I have this thought experiment....

Dimner

Dimner

Named Man
I currently have a bit of tikka fever. Being able to easily switch barrels with only a few tools and headspace guages makes me do alot of thinking. Non-Practical thinking, but interesting (to me) nonetheless. Also, I have been spending alot of time in a deer blind. Sitting there, silent, still, allows for all kinds of crazy ideas to popup.

This one is about rifling. through the year, I have been playing with my 7.7 arisaka and for an old, beatup, military surplus rifle, I can get 1 to 1.5 moa accuracy with NOE's 311-199-FN. Made me start thinking, is it because of the polygonal rifling? I cannot find it, but a while back, I found a brief comment from Fiver on the other site. In usual Fiver coded syntax, he alluded to the Type 99's rifling being very good for cast bullets. Is that something that you could elaborate on?

So the thought experiment is this:

Tikka receiver, with two barrels. Both made by the same manufacturer, same barrel contour, both using the same chamber reamer. Let's say 30-06. One is button rifled. One is cut 5R rifling. Will we see any noticeable difference in accuracy? Will we see any noticeable difference with recovered bullets? Will there be any other differences? This is also assuming we use a bullet mold that provides us with at least a good static/dynamic fit.
 
Ian

Ian

Notorious member
At least we don't speak dead languages...:rofl:

Polygonal and 5R are two different types of rifling. I have a 5R Rock Creek barrel on one of my Savages and it groups as well or sometimes not as well as a standard 4-groove button rifled generic AR barrel and a six-groove rack-grade M14...all using the same ammunition. I'm not familiar with the Arisaka rifling so I don't know if it's more like Glock or just has obtuse angles at the groove/land junction. I get the theory, and there may be something to it if the goal is maximizing obturation (bore/bullet seal) by reducing sharp angles and edges that have to be filled.
Anything we can do to reduce gas-cutting damage to the bullets improves bore condition and accuracy.

If I were to go pull a rifle out of the safe right now to go try and win a bet, I'd take my Micro-Groove Marlin 336 .30-30. IMO the shallow, high-count grooves Marlin uses or used to use is simply ideal for cast bullets: Low surface deformation, more torsional surface area than standard rifling either cut, hammer forged, or button made.

Lots of people rave about the accuracy and quality of JES .35-caliber re-bores and from what I read he only cuts three grooves.

In the end, I'm not convinced it really matters that much.
 
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JonB

JonB

Halcyon member
I think the Metford rifling on Arisakas does better with cast, than Jacketed. Mostly, because it's easier to make the correct size cast bullet, than it is to locate the correct size jacketed bullet.
That's my 2¢
 
Missionary

Missionary

Well-Known Member
Unless JES changed he did cut 4 and 5 groove for a few $$ more. We have 3 and 4 groove in 38-55. Neither is "more accurate" than the other with the 3 different molds we tried. Not a huge in depth study but enough for me to not spend the extra $$ on 4 groove.
 
Dimner

Dimner

Named Man
Metford rifling... thank you. That's the proper term.

And also, as a separate point of clarification, I'm not wondering about how many grooves are cut, it is the geometry of the grooves that I'm interested in. Regardless of button, hammered or cut 2/5/6/or 8 grooves, I have never really seen any difference. Or better stated, there have always been other obstacles to get through to make them shoot well.

So based on what Ian is saying, sounds like the 5R isn't that much of a departure from standard cut grooves. And my sample size of 1 that has left me drooling is Metford/Polygonal rifling. So evolving the hypothesis.... would poly/metford vs standard cut show us a difference? Is there anyone that even makes metford/poly rifle barrels?

1671220464031.png

1671220526906.png

Edit to add: I'm running .312 201gr Powder coated bullets (2150fps) and .311 150gr jacketed bullets (2650fps) ( in my Arisaka. Both excellent accuracy. I have not slugged or chamber cast the rifle. I tried .313 and .314, and the .312 just did better at higher velocities
 
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R

Rushcreek

Well-Known Member
My Tikka fever is spreading to using Tikka barrels to rebarrel other guns. I've bought three so far. My first T3 was a 22-250, last year I scored a 30-06 T3X barrel for $60, and switched it out. Now I have a crazy accurate lightweight 30-06. I reused the 22-250 barrel for a .218 Bee Topper stub rifle.
I have a 1922 Oviedo Mauser that will become a .257 Roberts via a re-purposed Tikka 25-06 barrel.
 
Spindrift

Spindrift

Well-Known Member
I don't know any barrel makers that use Metford rifling. But the Italian Sabatti use an interesting concept they call "multiradial rifling". I've never tried such a barrel, but always thought the concept sounds appealing for cast bullets

www.sabatti.it

Sabatti | The MRR rifling

The Sabatti MRR Multi Radial Rifling
www.sabatti.it www.sabatti.it
 
Snakeoil

Snakeoil

Well-Known Member
The MRR is interesting as it has a great chance of sealing the bore with PB bullets. I would also think that it is easier to manufacture since it would appear that you are "ironing" the entire bore in the swaging process which should remove any and all machining marks from the boring operation.

Ian said:
If I were to go pull a rifle out of the safe right now to go try and win a bet, I'd take my Micro-Groove Marlin 336 .30-30. IMO the shallow, high-count grooves Marlin uses or used to use is simply ideal for cast bullets:
Click to expand...
This comment made me chuckle. Not because I disagree or think it silly. But because I remember when Marlin introduced the 1894 Cowboy for CAS events, one of the features was cut rifling for cast bullets. At the time, there were a lot of people who said that the micro-groove .44 mag rifles sucked with cast bullets. Of course, we all know the old adage about opinions.

Getting back to the MRR rifling, be nice if you could buy those here for a reasonable price. I could see one in .32-40 screwed to a High Wall for a decent long-range gun.

The one question I would have for this type of rifling is, what is the chance that the bullet will not follow the rifling, at least when it first engages the rifling? I'm sure they have thought about that since they appear to be a modern target shooting mindset org which means jacketed bullets at mega speeds. So, would a cast bullet want to go straight at first? I would think that lead would smear easier than it would shear. But then again, micro-groove rifling probably has the same risk of the bullet not following the rifling at first.

I dunno. Just thinking out loud here.
 
RicinYakima

RicinYakima

High Steppes of Eastern Washington
Attached is the five groove Newton-Pope rifling system used on the early Newton rifles. Also a target from this rifle shot in 2006 with a Lyman 48 and post front. The center group is the Lyman 31141 and the bottom 311284. Ten shots each and same powder charge.
Newton_Pope_01.jpg
target newton a.jpg
 
Bret4207

Bret4207

At the casting bench in the sky. RIP Bret.
I'm going to step out on a limb here and risk appearing like the idiot I often am. Isn't the "ideal" form of cast rifling the one that deforms the bullet least while still having enough grip to give it the spin it needs? I mean, that' simplified, I'm sure, but looking at the Newton-Pope example I can see it working if you didn't push it to the point it skidded across the lands. Obviously it works well for Ric!
 
RicinYakima

RicinYakima

High Steppes of Eastern Washington
Bret4207 said:
I'm going to step out on a limb here and risk appearing like the idiot I often am. Isn't the "ideal" form of cast rifling the one that deforms the bullet least while still having enough grip to give it the spin it needs? I mean, that' simplified, I'm sure, but looking at the Newton-Pope example I can see it working if you didn't push it to the point it skidded across the lands. Obviously it works well for Ric!
Click to expand...
While I have not worked with this rifle for a few years, you are correct in that with cast bullets it is limited for velocity. Accuracy drops off pretty quick as you approach 2000 f/s. Since this is before PCing, it may be different now. Since it only weights six pounds and steel butt plate, never did much high recoil stuff.

My thoughts on Ian's micro-groove comment is that he is correct if you can keep gas leakage down. When I was only shooting linotype, 30 caliber micro-groove was very good, but leading started early.
 
Ian

Ian

Notorious member
RicinYakima said:
My thoughts on Ian's micro-groove comment is that he is correct if you can keep gas leakage down. When I was only shooting linotype, 30 caliber micro-groove was very good, but leading started early.
Click to expand...

There are several very important lessons to be learned from that experience. There was a time when I shot that same rifle regularly and it didn't get the bore cleaned for many years. It simply didn't foul. Fun fact: That barrel is also pitted, having come to me from my grandfather who shot it a few times with factory ammo and stored it dirty for years (it's a 1966 make and he bought it new, I got it in 1983). I have no use for linotype alloy except to firm up .22 caliber bullets that need it.
 
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