Shortened barrel….bad groups now

[bluedog69]

Buddy of mine has cut down about a dozen barrels and threaded them to use his can on. All of them have still been shooters when he was done.
He has a 6.5 PRC that was a great shooter and then he shortened it. Now it is a poor shooter. He recrowned it didn't help. He bought an 11 degree crown cutter…no change.
Any ideas why this barrel went bad when cut short? Any suggestions to make it shoot again?

 

[338 dude]

Buddy of mine has cut down about a dozen barrels and threaded them to use his can on. All of them have still been shooters when he was done.
He has a 6.5 PRC that was a great shooter and then he shortened it. Now it is a poor shooter. He recrowned it didn't help. He bought an 11 degree crown cutter…no change.
Any ideas why this barrel went bad when cut short? Any suggestions to make it shoot again?

Did he rework his ammunition?

 

[R. Cram]

I just set my barrel back ,cut off a inch and a half off the breach end and rechambered to get back to fresh rifling and had to totally change my load, the one I use for medium range went from 1/2 to 3/4 min for 5 shots to 1 1/2 min for 5 shots. I hate working up loads also

 

[bluedog69]

Did he rework his ammunition?

I have no clue on that. Not even sure what he thought what was good and now is bad. I know the kid(young guy) can shoot and work up loads. I will ask him.

 

[bluedog69]

I just set my barrel back ,cut off a inch and a half off the breach end and rechambered to get back to fresh rifling and had to totally change my load, the one I use for medium range went from 1/2 to 3/4 min for 5 shots to 1 1/2 min for 5 shots. I hate working up loads also

I'll pass on the info to him. I don't know if he got lucky on all the other rifle and this is his first rework needed or not.
Thanks!

 

[R. Cram]

I'll pass on the info to him. I don't know if he got lucky on all the other rifle and this is his first rework needed or not.
Thanks!

For shooting highpower I always shoot a 260 and that midrange load has been the same for thousands of rounds and dozens of barrels ,the biggest reason I don't change calibers is because normally the same loads work well but for this setback I had to change the load, he needs to try changing his load who knows why

 

[JSHKS]

Yup, changed the harmonics. A new load or different ammo. I would suggest complete start over and work up.

I refuse to shorten my barrels because of "can" length. I see a lot of folks do it, but I am not one of them.

 

[Sockeye66]

Curous if the poor grouping was both with and without the can on.

 

[skipglo]

Buddy of mine has cut down about a dozen barrels and threaded them to use his can on. All of them have still been shooters when he was done.
He has a 6.5 PRC that was a great shooter and then he shortened it. Now it is a poor shooter. He recrowned it didn't help. He bought an 11 degree crown cutter…no change.
Any ideas why this barrel went bad when cut short? Any suggestions to make it shoot again?

Harmonics!

 

[DENRIK89]

Buddy of mine has cut down about a dozen barrels and threaded them to use his can on. All of them have still been shooters when he was done.
He has a 6.5 PRC that was a great shooter and then he shortened it. Now it is a poor shooter. He recrowned it didn't help. He bought an 11 degree crown cutter…no change.
Any ideas why this barrel went bad when cut short? Any suggestions to make it shoot again?

I've been through this same thing myself, the barrel vibrates differently now (harmonics). If he was already at optimal charge weight rework the seating depth then shoot for the same velocity he was at, minus 20ft per second for each inch he cut off, that's will put him back in the money

 

[bluedog69]

I've been through this same thing myself, the barrel vibrates differently now (harmonics). If he was already at optimal charge weight rework the seating depth then shoot for the same velocity he was at, minus 20ft per second for each inch he cut off, that's will put him back in the money

Thanks to all for chiming in. I asked him about his loading. This rifle he had just bought and it was sub MOA all day with factory 143 eld x. So he never had a load worked up with this rifle.
Looks like he needs to get busy with powder and seating.
When you shorten barrels is it beneficial to switch to faster burning powders? Better chance at burning it all and maybe finding good harmonics in short barrel?

 

[Coyote Shadow Tracker]

With the exception of our SBRs (9") and Coyote ARs (20") we have 24"-26" barrels on our Hunting rifles and they wear Cans. Almost no shift in POI with or without the Can.
Don't see the need to cut the barrel down to fit a can.
If it is too long to carry get a Chassis with a split stock.

 

[338 dude]

Thanks to all for chiming in. I asked him about his loading. This rifle he had just bought and it was sub MOA all day with factory 143 eld x. So he never had a load worked up with this rifle.
Looks like he needs to get busy with powder and seating.
When you shorten barrels is it beneficial to switch to faster burning powders? Better chance at burning it all and maybe finding good harmonics in short barrel?

I recently went from a 26 to a 22 inch barrel. I dropped 10 grains of bullet weight to get me right back into my sweet spot.

 

[tobnpr]

He has a 6.5 PRC that was a great shooter and then he shortened it. Now it is a poor shooter. He recrowned it didn't help. He bought an 11 degree crown cutter…no change.

"He" shortened it- or paid a smith to do it? I've used a piloted cutter for crowning, but that's after the barrel's been dialed in on the lathe. Who shortened, threaded and crowned the muzzle on this initially?