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30-378 chamber specs needed.

 
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  #1  
Old 12-22-2006, 11:41 AM
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30-378 chamber specs needed.

Im about to start cutting a 30-378 chamber in my barrel. Ive been hesitating for a while, but time has come to get this project started. It will have 32-34 inches of usable bore and 1/8 turns per inch, 1,5" dia.

Does anyone here have information and or knowledge on 30-378 that could be helpful to me before cutting it? Are there variations of 30-378 that are being used, if so...pros and cons?

I would really appreciate any help on this matter.

Thanks.
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  #2  
Old 12-23-2006, 09:37 AM
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Posts: 734
Re: 30-378 chamber specs needed.

What will the rifle be used for? if it is hunting where you will be using factory ammunition go with a SAAMI spec long freebore reamer. If you are looking to handload for it and use match Projectiles i would look at getting a reamer made up with a 35-40 degree shoulder like a conventional case that will not allow a facttry round to chamber and a tight match throat and chamber. Call Dave Kiff at pacific Precision also talk to Kirby if he has a 300 Allen cartrige based on the 338 Lapua case improved it would be realy worth a look the other option would be a 300 Ultra MAg improved or standard. I take it the barrel is a 1 in 8 twist barrel? if so you would be well served to use 240gr MAtchKings or Richards Wildcat projectiles in Canada. I think he will be making projectiles up to 300gr if this is what you want to use i would get the projectiles and have the reamer made to suit.

Will the rifle be used as a single shot or a repeter?

What action will you be using?

Cheers Bill
Australia
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  #3  
Old 12-23-2006, 10:25 AM
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Re: 30-378 chamber specs needed.

The rifle will be used for target shooting, hopefully at longer ranges than my 300 ultramag. Im looking to get to 2000 meters or more this time. Feeling quite optimystic here. The 30-378 just seems to be the only 30 cal cartridge that I know of that can I can drive hard enough to achieve my goal. Didnt look any further tough, but will do now.

Yes, 1/8 twist.

The action is my own design with 5 set interrupted threads (15 total). Single shot. Whole rifle weighs in at 22 lbs, 43 inches long.

Why 30-45 degree shoulder instead of the double radius one on the original?
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  #4  
Old 12-23-2006, 10:57 AM
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Re: 30-378 chamber specs needed.

Hi Norz the reason i would go with the 35-40 degree shoulder is to make sure a factory cartrige can not be fed into the chamber. i would go 40 degree in the shoulder and improve the case to 6 thounands on an inch per inch of case sidewall. The minimum is 4 thou per inch. What is the tennon size? You may be able to chamber it for a case based on the 408 case. Kirby is working on a versian in 30 cal at the moment give him an email and i am sure he would be able to help you out. I would go that way as the 30-378 brass is made by Norma and is fairly soft if you ryn them to hard you will end up killing the cases in 1 or 2 shots. What projectiles were you looking at using in the barrel?

The minimum tennin for the 408 Chey Tac case is 1.125" but if you can make it larget that is better.
The case head is .635" the same as the Rim Diameter. Could you fit it into your action?

If so this case would be the best for you to look at.

Cheers Bill
Australia
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  #5  
Old 12-23-2006, 11:08 AM
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Re: 30-378 chamber specs needed.

Hi i forgot to add if the barrel tennin is large enough you could machine the rims doen 45 thou to Lapua/378WBY diameter and have rebated rims as long as the action will handle the pressure. I do not believe the 30-378 will get you to 2000m the Chey Tac case would definately be a better option. another option if the Chey TAc case will not work is the 30/416Rigby improved it will give you a larger capacity that the standard 30-378 as the 378 case was based of the Rigby case when it was designed. Brass is available from a few more manufacturers aswell as not having the belt.

Cheers Bill
Australia
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  #6  
Old 12-23-2006, 12:39 PM
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Join Date: Nov 2006
Posts: 6
Re: 30-378 chamber specs needed.

The action can accommodate a larger body than the 30-378. It can also handle 6 times that pressure (cad predicted though). The barrel is a full blank at the moment, started making the first run into it this morning. There is no bolt face cut yet as it is being hardened now, so there is still room for drastic changes.

Im in northern Europe, so I would prefer using Lapua or Norma brass to avoid the export fees and regulations in the states. Is 416 Rigby brass available from either of them?

The Chey/Tac and 416 are starting to sound like better options [img]/ubbthreads/images/graemlins/confused.gif[/img]

What is ruining the standard 30-378 cases so quickly compared to my 300 ultramag?
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  #7  
Old 12-23-2006, 10:11 PM
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Location: Riggins Idaho
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Re: 30-378 chamber specs needed.

people over working them. to much pressure would be my guess.
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I dont know who ever came up with the imaganary word of "Over Gunned"
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