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6mmRem to a 243Win.

Discussion in 'Rifle Country' started by Samclrk, Aug 25, 2013.

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  1. 243winxb

    243winxb Member

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    Cant use the 6mm data in 243.
     
  2. morcey2

    morcey2 Member

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    :eek:
    You can't fit 81 grains of powder in a 243 case. Ever. Period. You can't fit 81 grains of powder in 30-06 case.

    The 6mm chamber is bigger because the 6mm cartridge case is bigger. The 6mm actually operates at a higher pressure than the 243 according to SAAMI. 65kpsi v. 60kpsi respectively. Most reloading data has them both at about 60kpsi.

    There isn't a huge difference in performance between the two, but you can't fit the max load from most 6mm load data into a 243 case without going over the case capacity. You have a fundamental misunderstanding of case size, chamber size, and the physics of fitting 10 lbs in a 5 lb bag.

    Matt
     
  3. Samclrk

    Samclrk Member

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    Sorry,morcey2..I meant to say 51 grains..Not 81..Sorry.
     
  4. morcey2

    morcey2 Member

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    Regardless, which powder is it? There are a few powders that will go to the 51 grain area in 243, but those same powders load in the 54 grain max range in 6mm. Superform is one of them. Because of the similarity in case size, there will be significant overlap in the load data, but it's a really good bet to say that every 6mm Max load will be severe overpressure loads if crammed into a 243 case.

    Which powder are you using for the 51 grain loads?

    Matt
     
  5. Samclrk

    Samclrk Member

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    Win780..I also use the Mag. primers
     
  6. morcey2

    morcey2 Member

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    That's almost 2 grains above the max load I can find anywhere for any weight bullet for the 6mm with a standard primer. It's over 3 grains above the max for 243, again with any bullet I can find and a standard primer.

    I think you've blown way past pushing the limits and right into flat-out dangerous territory.

    Matt
     
  7. 303tom

    303tom member

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    Yes you can..............
    .243 Winchester.
    100 GR. SPR BTSP Hodgdon H1000 .243" 2.650" 44.0 2876 45,700 CUP 47.0C 3000 49,800 CUP
    6mm Rem.
    100 GR. SPR BT Hodgdon H1000 .243" 2.775" 47.0 2779 41,500 PSI 50.0C 2955 48,900 PSI
    Right out of the book................
     
  8. Samclrk

    Samclrk Member

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    I use a Lyman`s book ``Lyman Reloading Handbook,46th Edition``,,70grain bullet-Win785 52grains....I`ve been using this since 1963..The 6mmRem.=52grains Win 785.
     
  9. viking499

    viking499 Member

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    81 grains?

    Oops, now I see the correction.
     
  10. Samclrk

    Samclrk Member

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    LOL....Yeah,it`s late.....Sorry about that..
     
  11. Bexar

    Bexar Member

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    I wouldn't...Sort of like trying to get .357 mag velocities out of a 38 Special case. You might be able to stuff a .38 case with enough powder but the pressure curve is going to hit quicker because of the reduced .38 Special case volume. Same effect with the .243/6mm scenario...case volume is part of the safety equation along with pressure. You might get away with it in the ,243 if you use an extremely slow burning powder but that's not my advice or recommendation. I've got a 6mm Remington case on my keyboard right now and I occasionally enjoy picking it up and rolling it between my fingers. But I digress...since you're only shooting paper and the question of terminal velocity and bullet selection is moot...do whatever brings you the most enjoyment.
     
    Last edited: Aug 30, 2013
  12. Samclrk

    Samclrk Member

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    Thanks,Bexar...I agree.
     
  13. MachIVshooter

    MachIVshooter Member

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    Accuracy is not a function of the cartridge. Platform, barrel, load & shooter determine accuracy. Some cartridges are referred to as being "inherently accurate", but that's a misconception; some cartridges are simply less finicky when it comes to variation in load. Namely, shorter cartridges tend to get more uniform burning of the powder column with a wider range of powder types and load density.

    Kind of a moot point, though, as achieving best accuracy with ANY round in ANY rifle requires fastidious load development.

    As for rechambering a 6mm to .243, I think that one's been drilled home pretty well, but I'll just point out one other reason to NOT do it:

    In addition to greater case capacity, the 6mm also has a longer case neck and is used in mid-length or long actions; this gives you greater flexibility with bullet weights and profiles.

    Also, there has been some mention of the slow twist rate. Just to clear that up, the rifles in question have a 1:12 twist, and the barrel will be labeled ".244 Rem", which is a cartridge that has the exact same physical dimensions as the 6mm. But production rifles with barrels marked "6mm Rem" have a 1 in 9" twist. I believe the change occurred around 1967, and the only reason for the renaming was the change in twist rate of the rifles; Remington was losing sales to the .243 because the slow twist in .244 rifles didn't stabilize > 90 gr. bullets well, so the .244 was relegated to use on varmints and small deer or pronghorn. The name was changed as a marketing strategy only; there is no difference in the cartridge itself.
     
  14. Samclrk

    Samclrk Member

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    Thanks,mach...
     
  15. 243winxb

    243winxb Member

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    Put that 50.0 gr. Compressed, in the 243 for me. Photos please. :D
     
  16. 303tom

    303tom member

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    Thats just being ridiculous, I`m just saying you can use 47 grs. of H1000 in the 6mm Rem. & the .243 Win. safely.............
     
  17. HOOfan_1

    HOOfan_1 Member

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    I am pretty sure the OP was asking if he can use the reloading data for the 6mm Remington with the .243. Considering the 6mm starts out with a higher minimum and ends up with a higher maximum, the answer is NO!!!

    Do they have loads that overlap? Yes...but why would the OP look at the loading data for the 6mm Remington in order to find an overlapping load for a .243?

    USE THE LOADING DATA FOR THE CARTRIDGE YOU INTEND TO SHOOT!!!


    Why would we confuse the OP by saying anything else?
     
  18. DM~

    DM~ Member

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    +1

    dm
     
  19. morcey2

    morcey2 Member

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    I'm still trying to figure out if it's 51 grains of 780 or of 785. Either one isn't coming anywhere near a rifle of mine, be it 243 or 6mm. Both are too slow to work anywhere near optimally for a 70 grain pill. Something in the Varget/4064 thru 4350 range would work much better.

    There's a reason that they came out with 47, 48, and 49th editions since then. As pressure measurement technologies improved, many of the existing loads were determined to be way too hot. I don't know how 780 and 785 relate in terms of performance, but I'm pretty sure that they're not equivalent. Lyman 49 doesn't even list 780 on the 70 grn laods The slowest on in there is H4831 @ 50.5 grns.

    If you've been shooting the same load for 50 years, why are you asking? I'm going to make an assumption that your current 6mm barrel is shot out, which tends to happen when you're shooting a lot over 50 years, and you want to rebarrel it. 243 sounds enticing, but you want to keep the velocity you get from the 6mm. You've also run out of 785 since they quit making it at some point in the last decade (I think) and you need a new load.

    If that's the case, rebarrel it to the 6mm and work up loads using the existing 6mm data. If you rebarrel it to 243, work it up with the 243 data. The newer data is significantly more accurate in terms of pressure and are much better in terms of barrel life and keeping all of your eyes, ears, and fingers intact.

    Matt
     
  20. 303tom

    303tom member

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    Why would the OP be reloading without a Reloading Handbook ?.................This right here is the reason I don`t usually answer reloading questions, and I am done with this one !..............
     
  21. DM~

    DM~ Member

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    I agree, it's ALSO the reason i rarely give out load data on the net too.

    Anyone that's going to reload, should NOT be too cheeeeeep to buy the loading manual for the brand bullet they choose to use!!

    DM
     
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