38-55 Twist Rate - Heavy Bullets

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Aaron posted this 2 weeks ago

Seeking a slick bullet for the Cimarron 1885 in 38-55 Win has been a fun exercise. I do however have some questions for those of you who have paper patched for this caliber, as well as those of you using this caliber in the CBA Matches - either as a PP or a greaser.

The Cimarron (Uberti) 1885 rifle has a bore of .373" and a groove diameter of .379". It also sports a rifling twist of 1:18 inches. This twist rate is conducive to heavier than usual (lever action) bullets of a longer length. A 310 - 324 grain bullet at about 1.1 to 1.3 inches is just peachy for that twist rate according to the Greenhill Formula, using the specific gravity for pure lead. The twist rate varies slightly depending on the length of the bullet from 1.0 to 1.3 inches. Rates of 1:17 to 1:19 can be had with slight bullet length variation. Let's simply say that 1:18 is an "optimal" Greenhill Formula result.  

Slick diameter is irrelevant to the calculation since a bore slick (.366) wrapped to .372, or a groove slick (.372) wrapped to .379 will BOTH be spun at the .379 diameter prior to exiting the muzzle and the PP spinning off.

So we have a bullet of about 320 grains at 1.2" in length being spun by the "ideal" twist rate of 1:18 for optimum stability

Why then in our matches do we have shooters who have 38-55 barrels with twist rates as fast as 1:12" shooting 323, 325, and 331 grain bullets. If the twist rate renegades Barry Harmon, John Lahman, or Tom Acheson are reading this post, please educate me on why your twist rate differs from the "optimum" rate specified by the Greenhill Formula.

By the way to all readers. There is a WEALTH of information contained in the CBA Match Reports included in The Fouling Shot. If you are not a CBA member, consider joining us and receiving The Fouling Shot for you enjoyment.

With rifle in hand, I confidently go forth into the darkness.

38-55 twist-rate

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Tom Acheson posted this 2 weeks ago

Can't add much to this. My heavy full octagon Green Mountain barrel has a 1:12 twist, the bullets are NOE 330-grain, sized @ 0.386", no idea what the muzzle velocity is, won't even guess. 

Maybe like the warden in Shawshank Redemption said....."like a fart in the wind" I'll just continue to be an oberver on this subject!

Tom

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Ed Harris posted this 2 weeks ago

The 12-inch twist is standard for the .375 H&H and is a common and readily available blank in the trade.

Some barrel makers sort out their barrels that gage over .377 groove, to sell to the BP shooters

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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Aaron posted this 2 weeks ago

Jeez Tom. That clears it right up. smile

 

With rifle in hand, I confidently go forth into the darkness.

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Premod70 posted this 2 weeks ago

The ‘slick’ bullet for an 18 twist barrel is the Lyman 375248, an old standby that when fired with around 9-10 grains of Unique will do some fine shooting at 200 yards. The catch is finding an oversize mold that casts a bullet a couple thousandths over groove, some have success ‘beagling’ the mold. Good luck.

Forrest Gump is my smarter brother.

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Tom Acheson posted this 2 weeks ago

This won't clear it up but....a good friend gave me the Rolling Block AND the Green Mountain barrel blank. I was asked to oromise to build up a rifle for CBA BR matches, which I did. He told me ordered the 1:12 twist because he planned to shoot heavy bullets in it. The barrel was initially bought for his Marlin 336 lever action, to be chambered in .38-55. But the project was never completed.

He had a Sharps Model 74 chambered in .38-55 that he used in BPCR rifle silhoutte matches (scoped sight). Twist was whatever CSA provided (2010) in a Badger barrel, probly 1:15. We spotted for each other. He used Unique or 5744, even though they were black powder matches. Bullets weighed about 340-grains. Other shooters on the line would remark after Joun shot, that it sounded like he was shooting a .22! But...he hit the 500-meter rams more often than I did with my Model 74 chambered in 40 2 1/2 (iron sights).

Tom

 

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Aaron posted this 2 weeks ago

That sounds like one of those "shouldn't work" but yet it does things. When I ordered my Contender barrel in 38-55, I figured I would get a .375 groove which I did. Like Ed Harris pointed out, most barrel blanks for 37x caliber are .375". Fortunately I have two 375 bullet molds so they should work in that. I haven't worked up any loads for it yet but whatever I come up with ( a hybrid cartridge) will in all probability do just fine. That barrel will chamber any load I have already worked up with .380 bullets and 1.125" brass just fine. I can just picture those bullets squeeeeeeezing their way down that tube!

At this point, I figure I will just roll them and shoot them. Let's see what shakes out.

 

 

With rifle in hand, I confidently go forth into the darkness.

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Qc Pistolero posted this 2 weeks ago

My Pedersoli High Wall has a 1:12 twist.I use a beagled RCBS mould that comes out at 275gr in my alloy(25:1)and a 330gr Accurate 38-328M.

After trying medium fast powders(5744 down to Unique)and not getting good accuracy I settled on 4198 and 4895.The bullets have to be pushed a little faster than I like to stabilize(sorry no chrono;too lazy to set it up but according to loading data in the mid 1400)but that's the prize to pay for having fun with that great caliber.BTW,a 330gr at 1400 or a little more begins to rattle you a bit from the bench after 30 or 40 rds.

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Fitzpatrick posted this 2 weeks ago

I have a Browning High wall Traditions with a 28 inch barrel and a 1-15 twist , it shoots everything from 225 grainers to 400 grainers very well . I use the star-line long 2.125 brass and paper patch my standard lube grooved bullets size them down to .374 then patch them up to .380 , I have used reloader 7 ,10 and the 4198 both IMR and Hodgen with good results but my old stash of IMR 4759 is a sweet spot with 18 gr. 

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SkinnerD posted this 2 weeks ago

Forgive my ignorance re the dark arts of paper patching and the subtleties of casting, beagling, and distance shooting with this fine calibre. That out of the way I have some questions, possibly dumb ones lol.

Re the OP's statement "The Cimarron (Uberti) 1885 rifle has a bore of .373" and a groove diameter of .379". It also sports a rifling twist of 1:18 inches. This twist rate is conducive to heavier than usual (lever action) bullets of a longer length. A 310 - 324 grain bullet at about 1.1 to 1.3 inches is just peachy for that twist rate according to the Greenhill Formula, using the specific gravity for pure lead. The twist rate varies slightly depending on the length of the bullet from 1.0 to 1.3 inches. Rates of 1:17 to 1:19 can be had with slight bullet length variation. Let's simply say that 1:18 is an "optimal" Greenhill Formula result. "

All my metallic cartridge experience and reading in centrefire rifles says that high Ballistic Coefficient bullets require faster twist rates, BC being a function of bullet length relative to weight. It is the length of the projectile that requires faster twist to stabilize. Folk therefore translate or shortcut that to "heavier bullet = faster twist required "

But here in the wonderful world of cast and the 38-55 Cal, we seem to have the opposite stated. A slower twist, 1:18, supports a heavier bullet. Am I mis-construing something?

I ask cause I am playing a new Uberti 38-55 High Wall Sporter in 1:18 twist. I understood when I bought it that 250gn bullets would be its sweet spot. That 300+ would be a challenge to obtain stability. A 1:12 twist Pedersoli was available, but apart from the plus 30% price differential, I can buy 250gn in .379 dia Powder Coated and cast and that's it. As a beginner to casting I have a Lee mold just arrived, 250gn, and that's kind of it until a gain expertise and spring $$ for something other than Lee.

So difficult to get different weights of bullet to experiment with other than buying a mold I may end up with no use for.

Hence my interest in following this esoteric thread closely.

If someone has good experience of heavier than 250gn bullets in a 1:18 twist 30" barrel I'd be keen to hear details. Hopefully this still remains within the context of the thread somewhat.

Cheers

John - New Zealand

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Bud Hyett posted this 1 weeks ago

My first "Schuetzen" rifle was a gift, a Remington Rolling Block rebarreled with a take-off barrel of unknown origin. The barrel was .377 diameter wit an 1:18 twist. This rifle had a Redfield 75 rear sight and Lyman 17 front sight plus external adjustment scope blocks. The trigger was reworked to two pounds and crisp. I bought a 20X Lyman Super TargetSpot to use with this rifle.

The first molds were SAECO #373 and RCBS 37-250-FN. The RCBS was reworked removing the the gascheck shank. Later I bought a Hoch mold throwing 335 grains. Initial loads were fixed cartridge, later breech-seated with a plugged case. The bullets were cast with wheelweight alloy for the fixed ammunition and soft (unknown) alloy for the breech-seated. 

Reloder #7, SR 4759, IMR 4227 and Hercules 2400 powder were tried aiming for 1400 feet-per-second. The best accuracy was using IMR 4227 powder. 

In summary, the rifle shot sub-minute one day and Improved Cylinder the next day. After some load workup, the RCBS and SAECO bullets shot sub-minute for five-shot groups. The 335 grain bullet shot well and showed no sign of instability, but never grouped below two minutes. I thought this bullet was on the edge of instability.

I learned a lot about shooting cast bullets with this rifle. The action now sports a .45-70 barrel of sporter weight and shoots well.

Farm boy from Illinois, living in the magical Pacific Northwest

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Aaron posted this 1 weeks ago

But here in the wonderful world of cast and the 38-55 Cal, we seem to have the opposite stated. A slower twist, 1:18, supports a heavier bullet. Am I mis-construing something?

I don't think so. The Greenhill formula result, with its simplest data inputs of bullet length, weight, and diameter, yield a result of 1:18 inches. When longer bullets are used at 320ish grains, 1:18 is also the result. I am as surprised as anyone as to why the 1:12 twist rates are used by some with the results obtained in their scores in the competitions. Practical use obviates the 1:12 twist as realistic. My practical experience with the Lee 250gr bullet and commercial cast 260gr bullets by Badman and Hunters Supply, shows the 1:18 twist is just fine for stability with hunting accuracy in both the M94 Winchester as well as the High Wall SS rifle.

I have ordered some heavier slick bullets to PP and see if any substantial variation exists between them at 300gr, and the 250gr fodder I cast or purchased. Bear in mind too, that I am working with fixed sights on the M94 rifle and also with fixed sights on the High Wall. Both sport factory sights. When combined with my "older" eyes, I do not get the accuracy obtained like other shooters with optics installed for competition.

Note too that I am very pleased with the Lee 250gr (379-250-RF) bullet mold. It shoots well with both BP and smokeless propellants. I perused the Accurate Mold bullets and was interested in the 38-337L as a greaser with its bore riding nose. I have decided that I am just tormenting myself with the lure of yet another mold when I have a mold, several in fact, for the 38-55. I tried a N.O.E. mold but truthfully, I am very unhappy with it due to its meplat protuberance with the FP insert. As my first N.O.E. mold, it left me with a distaste for their product. The Lee mold casts much better bullets.

I will suggest to you that the 1:18 twist works just fine with a range of bullets and that the 1:12 twist will favor the heavier bullets. But as we both know, the proof is in the pudding. Hopefully you guys make pudding in the bottom half of the world. big_grin

With rifle in hand, I confidently go forth into the darkness.

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Aaron posted this 1 weeks ago

I ask cause I am playing a new Uberti 38-55 High Wall Sporter in 1:18 twist. I understood when I bought it that 250gn bullets would be its sweet spot.

I would say for the record that the 38-55 has been the most challenging cartridge I cast and load for. Just yesterday I troubleshot a chambering issue with the 1885 High Wall rifle. Each rifle, both the Uberti M94 and the Uberti 1885, have tested my patience and diagnostic skill.

With the 1885 I have learned that the RCBS Cowboy dies set is very useful for cast bullets EXCEPT that the roll crimp in the seating die should NOT BE USED with the 1885. It ever-so-slightly bulges the case mouth, preventing chambering with .379" bullets in the Starline brass of both lengths. The Lee Factory Crimp Die cured this problem.

Each rifle has its ammunition quirks and that has been my nemesis. Cartridges loaded for the M94 with its feeding idiosyncrasies, may not chamber in the 1885 and vice versa. I have learned to load for each rifle differently and separately. My 1885 will chamber both the Starline 1.125" cases and the 1.085" cases depending on the crimp and bullet diameter. Know that .0005" in this rifle chamber is like the Arizona Grand Canyon to a rifle. It's the difference between a "go" or a "no-go" with a cartridge being chambered. It's a fussy little lady regarding its ammunition.

Bullet length and nose profile is an issue in the M94 lever action. It is no issue in the 1885 with "standard" bullets. Heavier (longer) bullets can be more difficult for a novice handloader whereby there is not too much throat in the Uberti 1885. The rifle is much less forgiving for newer loaders who may get frustrated easily rather than diagnosing the issue and working around the findings.

Anyway.....enjoy that High Wall. Cast some bullets and get her to the range!

 

With rifle in hand, I confidently go forth into the darkness.

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