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Cartridge Considerations

 
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  #1  
Old 03-08-2002, 07:56 PM
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Join Date: Mar 2002
Location: Fairbanks, AK
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Cartridge Considerations

Greetings and Salutations,

I am glad I found this site. Now I can ask these questions without being considered, "strange".

I have been thinking about a light-medium bore since I already have a heavy rifle and a medium. I want a rifle with punch.

I have looked at both the .338 Lazz and the .338 A-Square and find them to be virtually identical. The dimensions as follows:
Lazz and A-Square respectively.
Base: 0.581 vs 0.582
Shoulder: 0.563 vs 0.553
Case length (max): 2.82 vs 2.85
Base to Shoulder: 2.3050 vs 2.30
Base to base of neck: 2.466 vs 2.433
Shoulder length: 0.161 vs 0.133
Neck Length: 0.354 vs 0.417 (!) [img]images/icons/shocked.gif[/img]

Pressures (max) again Lazz vs A-Square, Lazz using 27" with a 1:12" twist and A-square using 26" with a 1:10" twist.

200gr NoslerBT 111gr Rl-25 3475fps 54,400 CUP
250gr Swift AF 103gr Rl-25 3154fps 55,900 CUP

A-Square:
200gr NoslerBT 105gr 7828 3360fps 60,900 PSI
250gr SierraBT 120gr A8700 3120 @ 61,600 PSI

Now A-square in their book lists max pressures in both CUP and PSI. They are 54,000 CUP and 65,000 PSI respectively. While I know full well there is no linearity between the different methods, at points with different methods it gives us a good "idea" of where things are pressure wise. Using A-Squares maxes I see Lazz running around 67,286 PSI for their max load with the 250 grain bullet. Max load I saw was at 56,400 CUP which is in the area of 67900 PSI.

This leads me to believe there really isn't any difference between the two. Also, since I can find Weatherby brass almost anywhere and Lazz available from only one source (expensive too) I should go with the A-Square.

I have wondered though, I thought more case capacity would give less pressures. When I look at the commercial reloading pages I see the .338/378 Weath. is not living up to expectations. It really isn't any better than the Lapua and vica versa. Also, a .340 Weath with a longer barrel would appear to be able to catch both. Consequently I am still on hold about the idea of lengthening the body of the A-Sq. a little. I had thought of going 0.05" extra body to 2.350" which would shorten the neck length to 0.367". Still plenty to hold the bullet. I would also take the shoulder out to 0.563 like the Lazz. If I did that it would be custom and cost ~$200 for reamers. If I left everything the same I could have the reamer rented for $50.00.

I was thinking a barrel around 29-30", chromoly (I don't like looks of stainless) with muzzle around 0.850" and heavily fluted. I would have the barrel in front of the receiver cylindrical for about 4 inches for extra support by bedding it. The rest floated. Should I have an extra lug installed so I can put another screw into the barrel ala CZ?

Any comments appreciated, thanks. [img]images/icons/smile.gif[/img]

[ 03-08-2002: Message edited by: gman ]
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  #2  
Old 03-08-2002, 08:30 PM
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Join Date: May 2001
Location: Lock Haven P.A.
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Re: Cartridge Considerations

Why not look at the 338 RUM.....It will match the Lazz and A-Square in velocity.Use less powder, brass and die's are cheaper and If you get in a pinch factory load's are pretty much every where.....Just a thought..... [img]images/icons/grin.gif[/img]
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Old 08-19-2002, 08:38 AM
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Location: bluefield,va,us
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Re: Cartridge Considerations

what size is the case head on the .338 RUM, thanks,keith
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Old 08-19-2002, 12:54 PM
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Re: Cartridge Considerations

Kid

It is the same as any standard magnum such as a 300 Win Mag or 300 Weatherby mag.

Can be used on any factory standard mag action and most use the Remington or Sako actions for it.

Later
DC
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Old 08-19-2002, 02:09 PM
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Re: Cartridge Considerations

i have 2 win mod 70's in .338 win mag.so it would be no big deal to have one done up as a .338 RUM .would i have to use it as a single shot.not a problem if i did have to any way.if i went that route and went with a long barrel it would put me close to the .338 lapua,would it not,thanks,keith
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Old 08-20-2002, 07:44 AM
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Re: Cartridge Considerations

You are mistaken on the 338-378. What part of expectations is it not living up to. I started working with this wildcat around 1980 and it has performed as expected and although I have found some that would come close it is still my go to rifle because I have yet to find anything that will beat it. I currently own 6-8 of them and 2-3 of them necked to 358 and they will hold a solid 100+ fps advantage over the lapua and 200 fps over the ultramag which I have a few of those also. My pet rifles average around 3600 fps with the 200 and 3350 with the 250. All of mine have 28-30 inch barrels on hunting weight rifles. It is a spectacular cartridge and if you are looking for tops in velocity you will have a hard time beating it. There are other considerations other than velocity though and that is why I have the others and continue to work with them also.
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Old 08-20-2002, 10:39 AM
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Re: Cartridge Considerations

LTLR and to others here.

You are correct in the "Standard" 338/378.

The way to beat it is to Improve the case by blowing it out to a minimum tapor and putting a 35 degree shoulder on it. Now you have the powder capacity that my 338/416 IMP has except mine don't have the belt. This one will beat the velocities you mentioned quite handedly.
I am running the "300 Gr"in my 338/416 at 3310 FPS out of my ultra longrange deer and elk gun. Is is not however a carry gun.

The 338 Tomahawk (338 RUM Improved) is right there with the velocities your posting with your 338/378 and 250 gr bullets and that's on a Regular mag action and with 250 gr bullets also. I have a friend shooting the 338 Tomahawk and is well pleased.
He has stated many times that it is so close to his 338/378 that it's not worth mentioning the difference and he is doing it with a bit less powder.

With everything considered (cost wise), one getting into this game with limited funds would be well off looking at the 338 RUM on a standard mag action rather then going to a large custom or Weatherby action to handle the 378 case head.
The cost of any of the Norma, or specialty brass for the 378 is very high.

The next written material may be of interest to some on the forum who are trying to decide between a 30 cal and the 338 cal unless you use 300 gr bullets in the 338/378 or the 338/416 IMP.

I can run the 30 cal 240 Gr Sierra MK in my Tomahawk at 3225 FPS and that bullet has a BC of .711. Compare that to "any" 338, 250 Gr at 3350 FPS and you will find that the BC of that one is only in the .587 range and that's a Sierra MK.
With long barrels on each caliber, the 240 gr will take over at 400 yards and beat the 250 gr 338 from there on out in every aspect.

Point is, the 338/378 can be beaten with a 30 cal shooting the 240 gr bullet from a factory mag action.

I still have one 30/378 and one 338/378 rifle laying around here too. Just for test purposes.
The 338/416 Rigby Imp with 300 gr bullets is my "go to" rifle for longrange and ultra longrange hunting though.

I just ran the ballistics on the 338/378 pushing the 250 Gr at 3350FPS and the Tomahawk pushing the 240 Gr at 3225 FPS. This will be interesting to many of you, I'm sure.
At 1000 yards the 338/378 with 250 gr bullets Has a remaining velocity 1916 FPS and a Foot pounds of energy of 2039 FP.
The 300 Tomahawk with 240 gr bullets at 1000 yards has a remaining velocity of 2039 FPS and a energy level of 2216 Foot pounds. Clearly the winner is the Tomahawk between the two bullets and calibers used.

My opinion would be to anyone interested in LR hunting and the 338 caliber, would be to make sure you go to the 300 gr bullet in the 338 or if you can't build a long enough barreled rifle to handle the 300 gr, you might want to consider the 300 Ultra or 300 Tomahawk with the 240 gr bullets.

Just another opinion from someone who owns or have owned the calibers mentioned.

Darryl Cassel
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