16bore, you're kidding aren't you! I thought the recoil was handled by the bolt lugs and lug abutments. What is the purpose of the bolt body other than to hold the bolt lugs, bolt handle and firing pin assembly? I have one rifle with an aluminum bolt. Maybe it was fluted to make it stiffer.

Top one is for a 7-08, bottom for 223. Figured that it didn't need as much twist, since recoil of a 223 is so mild.

just figured since there was so much skullphuck theory on fluting, I'd help out.....

quote:

Originally posted by wasbeeman:
Now that is a reach! In fact, refer to my comments about "justification". But, if it makes you happy, I'm glad you had it done and I'm happy for you. Be sure and have the chamber AI'd so's you won't have to trim the brass as often.

Assuming this was in reference to the post above it .

Sooooo
lets look at the weight inferences of fluting a Kreiger #4 contour barrel 24" long with 6 longitudinal flutes of 1/8" radius x 1/16" deep ( from the cut edge) by 18" long and compare that to the equivalent weight per inch of a #4 contour barrel.
( .700" finished muzzle dia ( IIRC ).

You can do the calcs .........so you can believe the numbers.........He He.

- how many equivalent inches of barrel length the fluting removes in weight
- the polar moment of effort on the front hand effect......relative to a comparison between:-
- a round 24" #4 contour
- a round 24" #3 contour
- the fluted #4.
and the relative rigidity of the 3 options.
given that the rigidity increases at the rate of radius to the 4th power ( and directly calculable to the flute percentage).


Then you can tell me how much of a reach the effect of the work done was in justification & damn the techies.

Looks in the eyes of smooth round barrel lovers & 'kool' fluted barrel lovers aside........ there are technical justifications for fluting within rifle weight & balance objectives, whether you like it or not, or think the relative weight removal from fluting is myth.
The reality is significant in effect.
Doing it & testing the comparative results justifies the work & truth tests the myths.

BTW spiral fluting removes slightly more material than longitudinal fluting of the same flute groove size.......and delivers slightly less rigidity than a longitudinal fluted barrel.

He He ......Physics & maths are wonderful things when used appropriately.

Methinks you are going to be surprised at the amount of barrel material removed in fluting.

don't forget a 1/4" diameter mill cutter will remove more than its depth cut volume from a round profile barrel, (with depth cut taken from the cut edges)........
( You will find that the volume removed in the fluting was equal to more than the volume/weight of the last 2" of barrel at the muzzle...He He)

More techie info;
removing 2" of barrel from a 24" barrel removes approx 3 lb of upthrust effort from the front hand holding the rifle.
( you might like to examine the polar moments of that statement to verify .........or determine the effect experimentally ).

The end result of the fluting of the barrel did deliver what improvements I expected it to do regarding rifle weight & balance......no myth or reaching.........He He

I have/had several fluted and non flluted varmint guns. Some were factory and some custom. I can not tell any difference in them. Some think the fluting looks sexy, I used to think that.
I would not spend extra for fluting any more.

Thank you to Art S! His post on p. 3 is worth reading!

friar

I don't have a dog in this fight, having never owned a rifle with a fluted barrel, but it seems to me that a fluted barrel must be quite difficult to keep clean, with all those enclosed surfaces to trap dirt.

I do have a fluted barrel on my HiStandard Supermatic Citation, but they are very wide and shallow, and are as easy to keep clean as a conventional barrel.

Barrels have internal stresses and I would be worried that fluting would cause the barrel to bend or warp.

I am not going to spend the money on it. All target barrels in this neighborhood start off as blanks and end up turned on a lathe with no fluting.

And they don't last forever either. Barrels are consumables. You only want to put the money in the things that improve their accuracy, the lifetime depends on the cartridge.

Let me comment on the cooling aspect of fluting.

Might make a difference if you are not shooting a lot of bullets fast. Shoot enough bullets and the heat transfer rate between metal and air (or water) becomes a limiting factor. The barrel will simply get hotter and hotter in full automatic till it turns cherry red, because you cannot transfer the heat fast enough, regardless of the fins or water bath the barrel is in.

quote:

Originally posted by SlamFire:
Barrels have internal stresses and I would be worried that fluting would cause the barrel to bend or warp.

Internal stress translates into abnormal harmonics under shock load in inverse proportion to the rigidity of the barrel.
ie
any residual internal stress in a barrel blank becomes more of a factor as the amount of machining after the last stress relief of the barrel increases , and is in proportion to the change in the rigidity of the barrel caused by the machining .
with barrel rigidity changing at the rate of section radius to the power of 4 its actually pretty easy to see that average section OD is the primary determinant of barrel rigidity and that its a very powerful determinant.
No complex answer to the round or fluted barrel shape effects on rigidity other than average OD determining rigidity and barrel cross section determining weight.

Looks aside , the machining to be undertaken is an equation between the rigidity you want at the weight( and its cost).
He He............doesn't matter a tinker's cuss where weight ( or balance due to that weight) is not a factor.

largely the same compromise involved in Barrel length , velocity, weight, & balance.

balance being much more important to a hunter than a bench shooter.( bench shooter not having to hold the foregrip on the rifle).

the engineering consideration & equation in deciding machining of a rifle bolt is a different matter.
in that situation the bolt OD must be maintained & fluting is a means of reducing weight.
Spiral fluting is used because it produces even wear ..........longitudinal fluting would produce localised wear & grooving ( over time & use)
Fluting a bolt to 50% of its surface area does not result in a 50% reduction in friction in the action. The reduced surface contact of the fluting itself has NIL effect on friction.
The friction reduces by the reduction in weight of the moving component.......He He.

the cooling rate influence of fluting certainly is mitigated by the rate of transmission of heat within the barrel material to the point where the influence of the fluting is minimal at temperature differences between barrel & ambient air with firing rates of a shooter that values the working life of his barrel.

Heat is transferred from powder combustion & projectile friction into the ID of the barrel
- it is then conducted thru the barrel to the OD
-and transferred into the air at the barrel surface interface.

The rate of transfer of heat in the system is primarily determined by the slowest rate of transfer in any component in the system.
The amount of transfer is influenced by the temperature difference at the interfaces and across the medium.
its pretty easy to see that the temperature profile at the bore is high, the co-efficient of heat transfer across the barrel medium is fixed and the temperature profile between barrel and ambient temp air is low and that any influence of increased surface area due to barrel fluting is going to be quite low .
ie
cooling fins ( flutes) are efficient where the material in the fins & the body between heat source & cooling source has a high co-efficient of heat conduction.

He He ...........if the guy with the lovely stainless barrel understood the temp profile that the co-efficient of heat conduction of stainless generates , he would wait a little longer between strings ...........rather than start again when he can hold his hand on the barrel for more than 10 secs.

This whole fluting for cooling issue is like the old marketing myth that an aluminium beer can cools your beer quicker.
.........oh the aluminium has a high heat transfer rate , but its a negligible influence on the temp that the beer reaches in a given time......because the heat transfer equation is dominated by the rate of heat transfer in the beer itself......the influence of the heat transfer capabilities at the outside of the can is something like 0.0005% in the time to cool the centre of the can contents to a given temp.

Fluting is about equally as significant in the whole heat transfer situation of a barrel on a hunting or BR rifle.