270-338 RUM

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by 7ultra, Nov 3, 2004.

  1. 7ultra

    7ultra Well-Known Member

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    Anybody have any experience with this one? Case would be a 338 RUM necked down to the 270. If I would get one chambered, I would probably go with a 28" barrel. With this combo I would hope to drive a 150 grain bullet at 3400-3500 fps. Any comments, experiences, suggestions?
     
  2. budlight

    budlight Well-Known Member

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    Did you read this post about "Allen's"? http://www.longrangehunting.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=002521

    IMO - Cases that can hold 120 grains of powder have a very limited uses. I have a wildcat 7mm STW so it's slightly bigger than the production model. I can make 3300 fps with 160 grain bullets with only 80 or so grains of powder and have nice case life.

    I would think a 270 STW would be a fine weapon and not give up that may fps to the super cannons. That's why i use such long barrels
    [​IMG] [​IMG]
     
  3. 7ultra

    7ultra Well-Known Member

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    Thanks for the heads up, very interesting.
     
  4. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    7Ultra,

    I am designing and releasing a family of rounds based on the 338 RUM case. They will include the 257, 6.5mm and 270.

    My rounds named the Allen Magnums will be modified quite heavily compared to the standard 338 RUM parent case.

    These rounds are being designed along with Richard Graves of Wildcat Bullets in Alberta Canada who is designing some very impressive bullets for these new rounds.

    Just a few of them are the four new options for the 257 AM. A 130 gr Bonded Core FBHP, 145 gr FBSP, 150 gr FBHP and a 145 gr Rebated Boattail ULD design.

    For the 6.5mm version there will be the 140 gr Bonded Core FBHP, a 160 gr class RBT ULD and this winter we will be designing a 180 gr ULD for the 6.5 AM.

    The 270 version will also have new bullets but of more traditional weights such as 130 gr but also aome heavy 169 gr pills as well.

    The AM case will be the largest practical case for thes rounds and substantially more then the parent case 338 RUM simply necked down.

    The trick is to use heavy bullets to make this big case run hard.

    About the 338 RUM having 120 gr of usable powder volume, this simply is not true by any means.

    Comparing the 257 STW, 257 AM and the 25 RUM, the case capacities are as follows when filled to the case mouth with H-335:

    STW: 104 gr
    AM: 120 gr
    RUM: 128 gr

    Now if you compare usible powder capacity, its more like:

    STW: 80 gr
    AM: 95 gr
    RUM: 105 gr

    This is filled to the base of the neck. This is certainly alot of powder espeically if you plan on using light for caliber bullets but for the heavy for caliber bullets this case size will perform very well in a barrel length that you want to use.

    My AM rounds are designed around 30" barrels.

    Good Shooting!!

    Kirby Allen(50)
     
  5. budlight

    budlight Well-Known Member

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    Fiftydriver - I'm proud of the work your doing. One of my friends bought one of the first 30-378's to come out. I was very impressed when we got into the Chrono work. It made the 300 win mag. look like a 30-30 compared to 30-06

    I like the idea of your middle of the road approach between STW and RUM.

    So little time and so many choices!!!!!!!!!!
    [​IMG]
     
  6. 7ultra

    7ultra Well-Known Member

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    Fiftydriver,
    Those are definately some very interesting cartridges. You've definately got my attention. But for the rifle I have in mind, I want to keep it as moderate (10-12lbs) and mobile as possible. What do you think the longest barrel, given this criteria, would be best while still utilizing the cartridges capabilities. Specifically, I want a tube that is going to have a fair amount of rigidity and not have to be hung off of a barrel block. Thanks for the info, agian it's definately got my attention.
     
  7. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    7Ultra,

    All the prototype(if you will) AM rifles I will be building will be using a #6 contour Lilja Stainless steel barrel of 30".

    As I said, these are designed as hunting rifle, that being, carry rifles for use in open country where the 30" pipe will not be a bother.

    I have used my wifes 257 STW built on this same configuration, in fact it is the rifle I used to take my whitetail this year. This rifle is inthe 9.5 lb range ready to hunt with this barrel length and contour and I am getting 1 1/4" three shot groups at 500 yards so the stability and rigidity must be there.

    Also this barrel is totally floated. This was kind of an experiment to see how the #6, 30" barrel would perform as far as barrel flip was concerned. I do not see a problem as of yet and do not expect to.

    The barrel that is on order for the 257 AM is another #6 contoured Lilja Stainless 30" blank. The only difference is that I had Dan flute this barrel with the larger diameter flutes designed for the 50 BMG barrels.

    What this will do is give me the stiffness and rigidity of the #6 contour which is obviously working with a barrel weight slightly less then a #5 contour barrel. Put another way, I will be able to cut 1/2 lb off the rifle weight compared to my wifes 257 STW.

    I will also be using a Holland Signature Series Laminated stock which is about 1/4 lb less then the Boyds Thumbhole sporter I fitted to my wifes rifle.

    These are certainly portable rifles that will easily be under the 10 lb range.

    As you know there is always some sacrifice in accuracy trading rifle weight for portability, at least at a certain point.

    I am looking to build rifles that will perform as a portable rifle that will allow the hunter to engage deer size game, up to 500 lbs even, at ranges out to 500 yards without major sight adjustment.

    Here are a couple pics of her rifle. The three initial AM rifles will look similar to this but will have the heavy flutes and a traditional sporter Laminated wood stock.

    [​IMG]

    [​IMG]

    One could also go with one of the light weight composite stock as get down to very light rifle weights for a 30" barrel.

    I feel the #6 contour is as light as I would go out to a full 30" and still be comforatble with rigidity with these rounds.

    Again, with this barrel weight, there is no need for exotic bedding systems, just a quality pillar bedding job is plenty to support this barrel length on a Rem 700 action in my opinion.

    Good Shooting!!

    Kirby Allen(50)
     
  8. bigcat24

    bigcat24 New Member

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    I hunt with a 270 stw that is built from a Harold Broughton Built barrel. it shoots lights out. took a 145 class buck at 275 opening morning here in texas. no wonder Harold dubbed it the "270 SMF" love it I shoot 140 grain accubonds behind 78 grains of imr 7828. [​IMG]
     
  9. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    What kind of velocity are you getting out of your 270 STW? What barrel length are you using?

    Sorry for the questions, not to many 270 STW's out there and your performance data would be intresting to me when I start the load development stage of the 270 Allen Magnum.

    Good Shooting!!

    Kirby Allen(50)
     
  10. bigcat24

    bigcat24 New Member

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    I am gettin 3425 out of a 28 inch barrel with a muzzle brake no problem on the questions be happy to help you in any way.
    [​IMG]
     
  11. bigcat24

    bigcat24 New Member

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    thats 3425 on a 5 shot avg. sorry have had some fluctuation of + or - 20fps tryinf to figure out the cause. thats pretty hot load it is starting to get shiney on the rear of my cases. I'm not going to push it much more
     
  12. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Dusty,

    Thanks for the information. That is cefinately a serious load for any long range hunting.

    If you do not mind one more question, what load do you use for that round and velocity?

    I will be using load data for the 257 STW and 6.5mm-300 Wby as starting loads for my 257 AM and 6.5mm AM rounds. There is very little data for rounds in 270 the size we are dealing with. I have some computer figured starting loads but I would prefer to use actual data for the STW case size as astarting loads in the AM rounds.

    Thanks again, you have a very impressive performer there!!

    Kirby Allen(50)
     
  13. dakor

    dakor Well-Known Member

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    Not to start an argument or hurt anyone's pride but what do you gain by going from a 7mm STW to a 270 STW? I mean I can see going to a 257 STW but not a 270 STW. I have a Rem Sendero and I am shooting 140gr Accubonds at 3440FPS and 140 Barnes TSX at 3585 FPS both loads are not hot and both loads shoot well under an inch. in fact the 140 TSX load with 3 shots is in the .2's at 100 yards. I also have a 160 Accubond Load going 3276 FPS shooting 5 shots at 100 yards in the .5's. So I guess my question is do you gain anything going to a 270 STW?
     
  14. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Dakor,

    With conventional bullets, nothing really unless you want a big 270 which there are simple non of!!

    In my 270 Allen Mag, I will be using bullets in the 160 gr, 170 gr and 180 gr class with very high B.C.s, in fact much higher then any big game 7mm bullet onthe market. They will make the 160 gr Accubond look pretty weak in B.C. and with the larger case will far outperform the 7mm STW.

    That said, they will match a 7mm RUM loaded with the same bullets.

    ITs really just a personal thing. Alot of guys like the 270 caliber but when the 270 Wby is the biggest thing around, there isn't much choice but to go to a wildcat and the STW is a great case to use for a wildcat 270, very easy to load for and very good performance.

    Fortunately, most wildcat rounds are not designed for the only reason to out perform the larger caliber rounds.

    Good Shooting!!

    Kirby Allen(50)