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Cartridge Considerations

 
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  #8  
Old 08-20-2002, 12:14 PM
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Re: Cartridge Considerations

Darryl what sort of velocity increase does the 338 Tomahawk have over the 338UM? I have a Rem 700 338UM that I was thinking about eventually fitting with a longer barrel and stepping up to the tomahawk but I read in some of your earlier posts that the Rem action might not be able to handle the pressure that the 338 tomahawks could produce.
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  #9  
Old 08-20-2002, 04:16 PM
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Re: Cartridge Considerations

Jack

The 338 RUM is a fine cartridge especially when you rebarrel to a longer length.

When you improve to the Tomahawk you gain 8 to 9 more grains of powder capacity which is worth going to the improved case if you plan on a longer barrel also.

I have a friend who just put together a 338 Tomahawk on a Remington Mag action and a 34" barrel and he uses the 250 Gr Sierra MK bullet. His results are right there with the 338/378 he and I both have.

I would be a bit hesitant to shoot the 300 gr with full loads of say 108 to 110 grs of powder on the Remington but, I'm sure some are. My question to them is, do they have a long barrel on that rifle? Pressure seems to build in the longer barrels.

I know for a fact the 250 gr does well in the 338 Tomahawk with longer barrels. If you already have a 338 RUM the next step is the Tomahawk when you rebarrel. You could go to the "300" Tomahawk and shoot the 240 Gr Sierra MK with a BC of .711 which ballistically outperforms the 250 gr 338 bullet (.587 BC) all the way. The fellows shooting the 250 gr 338 don't like to hear this but, it's true.

Darryl Cassel
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  #10  
Old 08-21-2002, 12:23 PM
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Re: Cartridge Considerations

Hello LTLR


The 338/416 Rigby IMP I have has a minimum tapor and a 35 degree shoulder. The standard Rigby case has a much smaller capacity until you improve it.

With the improvement it does hold more powder then the standard 378 case by 12 to 15 grains of powder, depending on the case.
If you improve the 378 case to that of the 416 improved, you have nearly the same capacity. You MUST imp the 378 Case to do it though.

I have the first one Bruce Baer put together and he calls it the 33 Baer on the Rigby belt less case.

Yes, with longer barrels, you can blow the compitition away concerning velocity, in most every case or cartridge.

With an Improved case (30 Cal) I designed many years ago and a 30" barrel I was able to send the 190 gr MK out the tube at 3500 FPS.
The case was called the 308 DC Super IMP.
It had an Ackley 40 degree shoulder and I used the 8mm Mag case as the parent case.
It was blown out to a minimum tapor, the shoulder was moved slightly ahead and it would shoot 106 grs of ball powder. My good friend owns that rifle now and there are several chambered in it around the country. Clymer has the reamer.
It ended up being .002" larger in the shoulder diameter then the 308 Bear and was a longer case because I used the 8mm (375H&H) case instead of the 340 Weatherby case that Bruce did.

I called the cartridge the poor mans 30/378 and Bruce Baer says the same as I do concerning the match up between the 30/378 and the Improved 8mm or 340 Weathetby. Either of the improved 30 cals will stay with the 30/378 with a tad bit less powder.
This is especially true with bullets up to the 220 gr MK.

The best I ever did with the 30/378 and the 190 gr bullet coming out of my 37" barrel was 3600 FPS. The 30" tube and the 30 DC Super IMP did 3500 FPS with the same bullet. Ray Romain has the basic same case with his name on it also. His is called the 30/375 Romain and will walk right along with mine.

I mentioned many times on this forum that you don't really need to go to big actions and 378 size cases with the 30 caliber diameter cartridges. The Improved 300 Weatherbys and 300 ULTRA (without Improving it) will do it.
We prooved this many years ago.

I still have a long barreled 30/378 laying around but, seldom ever shoot it any longer.

Good shooting no matter what cartridge you use. It's still fun & smell of burning powder still makes me horney even in my older age. Of course diesel smoke does that to every time I fire up the Dodge Cummins of mine.


Darryl Cassel [img]images/icons/grin.gif[/img] [img]images/icons/wink.gif[/img] [img]images/icons/rolleyes.gif[/img]

[ 08-21-2002: Message edited by: Darryl Cassel ]
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  #11  
Old 08-21-2002, 11:04 PM
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Re: Cartridge Considerations

Darryl,
Remember my velocities are out of a 28" barrel hunting rifle. I think the velocities you posted from a 30 caliber tomahawk and 240 grain bullets were out of much longer barrels. When I said I haven't found anything that beat the 338-378 I thought we were talking about buying a factory rifle. I just didn't explain good enough.

I have several rifles off the ultramag case and agree improving it is the way to go on a budget. I have two in 338 using the full length 300 case and improved version. They are exceptional rifles and these along with the lapua and 338-378 wby are all right in there within probably 100 fps using the same barrel lengths. Really your individual barrel could make the difference on which would be faster. I have a 26" standard 300 weatherby that I love to show off to 30-378 owners. My accuracy load with a 180 grain bullet is 3475 fps, with the 200 grain bullet it is 3275 fps. Some barrels are just crazy.
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  #12  
Old 08-21-2002, 11:12 PM
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Re: Cartridge Considerations

I have never worked with the 416 rigby case and had no idea it had more powder capacity than the 378 wby case. I think I talked to you once before about yours but didn't realize it held more powder. Now I have got to have one of those. I have two ruger number one's in 416 rigby down in the shop that I planned to build something off the 378 case with. Now I may try the Rigby. Is yours an improved version of the rigby or just necked to 338?
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  #13  
Old 08-22-2002, 08:23 AM
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Re: Cartridge Considerations

Darryl,
As always thanks for all the info. I have never been a fan of the 30-378 and have advised people against it on forums since it got popular around 1997 I think. I tried it and it was a barrel burner like no other I have fooled with. It was very finicky to work with at top velocity loads and like you say could come very close to it with other cases that were not as bad at torching barrels. But that is just my opinion. I know there are many people out there who adore the cartridge. That is the reason I just fool with the 378 case in 338 and 358. I did build an 8mm-378 and thought it did much better than the 30-378 but the limited bullets wouldn't let it reach it's potential.

I also like your 6.5 gibbs you were talking about over on another thread. I think he was rechambering a 25 and wanted to stick with that caliber but I prefer the 6.5 and with the new 120 grain lost river bullets (.687 BC) it is one of my favorite rifles. In my arsenal it is about the best I have in a flat shooting, light recoil rifle for deer size stuff. I would not hesitate using my 358 or 338 gibbs on anything in north america. I liked the 240 gibbs so much as a varminter I got three of them with tight neck chambers. I am shooting the 70 grain ballistic tips at 4100 fps. One is twisted just for the 107 matchking and it is a great long range varminter.
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  #14  
Old 08-22-2002, 09:23 AM
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Re: Cartridge Considerations

Hello LTLR

Yes, the Gibbs line seems to work great in about any caliber Rocky chamber them to.

The 6.5 Gibbs with an 8 twist shooting the 142 Sierra MK is one of my favorite calibers.
It will do the job further downrange then my 25 Gibbs will. The 30 Gibbs is a dandy also and VERY easy to work with. With 180 and especially 190 gr Sierra MKs, they are fantastic.
To keep from wasting barrel steel, I fireform with the standard loading of the parent case while out woodchuck hunting or breaking in the barrel, which usually takes me about 30-35 rounds to do.

Keep shooting and let us know how the rifles are doing.
Anyone who has the time to use the equipment they have gathered and have several years of experiance doing so, as it sounds you do, is an asset to the forum.

Later
DC

PS Burn that powder and smell it----It will do wonders for you. You wife or girlfriend may want you to go to the range "More Often" [img]images/icons/wink.gif[/img] [img]images/icons/grin.gif[/img] Just a little something from my "bag of tricks." It worked so good, even my wife shoots and hunts with me. [img]images/icons/grin.gif[/img]
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