I am looking to get this done locally but have a few questions. First off shouldn't the barrel be shortened square with the bore? there is 0.005 difference between the top of the barrel and the bottom. would it be easier to just cut it flush with the bushing? how much would that affect accuracy? crown will be cut at a 45 degree angle any benefits of this?
Well, the flush cut is square with the bore, so if the barrel locks up off axis, then you will see a difference near the bushing. The 45 degree crown recesses the lands and grooves which can protect them from damage. Other than that it is more cosmetic than anything. You can ship the barrel, bushing and slide to a smith and have it done.
What kind of 1911? You realize the barrel in lockup has a different axis than the bushing or slide.
The OP mentioned that in his post and the next post addressed the issue also.
If a 1911's bushing has no slop in the slide (so the recoil spring can't force it off-axis) there'll be about 0.009" more barrel showing at the top than at the bottom. For the ultimate haute couture look, it would seem the only way to avoid this unsightly gaffe would be to angle the face of the bushing to match the angle of the muzzle - whatever that angle turns out to be when the gun's all put together and in battery.
And because you measured a difference of only 0.005" it may be a sign the recoil spring is pushing the bushing off-axis. If so, don't forget that because the bushing's locking tab is located at about the 4 o'cock position, its offaxisness will be... uh... off axis.
Then too, leaving the barrel as is avoids all that bazanga!
Didn't think about the bushing being off axis. Well I better go measure and see what I have.
It probably won't be (or can't get) off axis too much. It's only about 0.3° for an average GI 1911, but it doesn't hurt to check it - especially if the bushing seems real loose in the slide.
Don't forget about the photo when you're done.
Greg mentioned that a recessed crown will help protect the lands and grooves (which a stock rounded-edge barrel will do, too, but less deeply); cutting back can also fix damage to the muzzle, and a deeper crown helps to direct muzzle blast forward. I've heard one disadvantage of cutting it flush is that more powder gets on the font of the gun.
You definitely don't want to cut flush with the bushing. Everything done to the barrel's crown is to be done on-axis, or accuracy will suffer. Imagine a bullet clearing the muzzle in super slo-mo: there's the exact moment when the bullet stops sealing the bore and gas starts to jet out around it. If the muzzle is damaged or off-axis you're going to get gas shooting out of one side of the bullet first, pushing it to the side and destabilizing the spin.
Regarding the off-axis bore, it sounds like Niemi's suggestion is a good way to handle it, though possibly a bit tricky to pull off.
(1) angle the bushing face (the tricky part?),
(2) cut the majority of the crown on the barrel,
(3) assemble slide in lockup and hand-cut the last few thou of the crown to match the bushing face? maybe not too bad...
Another way that would change the look of the crown, but possibly be easier, would be to leave a small flat ring at the very outside of the crown that would be angled to match the bushing. the off-axis flat would be away from the bore, cutting it's effect on the escaping gasses. However if it is too small the angle may be visible on the face, and if too large it could impact accuracy.
A different procedure wouldn't exactly get rid of the angle, but it would conceal it. The crown could be cut a few thou back from the face of the bushing, then the crown's angle cut just a bit in to the bushing bore face.
You could also just leave the barrel face uneven with the bushing and blend it in. <.010" might not be noticeable if smoothed out.
Greg, you have some beautiful examples of this on your site. do you have a preferred procedure?
By design a barrel crown protects barrel rifling... this is why it is called a crown...
I haven't read what method will be used to cut the barrel crown... (one of
the most important aspects of a barrel)?
Will you use a lathe? (your better off using a big engine lathe or such)
Will you attempt to use a mill?
Will you attempt to use a drill press?
Or will you attempt to do this cut by hand?
We all know how important a barrel crown is... The biggest reason a crown is important is because it ensures uniform crown geometry that allows uniform gas pressure dissipation around the circumference of the bullet exiting the barrel to ensure consistent shop placement.
Airguns are real sensitive to having a proper crown. One of the favored methods is to use a grinding compound and a brass/bronze round-head screw and 'lap' a new crown in. A plug is inserted into the bore just before the crown to keep grit out of the barrel. The barrel is of course cleaned after the procedure.