Re-Indexing the Norc Bbl
- Thread starter 22rimfiredude
- Start date
Yes action wrench and barrel vise will be needed to turn it.
Increase or decrease headspace? A small amount (should be near negligible), depending on which direction you need to turn it. Quick S.W.A.G. say that 3 degrees turn would result in around 4 tenthousandth of an inch movement. So less than half a thou if you turn the barrel 3 degrees.
Increase or decrease headspace? A small amount (should be near negligible), depending on which direction you need to turn it. Quick S.W.A.G. say that 3 degrees turn would result in around 4 tenthousandth of an inch movement. So less than half a thou if you turn the barrel 3 degrees.
If the flash hider is leaning to the left/front sight post driven to the right, then centering it will increase headspace. If the flash hider is leaning to the right/front sight post driven to the left, then centering it will decrease headspace.
One other thing to mention is that re-indexing the barrel will true up your operating rod with the piston in the gas cylinder and make for a little more accuracy. You can actually see how much the barrel is off center from the alignment of the op. rod to gas cylinder better than how far off your flash hider is.
Before you re-index, loosen off that little screw on the right hand side that is pinning your barrel to the receiver. It is hidden from normal view by the operating rod.
One other thing to mention is that re-indexing the barrel will true up your operating rod with the piston in the gas cylinder and make for a little more accuracy. You can actually see how much the barrel is off center from the alignment of the op. rod to gas cylinder better than how far off your flash hider is.
Before you re-index, loosen off that little screw on the right hand side that is pinning your barrel to the receiver. It is hidden from normal view by the operating rod.
As pointed out by Grizzlypeg, any change in headspace from adjusting indexing is insignificant. A thread pitch of 10tpi, and a shift of 5 degrees - which is a very serious out of index situation - would result in a shift of 0.100x5/360=.00139". You could have more variation than that with different brands of ammunition.
Search for posts by Lazarus2000 and Hungry. All the questions that you have about tweaking a 305 are answered.
Don't even consider trying to alter indexing without proper tools.
Search for posts by Lazarus2000 and Hungry. All the questions that you have about tweaking a 305 are answered.
Don't even consider trying to alter indexing without proper tools.
Just a couple questions that keep popping in my head, but...
I noticed that outside the chamber there are feed grooves (Terminology?) below the mouth as well as cut in the receiver for guiding bullet tips into the chamber mouth. Do these need to be redone if you index the barrel and shift them left/right?
Also, if I have a barrel that's over-indexed (spacer between barrel / receiver is crushed) what can I use to fill in the gap and reindex it properly (I heard of shimming the gas lock with shims made from coke cans, is there a similar way for re-indexing / fixing spacers?
Othen than that, this thread brought more knowledge to my attention. Thankyou.
I noticed that outside the chamber there are feed grooves (Terminology?) below the mouth as well as cut in the receiver for guiding bullet tips into the chamber mouth. Do these need to be redone if you index the barrel and shift them left/right?
Also, if I have a barrel that's over-indexed (spacer between barrel / receiver is crushed) what can I use to fill in the gap and reindex it properly (I heard of shimming the gas lock with shims made from coke cans, is there a similar way for re-indexing / fixing spacers?
Othen than that, this thread brought more knowledge to my attention. Thankyou.
The receiver should be perfectly square/perpendicular to the bore line. The original NORC barrels, US GI barrels, and most aftermarket barrels, are undercut at about 1 degree from perpendicular, so that only the outside of the barrel contacts the receiver, with a bit of "crush" fit during final rotation.
If massively overindexed/overtightened, you will find that the outside edge of the barrel shoulder [ expecially the sometimes softer NORC barrels ] will deform quite a bit, and may not tighten up correctly with the proper torque/draw ] at the proper indexed location.
If you have a lathe, one solution is to roll the deformed barrel shoulder lip back down into proper location. Without a lathe, a teensy tiny hammer, a lot of patience, and a lot of light taps while rotating the barrel by hand, can be used to evenly beat down the lip.
LAZ 1
If massively overindexed/overtightened, you will find that the outside edge of the barrel shoulder [ expecially the sometimes softer NORC barrels ] will deform quite a bit, and may not tighten up correctly with the proper torque/draw ] at the proper indexed location.
If you have a lathe, one solution is to roll the deformed barrel shoulder lip back down into proper location. Without a lathe, a teensy tiny hammer, a lot of patience, and a lot of light taps while rotating the barrel by hand, can be used to evenly beat down the lip.
LAZ 1
- Location
- Houston, TX
Has anybody in Calgary got the tools & experience to do this? I think my barrel is a bit under-indexed, unfortunately Hungry had his clinic here back in November and I just got the thing ...
Headspace gauges would be a bonus!
Thanks,
Eric
Headspace gauges would be a bonus!
Thanks,
Eric
