of the bore is your 'groove diameter.'
In a 30 caliber rifle, typically, the bore diameter will be .300" and the groove diameter will be .308" but this can vary a tiny bit within a barrel from end to end and from barrel to barrel. A kink in the middle of a barrel can reduce the bore/groove diameter slightly, while cleaning rod wear can increase the bore diameter slightly on a muzzle.
If you want to check the barrel dimensions of a rifle, especially if its a foreign rifle where dimensions tend to vary more, you can slug a barrel. After slugging, the high spots on your slug would represent the grooves and the low spots, the bore.
I posted a bit on slugging awhile back.
http://forum.hunting.net/asppg/tm.as...ugging󒾞
Bore diameter- If you were to use a traditional way of making a rifle barrel, you would use what is called a rifle drill (go figure) to drill a hole through the barrel from end to end. The diameter of this hole would be considered the 'bore' diameter. The easy way to remember this is that you use a drill to 'bore' holes in things.
Groove diameter- After a barrel is bored, rifling is put in by pushing through a button that expands part of the bore, or a cutter is used to remove metal from the inside to produce the rifling. The distance from the deepest part of a groove on one side of a bore to the deepest part of a groove in the other side of the bore is your 'groove diameter.'
In a 30 caliber rifle, typically, the bore diameter will be .300" and the groove diameter will be .308" but this can vary a tiny bit within a barrel from end to end and from barrel to barrel. A kink in the middle of a barrel can reduce the bore/groove diameter slightly, while cleaning rod wear can increase the bore diameter slightly on a muzzle.
If you want to check the barrel dimensions of a rifle, especially if its a foreign rifle where dimensions tend to vary more, you can slug a barrel. After slugging, the high spots on your slug would represent the grooves and the low spots, the bore.
I posted a bit on slugging awhile back.
http://forum.hunting.net/asppg/tm.as...ugging󒾞
#2
RE: Bore diameter
The drill you refer to has no lead, so it bores straight. After boring barrels are reamed to the bore diameter, as the reamer leaves a cleaner hole. Then it is rifled. The hammer forged barrels have an oversized hole, the barrel is placed over a mandril that has the rifling in negative that is reversed, multiple hammers then pound the barrel to fit on the mandrel. [8D]
#3
Join Date: Feb 2005
Location:
Posts: 592
RE: Bore diameter
Good general discription of the post for people whom have asked. One note as you know is that no barrels have a straight rifleing bore in them,some more than most are. None perfect. Thats another reason for the crown to be 90% of the muzzle to helllp being the most accurate as possible as barrels can be. Theres a lot to barrels,accuracy,ect. and it fun to talk about it,and trying to have the most accurate riflee one can have. vangunsmith
#4
RE: Bore diameter
[quote]ORIGINAL: vangunsmith
Thats another reason for the crown to be 90% of the muzzle to helllp being the most accurate as possible as barrels can be.
You lost me here . . . . what do you mean by the crown being 90% of the muzzle? Roskoe.
Thats another reason for the crown to be 90% of the muzzle to helllp being the most accurate as possible as barrels can be.
You lost me here . . . . what do you mean by the crown being 90% of the muzzle? Roskoe.
#5
RE: Bore diameter
ORIGINAL: vangunsmith
Good general discription of the post for people whom have asked. One note as you know is that no barrels have a straight rifleing bore in them,some more than most are. None perfect. Thats another reason for the crown to be 90% of the muzzle to helllp being the most accurate as possible as barrels can be. Theres a lot to barrels,accuracy,ect. and it fun to talk about it,and trying to have the most accurate riflee one can have. vangunsmith
Good general discription of the post for people whom have asked. One note as you know is that no barrels have a straight rifleing bore in them,some more than most are. None perfect. Thats another reason for the crown to be 90% of the muzzle to helllp being the most accurate as possible as barrels can be. Theres a lot to barrels,accuracy,ect. and it fun to talk about it,and trying to have the most accurate riflee one can have. vangunsmith