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    • #24443
      VANN
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      Tax time is here and I’m going to build another 80% AR. The hard part is deciding what caliber to build it around. I’m planning on mainly using this rifle for 3 gun with a secondary use being a hunting rifle for my daughter. Shots will be limited to 100 yards for hunting use.

      I already have dies and brass for both, I also load for both just not for an AR, I load 7.62×39 for a custom Encore pistol barrel with a .308 bore, and I load the 300 BLK for a bolt action.

      Since I already load for both I’m pretty familiar with both rounds, I’m just trying to weigh out the PRO’S and CON’S of both rounds out of an AR platform. I seriously doubt that I’ll ever put a suppressor on it so subsonic loads are not an issue, but a big plus for the 300 BLK that really stands out is being able to convert all of my split neck 5.56 brass to a shorter round instead of recycling it. Other than possible feed issues with the 7.62×39, what other differences can y,all come up with as pro’s and con’s?

    • #24450
      Harter
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      Left to me I would choose the x39 . A few reasons are the ammo and brass availability and of course the range of bullet weights . I have an sks that’s closer to 8×39 than 7.62. I have shot 200gr cast to 1500 fps at magazine length and to 1800 single fed.

      I know you didn’t ask but I find that the 6.8 SPC is a better cartridge all around . Than both of the others . . I’m shooting mine at 2100 fps with a 278-124 NOE and getting very consistent sub 2 ” groups with a rifle that shoots 3″ with factory jacketed loads. 20-25 gr of nominal jacketed powder is doing the job . By mid may I expect to have pig damage pictures.

    • #24451
      VANN
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      Yes, I agree the 6.8 SPC is a great cartridge, but that would put me back to buying new brass that would probably be lost on a 3 gun range. That’s one of the reasons for trying to decide between the two .30 caliber rounds, that and I am already set up for casting and sizing .308 dia. bullets.

      I am open for suggestions on other rounds but I would like for them to be based on the 5.56×45 case so I can form them from my existing brass.
      I have put serious thought in to the 25/45 Sharps round, but once again that puts me into casting for another caliber. At least I’ll know my choices for my spare upper.

    • #24461
      Smoke4320
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      big plus for the 300 BLK that really stands out is being able to convert all of my split neck 5.56 brass to a shorter round instead of recycling it. Other than possible feed issues with the 7.62×39, what other differences can y,all come up with as pro’s and con’s?

      well you pretty much covered it for me ..Blackout all the way … you have a 223 so cases can be salvaged for it .. Range pickups of even purchasing once fired 223 are MUCH easier
      very little feed issues .. mags are the same .. I know you said Suppressors/subs are not a concern but that may change in the future .. why not build for the future .

    • #24490
      GhostHawk
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      Both!

      Like you I shoot both, unlike you both of mine are in single shot handi rifles.

      Each has advantages depending on application.

      I think the .300BO takes to suppressors better if that is a consideration.
      I think there are also more bullet options for .308 vs .310-311.

      I think the 7.62×39 has a lot more powder flexibility.
      .300BO is only going to cycle an AR well with 3-4 powders. I think the 7.62×39 can use a much wider range and still cycle.

      Brass was already mentioned, and it is a plus for the .300 BO. But it is also a cost to get setup to cut, trim, size, plus takes time.
      On the other side of the coin factory ammo for 7.62×39 is much cheaper across the board.
      For 6-7 dollars you can afford to load 20 rounds of tulammo, wolf, etc into mag and just let them rip.

      For me it would come down to what is this AR going to be used for?
      For hunting while both are better than the .223 (my opinion) the 7.62×39 has more case capacity, letting you use slower powder, still cycle, and probably better accuracy.

      If you are going to get into penitration, long range accuracy, be prepare to start splitting hairs.

      It is my experience that once you get down to that level that personal preference is going to weight heavier than the stats.

      In the long run I think either could be a good solution.

    • #24501
      Anonymous
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      the 300 Blackout is a great cartridge– fun to shoot
      in the great white north (Canada) surplus 7.62×39 is now getting up in price and the the only stuff you see on the ground/ trash is steel case so no reloading
      I have a 300 blk and my only concern in using it in compitions is will I be able to pick up my brass ??
      when i shot IPSC if i went to a club that did not let you pickup brass, I used brass on its last legs( no headstamp showing)

      If you do 300 blk you can also use the same mags for 223 for 7.62×39 you need totaly different mags

    • #24508
      Artful
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      I also own guns in both – but in the AR the 300 blackout wins – and if you don’t like it your only a barrel change from 223 – all other parts are the same.

      I miss the pre-clinton ban on 7.62c39 surplus imports from china and now ban on imports from Russia by Obama – of course I really miss the
      before ’86 ban on making your own machineguns under Reagan.

    • #24533
      seaboltm
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      I would say 300 Blackout. Brass is cheap and plentiful. With light bullets it is virtually identical to x39. With heavy subsonic bullets the powder capacity of the 300 seems optimum.

    • #24556
      VANN
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      I guess what makes me most apprehensive about the 300 BLK is the most ideal weight bullet for me to use is in the 125 grain area. The 7.62×39 is already there, how well do AR’S perform with the lite weights in the 300 BLK round? Most of what I have been shooting is a 31141 at 173 grains. I the longer throat going to hurt my accuracy?

    • #24561
      JPHolla
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      VANN;n2777 wrote: I guess what makes me most apprehensive about the 300 BLK is the most ideal weight bullet for me to use is in the 125 grain area. The 7.62×39 is already there, how well do AR’S perform with the lite weights in the 300 BLK round? Most of what I have been shooting is a 31141 at 173 grains. I the longer throat going to hurt my accuracy?

      AR’s work well with 125 grain bullets–that’s what the cartridge was designed for. It’s the heavy subsonic bullets that require more careful powder choice or an adjustable gas block. You also have to think about functioning through the action in addition to the throat and twist if you plan on shooting cast bullets. IIRC, some people have had good luck with 31141 and some haven’t. Seating depth can be critical to proper feeding, and that does not always align with the best seating depth for cast bullets.

    • #24598
      Artful
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      I just cast the Ed Harris 155 grainer from LEE, NOE, NEI and size .311 and am good to go in my 300/221.

    • #24624
      Larry Gibson
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      + another for the 300 BO in the AR. Cheap 7.62×39 brass and milsurp ammo is drying up very quickly or actually already has. Going to be lots of 5.56 brass around for years to come. Also the magazine and all other parts being the same for a 5.56 conversion on the AR is a real plus. The 7.62×39 is the superior cartridge in a bolt or single shot for hunting but not in the AR.

      Larry Gibson

    • #24627
      VANN
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      Well, I guess it’s settled then. 300 BLK it’ll be. I’ve got two billet 80% lowers. I keep thinking about a 9mm carbine build on the other one.

    • #24658
      rockrat
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      300BLK as good mags for the x39 in the ar platform are hard to come by.

    • #25235
      popper
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      7.62x40WT is designed for 125gr – don’t know how it does with cast – should be in the 2500 fps range so GC required. Same cost as good BO barrel. I shoot a 145gr. PB @ 2100, still room for more powder. Definitely in the 30-30 ballistics – good to 100 easy, 1/2 the cost.

    • #25271
      MTtimberline
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      VANN;n2649 wrote: brass that would probably be lost on a 3 gun range..

      This is the only pro I’d consider for the 7.62×39 in the application you are looking at. Everything else points to the .300 Blackout. That’s just my opinion though.

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