Turn down barrel contour?

[elktaker]

I have 6mmx45 bull barrel that I picked up for $80 on ebay awhile back. It is a shilen 1:10 twist. I think it is a 26".

It shoots .5 MOA or better on a non-windy days with Nosler 70gr BT out to 400 yd. This is with reloads using brass fired from ARs. I just loaded .5gr below max for H335 and with no load development I ended up with .5 moa groups. Only load or bullet I have tried.

My question is will I see any negative affects having the barrel turned down to a lighter contour other than the obvious reduction in weight affecting accuracy. I am looking to lighten it up for a backup deer gun with a little heavier bullets and bc it is cheap to shoot and gives me practice reading the wind. I would probably have it threaded for a brake also (maybe invest in a silencer one day)

I, also, could have it reamed to a new chamber for longer ranges. I know I do not really want 243 win and the 1:10 twist will probably prohibit me from using high BC VLD's.

 

[Bart B]

When button rifled barrels are turned down, their bore/groove diameters typically get larger, somewhat unevenly.

So, you'll probably see some accuracy loss if you turn it down.

Barrel weight has nothing to do with one's inheirent accuracy. But heavier barrels are more easily held steady.

 

[MTBULLET]

When button rifled barrels are turned down, their bore/groove diameters typically get larger, somewhat unevenly.

So, you'll probably see some accuracy loss if you turn it down.

Barrel weight has nothing to do with one's inheirent accuracy. But heavier barrels are more easily held steady.

how does turning bbl OD change bbl ID ?

 

[J E Custom]

I have re contoured many barrels for one reason or the other and the results were always better accuracy if the right load was used (normally it alters the harmonics and sometimes requires a load change). If it liked a bullet before it was re contoured, That normally doesn't change, but the powder charge may have to be adjusted.

In most cases the re contour improved the run out on the barrel. I have re contoured lots of bull barrels (The same diameter at the muzzle as the shank) and many of them were not very true to the bore and the re contour made a huge improvement in accuracy.

If done correctly, it is most always an improvement as long as the new contour is not to light. also this is a good time to have a brake installed because of the barrel set up. (It will be true to the bore)

J E CUSTOM

 

[FEENIX]

how does turning bbl OD change bbl ID ?

I was wondering about that too?

 

[Edd]

how does turning bbl OD change bbl ID ?

The bore can get larger, out of round, or crooked. What happens is dependent on the stress that is in the steel.

Not long ago, there was a discussion and a video about how threading the end of the barrel for a brake caused the bore ID to grow.

 

[Bart B]

how does turning bbl OD change bbl ID ?

Like fluting and milling flats on a barrel, any outside metal removal lets the tiny stress still in them move the metal. Hammer forged barrels get smaller inside, button rifled one get larger. Cut rifled barrels change the least because their rifling process puts the least amount of stress on the barrel.

Accuracy degrades only a little bit, but enough that those who shoot rifles the most accurate will notice it. Bore and groove dimensions change only .0001" or a bit more, but that's enough.

 

[J E Custom]

I was wondering about that too?

In theory any dimensional changes are possible under the right/wrong conditions.

If a barrel Is not "properly stress relieved" or is not contoured true to the bore bad things can happen. The barrel diameter change will be so minimal that it will be almost impossible to detect,
but barrel straightness will show up.

In my opinion buttoned rifle barrels are least likely to have any dimensional changes because they are double stressed relieved (Once before any work is done from the mill, and then again after it is buttoned and contoured to relieve the forging stress.

Cut rifling is only stress relieved at the mill because the cut rifling does not apply any more stress.

I recommend buying a barrel contoured and/or fluted from the barrel maker because it has met the straightness and diameter requirements before it is shipped if possible. but if modifications are necessary then they should be done with forethought and the best quality possible.

Like everything, the quality of the barrel and any work after can have an effect on It's performance
so if a barrel is not one of the premium barrels and the bore is not true and straight, I decline any work to avoid future problems. As one of the sages on this site says "It is hard to make a silk purse
out of a sows ear".

J E CUSTOM

 

[Bart B]

In my opinion buttoned rifle barrels are least likely to have any dimensional changes because they are double stressed relieved (Once before any work is done from the mill, and then again after it is buttoned and contoured to relieve the forging stress.

That's in stark contrast to what the top quality barrel makers say.

 

[shortgrass]

All this 'discussion' over a $80 bbl. , purchased on E-Bay, that "might be a Shilen". Go ahead, turn it down (if you can find someone who'll do it for you), if it no longer shoots what have lost?

 

[J E Custom]

That's in stark contrast to what the top quality barrel makers say.

Sorry but I have talked to almost all of the "Top barrel makers" and some of the not so top ones and the stress relieving procedures remain the same throughout the industry.

most will have a cover story that protects them from mullets that don't know what they are doing
just like Shilen's no fluting after there barrels are shipped. We all know it can be done under the right circumstances but they have to protect them selves from the less qualified gun smith or the DIY people.

This discussion has came up many times and being concerned about threading a barrel for a muzzle brake and did some testing and research and found zero issues as long as the criteria I posted earlier was met.

Poor workmanship on the barrel maker's or the smith's part can always lead to problems.

So it is probably good to be extra cautious when embarking down this road and not taking a chance
if one does not feel comfortable doing contouring or barrel threading.

Anyway, I feel comfortable with both procedures as long as I have all the facts and verify the quality before I start.

PS: I have a personal list of barrel makers that I will not use because of there quality control and inconsistent Quality.

Just my opinion based on my experiences.

J E CUSTOM

 

[FEENIX]

In theory any dimensional changes are possible under the right/wrong conditions.

If a barrel Is not "properly stress relieved" or is not contoured true to the bore bad things can happen. The barrel diameter change will be so minimal that it will be almost impossible to detect,
but barrel straightness will show up.

In my opinion buttoned rifle barrels are least likely to have any dimensional changes because they are double stressed relieved (Once before any work is done from the mill, and then again after it is buttoned and contoured to relieve the forging stress.

Cut rifling is only stress relieved at the mill because the cut rifling does not apply any more stress.

I recommend buying a barrel contoured and/or fluted from the barrel maker because it has met the straightness and diameter requirements before it is shipped if possible. but if modifications are necessary then they should be done with forethought and the best quality possible.

Like everything, the quality of the barrel and any work after can have an effect on It's performance
so if a barrel is not one of the premium barrels and the bore is not true and straight, I decline any work to avoid future problems. As one of the sages on this site says "It is hard to make a silk purse
out of a sows ear".

J E CUSTOM

Gotcha! Thank you Sir.

Ed

 

[elktaker]

All this 'discussion' over a $80 bbl. , purchased on E-Bay, that "might be a Shilen". Go ahead, turn it down (if you can find someone who'll do it for you), if it no longer shoots what have lost?

In search of someone to do it. It will depend on the pricing I find. That is what I will lose, the cost to do it.

probably got $80 out of it already, and tired of its weight. But at the same time I could just get new barrel for 340ish.

 

[shortgrass]

In search of someone to do it. It will depend on the pricing I find. That is what I will lose, the cost to do it.

probably got $80 out of it already, and tired of its weight. But at the same time I could just get new barrel for 340ish.

And there's the rub! The guy that'll do it for the least amount of money will probably mess it up! Participating in the shooting sports isn't a cheap hobby. Sometimes you'll get a bargain, but top notch preformance usually cost..... And, to top it all off, lapping takes place after contouring. So plan on losing an inch of barrel length.