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Thread: Made some 7.62x41 Herrett bullets from 6.8 SPC brass and some background.

  1. #1
    Boolit Master




    bruce drake's Avatar
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    Made some 7.62x41 Herrett bullets from 6.8 SPC brass and some background.

    For my fellow marksmanship, AR15 and bullet casting fans...

    I broke down and bought the 6.8 SPC bolt for the .30 Herrett AR15 wildcat upper that I had built this spring when a family friend from New Zealand and fellow Cast Boolits Forum member was visiting.

    I bought the new 6.8 SPC bolt on a Pre-Black Friday sale and the first time I've seen the 6.8 SPC bolts by themselves for sale for a while as the new .224 Valkyrie cartridge (The Hornady-designed competitor to the new .22 Nosler cartridge) has been taking off in sales leaving the bolts as an individual item shortage.

    Both the .224 Valkyrie and the .22 Nosler are specialty cartridges for folks who want to shoot long-distance (800-1000 yard matches/shots) with their AR15s using very long and heavy for caliber (75-90gr) .22 caliber bullets. Seriously they look like long fat needles and are almost as long as the case itself.

    The previous brass run and proof of concept test I made with the rebated rim 22 Nosler cases me to use a standard 5.56 bolt carrier group I had sitting on a shelf but I was starting to see some difficulty in finding the empty cases to convert to the 30 Herrett with a rebated 5.56 case rim. Nosler and Silver State were the only two companies making that specialized rebated rim 5.56rim & 6.8 SPC cartridge based brass while the base 6.8 SPC is made by all the major brass companies now.

    First photo - 3 stages to convert brass to load from 6.8 SPC to now named "7.62x41 Herrett".
    1) 6.8SPC case fresh out of the tumbler.
    2) brass is opened up to 7.62mm and shoulder pushed back to Herrett dimensions.
    3) brass trimmed back to .30 Herrett established length at 1.6 inches.
    4) 125gr .308 jacketed soft point loaded over a mild load of 22.5gr of AA1680 gunpowder for an estimated 2100fps which puts it into 30-30 Winchester class of cartridge. Hopefully, a nice deer hunting cartridge in the future.
    Click image for larger version. 

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    Second photo - a 7.62 Herrett cartridge loaded into a 6.8 SPC AR15 magazine to show overall length at 2.25". You can use standard 5.56 sized magazines but using 6.8SPC ar15 magazines helps ensure proper feeding of more than 5 cartridges in the magazine. I own 2 of these magazines that I would use in hunting to ensure that any followup shot feeds flawlessly if I should need it. For range or rifle match use, like I said, you can single-load using standard magazines also.
    Click image for larger version. 

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    Third photo - This photo shows two different cast lead bullet combinations. the bullet on the left is a Lyman/Ideal #311359
    Spirepoint 120gr gas checked and poly-coated lead bullet and the right bullet is a Lee Precision 155gr gas-checked
    and poly-coated Spirepoint bullet. I'm staying with spirepoint bullets as Round-nose and Flat nose design cast bullets hang up on the AR's barrel extension/star chamber lips.
    Click image for larger version. 

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    If folks are interested in the 224 Valkyrie or .22 Nosler cartridges, The NRA did a very good article on comparing both of those cartridges in May of this year (a month after Jeff Brown and I built our original AR15 upper in 30 Herrett.) and that article is linked here:
    https://www.shootingillustrated.com/...yrie-compari…/

    If your state allows .22 caliber cartridges for deer or varmint hunting and you need a cartridge to reach out and pop them. Great Plains deer and pronghorn antelope spring to my mind on those two cartridges for long shots with proper hunting bullets. That said... I do own a .22-6mm Remington Wildcat...(a 7x57 cartridge case necked down to .22 caliber)

    The original 30 Herrett was designed and built in the 1970's by trimming 30-30 Winchester brass shorter to allow the new case to use pistol caliber powder or more efficient rifle caliber gunpowders in specialty one-shot pistols like the Thompson Contender.

    Since the original 30 Herrett cartridge uses a rimmed case, I'm opting to call my Wildcat cartridge using 6.8 SPC brass by its Metric designation and founder as "7.62x40 Herrett". The guys who first considered this cartridge in and AR15 in 2012 called it the 7.62x40 HRT (Herrett Rimless Tactical) for sales marketing.

    This is for me to separate them from my previously loaded cartridges using the .22 Nosler rebated rim brass which will probably be shot off with the original 5.56 Bolt Carrier Group prior to fully shifting to the new brass and bolt combo.

    This Ar15 upper's barrel has a 1:8" twist as it was originally a carbine-length gas system barrel chambered in 300 Blackout AAC. I used a PTG Finish Reamer to manually recut the chamber to the new cartridge. I feel comfortable in being able to accurately shoot up to 30 caliber bullets up to 220gr in weight with this barrel as that's usually the max bullet weight for the 300BLK's cartridge in a suppressed mode. Those "heavy" bullets will not be barn burners but they should pop a target pretty good as even with its low velocity compared to the smaller bullets, there is still significant force being transferred by the bullet to the target. Myself, I think I'll stick with bullets up to 170gr in weight and try not to push it with those heavier bullets.

    I'll try to get to the range and add more target photos of this new bullet soon. I also need to do a shout out to Johnny_V from this forum as he provided the 6.8SPC brass in a Pay It Forward approach.

    Total rifle nut post but I was not harmed at anytime by any aggressive, semi-automatic rifle while working on this study in gunsmithing, reloading and bullet casting.

    Bruce
    I Cast my Boolits, Therefore I am Happy.
    Bona Fide member of the Jeff Brown Hunt Club

  2. #2
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    TCLouis's Avatar
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    As a fan of the 30 Herrett, I can only say congratulation Bruce, seems like a wonderful project.

    If one loads it down with heavy boolits, the amazing thing about shooting those big ol heavy bullets/boolits lumbering along subsonic is the way they hold velocity.
    One of the original features in the "Whisper".
    Last edited by TCLouis; 11-27-2018 at 06:42 PM.
    Nothing is impossible for the person that does not have to do it.

  3. #3
    Boolit Grand Master popper's Avatar
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    What is the difference between the 7.62x40WT? I'm doing 2100 with 145gr. PB cast from a 1:10 BO carbine. The 40WT claims 2400 with 125 but has a shorter neck. Another OP is pushing the 223 case to 39 for extra space. Just wondering what the differences are, sounds interesting but needs different parts?
    Whatever!

  4. #4
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    Quote Originally Posted by popper View Post
    What is the difference between the 7.62x40WT? I'm doing 2100 with 145gr. PB cast from a 1:10 BO carbine. The 40WT claims 2400 with 125 but has a shorter neck. Another OP is pushing the 223 case to 39 for extra space. Just wondering what the differences are, sounds interesting but needs different parts?
    About 200 fps faster with the 30 HRT.

  5. #5
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    bruce drake's Avatar
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    Quote Originally Posted by popper View Post
    What is the difference between the 7.62x40WT? I'm doing 2100 with 145gr. PB cast from a 1:10 BO carbine. The 40WT claims 2400 with 125 but has a shorter neck. Another OP is pushing the 223 case to 39 for extra space. Just wondering what the differences are, sounds interesting but needs different parts?
    The 7.62x40WT is built off a shortened 223 Rem case while the 30 Herrett Rimless Tactical (HRT) is built off 6.8 SPC cases

    I believe the 30HRT has a different shoulder angle than the original 30 Herrett case but its the same relative case as my self-described 7.62x41 Herrett wildcat with probably a miniscule difference in case volume. Most .30 Herrett-based wildcats will beat the smaller 7.62x40WT for velocity.
    I Cast my Boolits, Therefore I am Happy.
    Bona Fide member of the Jeff Brown Hunt Club

  6. #6
    Boolit Grand Master popper's Avatar
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    guess what I'm asking - with the extra case CCs can you run 170-190 fast like 30/30? 40Wt goes ok with 150,x39 & BOI guess is about the same, fps limit appears to be 2-2.1K. Allow use of slower powders?
    Whatever!

  7. #7
    Boolit Master




    bruce drake's Avatar
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    To be honest, I'm just getting started with reloading this cartridge for an AR15 and I've shot 120gr and 155gr cast boolits in this rifle when I was using the reformed 22 Nosler brass. I do have plans to try the 311413 175gr spirepoints with a good load of 4985 and 4064 when I have range time.

    Bruce
    I Cast my Boolits, Therefore I am Happy.
    Bona Fide member of the Jeff Brown Hunt Club

  8. #8
    Boolit Master




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    https://68forums.com/forums/showthre...-30-Herrett-AR
    76 pages of load development by the guys on this forum may have that answer regarding heavy bullets.
    I Cast my Boolits, Therefore I am Happy.
    Bona Fide member of the Jeff Brown Hunt Club

  9. #9
    Boolit Buddy
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    All I can say is I hope you have as much fun play'n with your Herrett as I have with my WT. In this case, the Journey is just as much fun as the Destination. (at least for me)

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check