Shortening barrel, accuracy effect?

[Thach2264]

Hello-

I am thinking of having a machinist shortening my barrel. Barrel is not choke, question is which end should I cut to have less chance of effecting the accuracy? I am thinking the chamber side because you don't mess with factory crown. What do you guys think?


I would like to shorten it a bit. Why not just buy a shorter barrel, not for $400 though. btw - I do not know anything about barrel.

thank you,

 

[Ca_Varminter]

If done correctly... No Effect at all...
Which end.... it depends on the configuration of the breech end...
Some are simple, just a straight cut and deburring... Other require a through-port and other features to be machine.
But the muzzle, no choke... Simple job... as long as you have the tools to cut a clean Crown... the Most important Feature....
Other than a target rifle... factory Crowns are not the Best!!
I alway recut my barrel crowns.... even on my barrel liner for my FX M3

Good Luck

 

[Thach2264]

The barrel I have both end are threaded, so any end will take the same amount of work + crown on the muzzle end. The machinist I will bring it to is not a gun smith, so I want to have the best chances. Thanks

 

[GeneT]

There is no magic to the factory crown. Cut and re-crown that end. Given that the machinist you will use is not a gunsmith, make sure they understand the importance of making the crown concentric to the bore and not the outside of the barrel.

Shortening the barrel may cost you velocity (depending on your tune) but should not otherwise impact your accuracy. In fact, all else being equal, shorter barrels are more accurate.

GsT

 

[Ca_Varminter]

It should not be a problem for a good machinist to shorten your barrel...
I would shorten the muzzle end...This gives you a Fresh clean sharp Crown.
This should be a no Brainer....
Shorten barrel to length desired...
True up the cut and bevel the circumference the barrel.
Single point cut the threads at desired pitched.
The cut the 11° target crown... a slight polish and you are done.....

 

[Firewalker]

On a protected barrel end, no bevel is needed if it remains burr free.

The bevel is solely a function of crown protection though there is much argument over this.

A bevel can also "cheat" a poorly done crown and direct gasses to buffer the projectile.

Have your buddy do a straight cut then face at high speed from the bore out with a sharp bit and only 0.001" deep.

 

[subscriber]

Have your buddy do a straight cut then face at high speed from the bore out with a sharp bit and only 0.001" deep.

This is for the OP, as clarification of Firewalker's statement:

Expect to use more than one facing cut on the lathe. The number of cuts required depends on the smoothness and perpendicularity of the saw cut. The idea is to keep going until the saw cut is completely cleaned up. The light cuts and direction Firewalker suggested are to minimize burr formation, and to make any burr "lean" away from the bore, rather than encroach on it.

If the saw cut is a bit skew, then facing with deeper cuts should be OK until a complete flat face is achieved. Then just do the last five facing cuts 0.001" deep each, using high rotational speed. Feed the cutting tool slowly and smoothly from from the ID to the OD. Do not let the tool chatter.

Do not use abrasive paper or cloth to polish the muzzle face, as soft materials tend to enter the bore in unpredictable ways. This may round over the lands at the crown in an uncontrolled manner. If you must break the square corner, a brass round headed screw, used as a lap is a better method. Firewalker's method should make it unnecessary to add a facet at the crown.

You can break the OD corner of the barrel muzzle with a file or the lathe tool turned at a 45 degree angle, but keep that facet very small. Just enough to remove any burr than might be there from cutting towards the OD.

Firewalker, if you deem my advice to be poor, feel free to offer a better or clearer message.

 

[Firewalker]

This is for the OP, as clarification of Firewalker's statement:

Expect to use more than one facing cut on the lathe. The number of cuts required depends on the smoothness and perpendicularity of the saw cut. The idea is to keep going until the saw cut is completely cleaned up. The light cuts and direction Firewalker suggested are to minimize burr formation, and to make any burr "lean" away from the bore, rather than encroach on it.

If the saw cut is a bit skew, then facing with deeper cuts should be OK until a complete flat face is achieved. Then just do the last five facing cuts 0.001" deep each, using high rotational speed. Feed the cutting tool slowly and smoothly from from the ID to the OD. Do not let the tool chatter.

Do not use abrasive paper or cloth to polish the muzzle face, as soft materials tend to enter the bore in unpredictable ways. This may round over the lands at the crown in an uncontrolled manner. If you must break the square corner, a brass round headed screw, used as a lap is a better method. Firewalker's method should make it unnecessary to add a facet at the crown.

You can break the OD corner of the barrel muzzle with a file or the lathe tool turned at a 45 degree angle, but keep that facet very small. Just enough to remove any burr than might be there from cutting towards the OD.

Firewalker, if you deem my advice to be poor, feel free to offer a better or clearer message.

Thank you for filling in all the details, I made a hasty reply.

 

[Vetmx]

Everyone is all concerned about the crown. But if you’re not dealing with an airgun smith, then you definitely don’t want him pissing around trying to cut a proper leade. If the barrel is already a good shooter for what you want to shoot out of it, definitely have him chop the muzzle end. Do overs are much quicker and easier on that end of the barrel. Do overs on the breech end cost you inches.

 

[Thach2264]

Thank you all for all the tips and suggestions guys, will definitely let my machinist see this thread when he doing that actual work. Thanks again!!!

 

[bigHUN]

In past years I collected some custom barrels (3 actually), all these were shooting well. But once (many months later) I pushed a new scope camera inside just out of curiosity I discovered the scratch marks from a crowning tool. That made me so nervous I could not stand that longer, toke the barrels to a gunsmith and recut about 1/2" (more less) all from the muzzle. Re-crowned them diy with a brass screw and happy again. But honestly the change was more mental value, the accuracy is about the same according to target rings pictures before and after.

 

[Vetmx]

In past years I collected some custom barrels (3 actually), all these were shooting well. But once (many months later) I pushed a new scope camera inside just out of curiosity I discovered the scratch marks from a crowning tool. That made me so nervous I could not stand that longer, toke the barrels to a gunsmith and recut about 1/2" (more less) all from the muzzle. Re-crowned them diy with a brass screw and happy again. But honestly the change was more mental value, the accuracy is about the same according to target rings pictures before and after.

I would have to agree that some things seen with a bore scope that have a guy reeling in disgust have little or no effect on accuracy.

 

[Scotty1]

In past years I collected some custom barrels (3 actually), all these were shooting well. But once (many months later) I pushed a new scope camera inside just out of curiosity I discovered the scratch marks from a crowning tool. That made me so nervous I could not stand that longer, toke the barrels to a gunsmith and recut about 1/2" (more less) all from the muzzle. Re-crowned them diy with a brass screw and happy again. But honestly the change was more mental value, the accuracy is about the same according to target rings pictures before and after.

I had 2 early RTI barrels, a 20” .22 and .25. Both had a ring perpendicular to the lands, about 3/8” in from the muzzle, from the crown tools pilot. They both shot much better than they looked, but man did it bother my conscience. The .25 also had no bevel cut at the breech end, and would just jamb trying to load from a mag, a brass ball nut and some compound and drill fixed that quickly.