Well this sure is a BIG surprise to me ... the 1894CB in .45 colt has a 1:38 twist!!

I just picked up a new 1894CSS (.357 Magnum) and was sniffing around the Marlin Owner's Forum today looking for information on how Marlin makes their barrels and came across a thread that suggests that Marlin incorrectly lists the twist rate of the 1894CB in .45 Colt as 1:16. Supposedly it is 1:38 just like the .44 Magnum version. When I get home I'm going to take a look down the barrel (which I've done many times) and see if the lands make at least one complete revolution. If they don't then the barrel clearly isn't a 1:16. If they do, then clearly it is.

Here's the thread ...
http://www.marlinowners.com/forums/index.php/topic,59500.0.html

Here's the 1894CB on Marlin's website...
http://www.marlinfirearms.com/Firearms/Cowboy/1894_45Colt.asp

Ed Harris said:

My understanding is that the early .45 Colt Cowboys were 1:38 twist, and the barrel specs were changed later after accuracy complaints.

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Well, my 1894CB in .45 Colt isn't one of the early ones and it definitely does NOT have a 1:16 twist as advertised on Marlin's website. I checked last night and the lands make just over 1/2 a revolution in 20". It follows that it must be a 1:38 twist just like the .44 Magnum. I can understand WHY Marlin chose such a slow twist rate since the CB model is "typically" used for CAS type shooting where slow velocities are the norm, and in fact are required. But for #$%@ sake, why leave erroneous and misleading information on the website for at least the last two years?!! I just don't get it. :banghead:

highorder said:

what bullet weights and velocities are best for the 1:16 vs. the 1:38?

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Good question. How many rev/sec are required to stabilize .45 Colt bullets? For example, a 250gr RNFP in front of Trail Boss has a velocity range between 600 to 750 fps which means an angular velocity range of 450 to 562 rev/sec. Assuming an accurate load exists in this range, in order to match the angular velocity from a 1:38 Marlin barrel, the velocity would have to be between 1425 and 1781 fps. This would mean that a powder like H110 would have to be used. I chronographed some 250gr OT bullets in front of 22.0gr of H110 and got an average velocity of 1466 fps or 463 rev/sec which is at the low end of the angular velocity range. Accuracy was decent IIRC. Anyone else got any ideas on this?

I don't know if the Greenhill Formula is appropriate with large bore pistol cartridges but here it is anyway.



C is a constant = 150
SG for lead bullets is 10.9
D is bullet diameter (in.)
L is bullet length (in.)

I measured the lengths of 200gr, 250gr and 300gr bullets from Oregon Trail and came up with the following twist rates ...

200gr > 1:56
250gr > 1:46
300gr > 1:39

If you look at Don Millir's Forumula and use Bryan Litz's spreadsheet HERE it seems that the 1:38 twist is "ideal" for 250gr and 300gr bullets at around 1,450 fps and 1,200 fps respecively. Lighter 200gr bullets will do better at CAS velocities around 850 fps. What this suggests is that if you want to hot rod .45 Colt loads, use a 250gr or better yet a 300gr bullet. If you want CAS velocities then use a 200gr bullet. Maybe the 1:38 twist lets you have your cake and eat it too!!