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"Sighting in" my Cowboy 38-55

Several months ago I posted about finding a used Cowboy 38-55 in the LGS. My first outing was with Winchester brass and .378 cast bullets purchased from a local manufacturer. Results were dismal. Starline finally made some of the longer brass, and Oregon Trail sent me six free .380 240 grain bullets - I don't want to buy a whole box of bullets until I'm sure it I have the right size - and most postings here lead me to believe the bore on these rifles is .380.

I know it is not much to go on but here is my target with the six rounds - Starline 2.125 brass, Oregon Trail .380 240 gr. bullets , 22.0 grains of 5744 and CCI primers. Shot kneeling with leather sand bags at 50 yards. The last two shots are at 10 o'clock - can't explain those (sweat in my eyes? - had just shot a CAS match). I was pleased with the 6-12, but the 3-9 spread could be a lot better (I've seen some of the targets posted here shot from 100 yards with some really tight groups).

Any thoughts on the load or what I might look at on the rifle would be greatly appreciated.

OVW
 

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Re: "Sighting in" my Cowboy 38-55

I haven't done any cast with mine yet, it sure liked the Winchester factory 38-55 and my reloads of 220 gr hornady and IMR 3031. Mine is wearing a Weaver K 2.5, I know "NOT ON A COWBOY!", but the eyes just don't like irons if i'm checking for groups. I have some Master cast and Oregon Trails lead as well as a few from a local caster that I need to try. I haven't used that powder, but have used 3031, RL-7 and Accurate Arms 1680. I noticed the 1680 warms the barrel more than the other 2. DP
 

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Re: "Sighting in" my Cowboy 38-55

Hey there OVW -- Go ahead and order a box of the Laser-Cast 240's sized .380". I don't think you can go wrong with those. If you don't like them, I'll buy the rest off ya!! I've had real good results with dumping ten grains of Unique in the case under them. For the initial trials, you might consider a rest of some nature for the rifle. I'll bet two nickels your group tightens up. Best regards. Wind
 

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Re: "Sighting in" my Cowboy 38-55

If you have any on hand try 21.0 grains of IMR 4198 under the same lazer cast bullet (380 dia) in either Starline or W-W brass. Shenandoah
 

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Re: "Sighting in" my Cowboy 38-55

.381 diameter is what you you need.Oregon trail .380's didn't do it for mine.I got groups like yours.I shot about 200 of them.As soon as I got the .381's the bad groups became a thing of the past.I've shot 300 of them.The .380's did better with Trail boss then anything else,then Unique.The 260 gr. .381 diameter from Hunters Supply shot better with every load then the same load with .380's.10 grs of unique for 1298 FPS.Put a gas check on them with 19 grs of 2400.Didn't chronograph them,I'm guessing 1550 FPS.About 3-4 inches at 200.I'm using the long Starline brass and CCI 200 primers.
 

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Re: "Sighting in" my Cowboy 38-55

The 38 in 38-55 means 38 cal.

They seem to be most accurate in the 1100 -1300 fps range.

Mine likes 9gns of Unique
 

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Discussion Starter #7
Re: "Sighting in" my Cowboy 38-55

Thanks for all the replies. I am going to get some .381 bullets and try those. I also have some 3031 and Unique under the bench and will work up some loads (had never considered Unique for rifle). I'll post another target picture if it is a marked improvement over this one ;D.

Now - what to do with all those .378 bullets? Guess I can try them in my Marlin .375 Win or my "Mirochester" 1885 .38-55 single shot.
 

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Re: "Sighting in" my Cowboy 38-55

Old Vark WSO said:
Now - what to do with all those .378 bullets? Guess I can try them in my Marlin .375 Win or my "Mirochester" 1885 .38-55 single shot.
Slug your barrels and see which one can use them best. The 375 would be my first choice.
 

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Re: "Sighting in" my Cowboy 38-55

I can't count the different cals I've tried 5744 in, and to say the least one out of 6 shot it well and that was a single shot H&R 30-30.

Your 38-55 may shoot them .378s pretty good with a different powder. 9-11 gns of Unique which is faster burning and peaks a lot quicker may make them bullets obturate quick and fill and seal the grooves better.

Lacking Unique try some mag pistol powder, the key being getting it burned faster and bringing up the pressure quick.

One other thing try that same load again with mag primers, that may be enough.

My 38-55 shoots anything from .377s on up with equal accuracy with the Unique.
 

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Re: "Sighting in" my Cowboy 38-55

My 38-55 likes the .381" bullets best. They'll do five touching at 50 yards over 10 grains of Unique. Size them to .380" and the group size expands to 2-3" at 50. Go .379 and a 4-6" group is the best I can do. Size matters.

Unique will get it there. 10 grains gets us right to 1300 fps - two rifles tested. It'll reach a 1,000 yard dinger.

http://www.youtube.com/watch?v=HO6ihrcukcc
 
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