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338 rcm

 
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  #8  
Old 08-27-2011, 07:57 AM
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Re: 338 rcm

Quote:
Originally Posted by Autorotate View Post
Interesting build...that sounds like an excellent rifle for future Alaska hunt

That is very consistent velocities...factory ammo nonetheless makes it that much more special.

Varminator 911-I would guess on 18-21 fps per inch with the slightly quicker powders/200-225 gr weight bullets, and 22-27 fps per inch with slightly slower powders/250-300 gr weight bullets.

JE Custom would know best on what improvements to case capacity might be seen with a different throat. My opinion would be the biggest benefit might not necessarily be a velocity gain from an increase in capacity, but better load density with the next slower/faster powder up or down the chart.

Example-338 Lapua Ackley Improved. It sees a 11 grain increase from virgin unfired brass, to fully formed brass with 2-3 firings. The virgin cases "cube out" before you "pressure out" with Retumbo....in otherwords you can't put enough Retumbo in the case with the 300 grainers to get yourself into pressure trouble....but with H1000 you can "pressure out" before you "cube out"...and definitely get yourself in pressure trouble. After firing, the formed cases now run into pressure/load density constraint at nearly the same time with Retumbo around 103.5 to 104 grains with 300 grain bullets.

The biggest benefit from lengthening the throat on this 338 RCM, may be the same as happens above...you might be able to move into a new class of powders, where as before load density kept you from doing so.

If this is insulting to your knowledge level, I definitely didn't mean it that way at all, just sharing my perspective/experience. I'm here to learn from all the smart fellas like JE Custom on here.
Very good comments ,and very true In my opinion. One of the first things I look at when trying
to decide on a cartrige after deciding use and distance,is case density.

I want the max velocity,(For energy and trajectory) with 100% case density using the optimum
bullet weight for the cartrige selected.

With the 338 RCM the 180 grain bullet produces=3647 ft/lbs of energy @ 2980 ft/sec velocity.
The 200 grain bullet produces = 3864 ft/lbs of energy @2950 ft/sec velocity.
And the 225 grain bullet produces=3778 ft/lbs of energy@2750 ft/sec vel.

These are 100% powder density,Max loads for each bullet and in a compact rifle a bigger/heavy
bullet would only increase BCs so the 200 grain was chosen for a max distance of 675 yards
for 1500 ft/lbs of energy at the POI for ELK.

If I were going bear Hunting I would probably choose the 225 grain bullet and limit distance to
under 400 yards.

There are so many great 338s that will shoot the 250 and 300 grain bullets for 1000+yards
I felt there was no need to increase case capacity or improve the case based on its use and
as is potential.

It is a special purpose rifle, just like most of the long range rifles that are intended to shoot
well beyond 1000 yards.

As said earlier it is a compact cartrige that is equal to a 338 Win Mag, and we all know what
it can do.

I would not hesitate to carry it in Alaska or any other place knowing what its capabilities are.

I appreciate all comments from all on this site and feel better about my choice after hearing
them,And best of all Its Fun to shoot.

J E CUSTOM
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  #9  
Old 08-27-2011, 05:20 PM
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Re: 338 rcm

The 338 RCM is very interesting. Seeing I have two I will comment on them and hopefully add to this thread.

I first made a lightweight 338 RCM in an old M77 Tang safety Ruger. Pacific Tool and Gauge made me the exact spec reamer that Hornady uses. I know because I had a long chat with Lonnie at Hornady.
The barrel is a 22" #2 Lilja SS 1 in 10 twist.

I originally used some 215 sierras I had hanging around. After break in tried some 180 ballistic tips. Ended up with finalized hunting load using the 225 accubond. Mag box was altered to approx 3.050". OAL with 225 accubond is 2.980"

225 accubonds: worked up to 61 gr of RL-17 / 2750 fps with Fed 210 match primer.
180 nosler bt: worked up to 64 gr of RL-17/ 3045 fps. 62 gr had same POI at 225s.
215 sierras: worked up to 55 gr of Varget, most accurate 54 gr/ 2730 fps.
215 sierras: worked up to 64 gr of H4350/ 2865 fps
as a lark I tried 300 gr sierras seated kissing the rifling, OAL was too long for magazine.
Much to my surprise during testing two touched at 200 yds with 57grs of RL-17/ 2450 fps



The second rifle was just something I had to try. The long throated 338 RCM was something I was easily able to make as I already had the 338 RCM reamer. I had an ill fated 30" 1 in 7 twist 7mm barrel that Dan Pederson bored out to 338 then long throated (approx. .085 longer) to accomodate the 300 gr Sierra. Finished barrel length is 29", twist is 1 in 9.

I wanted to use the Berger 300 hybrid but it was under development to become the second generation.

300 gr sierra kissing rifling 57.5 gr RL-17/2540 fps accurate out to 500M fed 210 match primer
Finally the 300 gr hybrids came a few weeks ago. Finalized load 57 grs RL-17/2579 fps 210 match also
the most amazing part was the consistent velocities as well as the accuracy out to 500 M (longest distance at rifle range )
56 gr had all three test rounds reading 2524
57 gr had all three test rounds reading 2579 NO ES!!

The 29" barrel is in a Russo stock and weighs approx 14 lbs. I intend use it on a coues wt hunt this Nov.

Last edited by AZShooter; 08-27-2011 at 06:16 PM. Reason: typo
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  #10  
Old 08-27-2011, 07:47 PM
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Re: 338 rcm

Thanks AZShooter !!
I will try some of your loads. You said I would like it and you were not wrong.

It is an interesting cartrige. and it has surprised me in every way.

This is one time that someone listened to the wildcatter's. The 325/338 is the same cartrige
as far as I can tell.

Everyone though that Winchester would do this but they decided on the 325 WSM instead.

On the next trip to Colorado it will be my pack rifle .

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  #11  
Old 08-28-2011, 10:43 PM
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Join Date: Jan 2008
Location: new jersey
Posts: 162
Re: 338 rcm

hello.I need a good loading for a rifle in process of being built.Its a rem 700 mt.rifle getting a face lift to .338-06. 25in.shilen #3 barrel.kevlarstock open&beded. I'd like to use 210 Partitions&225 Accubonds.Any comments.this will be a bear,elk and moose medicine! dzs
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  #12  
Old 08-29-2011, 06:36 AM
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Re: 338 rcm

Quote:
Originally Posted by Dskiper View Post
hello.I need a good loading for a rifle in process of being built.Its a rem 700 mt.rifle getting a face lift to .338-06. 25in.shilen #3 barrel.kevlarstock open&beded. I'd like to use 210 Partitions&225 Accubonds.Any comments.this will be a bear,elk and moose medicine! dzs
I would try the 200 or 225 grain Accubond for the velocities of the 338/06. the Partitions
are one of my favorite bullets but a little tough at the 338/06 velocities. (May not open
consistently).

As far as powders, 50 to 54 grains of H 4895 for the 200 grain bullets and 51 to 55 grains
of IMR-4007-ssc for the 225s should get you started. (Start with the lower charges and
work up).

Hope this helps.

J E CUSTOM
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  #13  
Old 12-25-2011, 12:46 AM
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Re: 338 rcm

Bump to top for question on thread.

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