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Loading for the Marlin 336CB 38-55


Red Cent

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The ongoing attempts even as I wait for a new rifle.

 

A few days ago I went to the shop and arranged my notes on the Marlin lever gun.  I have a copious number of load and pages dedicated to the search. First. some discoveries. When I first started shooting the rifle, I was a little ignorant about loading cast lead bullets in a rifle. And the loads were for a....a.....lever gun. We all know they are not accurate. The 38-55 lever gun is noted for an atrocious chamber and owners do different things to the chamber to improve accuracy. The 38-55 lever gun is also known to slug .379 but the owner is unable to load and chamber a .380 bullet . So they throat the chamber.

Recently, I came to the conclusion (lightbulb time months late) that mine was throated since it slugged .379 and I could chamber the .380 bullet easily. I talked to a reputable national and world champion BP shooter and he loaned me a reamer to decrease the leade angle from 3* to 1.5*.

After trying some different loads over time, I was not satisfied and was ready to sell.

Back to the notes. The new rifle will be another month so I decided to try some more. As I was looking through my notes some posts/articles/books came to mind. Neck expanders, neck tension, and, something I will purchase, a concentricity gauge. Looks like my old arrow shaft concentricity gauge :) . The something occurred to me. I have been loading bullets in unsized, uncrimped (are those words?) cases. In other words, kinda hangin' out there since that throat was so big. So I started again.

I loaded .379s and .380s in full length resized brass or unsized, uncrimped cases. I loaded them at "barely touching the lands" and I loaded them seated to the groove, crimped and uncrimped.  Not surprising, I got some good "patterns" and a surprise group. My conclusion later.

I include a picture of the "groups" fired off bench sticks, sandbag under the butt piece, and sporting a 4 X 12 power scope turned to 12 power. 100 measured yards.

 

IMG_0719.JPG

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The rifle sports a 2# very safe trigger. The rifle was wearing a 4x12 power scope set at 12X. All loads were the "standard" load of Unique. I removed the mag tube and inserted a shortened replacement that comes to the forend cap. Shimmed the cap captured the replacement tube so that this is the only place of influence on the barrel. Rifle is rested at the cap on the sticks.

 

The top left target was fired with a .379 bullet, crimped at the groove and unsized. 3 1/2  wide and 3.7 tall.

The top middle target was fired with the .379 bullet seated long at COAL 2.80". Full length resized and crimped long. 2.80"  3.9 wide and 3.2 tall

The top right target was fired .379 with no resize, no crimp and long. 2.80"  2 wide and 3.4 tall

Second low left was fired with a .380, crimped in groove full length resized. 2.5 wide and 1 tall

Second row middle was fired .380 with no crimp, seated to groove. 2.8 wide and 5 1/2 tall. With all fairness, these were the first five rounds fired.

Second row right was fired with full length resize, crimp, and long.

Bottom row middle was fired with .380 full length  resized crimped at groove.

 

The bottom middle target includes the bottom five shots to the right of the target in the shape of a V.

 

 

Summary: If you have a 336 that has been throated, it is better to full length resize, light crimp, and crimp at the groove. Might be a sweeter spot a little longer. I will find out. I think this positioning  is really centering the bullet as it points at the bore. Something is happening with a factory COAL and full length resizing.

I will load a number of .380s in new Starline brass (short) that has been FL resized and I will crimp in the groove and a few a little farther out.

 

Oh yeah, Murphy's law says that I will only have four bullets of the best load :) 

 

 

 

 

 

 

  

                   

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Red Cent,

I had a 336CB 38-55 years go when they first came out. When I got the rifle I checked the barrel and it was .379 but the chamber was cut for .376" bullets. Off to Marlin it went for opening up the chamber. When I got it back I tried many loads using Unique powder and had one that was just "okay". I was a little perturbed but a buddy recommended 5744 powder and after some trial and error I found a great load and that rifle was a shooter. I do not have / cannot find my load data card for my pet 38-55 load or I would PM you the info. I may have put it in with the gun when I sold it. Moral to the story was the 5744 powder changed everything for a rifle that I thought was going to be a mediocre shooter.

 

Good Luck

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Have you done a chamber cast so you know exactly what chamber dimensions you have

 

SD, no I have not done that. With the ability to chamber a .380 bullet without resistance and a groove diameter of .379 I would think the exercise would be futile. When I touch the lands with nose of the bullet, I am gonna guess the bullet is supported by the case neck and the lands. Ideally, the throat should be .379 or maybe .380 but it is bigger than that.

 

Pat, I find that Unique is the most used powder. Certainly, 5744 is around the top of the list along with 4227, 3031, and 4198.  The 45-70 shooters around here like 5744. I will pick up a pound of 5744 and tinker.  

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Reason I ask is there are two different lengths of brass for the 38-55. (2.082" and 2.125)

 

Only a chamber cast will tell you which one you should use. It will also reveal of the chamber has any flaws, was reamed too large by the previous owner, etc.

 

 

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I believe the chamber has been enlarged past any fixing. On a number of forums, there are a number posts regarding the long and short brass. While the smokeless loaders have found very little if any difference in the brass, the BP shooters gain a grain or so with the longer case. Most Marlin owners of the 336s find that the short case is the correct case.

I think tweaking one load in particular that I can shrink the group down to about 1 1/2".  Who knows, I might find a big pot of gold at the end of that rainbow :) 

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Since a .380 bullet goes easily, I have to think the "chamber" is at least .381. The groove is .379.

 

Are you guys working towards a "fit the throat and it will shoot" goal?

 

I may need some "perfect" bullets to see if they will enter the bore super concentric and leave the barrel the same way.

 

For some time, H&R, Marlin, and some Uberti single shots left the factory with .379 grooves but one could not chamber a .378 bullet. These rifles created the "lets open the throat' movement. From all what I have read, these throated guns suffered even more in the accuracy department. Since those days many a shooters have picked up cheap Glenfields and others and taken them to JES Rebore/rebarrel. http://35caliber.com/

However, the chamber he installs is a 38-55 with chamber and neck dimensions of the 375 Winchester. 366 Bore-376 groove.

 

The later Pedersoli barreled Ubertis did not have this problem. Pedersoli uses the .379 groove.

 

 

 

 

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The Marlin 336CB 38-55 has always been known to have a tight throat. Those that reamed them never could get accuracy afterwards. They do like the 38-55 long brass from Starline without being reamed.

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CK, mosey on over to the Marlinowners.com forum. There are a few there that will post 1" groups using the 2.080" brass and crimping them in the groove.  'Specially look up posts by JBLEDSOE.

When one gets strung out trying to make a finicky rifle shoot, step out of the box. I have built a few bolt action rifles. All have the barrel floated 'cept one. A 22" straight taper Premium Douglas in 6MM and the barrel screwed into a Savage 110 action. Laid into a beautiful Bishop stock with a twist for the 100 gr bullet. Frustrating until I bedded the barrel under the fore end tip.

 

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HI. For what its worth. In a Marlin 38/55 I loaded Winchester brass and fired .379 bullets the layman  249s with unique. In a pedersolie rolling block I load the same round and they shoot even better. The HR 38/55 buffalo well the story goes these were short cut chambers to 375 Winchester dimensions. The brass jammed into the rifling and would not extract if not fired. SO I cut the 38/55 brass to 375 Winchester length and loaded and fired .379 bullets just fine. All these guns were new from the factory and not FIXED in any way.

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When I got my Marlin a cartridge with a .380 bullet would only go into the chamber about 1/3 of the way. The chamber had to b

13 hours ago, Coyote Kincaid said:

The Marlin 336CB 38-55 has always been known to have a tight throat. Those that reamed them never could get accuracy afterwards. They do like the 38-55 long brass from Starline without being reamed.

When I got my Marlin a cartridge with a .380 bullet would only go into the chamber about 1/3 of the way. The chamber had to be reamed. t was a good shooter with the right load.

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Pat, mine was the same way. When I got my reamer to do my H&R 38-55 Target, I was going to do the Marlin as well. I talked to some of the folks that that shoot the Quigley Challenge and they all said not to do it. These guys had more knowledge than I ever had, have now and will ever have in the future. They said to run Starline brass because the walls were thinner. The Marlin 38-55 chamber is actually cut to the 375 dimensions yet the bore is 380-381. 

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8 hours ago, Coyote Kincaid said:

Pat, mine was the same way. When I got my reamer to do my H&R 38-55 Target, I was going to do the Marlin as well. I talked to some of the folks that that shoot the Quigley Challenge and they all said not to do it. These guys had more knowledge than I ever had, have now and will ever have in the future. They said to run Starline brass because the walls were thinner. The Marlin 38-55 chamber is actually cut to the 375 dimensions yet the bore is 380-381. 

Interesting. Thank you. I learned something today. I did have the chamber cut and maybe that was a good thing considering at the time I was at a loss on what to do. I had just spent a bunch on a rifle that I couldn't shoot and had already purchased a boatload of brass (I can't remember what brand) and I was new to 38-55 so I took the advice of the Marlin rep that I called and shipped the gun to them for reaming.

 

Once I found a load that worked it was a pretty accurate rifle but I sold it a couple of years ago. The only regret I have in selling it is I sold it for less than what I should have but at the time I wasn't shooting CAS. 

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