Cut rifling v buttoned rifling

[ovenpaa]

I understand the process involved in the manufacture of both the cut and button rifled barrels and shoot both Border and True-Flite barrels, both have served me incredibly well. What are the forums views on the relative merits of both processes when applied to competition barrels?

I am interested in one type of manufacture proving better for particular calibres, or for longevity or even trueness and for the record I actually prefer my True-Flite in some ways.

Also any views on hammer forged barrels for modern competition rifles? I have a feeling F Hall Gunmakers Ltd in Chesterfield (UK) Do or used to do hammered barrels but they always seemed quite reluctant to discuss what they actually did for a living.

[woody_rod]

I understand the process involved in the manufacture of both the cut and button rifled barrels and shoot both Border and True-Flite barrels, both have served me incredibly well. What are the forums views on the relative merits of both processes when applied to competition barrels?

I am interested in one type of manufacture proving better for particular calibres, or for longevity or even trueness and for the record I actually prefer my True-Flite in some ways.

Also any views on hammer forged barrels for modern competition rifles? I have a feeling F Hall Gunmakers Ltd in Chesterfield (UK) Do or used to do hammered barrels but they always seemed quite reluctant to discuss what they actually did for a living.

Some people have rigid ideas on barrel making (mostly armourers and so called experts), but a high proportion have litte idea on the mechanical or metallurgical processes involved. I am no expert, but do have a good idea of both processes also.

A barrel is a piece of bar with a hole drilled down the middle, reamed, honed (or whatever process is used) then rifled by either cut or button process. There is no evidence to show one process being any better than another.

The test I use, and one which nobody yet has proven incorrect, is to go to a range anywhere, where the shooters are not known to the observer. The idea being to pick the barrel brand or rifling process by looking at the scores alone. This is impossible, and shows that the idea that one is better than another is a fairy tale.

We use buttoned barrels almost exclusively (Pac Nor), this is a business decision more than anything else. We can get the barrels in a decent time frame, they are a good price and shoot extremely well. The one thing I have seen better in the button barrel, is the finish. The top grade of barrel has an extremely fine polished finish, which is as good (or better) as anything I have seen in big name brands. We can buy two barrels for the price of one cut rifled "name brand" unit. There are a some very big scores being shot by these barrels, and there is no way the cut barrels are doing any better.

This is one thing I would love to have a go at - making barrels. It is an interesting challenge, and might prove to be quite useful to us, being a rifle manufacturer. I would use the button process.

[Laurie]

In theory, cut-rifling imposes fewer stresses on the blank than button-rifling, so gives a more consistent perfroming product than blanks rifled by other methods. Years back, I paid a visit to Border Barrels when it was much smaller to write a magazine feature on them. Geoff Kolbe showed me round and gave me the spiel on the pros and cons of the various processes, and (unsurprisingly!) cut-rifling was way, way, way superior to the others.

Just before we finished, Geoff pointed out a shrouded bit of plant - and there's our new button rifling machine, says he! The stated intention was to get into the Volquartsen type market for 10-22 barrels as well as replacements for smallbore target rifles, but now we have Border Barrels 'Archer' brand in fullbore calibres !!

I think this tells you a lot. Personally, my best shooting rifles have American Bartlein (cut), Broughton (button), and NZ Tru-Flite (button) on them, and I must mention my first ever rifle to have a really good barrel put on it, a Remy 700 rebuilt in 6BR with a Border, (now shot out and getting a Tru-Flite). I can't tell any difference - they all shoot better than I can. I suspect that the quality of the reamer and the skill of whoever does the chambering job now counts for more than minor differences in the barrels - and that's down to Vince Bottomley (Gun-Pimp), Stuart Anselm / Osprey Rifles (Sanselm), Peter Walker / Walker Rifles, and Norman Clark for this quartet.

Some gunsmiths still only fit 'best quality' cut-rifled barrels. The point is that they trust them 100% and also since they charge a lot of money, they really don't want to have to redo a build or rebarrelling job if a barrel turns out to be a non-performer. That applies to Norman Clark for instance who will only put a Krieger on for you.

Going to the other extreme, I'm getting Stuart Anslem to put a £150 Spanish hammer-forged Bergara onto a P'14 action .300 Magnum F-Class rifle in early 2011, and we'll see how well this budget make performs in .300WSM with a good chamber and quality ammunition components. It may very well saurprise us all! (If it works, I'll buy another couple of blanks to follow up with .300 Rem SAUM and .30-06 Springfield.)

[Laurie]

Correction to my last post - Gun-Pimp tells me the Bergara barrels are button-rifled. Wow - even better value!

[woody_rod]

In theory, cut-rifling imposes fewer stresses on the blank than button-rifling, so gives a more consistent perfroming product than blanks rifled by other methods. Years back, I paid a visit to Border Barrels when it was much smaller to write a magazine feature on them. Geoff Kolbe showed me round and gave me the spiel on the pros and cons of the various processes, and (unsurprisingly!) cut-rifling was way, way, way superior to the others.

Nice sales pitch. There is no evidence to support the idea that cut barrels perform better. There is no evidence to support the idea that cut rifled barrels are more consistent. Does anyone have any evidence?

It is a fact of life: time = money. The button process is a lot shorter in terms of the rifling process, otherwise the same. A lot of people in AU use Archer barrels thinking they are cut rifled. My question is always the same: how does it perform? If it is good, then what does it matter? I think they are WAY over priced (like most button barrels), but that it just my opinion. People here are basically paying double what they should for an ordinary product. I have it on good authority (and not from a barrel maker) that it is more likely to get a better finish on a button barrel than cut.

I suspect that the quality of the reamer and the skill of whoever does the chambering job now counts for more than minor differences in the barrels -

That is true enough.

Some gunsmiths still only fit 'best quality' cut-rifled barrels. The point is that they trust them 100% and also since they charge a lot of money, they really don't want to have to redo a build or rebarrelling job if a barrel turns out to be a non-performer. That applies to Norman Clark for instance who will only put a Krieger on for you.

I have seen some ordinary "best quality" barrels. To me, they are just words people use to try and impress their mates. One that was so poor in bore size, I refused to fit it. The supplier (small time importer) said to just fit it, and it would be ok. I told him to stick it where it belonged...others have been bent, the wrong reinforce size, big scratches in the bore. Maybe we get the crap others don't want. The big name you mentioned is one I certainly won't use by choice.

[woody_rod]

Here is an artical writtten by Robert Chombart some time ago on the subject of barrels. It is an interesting insight into barrels from a metallurgists point of view, and one that has no affillitation with any maker or brand name. For me, RGC's knowledge on the subject of metallurgy cannot be questioned.

This is posted with Roberts permission.

BARRELS

By Robert Chombart

Making barrels is just plain machining.

Starting from the material :

It will be question here mostly of the so-said stainless steel quality; the CrMo variety, despite its obvious advantages, seem to be quite neglected these days.

Except one manufacturer, for corrosion-resistant steel (the term Stainless is improper here), all uses the same alloy, and it is the 416R (+S), Euronorm X12CrS13).

Barrelmakers may say theirs are ultra-sonic tested, Aircraft quality, Quality certified blanks or bar stock material….., it remains the same metal, as made by a few plants worldwide. Might be sold eventually under different labels, the physical, mechanical and chemical properties remain those and within the norm tolerances of the same alloy.

This metal is the preferred for its machinability, as alloyed with sulphur. A blessing for the machinists, but on the detriment of the qualities one could normally expect from a barrel: Quite soft, poor friction coefficient, prone to hollow corrosion… But it polishes so well and easily that the shine attracts at first. (Also) Claimed to be easier to clean as well, but this depends mostly of the finish roughness…

One large (and probably the largest in terms of target barrels) barrelmaker - Lothar Walther in Germany, uses a different alloy, AISI 420 (EuroNorm X20Cr13), which possess all the properties one could ask for such a purpose. Walther’s primary business is deep bore drilling for all the industry branches, and they master this process since decades.
Their ‘savoir-faire” is unique, and they are the only capable of using industrially this 420 alloy (for deep boring and barrelmaking). It might well be not too much liked by those who have to machine it afterwards for chambering and fitting, but, quality-wise, the result is certainly worth the effort.

-The 416, supplied in annealed condition, is about:
Brinell Hardness : 170
Rm: 630MPa
Modulus of Elasticity: 200Gpa
Estimated tensile strength: 84,000 psi
-While the 420 is:
Brinell Hardness 205
Rm: 725Mpa
Modulus of Elasticity: 200GPa.
Estimated tensile strength: 97,000 psi

One mill (Crucible) claims having a specific brand for barrels, but others, at least 2 in USA and 3 in Europe, are offering exactly the same material and under the same alloy specifications…..

The Walther 420 is supplied by Boehler-Udderholm from Austria under Walther’s specifications.

Just a quick mention here of the CrMo steels used for barrels. The various alloys used are all of higher mechanical and physical properties than the 416 (and even the 420 BTW).

Now on the machining in itself:

The machining process can be divided in 3 main headings (no mention of outside finish or final treatments):
-Deep hole boring.
-Reaming of the bore.
-Rifling
Methods of rifling:
Cut Rifling.
Buttom rifling.
Hammering.
Broaching (obsolete and mass production) for mention oly.

Deep hole drilling:

This is accomplished on specific machines and deep boring drills. The tools have little in common with the conventional 2 lips helical drills used in engineering. Central hole in the drill rod allow high pressure lubricant.
Modern deep boring machines are CNC-controlled.

Manufacturers of deep drills are very few and all well know worldwide manufacturers of cutting tools. Again, the choice is very limited.

Reaming;

Here again, the choice of tools is quite limited. We come here to the point of surface finish produced by reaming:

A surface finish is well expressed by ISO specification in microns. I will not enter in the definition of roughness and various criteria, just mention Ra, which is the mean arithmetic deviation of the surface profile and is expressed in micrometres.

It is utopic to expect a reaming (swarf removal) process to have a Ra measurement under 0,4 microns. Such a finish inspected with a special borescope will show shadows looking like an alpine panorama….Moreover, tolerance allowed by reaming are on the ISO H6 level, in other words for average bores diameters -0 , + 8 microns (.000 to +.008mm)… Quite different to what is usually announced. The only possibility to improve the bore finish and tolerance would be burnishing…

Rifling:

Cut rifling.
The cut rifling is most often made on machines who have
contributed to the war effort (some of them of a concept suggesting they have done those of WW1 too!!). I have seen however purpose-built ones with a CNC 2-axis drive allowing infinite twists range and progressive twists.
But cutting tools are similar of the old model. They can however vary in style (conventional, narrow lands, 5R, ratchet rifling, etc)
Cut rifling can be assimilated in engineering as broaching, and this process allow only roughness of over 0,4 microns as well. No less…Grooves diameter tolerance are also in the range of ISO H6 as well.

Button rifling.
The process works by metal displacement and, as there is no metal removal, it is only dependant of the forming tool finish and lubrication. As it compares to burnishing, the finish can be as low a 0,1-0,2 microns. The displacement of metal provokes a surface work-hardening who can be beneficial for wear resistance. Also, grooves diameter tolerance will be closer than with cut rifling.
Stresses as often mentioned? Maybe....
BUT, even if the grooves are well polished, the bore remain as reamed..
I wonder if the real solution would not consist in using the two processes, first cutting to near final dimension, and buttoning in a second operation, but taking this opportunity of less metal displacement during the second operation for also ‘ironing’ the bore asperities left by the reamer.

Hammering.
This is a process consisting of, starting from a blank of some 1/3 of the final length, by a high frequency concentric multiple hammering, to form the rifling by imprint of a mandrel having in reverse the final bore shape.
In this process lasting a very short span of time, the stresses to which the metal is submitted is enormous, and it come out of the operation extremely hot. Hammering machines are enormous, very few in the industry, and I only know two examples of match type barrels made by this process: Steyr-Mannlicher and the old Suh (ex East German concern), now owned by Steyr as well. I have no examples of hammered barrels made other than from CrMo metal.
The finish is dependant of the quality of the mandrel, and can be in the same range as button finish, but on the whole bore profile, as the bore is also formed during the process.
This can only work for mass-production, due to the machinery involved and mandrels.

All this to say:
Any competent machinist, possessing the right equipment and tooling can manufacture good quality barrels. There is no magic in this, just skill and devotion.
As all barrelmakers have those qualities at the highest degree, use all the same material, equipment, tools and techniques, there is little difference between one brand and another, quality-wise and subsequently shooting-wise.

My point only, FWIW.


Robert Chombart
Normandy France.

[ovenpaa]

Thank you Rod for posting and Robert for allowing the post, I think the article sums things up very nicely.

[Robin128]

Wow, what a read and reference...didn't know I knew so little.



Rob

[dromia]

Its a small world right enough.

[The Gun Pimp]

Nicely summarised by Robert.

Especially the bit on button rifling - quote "but even if the grooves are well polished the bore remains as reamed"

Bergara barrels - as I understand it - have the hole/bore honed after reaming which gives superior finish - evident in the bore-scope.

Robert also mentions the vagueries (is that spelt right?) of the button rifling process - which is why a system of 'gauging' is usually used to grade the barrels into quality categories.

Cheers
Vince