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Help me design a .338-375CT projectile

 
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Old 07-25-2010, 03:43 AM
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Join Date: Sep 2008
Posts: 327
Help me design a .338-375CT projectile

With little choice in ultra high BC hunting bullets suitable for the big .338's and .375's I've decided to look into swaging my own for personal use and if they prove to work well, I may decide to Take it further and sell some aswell, there seems to be a large gap in the market where the bullets have not kept up performance with the advances in new cartriges.

To start with I'm looking at doing a .375cal rebated boattail design around 380-400grns to work in a 10 twist barrel or tighter. Overall length would be about 6 calibers, and if successful I'd move onto a .338 version of a similar design. I've been playing with some numbers on the JBM websites bullet drag calculator and it would seem not too difficult to get a BC better than 1.0 Whilst not deviating to far from convensional designs.

What I am unsure of is the finer details like jacket thicknesses in order to be able survive 3400fps muzzle velocities without 'nose slump' or exploding bullet issues, yet still expand and provide good terminal performance on game. Any help in these finer design elements would be greatly appreciated and perhaps together we could produce some great bullets that we all can enjoy, maybe they could even be sold thru the LRH site once they're up and running since it would be a product created jointly by LRH members
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Old 07-26-2010, 03:53 AM
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Posts: 327
Re: Help me design a .338-375CT projectile

So far i have come up these design values;

Bullet caliber = .375
Bullet weight = 400grns
Sectional density = .406

OAL = 6 calibers (in .375cal thats about 57mm or just over 2 1/4in)
Nose length = 3.5 calibers
BT length = 0.9 calibers
Base Dia = 0.75 calibers
Secant Radius = 18 calibers

Calculated BC brackets are - 1.108 @ 2791fps, 1.011 @ 1786fps, 0.829 @ 1228fps and ideal twist rate is 9.9in.

Im undecided about the Meplat whether do go for a AL tip or a simple HP like a SMK... you get a higher BC with the AL tip but adds cost and complexity by using them.

Can anybody see any problems by using such a design outlined above? Once i have settled on a design, its a simple process to order some custom dies and get started
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Old 07-26-2010, 08:43 AM
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Join Date: Jan 2004
Location: Blackfoot, Idaho
Posts: 8,205
Re: Help me design a .338-375CT projectile

Quote:
Originally Posted by groper View Post
Once i have settled on a design, its a simple process to order some custom dies and get started
I'd stick with the typical open point as a start as things aren't going to be as "simple" as you may think. There are certain to be challenges/hurdles along the way. Remember that "there ain't no free lunch".

Proper jacket design will be tricky. There should be little tendency for dusting if the bore they are shot in is constructed properly. A bullet with that diameter should be fairly forgiving.

The RBBT introduces some stress points if not done correctly. There's not much that can be said against a Berger type boat tail.

Look at Nosler Solid Base jacket design. They hold up very well in a very tough barrel configuration. A better boat tail will help them out. Though there must be a reason their boat tail is so dinky.

Also be a bit conservative with the ogive/point length. I've shot some that break off in the media. Note these were Aluminum tips but still broke off behind the tip shank. BC ain't everything.

I'm looking forward to your success with this project. Selfishly so. I have a super hooty 375 in the final building stages and a BC much greater than 0.8xx is what that cartridge is waiting for.

My bucket list has a dead rock, one shot, 3k+ towards the bottom.
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