6.5 PRC Barrels - best options?

[Jvoelcker]

100 grain are the lighter 6.5mm bullets you can actually buy in the uk on a regular basis . i shoot 100 grain seirra varminters for smaller things like fox , crow etc . 100 grain barnes TTSX for all uk deer and 120 TTSX ocasionally , in lead its mainly 120 grain . My twist is 1-7.5 and its stabilizes all the above and will do ELDX and other longer bullets . 6.5 PRC isnt my choice , i went 260 rem because i have a whole load of brass from 243 - 308 as well as the ready formed 260 to go at . Simply neck up or size down , can get up to 3300 with 100grain and the powder is easily burnt on a 20" barrel .
if you go fast twist with the 95 v max too great a velocity with a fast twist you might just run into a few bullet break -ups at 3500 fps and its totally not needed besides the lower barrel life
remember twist rate is about bullet length not weight and copper is long for weight faster twist for longer bullets , shorter bullets will still stabilize but the fater the velocity the more you can slip into "dusting" in flight

The Blaser 6.5PRC is 1-8.66, but because the rounds are faster I don't think there are stability issues as far as I can tell.

 

[Jvoelcker]

Stability is down to the rpm which is linked to twist rate and velocity. A longer barrel should allow you to eek out a bit more velocity which in turn will give you greater rpm. A faster twist rate does this more dramatically.

A 300 Blackout and a 300 Norma Magnum will both stabilise the same 200 grain bullet but at very different velocities and so use a different twist rate to achieve that.

Thanks. Slowly getting me head around it all

 

[Bowland blades]

The Blaser 6.5PRC is 1-8.66, but because the rounds are faster I don't think there are stability issues as far as I can tell.

Slow twist that for a modern 6.5mm i should keep to the 100 grain in TTSX when talking copper

 

[kripton]

Just to add a little flavour to this discussion would there be any advantage/disadvantage in having spiral barrel fluting rather than straight fluting?

 

[norcan]

Just to add a little flavour to this discussion would there be any advantage/disadvantage in having spiral barrel fluting rather than straight fluting?

The difference is completely aesthetic.

 

[norcan]

Regarding barrel twist rates, the 8.6 Blackout uses 1:3 to stabilise bullets up to 350 grains at subsonic velocity, which is the tightest I’ve ever heard of. It almost looks more like a worm-drive gear than a rifle barrel.

 

[Jvoelcker]

Slow twist that for a modern 6.5mm i should keep to the 100 grain in TTSX when talking copper

I currently don't need to worry about copper so will avoid that hurdle for as long as possible.

 

[Mungo]

Really - don’t overthink it.

Any bullet that can kill a deer will kill a fox, so no need to worry about the light end. The opposite isn’t always true - I would worry about trying to shoot a heavy bodied animal with a 95gr vmax!

Anything in the 120-147gr range will do everything you need it to.

My experience is that it’s a very forgiving cartridge that’s easy to shoot accurately and kills very effectively.

 

[Jvoelcker]

Really - don’t overthink it.

Any bullet that can kill a deer will kill a fox, so no need to worry about the light end. The opposite isn’t always true - I would worry about trying to shoot a heavy bodied animal with a 95gr vmax!

Anything in the 120-147gr range will do everything you need it to.

My experience is that it’s a very forgiving cartridge that’s easy to shoot accurately and kills very effectively.

I use 87gn vmax through my 243 for everything south of the border with deer only making up 5-10% of what I shoot so was just going to carry on along those lines, but also work up a heavier load if needed.

 

[NullMac]

‘Most of its rigidity’ is the worrying phrase here.

No one seems to have any clear idea about quite how much rigidity is actually retained. And there seems to be considerable uncertainty about what happens to the dynamics of a barrel when the flutes are cut.

I have read a number of your posts and your adamant positions. You are full of **** pal and should not be giving advice.

Plenty of people have a very exact idea of how much rigidity is retained, you on the other hand are a blunt chisel and don't. You can calculate the Second Moment of Area of the barrel precisely from its geometry. Compare that to the second moment area of an unfluted barrel. Divide one by the other, multiply by a hundred and you have a percentage of the retained "rigidity". I can't be arsed, but feel free.

The whole point is that a deep flute for much of the barrel length will make a significant weight reduction in the barrel which will be a much higher percentage than the reduction in the Second Moment of Area which, as you know, is a key variable in the formula for the bending of a barrel.

Again the effect of vibration of a barrel is not uncertain, you can infer the change from the reduction in 2ndMOA (or is it the Second Polar Moment of Area?) in the appropriate equations. The precise engineering dynamics of vibration in such an object is in the distant past for me so I will not be attempting anything like that.

So less of the "utterly utterly" pointless, and "no applications" bull****, 'cos you don't know what you don't know.

 

[Mungo]

I have read a number of your posts and your adamant positions. You are full of **** pal and should not be giving advice.

Plenty of people have a very exact idea of how much rigidity is retained, you on the other hand are a blunt chisel and don't. You can calculate the Second Moment of Area of the barrel precisely from its geometry. Compare that to the second moment area of an unfluted barrel. Divide one by the other, multiply by a hundred and you have a percentage of the retained "rigidity". I can't be arsed, but feel free.

The whole point is that a deep flute for much of the barrel length will make a significant weight reduction in the barrel which will be a much higher percentage than the reduction in the Second Moment of Area which, as you know, is a key variable in the formula for the bending of a barrel.

Again the effect of vibration of a barrel is not uncertain, you can infer the change from the reduction in 2ndMOA (or is it the Second Polar Moment of Area?) in the appropriate equations. The precise engineering dynamics of vibration in such an object is in the distant past for me so I will not be attempting anything like that.

So less of the "utterly utterly" pointless, and "no applications" bull****, 'cos you don't know what you don't know.

I’m merely expressing the fact that that when you go looking for evidence of what happens to accuracy when a barrel is fluted, you find absolutely no consensus, a lot of very strong opinions, some heated arguments and little empirical evidence.

The gains are small, and can be achieved in other less invasive ways. The effects appear to be unpredictable.

Curiously, almost every discussion about it seems to bring out the worst in people.

 

[Muntybuck5803]

I don’t have a horse in this race other than experience of a number of rifles that have features of which have been referred to here.
So fluting is not purely aesthetic and does serve to save weight. Admittedly not a massive amount but when you’re talking about heavy rifles that need to be hand balled everywhere every little helps.
If it were detrimental to accuracy the biggest names in the precision rifle industry would not offer it.
Straight flutes on the L115a3 as seen above will definitely help to shave a fair chunk of weight off the heavy gauge 27inch barrel to allow more ammo to be carried in lieu of it.
Helical flutes as seen above on the PGWDTI Timberwolf will save more weight as a helical flute along the same length of barrel will ultimately end up longer if ‘straightened out’, therefore saving more weight.
I’ve used both of the above and they don’t suffer any accuracy issues.
A similar argument is seen with bolt fluting - on hunting rifles it can end up purely cosmetic but the idea comes from rifles with a very real effect being achieved, especially when a rifle failure means s*@t
hits the proverbial.
Only you can decide if it’s something you want on your hunting rifle that may have little impact.
I have fluted bolts on my hunting rifles as I like the aesthetic. But they don’t serve the same purpose as they would do if on a rifle where the idea originated.

 

[nun_hunter]

View attachment 281913
View attachment 281914
I don’t have a horse in this race other than experience of a number of rifles that have features of which have been referred to here.
So fluting is not purely aesthetic and does serve to save weight. Admittedly not a massive amount but when you’re talking about heavy rifles that need to be hand balled everywhere every little helps.
If it were detrimental to accuracy the biggest names in the precision rifle industry would not offer it.
Straight flutes on the L115a3 as seen above will definitely help to shave a fair chunk of weight off the heavy gauge 27inch barrel to allow more ammo to be carried in lieu of it.
Helical flutes as seen above on the PGWDTI Timberwolf will save more weight as a helical flute along the same length of barrel will ultimately end up longer if ‘straightened out’, therefore saving more weight.
I’ve used both of the above and they don’t suffer any accuracy issues.
A similar argument is seen with bolt fluting - on hunting rifles it can end up purely cosmetic but the idea comes from rifles with a very real effect being achieved, especially when a rifle failure means s*@t
hits the proverbial.
Only you can decide if it’s something you want on your hunting rifle that may have little impact.
I have fluted bolts on my hunting rifles as I like the aesthetic. But they don’t serve the same purpose as they would do if on a rifle where the idea originated.

They're not that concerned about weight if they are willing to put a ratty old Harris bipod on such a nice rifle!

 

[Jvoelcker]

I have read a number of your posts and your adamant positions. You are full of **** pal and should not be giving advice.

Plenty of people have a very exact idea of how much rigidity is retained, you on the other hand are a blunt chisel and don't. You can calculate the Second Moment of Area of the barrel precisely from its geometry. Compare that to the second moment area of an unfluted barrel. Divide one by the other, multiply by a hundred and you have a percentage of the retained "rigidity". I can't be arsed, but feel free.

The whole point is that a deep flute for much of the barrel length will make a significant weight reduction in the barrel which will be a much higher percentage than the reduction in the Second Moment of Area which, as you know, is a key variable in the formula for the bending of a barrel.

Again the effect of vibration of a barrel is not uncertain, you can infer the change from the reduction in 2ndMOA (or is it the Second Polar Moment of Area?) in the appropriate equations. The precise engineering dynamics of vibration in such an object is in the distant past for me so I will not be attempting anything like that.

So less of the "utterly utterly" pointless, and "no applications" bull****, 'cos you don't know what you don't know.

So am I right in my theory that given two identical barrels, if you flute one you will weaken it?

 

[25 Sharps]

95gr VMax - N550, RS60, RL17. In the 57.5gr - 58.6gr range (brass and barrel length dependent) - producing 3550-3600 in a 26in barrel. Same trajectory as a 26in 22.250 shooting 50gr VMax at 3850 - with half the wind.

Is that pressure tested, published load data?

 

[25 Sharps]

I currently don't need to worry about copper so will avoid that hurdle for as long as possible.

It would be fine, 8.66 is the pretty much same twist as my CZ 6.5x55 and that stabilises the long yew tree 114 tipped TLR very well at 2900 fps. You’d be pushing them a lot faster so you’d have no issues.

 

[finnbear270]

I currently don't need to worry about copper so will avoid that hurdle for as long as possible.

Must be something wrong with the re barrel from Ronin then, my 6.5 PRC is good with TLR's.

 

[nowler]

So am I right in my theory that given two identical barrels, if you flute one you will weaken it?

Removing material weakens it. The unfluted barrel will be stiffer if they were the same dimensions prior to fluting.

It would be interesting to see how much stiffness is retained with spiral fluting. It’s been a long time since I had access to good FEA software but I’d be keeping my flutes in line with the bore of if I was getting any of my barrels fluted. Keep the spiral flutes for bolts.

 

[Jvoelcker]

Removing material weakens it. The unfluted barrel will be stiffer if they were the same dimensions prior to fluting.

It would be interesting to see how much stiffness is retained with spiral fluting. It’s been a long time since I had access to good FEA software but I’d be keeping my flutes in line with the bore of if I was getting any of my barrels fluted. Keep the spiral flutes for bolts.

Thought so, removing material on a barrel will always weaken it - it's not like shaping tin to increase rigidity.

 

[Selous]

I had one barrel fluted, it was a belter and shot very well. When considering a second I was told by a wise man that fluting can only make accuracy worse or at best be unchanged compared to an unfluted blank. This makes sense to me…If there are stresses remaining in the steel from the rifling process E.g button rifling will this make dimensional changes in the bore more likely once the barrel wall has been weakened by fluting or by the pressure of firing? If fluting it to be done should a cut rifled blank be used? Lots of questions about a fluting where a carbon wrapped barrel can save more weight!!