Comparison of seven barrel contours in .260 Remington.

[MCMXI]

I'm in the process of assembling a new rifle and took Zak Smith's excellent advice (read his articles, PM etc.) and settled on the .260 Remington as the cartridge/caliber. I already have a custom rifle for F-Class in .308 Win so the .260 seems to be the best way to go for steel plate matches or F-Class Open. I have an action, have ordered a trigger, will be ordering a folding AICS and now need to select a new Krieger barrel. I decided to compare seven popular contours using SolidWorks and a simple application called rifle_frequency_1_2 written by Tom Irvine (sent to me by member Bart B.) which calculates the frequency at which a barrel vibrates as it's excited by a bullet.

Here are the results showing the weight, fundamental frequency and displacement of the muzzle due to the barrel's weight. The barrel frequency (and weight) is calculated using 416 stainless whereas the deflection calculated by SolidWorks uses material properties of 304 stainless with the weight of 416. This discrepancy won't make much, if any, difference to the results. Also, Tom Irvine's utility doesn't account for the chamber or the lands in the barrel so I didn't either in the SolidWorks models. I plan on running these models again with 6 (1/4") or 10 (3/16") flutes along the barrels.

I would imagine that a barrel with a higher frequency but smaller amplitude (less deflection) would have a wider sweet spot in terms of load sensitivity. However, Zak has managed some phenomenal shooting with his .260 Rem with a 26" Standard Palma barrel (suppressor attached). The Standard Palma has the lowest frequency of all seven barrels and the second largest deflection but Zak has shown that with the right load it's very accurate.

 

[Zak Smith]

How does the frequency change with 17 oz of suppressor on the end?

I have friends with 22-26" heavy contour barrels (ie MTU or thicker), and I have had a thick but fluted 25" barrel in 6.5. I don't know that we've noticed any pattern of accuracy as a function of length vs. profile, with or without suppressors attached. The common thread is a premium match barrel installed right with a true chamber and they all shoot great provided the load is halfway decent.

 

[MCMXI]

How does the frequency change with 17 oz of suppressor on the end?

Intuitively, the frequency is going to be a lot lower and the amplitude is going to be a lot larger too. You mentioned how your barrel "whips" with the suppressor on the end.

The common thread is a premium match barrel installed right with a true chamber and they all shoot great provided the load is halfway decent.

So barrel choice may be down to how much weight you want to carry and aesthetics. I like the look of a fluted straight taper barrel and the extra heat-sink that comes with a heavier barrel. The added mass seems to help during rapid fire stages. I'll most likely order a heavy target barrel with 6 (1/4") flutes. The barrel will have a similar weight to the standard non-fluted target barrel but will deflect less.

 

[52grain]

Can you run a simulation with sporter weight barrel? I think that it would be an interesting comparison if you have the time and desire.

What makes you think that the higher fundamental frequency would result in reduced load sensitivity? I would guess that a higher frequency would dampen faster. Is this what you were thinking?

I'm a EE not an ME so I may be missing some fundamental (no pun intended) concept.

 

[Zak Smith]

This is the stiffest barrel I've used:

 

[MCMXI]

Can you run a simulation with sporter weight barrel?

Do you have a particular sporter contour in mind? Krieger has some contours/dimensions here.

What makes you think that the higher fundamental frequency would result in reduced load sensitivity? I would guess that a higher frequency would dampen faster. Is this what you were thinking?

Only because higher fundamental frequencies are indicative of stiffer barrels, and stiffer barrels have lower amplitudes in terms of vibration. I don't know what effect damping would have on a bullet since typical barrel time is on the order of 1 millisecond. During load development I would expect to see more nodes that are closer together with stiffer barrels.

 

[hardluk1]

why not ask Krieger ?? They should have a better chance to get what your looking for right. I have a 28" krieger in 7 rem mag wih a #5 contour that is a great shooter.

 

[Dr. Tad Hussein Winslow]

I'm sorry, but I must advicse against getting a bent barrel like in the pictures.

 

[Maverick223]

Tag for proof that engineers overthink everything.

Would it be too much of a pain to run a fluted bbl (Hvy. Target Kreiger), and the solid blank (CM or SS is fine by me...I know you like SS) through SolidWorks? I would prefer a light target contour for a solid bbl, but a heavy target if fluted. My own background in engineering (as a lowly CE) would lead me to believe that the frequency would be higher and deflection less than the light contour at about equivalent weight, with similar "heat-sink" properties (conduction), of course with a higher rate of convection due to the greater surface area. Conversely I believe that the solid blank will perform poorly in comparison, and at the expense of much greater weight.

Great work, 1858.

 

[Jim Watson]

The purpose of a Palma contour is to get a long iron sight radius without making the gun too muzzle heavy for sling shooting, as a 30"+ "target contour" would.

How much rifle humping in your steel plate shoots? Are you walking a field course or shooting from a static position? Bipod, sling, or position?
If you are going to be moving around much, get something you can carry.

If not, load it up with a heavy target profile. I would not (did not) bother with flutes; as the late Mr McMillan said, the main effect of a fluted barrel is more money in the vendor's pocket.

I would talk to them about a longer straight breech end ("B" on the chart), so as to allow room for the barrel to be set back and rechambered when the throat has advanced far enough to affect accuracy.

 

[USSR]

...as the late Mr McMillan said, the main effect of a fluted barrel is more money in the vendor's pocket.

Just one more thing that I disagree with the late Mr. McMillan on.

Don

 

[MCMXI]

Why do barrel makers offer such a wide variety of contours if as Zak states, with a half-decent load, any well-built barrel should be accurate. Shouldn't we choose the lightest barrel available then? Krieger's barrels are all around the same price so surely it isn't just marketing. For me it's an optimization problem. I want the stiffest barrel, with the least amount of weight, the largest heat sink and the largest surface area. Is this wrong?! I'm convinced that during rapid fire stages such as 10 rounds in 60 seconds at 200 yards or 10 rounds in 70 seconds at 300 yards, barrel choice becomes important.

why not ask Krieger ?? They should have a better chance to get what your looking for right. I have a 28" krieger in 7 rem mag wih a #5 contour that is a great shooter.

I know what I want and posted here to help (or confuse) others with their decision. I have two Krieger barrels, both with the MTU contour and both fluted. I'm completely sold on Krieger .... both barrels are very accurate and neither fouls even after a 100 round match. I just run an oiled patch and a nylon brush through them a few times to remove the powder residue and I'm done.

How much rifle humping in your steel plate shoots? Are you walking a field course or shooting from a static position? Bipod, sling, or position?
If you are going to be moving around much, get something you can carry.

This rifle will be used for matches similar to the ones that Zak runs so weight is definitely a concern. IIRC, Zak mentioned that his rig is about 18lb. As for fluting, I really don't care much for Gale McMillan's view on anything (that I've read). I'm with Don on this one. GM's "If I'm not doing it then it's not worth doing" attitude was arrogant to say the least, so I will go with what I like and know which is a fluted barrel. Your suggestion re a longer chamber dimension (B) is a good one, particularly since the action I'll be using is a Badger Ordnance M2008 which requires almost 50% more thread length on the chamber end of the barerl compared to a Remington action.


Dr. Tad Hussein Winslow, good one!!

Mav, thanks .... and I'll try to run that for you but it's a lot more involved.

 

[Zak Smith]

I have done extensive accuracy testing with long strings of fire with my rifles and to the extent that I can shoot benchrest-style groups, I can't tell a difference in accuracy or POI when my barrel is cold or too hot to touch. (Shooting with a suppressor retains a lot more heat.) Since fluting costs more, I'd just as soon get the cheaper non-fluted barrel for the same weight.

 

[MCMXI]

I have done extensive accuracy testing with long strings of fire with my rifles and to the extent that I can shoot benchrest-style groups, I can't tell a difference in accuracy or POI when my barrel is cold or too hot to touch. (Shooting with a suppressor retains a lot more heat.) Since fluting costs more, I'd just as soon get the cheaper non-fluted barrel for the same weight.

I've found this to be true with my Krieger barrel (MTU .308) as well. Since I don't have anywhere near your experience, I put it down to the WEIGHT of the barrel and also the QUALITY (single point cutting, hand lapping etc) but I believe your position is that it's due to the QUALITY alone. So why did you choose a Standard Palma barrel rather than a Light Palma barrel? You could have saved around 1/2lb in weight.

As for fluting, I don't mind paying $125 for aesthetics and a bit of added stiffness ... but that's just me. When you think about the cost of ammuntion, factory or reloads, $125 gets lost in the noise.

 

[Zak Smith]

but I believe your position is that it's due to the QUALITY alone.

I'm not sure I'm prepared to go that far-- I was recounting my experience with various profiles; however, none of the tested profiles were lighter than med Palma.

 

[MCMXI]

I'm not sure I'm prepared to go that far-- I was recounting my experience with various profiles; however, none of the tested profiles were lighter than med Palma.

OK ... 80% quality and 20% contour then? Come on Zak, give us a number.

I think we can all agree that premium match barrels should have less residual stresses in them. Therefore, POA/POI changes as the barrel heats up should be minimal or at least significantly less than factory fodder. So worry more about the barrel maker rather than the contour?

Zak, I for one really appreciate the wealth of knowledge and experience that you bring to this forum, and to be honest, would never have considered .260 Remington if it weren't for your articles. Thanks.

 

[Zak Smith]

So worry more about the barrel maker rather than the contour?

There are at least a half dozen top barrel makers and it probably doesn't matter whose you get from that echelon. But I agree with your statement, in general, but to a point. I get a kick out of heavy factory barrels on economy-class factory rifles. Why bother with a heavy barrel if the thing isn't going to shoot anyway?

My original 17" 3-Gun rifle from.. 2004.. has a very light profile for a match gun (0.7-ish under the handguards), but it's a Krieger. It was put together by Paul @ MSTN. When it was new, it would shoot 1/3 MOA and it'll still shoot just under one minute.

Now back to bolt guns- I don't know how light of a contour you can go and not get accuracy problems. My experience has been that I can hang at least 20 oz of suppressor off the end of a med-Palma .260 or .208 and shoot it until I can smell the paint burning off the suppressor and can't grab the barrel (at the rear even).. and the accuracy and POI will not change.

I hesitate to speculate further. It would seem "reasonable" that as you made the contour lighter and lighter, eventually you would get to a profile where the accuracy/poi would degrade, or degrade when hot. However, the same conventional wisdom that makes that seem reasonable is what convinces many they need a much heavier profile than med-Palma to shoot accurately in the first place. And I am convinced that is debunked, even if it only applies to rifles built a certain way.

I will tell you my criteria for ordering a barrel. I cannot necessarily back up all of these preferences with a lot of data, but my experience following it has been very good. I prefer a cut-rifled barrel with 5R/5C profile. I prefer unfluted. I prefer med Palma in 24-26" lengths for .308-sized cartridges and heavy Palma for 7mm-.30 caliber magnums. My Border, Krieger, Broughton, and Rock Creek barrels have been excellent. (My Satern barrel was also excellent; it was button rifled.) I don't care too much which particular barrel maker it is- if I have GAP chamber and finish a barrel for me, I usually just go with whatever they are having the best luck with recently, that meets my critera.

If I were to build a lightweight "hunting" precision rifle, I would use the same type of barrel as my normal criteria, just get it in a lighter profile.

 

[Maverick223]

Mav, thanks .... and I'll try to run that for you but it's a lot more involved.

Thank you, you did a great job, there is some great information here. I understand if you don't have time for my request, no doubt it is a fairly complicated subject to model.

As for fluting, I don't mind paying $125 for aesthetics and a bit of added stiffness ... but that's just me.

I don't care for the look of fluting too much (though it doesn't bother me either), but I like the added stiffness and will gladly part with the additional $125.00 for it as well (depending upon the rifle of course).

So worry more about the barrel maker rather than the contour?

No expert, but I certainly do. I'd take a light sporter profile Krieger over a solid blank from Remington hands down.

 

[52grain]

Do you have a particular sporter contour in mind? Krieger has some contours/dimensions here.

I would be most interested in something like a #2 standard sporter, but only if it's not too much trouble. What I am going after is a comparison of a target rig to a hunting rifle.

The Remington Varmint would be interesting because I have 2 of them, but I would guess that it would be fairly similar to the Light Palma.

This is some really interesting information. Thanks for posting.

 

[rangerruck]

I'm of 2 minds on this; normally I would say as heavy as you can go-- but then I have thoughts of repeatability of the smallest wave node you can get, and then match your load to it for max accuracy.
I personally don't have enough experience on the practical side, though I do love the mathematics side, and study that stuff continuously, and then certainly you have to consider a wide variety of environmental factors as well.
So all things considered I say I would go with my second though; go for repeatability of harmonics and then tune your load to it....

 

[MCMXI]

If not, load it up with a heavy target profile. I would not (did not) bother with flutes; as the late Mr McMillan said, the main effect of a fluted barrel is more money in the vendor's pocket.

Krieger offers 10 flutes with a 3/16" cutter or 6 flutes with a 1/4" cutter. Their standard flute starts 5~7" from the breach and ends 2" from the muzzle. For a 26" barrel, that would mean at least a 19" long flute. If you do the math, 10 (3/16") flutes reduces barrel weight by 0.75lb and 6 (1/4") flutes reduces the barrel weight by 0.80lb!! Now that's a significant reduction in weight in my opinion.

I would talk to them about a longer straight breech end ("B" on the chart), so as to allow room for the barrel to be set back and rechambered when the throat has advanced far enough to affect accuracy.

After reading your comment I noticed that Krieger offers a Hunter contour which has a 4" long B dimension with an O.D. of 1.250". I ran that contour through SolidWorks and it's the stiffest of the bunch with the highest natural frequency of 71.0 Hz. I think I'll be ordering a Hunter with 6 (or 10) flutes. The weight will come out close to 5lb which puts it into Standard Palma territory.

Mav, I'm trying to figure out how to flute a tapered barrel in SolidWorks. A non-tapered barrel is easy enough but that doesn't help. I ordered a SW book from Amazon since I don't seem to be making any progress. I'll get back to you once I figure it out.

klineia, I can run a #2 sporter barrel but will have to guess at the radius of curvature where the chamber reinforcement "blends" into the barrel.

 

[taliv]

flute it first, then taper it?

 

[Maverick223]

Now that's a significant reduction in weight in my opinion.

Agreed, I rather like the 6 flute bbl, but that is mostly because 10 flutes looks funky to me. ...and I didn't realize it, but all this time I was saving about 5/100s of a pound...yay!

Mav, I'm trying to figure out how to flute a tapered barrel in SolidWorks. A non-tapered barrel is easy enough but that doesn't help. I ordered a SW book from Amazon since I don't seem to be making any progress. I'll get back to you once I figure it out.

If I can get my hands on a full fledged copy of ACAD (we mostly use lite, and/or Civil3D) I can draw you up a wireframe (or get one of the drafters to pencil it up if they aren't busy). Just don't know if we have the software to do it (I used to have a personal copy, but it won't work on my x64 machines ). Just let me know if you think it will work in SW (no experience/help there).

 

[USSR]

Krieger offers 10 flutes with a 3/16" cutter or 6 flutes with a 1/4" cutter. Their standard flute starts 5~7" from the breach and ends 2" from the muzzle. For a 26" barrel, that would mean at least a 19" long flute. If you do the math, 10 (3/16") flutes reduces barrel weight by 0.75lb and 6 (1/4") flutes reduces the barrel weight by 0.80lb!! Now that's a significant reduction in weight in my opinion.

While 3/4 of a pound might not seem like a lot of weight reduction to some (when you are considering a total rifle weight of perhaps 16# or more), it's the location of the weight reduction that is important. When you install a long, heavy barrel on a rifle, the balance point shifts dramatically towards the muzzle. I had a muzzle heavy rifle once (always felt like it was going to fall out of my hands), and I said never again. It is MHO, that the balance point of a rifle should be within 1 inch of the forward receiver bolt.

Don

 

[Offfhand]

Post from above, from Mr. Zak

"I have done extensive accuracy testing with long strings of fire with my rifles and to the extent that I can shoot benchrest-style groups."

Question, what type of benchrest are you using? Or did I misunderstand the statement?
Thanks,