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Big Bore Semi Guns...........

Discussion in 'Big Bore Rifles' started by Michael458, Mar 24, 2019.

  1. Michael458

    Michael458 Active Member

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    I have a few big bore semi guns. I confess they are the least interesting to me of any of the B&M cartridges. I had the designs for a long time, and the rifles in which to put them on. But these were way on the back burner for me. Finally JD called up and wanted to do the the B&M SA--(Semi Auto), so we went to work on the first two, which are both on AR 10 Platforms.

    Back in the day, DPMS made some rifles chambered in 300 RSAUM. The B&M case is a 1.95-2 inch RUM case, and these would be easy conversions to big bore. No bolt face work at all, and magazines already designed for the fatter cases. I had a couple of these, so sent those up to JD at SSK.

    The first gun was a .500 caliber rifle, we call it the 50 B&M SA. The second was a 458 version of the same case, the 458 B&M SA. In my data here I show the first loads went down range in January of 2010. After going through the basics of getting them to work, which was really easy, some magazine tweaking by Brian at SSK solved all issues. Both rifles had 18 inch barrels. Both are heavy as hell at 10 lbs.

    After getting basic data and making sure they worked, I put them to the side and did not mess with them at all for several years. I did not have much interest in them, and was heavy hunting during those years, and semi just had no place in my agenda at all. SSK built several rifles over the years, but I turned everything over to JD and SSK with these, I didn't want anything to do with them. They served no real purpose for me, other than just something to play around with.

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    Then in 2014 I more or less officially retired from Hunting. I got bored. So looking at these things in the racks, I decided to just find out what potential they had. I went to work on some serious load data for these things.

    What I found with the 50 B&M SA;
    300 gr Hornday 2400 fps
    335 Raptors 2300 fps
    350s 2200-2250 fps
    375s to 2150 fps
    400s to 2050 fps

    I personally like the 458 B&M SA better;
    The 250 Socom Raptor by CEB is a very serious .458 caliber bullet, and it is made for things just like this, along with the various bolt gun cartridges as well. And the main load for this gun
    250 Socom Raptor 2670 fps
    300 North Fork 2436 fps
    300 Barnes TSX 2421 fps
    325 Safari Solids 2327 fps
    325 Hornady Flex 2350 fps
    Various 350s from2150 to 2250 fps.

    Once I got that done, lost interest again.... HEH......... Loaded up a few hundred of these in case there was a Zombie Apocalypse, and put them back in the rack again..........Where they remain today.........
     
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  2. Michael458

    Michael458 Active Member

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    Later in 2015 my buddy Sam Rose had a WSSM Upper from Olympic I believe....... AR 15. This was interesting, as bolt face and magazines would work with the B&M Super Shorts. I got the Upper from him and sent to Brian at SSK to build a 458 B&M Super Short. 1.65 inch WSM Case to .458 Caliber.........We had high hopes for this one, 458 SS is capable of that 250 Socom Raptor at 2600+ fps in a bolt gun, but pressures are running at or around 62000-63000 PSI in the bolt gun, way too much for a AR Platform, which needs to be kept at or around or under 55000 PSI in most cases...........

    Had the gun done with 16 inch barrel. And it turned out well. Feed and function great, no issues. This one would not feed the solids, some bit of a disappointment, but not a real surprise. I am sure if I took enough interest this could be solved. I do have a gun set up to do pressures, so I did some special work to get top end loads for the thing........

    458 B&M SS in AR 15;
    250 Socom Raptor 45/WW 296 2390 fps 52000 PSI
    250 Hornady Flex 45/WW 296 2347 fps 54000 PSI
    325 Hornady Flex 41/LilGun 2144 fps 54500 PSI

    And I more or less lost interest at that point................. While 2350 or better with the 250 Raptor is very effective, its just not where I hoped it might be. But this platform has to be kept at those pressures or you start breaking things
    at some point. And, this gun would talk back to you, it did not like anything over 55000 PSI........ Things would start to get sticky, and it did not like to be pushed.......

    The magazines from Olympic seem to be a little chincy, but they have worked so far, its hard to complain about them. I think if there is ever an issue, it would be with those magazines............

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  3. Combat Diver

    Combat Diver Well-Known Member

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    Always wanted a M1 Garand in either .35 Whelen or 9.3x62mm.

    CD
     
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  4. Michael458

    Michael458 Active Member

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    I can't see where that would be terribly difficult to do.......... Sometime call Brian up at SSK and ask him what he thinks.
     
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  5. Combat Diver

    Combat Diver Well-Known Member

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    Just need a barrel change as both cartridges have the same case head (.473) of the 30-06 and same overall length. Add a Shuster gas plug.

    CD
     
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  6. Michael458

    Michael458 Active Member

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    Yep, I think so as well. Don't think it would be a big deal to do.
     
  7. Michael458

    Michael458 Active Member

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    Ran across this photo just now, thought it would give some insight to what this is...................

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