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38-55


Marshall Mike

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Mike, read this technical write up by Missouri Bullet Company about bullet diameter and obturation

https://missouribullet.com/technical.php

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The BHN of the bullet interacts with the pressure generated by the burning powder.  The mechanism of this involves the effect of the generation of thousands of pounds per square inch of pressure which causes the base of the bullet to expand, or “obturate”.  Properly obturated, the base will have expanded beyond its original diameter which has the effect of “sealing the bore” against the explosive pressure of the gases burning behind it.  Properly sealed, and working in conjunction with the lubricant in the lube groove, the bullet will thus not allow gases to escape forward from around the base of the bullets, which prevents it from shaving lead from the bullet body and forcing it into the bore grooves (otherwise known as “leading”.)

 

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A bullet which is too hard won't obturate and seal the bore, because the gas pressure is insufficient to expand the base of the bullet.  A bullet which is too soft at a given pressure will experience excessive base expansion and vaporization of the lead, causing leading.

There is a formula for optimal bullet hardness which is simple and it is worth knowing:

Optimum BHN = PSI / (1422 x .90)

 

So it depends on bullet hardness for proper obturation.  Standard smokeless bullets will obturate properly in the grooves so buy your bullets with a 0.382 and your good to go with proper obturation.

I have 4 38-55's, all with different groove diameters which requires me to buy molds for those groove diameters,including the Uberi with groove less than 0.382

PS, none of my 38-55's are larger than 0.379 ... so maybe your measurement is not correct ,example my Uberti @ 0.378 measured with an inside caliper

 

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Cimarron (an Uberti importer) publishes what specifications they believe Uberti barrels are built at.

 

https://www.cimarron-firearms.com/bore-groove-twist

 

They put a 38-55 barrel at 0.379" groove diameter, so I would be tempted to try a 0.380" soft (perhaps 1:40 or 1:30 alloy) bullet.

 

For example bullet selection, Missouri Bullets has a 38-55 Ballard style bullet cast in 18 Brinell hardness (harder than I would like, but you may enjoy it).

#1 Ballard
.379 Diameter
245 Grain RNFP
Brinell 18

 

Folks who get serious about cast bullet rifle shooting often start casting their own bullets.  That way, they get exactly the diameter and alloy (hardness) that their gun performs well with.   Not too hard to get started, if you have the room for equipment and a safe place to cast.

 

Good luck, GJ

 

 

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Drive a pure lead 45 cal ball down a lubricated barrel to get your measurements and do what John Boy says.  My own Uberti is .382 and I use a 381 bullet out of an Accurate Mold.  My Marlin CB is  .380 and it is scary accurate with the Lee bullet dropped out at .380.  I routinely use a charge of 5744 that pushes them at blackpowder velocities.  

 

The key to loading so called overbore rifles (they really aren’t) is to use the correct brass. Both the Uberti and Marlin are designed to use the original 2.12 long brass which is also thinner in the neck (Starline) than the short Winchester brass.  You probably can’t chamber any bullet over .379 in Modern WW without the chamber being relieved and even then the chamber is still short.

 

Get you some Starline Brass, Rcbs Cowboy dies withe correct expander, and order up some .380 bullets that aren’t hard as brickbats.  

 

Finally , get a copy of Ken Waters Pet Loads for the 38-55.  He goes into detail on the problems trying to shoot older style rifle chambers/bores with too thick brass
 


 

 

 

 

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The only 38-55 rifle that has to have the chamber reamed to shoot lead bullets is the H&R Target rifle.  Reason is because when Green Mountain made the barrels they were told to chamber for the 375 Winchester which was the round used for proof testing.  Otherwise, the 38-55 lead bullet round will not seat fully in the chamber

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3 hours ago, VICIOUS, SASS#8014 said:

Howdy; H and  R chamber is as stated short for a 38-55. So I shortened the 38-55 brass WW cases to 375 Winchester length and loaded .379 diameter bullets. This worked for my needs.

You must have had some older and desirable WW cases of original specs.  Modern 38-55 (well, the last 40~years) are already .375 Win length at 2.02 in.

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2 hours ago, Sgt. Hochbauer, SASS #64409 said:

Not to hijack this thread as I had a 38-55 question how can I tell which length brass to buy? Its for a Winchester 94.

 

Hochbauer

Pre-64 model 1894 is 2.12 inches.  Its my understanding that the Commemoratives they chambered for 38-55 or at least the ammo back in the 70's and 80's were chambered for the long 2.12 but the factory ammo offered is  2.02.   It likely wont make a difference but I'd get the thin necked Starline 2.12 as first choice and the shorter 2.02 in a pinch.

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Howdy; Modern Winchester  ,WW  38-55 stamped mike to 2.075 length then trimmed to 2.010 for use in H and R

         This brass was purchased a few years back from a gun store in bags sealed from Winchester.

The length of brass match Lyman reloading book 49, pages 281 and 283

 

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Not to hijack this thread as I had a 38-55 question how can I tell which length brass to buy? Its for a Winchester 94.

Hochbauer ... Read this article ... https://www.starlinebrass.com/articles?id=2540

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For most shooters loading conventional cast bullets in guns with standard 38-55 rifle bores and correctly cut chambers, using the 2.125-inch long, thin-necked, Starline 38-55 Winchester cases can provide a significant accuracy improvement.

In all of my 38-55 rifles, the Starline 2,125 cases are the only length that I reload

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I have the same rifle, from Taylor's.  I bought .382 bullets from Rimrock Bullet.  They work.

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  • 3 weeks later...

I too shoot the Starline 1.125 brass in my Marlin, Bear Creek .380 dim. Marlin said to use .380 dim.  Same brass in my Browning Highwall  Bear Creek .377.

I had a H&R target rifle, shot the Starline 1.125 brass Bear Creek .380 dim. shot very good. Winchester wouldn't chamber with that bullet. I would for sure slug your barrel then decided what to use.

   Rob

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