Optimum rifling config. for CB's

[Sky C.]

Howdy Gents-

Am starting some research for a possible project. I'd like to know what experience has shown to be optimum rifling configuration would be for cast bullets.

Number of lands?
What percentage of land to grooves?
Lead config of throat?
Other???

The project I'm considering is to convert one of the M-1895 reproduction rifles. Starting point would likely be one of the Brownings in .30-06 that I believe would only require reboring & re-rifling & throating to .35 Whelen. How say you to twist of 1 in 16"? Aiming to use bullets in the 250gr ~ 270gr. range (max); probably on the order of 1.2" bullet length.

Comments suggestions welcome!

Thanks-

Sky C.

[felix]

Twist 14 would be a guarantee. 6 lands 0045-0048 tall will assure the use of the most tenacious lube for at least several outings in 100 degree weather, and should deliver a five shot group in 0 degree weather with 5 minutes between shots. I would go for a 60 percent groove, 40 percent lands with a 5-10 degree angle slope off of a straight up 90. ... felix

[Bass Ackward]

I'd like to know what experience has shown to be optimum rifling configuration would be for cast bullets.

Number of lands?
What percentage of land to grooves?
Lead config of throat?
Other???
How say you to twist of 1 in 16"? Aiming to use bullets in the 250gr ~ 270gr. range (max); probably on the order of 1.2" bullet length.

Sky,

You are trying to open a can of worms, I can see. There are two ways to increase the drive area of rifling. Either increase the height of the rifling or increase the number of rifling without losing height. Just think about that.

I lose stability with a 265 grainer at 1500 fps with a 14 twist. If you want to hang around those velocities, you need a faster twist than 16. 250s stabilize down next to nothing with no problems at any velocity. And the 250 is about the ideal weight for a standard SAAMI throat from the base of the neck.

Now that Remington has standardized the Whelen, you get their specs on a standard reamer. Those usually come with the typical Remington philosophy of larger than necessary necks, .250 freebore and a .360 throat. If you need to buy the reamer, then load up a dummy round and send it to JGS and they will make your reamer to fit that dummy cartridge and cut any throat angle you want. M...u...c...h tighter tollerances.

[beagle]

Sky...I think Jumptrap's been there and done that on the M95 Wlelan with a 1-16 twist and has a bad taste in his mouth. Maybe he'll weigh in here shortly.

I beleive 1-14 would be the slowest twist for that weight/length bullet and I'd prefer 1-12.

I have shot and stabilized the #3589 in my 1-16 twist .35 Rem but that was a limited test and I need to play with it some more./beagle

[felix]

Beagle, a 14 twist is perfect for a very flat nosed 280 grainer (flatter than the Lyman version by a long shot, more like a rounded wadcutter, see boolit on castpics) in Sundog's gun. 2 inch groups at 200 consistently. ... felix

[Buckshot]

"I'd like to know what experience has shown to be optimum rifling configuration would be for cast bullets."

...........I don't think there is such a thing. I do not believe any one number of rifling lands/grooves has proven itself to be consistantly more accurate over another. You have a couple 2 groove designs. Then a few have tried 3 groove. The ever common 4 groove, 5 groove, 6 groove, 7 groove (Henry for one), 8 groove and the micro 12 & 16 groove barrels.

Then besides numbers of lands and groves you have the wide groove narrow land (Mauser-Springfield), equi-width lands and grooves (Enfield, Swede, Turk), ratchet or buttress, proggressive depth, gaintwist, polygonal, Henry, Metford and any number of others.

If you were going to set a strict limitation on your boolit selection then you might get a bit closer to picking an optimum configuration. Suppose a decidedly bore rider was the boolit, then I would go with a land biased design, regardless of the number of lands and grooves.

Maybe you could dabble with the odd number of lands and grooves going with the theory of a land opposing a groove, and having it a 50/50 deal. So you have now decided on the Enfield/m1917 design.

I think more then anything else it is the quality of the barrel and the quality of it's chambering and installation that does more for accuracy then any particular rifling type/design.

.............Buckshot

[9.3X62AL]

The 35 Whelen's European cousin (9.3 x 62) has turned out to be a GREAT casting flinger. The CZ-550 has a Mauser-pattern 4 groove arrangement, about 1/3 land and 2/3 groove, with TALL lands--about .007". The twist is about 1-13", probably 3 turns/meter. More recent CZ's in 9.3 x 62 supposedly have a 1-9.5" twist (4 turns/meter) to accomodate the 300 grain-plus bullets that some shooters prefer in this caliber. The slower pitch in my rifle works just fine with the MM 270 grainer at 1400-2000 FPS, and with the Nosler Partition 286 grainer to 2300 FPS (ouch.....).

Hard to understand why any bullet heavier than 286 grains might be wanted in a 35-36 caliber rifle, but to each his/her own. For me, the 286 grainers at 2300 FPS yield enough entertainment from the bench to satisfy the most jaded of recoil enthusiasts.

[Sky C.]

Gentlemen-

Thank you for your comments and recommendations. My further investigation shows that Remington used a 16 twist in their M-700's but it seems here that concensus is that would not be sufficient to stabilize bullets in the 250gr.+ range.

As I give it more thought to it - I think 250gr. to 265gr. may be as heavy as I choose to go bullet wise but I'll wait till I have rifle in hand to see what the limitations are for max OAL to feed from the magazine. That will in turn halp to establish how to have the rifle throated (suggestion for custom reamer sounds like the way to go).

Question... When is rifling twist too fast (for CB's)?
I want enough twist to stabilize the bullets but it is my understanding that too fast a twist is problematic for CB's. I don't have any specific experience about how fast is too fast when it comes to twist & CB's. I suspect there is a relationship between bearing surface of rifling vs. velocity vs. bullet mass & alloy strength... My .375 Win has a 12 twist (does not behave well with CB's to date) & it has been suggested that this fast twist (coupled with long jump to the rifling) is the cause.

Thanks again-

Sky C.

[beagle]

Felix...I'd have thought so too but Shuz's .35 Whelan is a 1-12 as well as I remember and he swears by it with the 358009./beagle


Beagle, a 14 twist is perfect for a very flat nosed 280 grainer (flatter than the Lyman version by a long shot, more like a rounded wadcutter, see boolit on castpics) in Sundog's gun. 2 inch groups at 200 consistently. ... felix

[beagle]

Sky....Just my opinion here but I had a Marlin M1894 rebarrelled with a Douglas 1-18 twist barrel once.

My reasoning was that if a pistol shot 300+ grainers from a 1-18 twist, a rifle would too. I paid dearly for that piece of education. It would shoot the .300 grainers and larger but not the shorter, lighter bullets to any degree of accuracy. As a result, I dumped it and went with a 1-26 twist Winchester Legacy.

Felix and myself kicked this problem around all winter one year. We eventually figured out from the greenhill formula (which ain't really the gospel) and kicking dimensions from bullets I had on a computer model that gave good accuracy that the optimum twist for a .44 Magnum was 1-25 and some change. The 1-26 twist Winchester and Ruger selected is about as close as you can get.

Now, getting to overstabilization. From our discussions off site, overstabilized bullets will work all right...IF....they're perfect and all of us know that cast bullets aren't. Too many internal voids and problems with fill out that us casters induce.

What we concluded that any bullet imperfections were amplified by overstabilization and inaccuracy resulted.

I may be wrong but that was my take on the conclusions reached at the time./beagle


Gentlemen-

Thank you for your comments and recommendations. My further investigation shows that Remington used a 16 twist in their M-700's but it seems here that concensus is that would not be sufficient to stabilize bullets in the 250gr.+ range.

As I give it more thought to it - I think 250gr. to 265gr. may be as heavy as I choose to go bullet wise but I'll wait till I have rifle in hand to see what the limitations are for max OAL to feed from the magazine. That will in turn halp to establish how to have the rifle throated (suggestion for custom reamer sounds like the way to go).

Question... When is rifling twist too fast (for CB's)?
I want enough twist to stabilize the bullets but it is my understanding that too fast a twist is problematic for CB's. I don't have any specific experience about how fast is too fast when it comes to twist & CB's. I suspect there is a relationship between bearing surface of rifling vs. velocity vs. bullet mass & alloy strength... My .375 Win has a 12 twist (does not behave well with CB's to date) & it has been suggested that this fast twist (coupled with long jump to the rifling) is the cause.

Thanks again-

Sky C.

[felix]

You are not wrong, Beagle!m Conclusions are right on! No need to overtwist the Whelen. 14 twist is correct for the 280 grainers, and will shoot the 158 grainer pistol boolits equally good, and at 2400-2600 to boot. Sundog has a good barrel, I have to admit. Good ol' Ed Shilen himself must have slicked that one down. ... felix

[StarMetal]

Beagle,

I dunno. I think alot has to do with the particular gun itself. I had a TC Hawkens that had the 1in45 twist. It shot the almost 400 gr Maxi-Balls terrific, and it shot the very much lighter patched roundball terrific too. But that's blackpowder. It's true that the bullet has to be perfect for overstablization, but that's true of a jacketed bullet too. I have my 7mm-08 with a 1in9.5 twist shooting cast, both light and heavy, excellent. My 260 Rem, which I've had problems with cast, is now shooting the light new 6.5 Kurtz pretty good. My AR15 with 1in7 twist shoots EVERYTHING in jacketed good and does pretty well with cast. My Marlin 45 LC with 1in38 twist shoots EVERYTHING well, both cast and jacketed. My Smith Model 25 in 45 LC shoots EVERYTHING well, cast and jacketed. I'm not sure there's an actuall dead-on science to all of it.

Joe

[felix]

Joe, boolit form enters the equation when approaching the critical twist. A more pointed boolit at a particular length lessens the twist demand considerably at this juncture. Sundog's version of the 280 grainer is definitely a rounded wadcutter exactly like 311440. Shoots two inches at 200 all day long. ... felix

[beagle]

Joe...you're right. It depends on many things.

I wouldn't have beleived a 1-16 twist would stabilize a 3589 bullet in the .35 Remington until about a month ago but my old Marlin put 25 on a a target in two groups with nary a oblong hole. Go figure./beagle


Beagle,

I dunno. I think alot has to do with the particular gun itself. I had a TC Hawkens that had the 1in45 twist. It shot the almost 400 gr Maxi-Balls terrific, and it shot the very much lighter patched roundball terrific too. But that's blackpowder. It's true that the bullet has to be perfect for overstablization, but that's true of a jacketed bullet too. I have my 7mm-08 with a 1in9.5 twist shooting cast, both light and heavy, excellent. My 260 Rem, which I've had problems with cast, is now shooting the light new 6.5 Kurtz pretty good. My AR15 with 1in7 twist shoots EVERYTHING in jacketed good and does pretty well with cast. My Marlin 45 LC with 1in38 twist shoots EVERYTHING well, both cast and jacketed. My Smith Model 25 in 45 LC shoots EVERYTHING well, cast and jacketed. I'm not sure there's an actuall dead-on science to all of it.

Joe

[beagle]

felix...we're working on the 358315 based variable weight .35 "bullet from hell" right now. It will have the .350" nose and a shape like a 311440. It will have two punches. One solid and one for a HP.

Weight and length are varied by adjusting the two interchangeable punches. I'll post pictures when it gets done.

The adjusting attachment is finished. Now, we're to the mould cutting part.

Only drawback will be a light ring where the nose punch and cavity come together. That should be able to be smoothed out with a TP during sizing./beagle




Joe, boolit form enters the equation when approaching the critical twist. A more pointed boolit at a particular length lessens the twist demand considerably at this juncture. Sundog's version of the 280 grainer is definitely a rounded wadcutter exactly like 311440. Shoots two inches at 200 all day long. ... felix

[felix]

Beagle, that variable length 35 boolit would be a wonderful play thing, and that's for sure! I would use it to obtain a boolit that will go 2400 fps with a "standard" load in that gun on the shelf. ... felix