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.375" 350 gr Sierra HPBTM?(new announcement added)

Ray BRay B Member Posts: 11,822
edited June 2012 in Ask the Experts
A friend said he had seen some match bullets made for the 375 RUM- Anyone have any info on this?


  • charliemeyer007charliemeyer007 Member Posts: 7,305 ✭✭✭
    edited November -1
    No matchking listed but they have 2 gameking in .375. call them.
  • Alan RushingAlan Rushing Member Posts: 9,002 ✭✭
    edited November -1
    I found nothing "off the shelf" neither now nor when a brother was looking several months back.

    If you were hand loading that may be a very different story. My brother was to look into the "CEB .375 Solid Copper Bullets" in both the 320 gr. and 330 gr. listed with Sinclair International. I have no idea at this point if they produce other wts.

    ( In my brother's quest he spoke to staff at a couple of bullet manufacturers. They do have occassion to do special runs of non-listed wts. for research purposes or special requests, however the minimum orders are greater than any of us could absorb! )

    There are some individuals here that would have much more extensive knowledge and experience than yours truly on this request. They will no doubt be along sooner or later. Good luck in your quest and searching.


    Regarding Contacting Sierra Bullets:

    Sierra Bullets
    1400 West Henry Street
    Sedalia, MO 65301

    Phone: (660) 827-6300
    Fax: (660) 827-4999

    Technical Support: 1-800-223-8799
    Toll Free Support: 1-888-223-3006

    Email: [email protected]

  • Riomouse911Riomouse911 Member Posts: 3,493 ✭✭✭
    edited November -1
  • Ray BRay B Member Posts: 11,822
    edited November -1
    I got in touch with my friend & learned that Sierra made a special run for an unidentified agency/govt. Whoever ordered them didn't want the entire minimum amount that Sierra required to produce it, so the extras were sold through one of the mail order suppliers- possibly Grafs, but he wasn't sure. If there is a way to post a photo of it, I could show it, but it appears similar to a .308 168gr expanded to .375". I'm guessing that someone out there is developing a tactical rifle that is inbetween the 338s and the 50s. It would be nice to know who that is, but Sierra isn't talking.
  • Ray BRay B Member Posts: 11,822
    edited November -1

    If this works I'll have learned something new today. The .375 350gr (I weighed it) is flanked by a Berger .257 115gr VLD and a Sierra .308 168gr HPBTM
  • nononsensenononsense Member Posts: 10,931 ✭✭✭✭
    edited November -1
    Ray B,


    This is the news release statement from Sierra regarding these bullets. I have added the photographic rendition of the technical data below. The official part numbers have been released so ordering them should be a matter of a phone call. I didn't see them listed on the website as of Friday evening and I haven't had time to check other websites selling components.

    On the other hand, regarding data for the RUM; as I'm still testing on the high desert so I can't access my data. But I have run a quick 'What If' by computer modeling to give you a small glimpse of the potential.

    Using a 28" barrel and an OAL of 3.9" with double base powders, you can achieve something along the lines of 2700 FPS at the muzzle. Several other powders will yield 2600-2650 FPS without the energy boost of the double base powders. To step up these results you have to add more horsepower and longer barrels. This generally requires a bigger action to utilize the bigger cartridge cases. Longer barrels and bigger actions will significantly increase the overall cost of a project such as this.



    May 30th, 2012

    New 350gr .375-Caliber MatchKing from Sierra

    Sierra Bullets has just announced a new .375-caliber, 350 grain HPBT bullet - the latest in Sierra's MatchKing line of projectile. Designed for custom long-range applications, this 350-grainer is the largest MatchKing Sierra produces, and it offers a jaw-dropping 0.805 G1 BC (at 2,200+ fps).

    With that impressively high BC, the new .375-caliber MatchKing should "buck the wind" very well at long range. The new bullet features an 11-caliber ogive, and 9-degree boat tail. Sierra says the overall shape is "forgiving" to tune and should work well at a variety of seating depths. These bullets will be available in 50-count boxes (stock #9350T), or bulk boxes of 500 bullets (stock #9350).

    Sierra MatchKing SMK .375 caliber


    There are always new arms and cartridges being tested and rejected by the armed forces because we fund those programs. The .375 cartridges have been under consideration for several years now, not unlike the .416 variations under proposal as well. These cartridges and the bullets have filtered their way into the civilian mainstream through the surplus side and through the secondary resellers also. Here is a recipe for a load featuring the bullet from Sierra used in a cartridge named the .375 SnipeTac:

    Recommended Load Data for 375 Sierra Match King Projectiles

    350 grain Sierra Match King
    Hodgdon Retumbo
    Max Load
    139 grains
    Cartridge Overall Length
    4.100 inches
    Magnum Large Rifle
    Average Velocity
    3,200 fps

    Most of these larger intermediate cartridges are not for the faint of heart based on the recoil exhibited in the lighter rifles. However, the recoil can obviously be defeated to a certain extent by increasing the rifle weight and by adding a muzzle brake or suppressor to the mix. Also, an increase in the barrel length is requisite to achieve the velocities and distances to support the advertised specifications, all while maintaining a semblance of still being 'man portable'.

    The Match VLD solids on the other hand are seeing lots of air time in competitions. Here, the drawback is powder capacity vs barrel length to counteract the length of these bullets. It takes a bunch of powder and longer barrels to get these bullets moving at an appropriate velocity. Some of these solids approach 2" in length which encroaches into the case space thereby reducing case capacity. Often this will require a special chamber reamer or an additional throater at the very least to prevent or minimize the intrusion into the case and maintain a greater usable capacity.

  • Ray BRay B Member Posts: 11,822
    edited November -1
    Thanks for the info- I researched the SnipeTac which led to CheyTac and the basic case used for forming-505 Gibbs; and a bunch of "rifles", somewhat on the line of reduced scale Barrett 50s. WOW, I had no idea that equipment for long range shooting was so developed. My previous idea of long range rifles had gaps between 300 Win Mag to 338 Lapua to 50BMG. It's nice to know that companies/govt are researching the middle ground.

    Is there any load development of loads for the 350 SMK for lesser .375s such as the RUM or Weatherby?
  • nononsensenononsense Member Posts: 10,931 ✭✭✭✭
    edited November -1
    Ray B,

    I'm currently out of position to retrieve any of the .375 data I and others have worked on. I will make some notes and look at my files when I get back to my office.

    The Sierra bullets were originally developed for Cheyenne Tactical for use with their .375 version of their original .408 cartridge. Business and partners being what they can be, things went south ultimately allowing some of these bullets to get into the mainstream consumer pipeline. This is short version of a long protracted downward spiral but it will suffice for the time being.

    Be aware that these bullets are 1.750" in length and therefore take up a lot of space in the case when the OAL is limited to the absolute magazine length of 3.600". However, when you either have a reamer ground for this specific bullet or use a throater to lengthen the chamber on a one-time basis, you can single load a cartridge with this bullet to test either case individually but not both obviously.

    The original BC claim from Sierra was computer modeled and generated but slightly overstated. Bullets have to be fired on a range with chronographs to establish BC even though computer modeling can be fairly accurate given excellent data input. Sierra is listing 0.805 as the BC for a velocity level of 2200 FPS although field results have this at a slightly reduced value. The design form factor for the Sierra bullet models simply doesn't support a BC of over 0.800 when using field achieved results.

  • MIKE WISKEYMIKE WISKEY Member, Moderator Posts: 9,903 ******
    edited November -1
    hmmmm, it lots like I may have to 'improve' my .357 H&H (and lenghten the magazine so more) [;)]
  • Ray BRay B Member Posts: 11,822
    edited November -1
    I seated the bullet in a sized RUM case and gradually set it deeper until the bullet was just off of the rifling. The OAL is 3.95" which is about .3" too long to use the magazine (seating to 3.6" is not really an option since the bullet taper is in the caseneck), but in checking the position of the bullet in the case, the front edge of the boattail is on line with the base of the neck, which calculating the portion of the powder area being displaced results in about .026" or about 6%. So that should be a very workable round for long range single shot target work. I got a reply from Sierra- they said the bullet was made for a confidential customer and the contract of confidentiality was still in effect, but when it lapsed they(Sierra) would be releasing information regarding the bullet (BCs, load data)as well as producing the bullet for the open market. So I may be able to get more than the one bullet and a starting point for loading. I can hardly wait to get the project on track!!
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