mikecr said:
The important thing is that the bore at the muzzle is tightest.
If you contour/flute a button rifled barrel after lapping, too near the muzzle, you risk opening to bore at the muzzle.
With cut rifled, there is way less(if any) risk.
With hammered (such as with a LW), the bore actually gets tighter with further contouring.
Hi Mikecr,
I will give you a few examples of things that go against what you just wrote.
Do not take it badly, I think a Lot of what you just wrote could be true especially in short distance br or to shoot the ass of a fly.
The choke on the bore seems to be important when shooting 22lr lead bullets, and I believe that the best br barrels out there are lapped that way because lead does not spring back . Once that bullet looses some of its material with the friction in the bore the only thing that can keep it exiting straight is that choke on the last few inches of the barrel.
With a jacketed bullet, the jacket may be "gliding " in the bore with out loosing so much material, so a bore with uniform and consistent dimension should be enough to guide it straight. I have seen tests performed on rifle where the accuracy actually increases as the barrel is cut down an inch at a time : ( there is a point where it reaches a nod and is t it's best with that test load and then groups reopen a bi after, but in no way are the groups opening bigger than when the barrel was shot at its original length).
In New Zealand, as well as UK, France and Scandinavia, a lot of factory rifles get their barrels fitted with after market sound moderators and the accuracy generally improves. I recently had a friend of mine who bought a second hand tikka varmint in 308. He got he barrel shorten by 2 inches and threaded at 1/2"x28: that means no much more than 2 mm of meat left either side of the bore at the muzzle! (I hate those small threads!) he fitted a suppressor on it and managed to produce several groups under 1/2 inch at 100 yards with factory hornady match Ammo. Go and figure out!
Regarding cut rifle barrels you are certainly right. One trick from barrel makers to get a uniform bore is to profile and cut the flutes after the blank of steel is gundrilled but before it is reamed out, that way they know the bore is very close to perfect in dimensions as the outside wont get touched again.
I believe Lothar Walther barrels are button rifled and not hammer forged.
Sako/ tikka ar hammer forged .
As to the hammer forged barrel bore getting tighter as the outside is contoured, maybe to a certain degree, but I have pushed some lead bullet through some 22 lr hammer forged barrels ( BSA and cz) and the further you push the lead to the muzzle end the looser you can feel the bullet slipping in the barrel. And funny enough, when pushing the lead bullet from the muzzle( the thin part of the barrel) back to the chamber( the thickest outside contour) you can feel the bullet getting tighter and tighter.
Again, I don't think I hold the truth, but these are a few real experiences that defy the general theory .
Nic