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Thread: 300 AAC Blackout

  1. #1
    Boolit Master MGySgt's Avatar
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    300 AAC Blackout

    I am looking for any success stories with cast and 300 AAC Blackout. I am not sure what boolits are suitable to use in the 300.

    I have the RCBS 165 gr GC Sil that I am going to try when my dies come in. (Dies ordered but shipping department was shut down for Christmas/New Years Holiday).

    Any input will be appreciated. I will have 3 of these things to feed (Son and Grand son besides mine).
    Big Bore = 45+

  2. #2
    Boolit Master
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    That boolit should feed well for you. I have a MP 180 Sil and it feeds fine in mine. The best all around cast boolit seems to be the Lee 312-155-2R. Haven't heard of anyone yet that has any feeding or accuracy issues with this boolit. If you want to shoot subsonics you'll have to do some more research as I haven't shot many subs.

    H110, Power Pro 300 MP, AA1680, 4227, 4759, AA5744 or RE7 will be your powder choices for a heavier supersonic load. 4198 is probably just a tad slow for a 165gr boolit for supers. Lilgun is another good powder for this round but too fast for the 165gr to provide reliable cycling.

  3. #3
    Boolit Master

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    There is a great deal of discussion regarding the 300 bulk over on the 'CB loads Military Rifles' and 'CB loads favorite cartridges' threads. I've assembled the dies/molds/sizer and have an upper on order. There is also great threads on 300Blk talk, another web discussion board.

    This weekend, I was able to score a built 300 blk at a gun show so I can start assembling loads for testing. The Mrs really liked her AR in 5.56 (just finished) and when I told her I was building a 300 blk she chimed in with 'I want one.' This first one is hers and I will use it to work up loads in preparation for my upper coming in.

    I will be starting with the Lee 312-155 2R, IMR 4227, gas checks made with a CheckMaker die, powder coated with a Harbor Freight ES powder coat gun, and sized with a Lee push through die. I've made up 400 pieces of 300 blk using LC 5.56 brass.

    As this is a SAAMI cartridge there is a wealth of load data from Sierra, Hodgdon, etc., from various powder manufacturers. As far as cast goes, lots of folks are working up subsonic loads for use with 200+ grain boolits that cycle AR platform rifles with or without a suppressor. As stated earlier, I'm going to start with the 312-155 as there is a lot of data with that and 4227 powder. I'm already using 4227 in my 5.56/.223 loads for my AR and Mini 14 rifles. This will be a fun project, especially now that I can actually start load development and do some testing.
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  4. #4
    Boolit Master Jupiter7's Avatar
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    Another vote for the 312-155. I've shot it 90-1 of all other boolits combined. Best accuracy has been with noe 311-165 sized .310 and tumbled in LLA over 13.5grs of lil gun(1690fps) sub-moa from a 10" AR pistol. Doesn't feed well enough for everyday use though.

  5. #5
    Boolit Master MGySgt's Avatar
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    Thank you for your responses. Gives me a starting point.

    Finally got a chance to shoot this thing. - Anyone that wants to shoot a rifle and may be recoil sensitive can shoot these. I have an in-expensive tactical scope that I put on it. Not really happy with the accuracy - probably the scope is too busy. I will swap it off before I start load development.

    I have a number of the RCBS 165GC cast - with a number of them sized and lubed also. That is where I am going to start only because I have them.

    I have the Lee 312-155 also, thought I had some cast up but can't find them. Time to fire up the pot and get some cast. I just need to find the correct top punch for it. I have it written down someplace - just need to find it again.

    I was hoping that some one would come through with a load with 2400. I have shot it in the 5.56 AR platform, but it would not cycle, that is it would eject but not pickup the next round.
    Big Bore = 45+

  6. #6
    Boolit Master
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    Quote Originally Posted by MGySgt View Post
    I have the Lee 312-155 also, thought I had some cast up but can't find them. Time to fire up the pot and get some cast. I just need to find the correct top punch for it. I have it written down someplace - just need to find it again.
    467

    http://www.castpics.net/subsite/TopPunches/Lee.html

    Quote Originally Posted by MGySgt View Post
    I was hoping that some one would come through with a load with 2400. I have shot it in the 5.56 AR platform, but it would not cycle, that is it would eject but not pickup the next round.
    2400 is a great powder and does well in a bolt gun but as you discovered it is too fast to provide enough gas volume for reliable functioning.

  7. #7
    Boolit Master MGySgt's Avatar
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    Thank you Jailer.
    Big Bore = 45+

  8. #8
    Boolit Master
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    My 300 BLK is accurate with a wide variety of boolits. My favorite is the Lee 312-160, which is a TL mold. I have two so I can cast them fast. Has to be loaded to about 1.985 (if memory serves) or it won't chamber. It also likes the Lee 309-170 a lot. Both these rounds cycle the action of my carbine with fairly low loads (16 grains #7). The heavies are a little less fun for me 'cause they're harder to get to cycle. I have the Lee 309-230-5R. Shoots good, but haven't cycled it yet. You can put a gas check on the 230 if you like. It squeezes right on to the boat tail like it was made for it. Fun gun.

  9. #9
    Boolit Master MGySgt's Avatar
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    Just got my dies yesterday - and will start working on a load for the RCBS 165Gr GC Sil. Suppose to be warmer were in the next few days so I can go to the casting shed to cast up some of the Lee's.

    Report will come after the initial tests
    Big Bore = 45+

  10. #10
    Boolit Grand Master
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    If somebody has a proven 300 BO load using 4759 for a supersonic with any bullet weight I would love to hear it. In these tough powder days I have about 10# of it left from previous endeavors. Also, does anyone have a good supersonic load using Accurate #9? (I know it's a stretch, but I've got a bunch of that, and I know it worked in some other relatively small rifle cases.

    TIA ~ Froggie

    PS Is anyone using either the Ideal 311359 GC bullet designed for the M1 Carbine or the 3118 PB designed for the 32-20 to make a round for the 300 BO? Can you get enough pressure behind one of them to reliably operate the AR mechanicals?
    Last edited by Green Frog; 01-09-2014 at 10:57 AM. Reason: Add PS
    "It aint easy being green!"

  11. #11
    Boolit Master
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    Im interested in any RCBS 165 sil data for the 300 blk
    I have shot the 180g sil and 1680 and had 95% full function with start up loads on a brand new rifle (less than 50 rounds total through it)
    have some 165 sil loaded up for testing but it is so cold out, I dont want to go to the range to have frozen lube problems
    also have problem with hands so after shoveling snow can't feel trigger finger

    not sure on accuracy as was using a red dot (less than 2-1/2 5 shot groups at 50) with red dot at max -->now changed

    First loads were on the light side/ loaded a bit long and gave me a dirty action----> fail to feed (hang up on ramp)

    1/8 wilson 16" barrel

  12. #12
    Boolit Grand Master
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    How about the Lyman 311410 bullet (PB 130 gr) designed for the M1 Carbine? I just found that design on the I-net and it looks promising, based on what I have already read... :coffee com

    Froggie
    "It aint easy being green!"

  13. #13
    Boolit Mold
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    Quote Originally Posted by Green Frog View Post
    Also, does anyone have a good supersonic load using Accurate #9? (I know it's a stretch, but I've got a bunch of that, and I know it worked in some other relatively small rifle cases.

    TIA ~ Froggie
    Accurate #9 works great for 300 BLK supersonic loads.
    15.5 grains under a 110 grain bullet is a safe place to start.

  14. #14
    Boolit Grand Master
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    Quote Originally Posted by Dr.Phil View Post
    Accurate #9 works great for 300 BLK supersonic loads.
    15.5 grains under a 110 grain bullet is a safe place to start.
    Cool, Dr Phil! Many thanks. Sounds like just what I need. That 12+ lb of it I bought will go very well and last a long time. Now to get my Mihec mould in that weight to appear...

    Froggie
    "It aint easy being green!"

  15. #15
    Boolit Mold
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    Quote Originally Posted by Green Frog View Post
    Cool, Dr Phil! Many thanks. Sounds like just what I need. That 12+ lb of it I bought will go very well and last a long time. Now to get my Mihec mould in that weight to appear...

    Froggie
    No problem...
    FYI, N110 is by far the best powder for supersonic 300 BLK loads.
    Super clean, very accurate and close to 100% case fill.
    The AA#9 works well, but the case fill is only about 75% which can lead to consistency issues.
    It is possible to over charge the 300 BLK case with AA#9 to the point where I would be concerned about case failure.
    Have fun, but be careful...

  16. #16
    Boolit Master MGySgt's Avatar
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    The RCBS 165 gr GC Sil will not work in my 300 AAC Blackout - will not chamber all the way. The front of the nose is too large and jams into the rifling.

    Had a rough time getting the round out of the chamber.

    My upper is a S&W M&P 300 Wisper/AAC Blackout in 1-7.5 twist.

    Need to cast some of the Lee's 312 155. Now that the weather is a little warmer I can go to the casting shed. I really need to make a chamber casting of mine and my son's to see just what we have here.
    Big Bore = 45+

  17. #17
    Boolit Master MGySgt's Avatar
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    N110? Is that the same as H110 and Win 296?
    Big Bore = 45+

  18. #18
    Boolit Master on Heavens Range
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    NO! ... felix

    N110 is associated with 2400, WW820 (faster lots), AA9. ... felix
    felix

  19. #19
    Boolit Master mtnman31's Avatar
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    Quote Originally Posted by MGySgt View Post
    N110? Is that the same as H110 and Win 296?
    No, not the same. N110 is faster burning than H110/W296.

  20. #20
    Boolit Master MGySgt's Avatar
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    That is what I thought - Just wanted to be sure.

    Thank you Felix and Mtnman31.

    Don't understand Dr. Phil's statement that N110 is about perfect for the 300 where as 2400 won't cycle it..
    Confusing as usual!
    Big Bore = 45+

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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