Bear with me here

Discussion in 'M1 Carbine' started by DWFan, Sep 22, 2010.

  1. DWFan

    DWFan Handgunner Forum Contributor

    A little brainstorming, if ya'll don't mind. I've read more than a few times about folks wishing the M1 was chambered in 7.62x25mm. I don't know how well that would work as the 7.62x25mm is approx. the same, powerwise, as the .30 Carbine. It did get me to wondering though. Why not a shortened .300 Whisper?
    According to my math, a .300 Whisper with the neck shortened to create a 1.26" case and loaded with the 125gr Sierra HP-FN will have approx. the same overall length as the .30 Carbine cartridge. The neck length should wind up being very close to that of a 7.62x25mm or .30 Mauser. The reamer should be very inexpensive since the only difference is the shorter neck. Case forming dies for the .300 Whisper are easy to get as are neck sizing/crimp dies for the 7.62x25mm. No custom (ie. expensive) dies are required and brass is very inexpensive. Powder charges should be easy to extrapolate from existing .300 Whisper data. You can't use the longer/heavier bullets because they won't fit, but you shouldn't anyway because the M1 has a 1:16 twist and wouldn't stabilize them.
    The power increase should be considerable, possibly even equalling the .30-30 Winchester, .30 Herrett or 7.62x39mm.
     
  2. oldjarhead

    oldjarhead G&G Evangelist

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    As the M1 Carbine can be, and has been, converted to several different pistol cartridges from 9mm to .45 win mag, and other wildcat conversions that have never really been accepted, your idea is probably do-able. I do not, however, see any advantage in converting the 7.62x33 to a 7.62x25 format.
    The .300 whisper conversion would be a costly project with little gain. The rated muzzle velocity/muzzle energy difference would not really be worth the effort and would not gain any better performance. The .30 Carbine rates at MZ 1990fps vs .300 Wh at 2100fps yield is a slight difference to the plus side; ME however drops from 1311fp for the carbine to 1224 fp for the whisper which is significant.
    IMHO, although the thought of such a conversion is worth the effort, I believe the cost of the endeavor resulting in no gain is not...and, believe me, I love playing around with the M1 Carbine.
    Going to a smaller conversion, such as the .22 Spitfire or even the .17/30, will yield you much better performance and overall gain and you can do the .22 Spitfire yourself.
    I have obtained a couple hundred rounds of .17/30 but can find absolutely no information on it other than the caliber was experimented with. I hope to delve into that one soon but need to restructure my current budget.
     

  3. DWFan

    DWFan Handgunner Forum Contributor

    Ok, so I was optimistic about equalling the .30-30, .30 herrett and 7.62x39mm, but according to my calculator..
    .30 Carbine: 110gr bullet at 1900 fps develops 882 fpe.
    .30-221: 125gr bullet at 2100 fps develops 1224 fpe.
    That's close to a 50% increase.
    Even if you launch the 125gr at the same 1900 fps at the 110gr, it still develops over 1000 fpe.
    How is a conversion that requires a custom barrel more cost effective?

    Just as a note: according to Accurate Arms data, the .30 Herrett launches a 130gr bullet between 2125 and 2160 fps from a 14" Contender barrel. The .30-30 from the same length barrel and same bullet only reaches 2270 fps.
     
    Last edited: Sep 22, 2010
  4. oldjarhead

    oldjarhead G&G Evangelist

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    It seems the ME for the carbine varies, depending on what book you look at.
    In all fairness a replacement barrel vs rechambering will probably be close to a wash...with my experience; although I didn't say anything about one being more cost effective over the other.
    Thinking outside the box may produce a very popular conversion or an unpopular blunder...either way, it's the fun of the chase and who knows what will come about.
     
  5. jimb2

    jimb2 G&G Evangelist

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    Just remember that the carbine is designed for 40,000 PSI. Many of the rounds being discussed are above that level. The bolt lugs probably won't take too much more pressure. Its not that uncommon for them to fracture with the proper .30 carbine round.
     
  6. DWFan

    DWFan Handgunner Forum Contributor

    This was the article that got me started thinking about other caliber options for the M1...
    Universal Firearms Corp.
    ...that and, like I said, the posts about a 7.62x25mm conversion.
    Here's a pic of forming a rimmed Whisper...
     

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    Last edited: Sep 22, 2010
  7. DWFan

    DWFan Handgunner Forum Contributor

    and here's one of the lesser known .30-357 AeT
     

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  8. oldjarhead

    oldjarhead G&G Evangelist

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    Universal came out with some unique variations. Too bad they tried to save money at the expense of quality during the later years.
    A friend purchased a green teflon coated carbine when they came out. Different looking but was a cool use for teflon. A true all-weather gun.
    Did you notice the crack in the slide of the teflon coated carbine shown in the article...that was one of the worst notorieties that caused Universal to fail; along with soft steel used in making the bolt.