AR 15 pistol vs rifle builds

Discussion in 'AR 15 Forum' started by cannonman, Jul 6, 2020.

  1. cannonman

    cannonman Active Member

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    I want to build an AR 15 pistol for 5.56 and .300BO. I want to keep the .300BO to about 11" and have a pistol buffer tube. For the 5.56 - and I say that because I want to be able to shoot both the 5.56 and .223 - I want to keep this short, around 8" also with a pistol buffer tube. I'm told that the .300BO will have issues with three areas: Supersonic, Sub-sonic and Sub-sonic suppressed. For the 5.56 I hear that there may also be cycling issues dependent on length. In essence I would like to know which gas block for which build and which buffer. I know that JP has some nice stuff that's very adjustable but is also a pricy. Or am I even barking up the right tree?
     
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  2. howlnmad

    howlnmad Old Guy Doing Things Moderator Supporting Member

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    I'm thinking @zant would have the answer you are looking for.
     
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  3. zant

    zant Well-Known Member

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    10.5 for .300BO/minimum of 10.5 for 5.56....What is the purpose????Do you want a toy(8"5.56)to make fireballs or ????....Purpose determines everything-for a serious firearm that may save your life or just a loaner/something to have around??....Until you determine that,it's hard to recommend anything.......The same as suppression-do you want quiet or hearing safe?Big difference....Real short 5.56s don't run CONSISTENTLY nor have terminal ballistics......shooting 20rds and thinking it works is far different than shooting a 500rd course in 2 days....and it fails 1/2hr in.
     
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  4. cannonman

    cannonman Active Member

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    I want well working dependable HD pistols. I've been studying the problems with the loads for these and have a post in re-loading. I think the .300BO in 10.5" will have good results. I believe this is designed to be suppressed. I think the history of how this caliber came about should be portrayed. I made a jig to cut and form the .300 brass and have Hornady's projectiles. Powder I'm not sure of. The 5.56 is something that I'm not sure can be done well. I think it needs a very fast powder and believe a heavy projectile should be used. The projectile needs to get a decent amount of spin on it or who knows where it's going? It's the gas blocks and buffer and buffer spring that bothers me. Just playing around with parts is getting me nowhere. A subsonic 5.56 or .223 I think is a hyped up pellet gun? So the 5.56 is for a range toy. But I want to make a dependable range toy. Nothing better than showing off one of your custom builds that doesn't work. And thanks ZANT for spending some of your time with me. Oh the hearing, the supersonic speeds of the 5.56 can only be hearing safe. In my humble opinion. However the .300BO? I'd love to hear Sig's 300 integrated can. I was telling my Wife what a wonderful platform a .300 BO suppressed pistol would be for HD. A few years later and I see the military picking Sig for the thing. I think they might have stolen it from me! snicker....
     
  5. zant

    zant Well-Known Member

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    OK,for now just stick with the .300BO pistol----all pistol powder(NOT rifle powder 1680/4198/etc)will burn in 9.5 inches...so a 10.5 is perfect-the simplest way to go is a adjustable gas block(Superlative is the best,but 70-80$),buffer and spring -just use a carbine set-3.4oz buffer/carbine spring.That's the way my 10.5 is setup for suppressed-over 1500 flawlessly 247gr through it so far-just buy decent parts-cheap parts break and the really pricey stuff is fine if you have spare bucks but I've found good quality middle of road works fine.With the right handloaded subs,it's quiet-I shoot out window/door/off porch-my animals and humans in house don't hear anything but the steel ringing.......
    For supersonic .300,my 10.5 PDW uses a Geiselle G42 buffer and spring-cycles flawlessly.
    As long as all parts are specc'ed to work together,you'll have no problems with the .300BO pistol....short 5.56s under 10.3 have problems-that's why SOCOM has suppressors on MK12/18,besides being able to talk while shooting,the backpressure keeps the 10.3 running-take off the suppressor and it's unreliable.The best length for a 5.56 pistol is 11.5/12.5 which is the max optimum length for a carbine gas system......I have 1-12.5 with a mid-length that shoots real soft,just like my 14.5 rifle gas system-with a VG6,there is no rise in F/A.
    Hope this helps,the most important thing to me is 100% reliability-it's MY life:)
     
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  6. cannonman

    cannonman Active Member

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    Absolutely agree. Thanks. Great response. Data I can work with. Questions: What gas port for the .300BO? I think the cycling stops because the next round does not go fully into battery? Is this because:1. not enough gas to compress the buffer spring? 2.Or the buffer weight is too much? 3. both? And, is there a minimum buffer tube length? I like Strike Ind. product of a 5" tube. Do you think this would be too short for a .300BO? Last thanks ZANT! I really appreciate your time.
     
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  7. zant

    zant Well-Known Member

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    Don't mess around with the buffer tube,etc-those are for pistol caliber(5")-you're going to use a brace right???SBA3 or 4 with 5 position adjustment are the best....all the fancy, wire/collapsible/folding stocks look groovy/cost a lot-I would'nt use one but that's me.As I said before you have to look at the whole system-everything has to work smoothly.
    If you're having a short stroke problem now,where the bolt does'nt fully close-it's a gas or spring problem...a lot of buffer springs out there are the wrong length,wrong type spring,just cheap and hold up for a couple 100rds and start failing.....I don't mess with gas port size-I buy quality barrels that cost more, after talking with company about specs-quality barrels generally have been flow tested before production.....besides it's difficult to open up the gas block hole properly,so hogging out the barrel port does'nt help.
    So what exactly do you have now for a .300?
     
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  8. cannonman

    cannonman Active Member

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    IMG_0245.JPG
    I've put two AR platforms together. I'm one of those guys who believe that a .300 BO pistol, suppressed, sub-sonic .300BO is THE HD. Eh, I do believe that and would prefer that over a 12g. or bedside pistol. If you would, please tell me more about springs. I understand flat springs are better but have no idea why. JP puts out some neat stuff and for this build I really want something reliable. The two afore mentioned AR's were mostly parts I had around and then buying cheep barrels at gun shows. I know the sub-sonic suppressed build is completely different than a supersonic and I don't intend to mix the two. Once more, I appreciate your time!
     
  9. cannonman

    cannonman Active Member

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    BTW, the positional stock is pinned and neither one looks like this now. I keep taking them apart and re-building them. Great fun for a retired guy!
     
  10. zant

    zant Well-Known Member

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    A carbine buffer tube is 7.25"-how long are those?...Is the one on the right the one with cycling problems???You want carbine buffer tubes NOT shorter "pistol"(for handgun calibers)tubes.JP flat springs are nice,have them in my DMRs....all a subsonic .300 needs is a normal carbine spring-approx 10.5"-32-39 coils-this is where cheap parts go bad-wrong length/wrong coils,etc.
     
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  11. cannonman

    cannonman Active Member

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    When shopping for the buffer, spring and tube. It seems 5.5" works for the .300BO and 9mm? Their about $100 and claim mil spec so I think this should work? I really want to keep these as pistols and the buffer and barrel are the only items I can control. I'm told 10.5 for the .300 is the min. I should go? That's why I wonder about the gas block. Am I right that there are really about two choices? I can make these. Probably because there a block with a hole in it. I am a novice with my lathe and mill but I have made some custom parts for me and others.
     
  12. zant

    zant Well-Known Member

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    Read post#10...a carbine tube is used with a rifle round......a pistol tube is used with a handgun round....Post#5....yes 10.5 barrel-spend an hour on line looking for barrel sales,,last 1 I bought was a 225$ B.A. for 109$ discontinued,great deal,cheap money.
     
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  13. cannonman

    cannonman Active Member

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    Not familiar with B.A.? What twist I would guess is the easy question? Who's and what to look for is the harder? Type of riffling? Made of what? ect.? Thanks for putting up with ZANT. great source of info. How about a pic or two of some of your builds?
     
  14. zant

    zant Well-Known Member

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    Ballistic Advantage-1/7 for heavy cast.I only shoot cast bullets subsonic.....Have an upper I working on with a 6 1/2 twist for real heavies.
     
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  15. cannonman

    cannonman Active Member

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