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Twist Rate for 300gr SMK's in 338/300 RUM?

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Old 12-27-2005, 05:03 PM
Bronze Member
Join Date: Sep 2005
Location: Idaho
Posts: 51
Twist Rate for 300gr SMK\'s in 338/300 RUM?

Have any of you built a rifle in this chambering? I plan to shoot mostly 300 Grain SMK's but may try some higher BC VLD bullets down the road.

Recommended twist rate that will stabilize the longer 'custom' 300 grain VLD bullets out there without winding the 300 SMK's up too fast?

Recommended chamber neck diameter using Fed. Gold cases and Rem. cases?

Also which bullets would you recommend my trying out besides the SMK?

Currently considering:
338/300 RUM throated for 300 SMK
Tight neck (not sure what to get here....)
Pac Nor 30" Supermatch barrel
Holland Brake
1:10 Twist 3 Groove

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Old 12-27-2005, 06:11 PM
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Join Date: Feb 2004
Location: Pennsyltucky
Posts: 2,625
Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

butch keen just built one of these,can shoot the 250 gr lapua at 3400.not sure of barrel length,at least 30".killed a few with it this year,600 was the farthest.excellent wound channels.i'm leaning towards building a lapua. better brass, not a wildcat.
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Old 12-27-2005, 06:40 PM
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Join Date: Feb 2005
Posts: 628
Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

thats the same as Shawn's 338 edge do a search for it. it went about 80 post deep
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Old 12-27-2005, 07:40 PM
Join Date: Jun 2007
Location: North Idaho
Posts: 1,849
Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

I mostly use 30" Hart barrels 1-10 twist with the 300 gr SMK, H1000, Retumbo, or RL25. 2900 fps or so. I have yet to build on of these that won't go under 1" @ 300 yards. I don't tight neck them, I don't believe that it is a great benefit here for the extra work. I use minimum spec demensions for the 338 Ultra in the neck area. Some guys neck down 375 Ultra and then turn the necks. I have run oal's from 3.685" to 4.000" and seen less than 50 fps difference in velocity when seated to the lands. I would give the wildcat bullets a try I used some of the 300 gr.WC bullets with great results. I keep bitching that Nosler doesn't make a 280-300 gr. Accubond, that would be hot.
Shawn Carlock

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Old 12-27-2005, 08:10 PM
Bronze Member
Join Date: Sep 2005
Location: Idaho
Posts: 51
Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

Thanks for the tips guys. I have a 338 LM Armalite and like it quite a bit, but based on what I have read, I am 99.95% convinced that the 338 LM is not a safe round in the Remington 700 or Savage 110 actions which is what I would be building the rifle on. I am plenty happy with the last batch of Remington 300 RUM brass, getting sub 1/2 MOA groups with my 300 RUM and 180 SMKs, but I will definitely try the Fed Gold 300 RUM cases.
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Old 12-28-2005, 10:16 AM
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Join Date: Jun 2004
Location: Fort Shaw, Montana
Posts: 6,833
Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

A properly fitted Rem 700 will easily handle the Lapua case. That said, the 338 Edge is a much easier fit in the Rem 700 and will get you the exact same performance as well.

As far as rifle build cost, the 338 Edge will cost less because there is no need for bolt mods like there is with the Lapua case head size. Thats one of the best features with Shawns Edge, Lapua performance in a simple to build package!! Good design, more practical then some of those crazy wildcats that loon north of Shawn is building in Montana [img]/ubbthreads/images/graemlins/grin.gif[/img]!!

Good Shooting!!

Kirby Allen(50)
Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

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Old 12-28-2005, 10:02 PM
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Join Date: Sep 2005
Location: Idaho
Posts: 51
Re: Twist Rate for 300gr SMK\'s in 338/300 RUM?

Savage did some extensive pressure testing work on the WSM rounds and found that the WSM in a barrel with a 1.05 shank had a 98% safety margin window, which is enough for a reasonably safe build, but it still isn't 100%. They now only chamber the WSM's and RUMs in their larger thread size to exceed the 100% safety window.

The Remington thread shank at the root is even thinner than the Savage at 1.010".

The Lapua case is 6.5% larger in diameter than the WSM cases reducing the already too thin chamber wall even more. The LM case head is also 9.5% larger than the WSM case head, increasing the bolt thrust on top of the too thin chamber walls.

I don't know how those numbers relate to the 98% window but they definitely reduce the safety margin even more.

If you are loading the LM to the same pressure levels of the WSM, it sure looks like an unsafe build to me.
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