338 rcm

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by J E Custom, Aug 23, 2011.

  1. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    As promised this is an update on the latest build.

    The rifle is based on a Model 7 Remington with a laminated stock.

    Barrel is a 22" #4 Lilja 1 in 10 twist Stainless 6 grove.

    Scope is a 2.5x8x40 Leupold.

    Ammo used is Hornady Superformance 200 and 225 grain SSTs.

    During break in, velocity for 5 shots was 2941,2945,2940,2941 and 2943 (Very consistant
    for factory ammo)with the 200 grain ammo.

    Recoil was brisk in the 8.7 pound rifle (Scope, mounts and rings included).The most noticeable
    thing was the muzzle rise. (May have to install a muzzle break to minimize this).

    Temperature was in the high 90s, and the loads appeared to be Max so after shooting 3 rounds
    fast and heating up the barrel I chambered another round and let it set for a minute then fired
    it to see if it would show signs of pressure. (It did) so I determined that the factory ammo is
    a Maximum load in hot weather.

    The rifle shot 3/4 to 1.25 MOA at 100 yards with the factory ammo and I feel like good reloads
    will improve that.

    With almost 4000 ft/lbs of energy at the muzzle, this is a power house for a small carry rifle.

    Sorry: no pictures. maybe someday I will learn how to post pictures.

  2. WyoElk2Hunt

    WyoElk2Hunt Well-Known Member

    Aug 15, 2009
    Sounds good I am waiting on my 338 Sin in Tikka T3 Lite. Should be about same going to use cutting edge 225 bullets.
  3. rscott5028

    rscott5028 Well-Known Member

    Apr 18, 2010

    Nice review.

    How many rounds will the rifle hold?

    Does it feed well?

    Did you do anything special with the throat/freebore/magazine to accomodate the longer VLD's up to the new Berger Hybrid?

    Or, would you recommend doing so for another build in this cartridge in a heavier LRH rifle?

    Do you think you need an Edge, RUM, LM to push the 300 grainers effectively?

  4. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    Thanks Richard.

    It will hold 3 rounds in the mag ,but it is full and functions flawlessly with two + 1. There
    were no problems with feeding.

    I went with the standard free bore to get the max velocity out of the compact case.
    and my intentions are/were to use 200 or 225 grain Accubonds and limit the distance to
    4 or 500 yards.

    I have several big 338s for the bigger bullets and I am in the process of building another
    based on a 375 RUM case pushed to the max powder volume.

    This project was to build a very compact rifle with plenty of power.

    I had even thought about blowing out the case to the same body length as the 7 WSM and
    adding another 8 to 10 grains of capacity but went back to my original thought and left
    it alone to make it easier to load and buy ammo for.

    The closest thing to the 338 RCM is the 325 WSM and the ammo for it runs $50.00 to $65.00
    a box. The 338 RCM is from $38.00 to $42.00 so this was a consideration plus there are
    Lot's of 338 Bullets to chose from.

    PS; I just put a muzzle break on it for the faint of hart and need to see what difference it
    made in recoil and accuracy.

  5. Varminator 911

    Varminator 911 Well-Known Member

    Dec 7, 2007
    In another thread AZShooter said he's getting 2579 fps out of a 338 RCM shooting the 300 Berger with 57 gn RL-17. That's only about 200 yds short of the 338 RUM in terms of down range energy. I wonder what barrel length would be needed to achieve that velocity in a long throated chambering?
  6. Autorotate

    Autorotate Well-Known Member

    Apr 2, 2007
    Interesting build...that sounds like an excellent rifle for future Alaska hunt :D

    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. gun)
  7. Autorotate

    Autorotate Well-Known Member

    Apr 2, 2007
    Richard-I know you asked this question to JE specifically, but I can't help but to put my two cents in here. Then I'll butt the heck out of this thread for good!

    I would evaluate the maximum distance you will engage your intended target. I'm assuming furry critters since we're on LRH:D Evaluate the ability of your LRH to achieve a reliable, accurate, precise, and repeatable range at that distance on a non-reflective target like a critter. Then I would plug in the atmospherics for your intended hunting AO into JBM, and evaluate wind drift in the worse case scenario for that distance. You'll be able to solve all the other riddles associated with the LR shot with technology/practice (Coriollis, spin drift, elevation solution) but the wind drift will still be undeterministic factor as Mr. Litz refers to it....or the unknown for a common'er like me.

    I think when you look at the wind drift differences between a 300 gr Berger for a 2500/2700/2900 fps....you might not realize a real benefit until you start shooting past 1K. Hope that helps!

    Good luck.
  8. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    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 [email protected] 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.

  9. AZShooter

    AZShooter Well-Known Member

    Dec 12, 2005
    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: Aug 27, 2011
  10. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    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 .

  11. Dskiper

    Dskiper Well-Known Member

    Jan 12, 2008
    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
  12. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    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

    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.

    Mike 338 likes this.
  13. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    Bump to top for question on thread.

  14. RevJim

    RevJim Well-Known Member

    Dec 25, 2014
    Not trying to hijack the thread, but really need opinions/info on the 338 RCM, so please bear with me.
    I'm having my Mod 77 All Weather in 338 Federal (22"bbl, already has a brake) converted/rechambered to the 338 RCM currently. I have used the Nosler 180AB on a huge Aoudad around 250yds going 3500fps ( RUM) and my SIL used the same bullet (338 Federal) on a medium sized muley buck around 30yds, both kills were pass throughs and worked like Partitions hit them, perfect! From the RCM, do you think it (or would the 180/185 Monos work better?) has enough pizzas to hammer elk on a hard angling shot or break the shoulders and how far out? All opinions welcomed.