AR10 vs AR15 762.39

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  • smokey

    2A TEACHER
    Jan 31, 2008
    31,412
    6.8 spc II is pretty hawt too though. I don't see a real advantage of going from a 5.56 to a .300 blk or 7.62x39 when you've got some great 77gr loads available. If you're going to move away from the standardized 5.56 AR, might as well bump up to a 6.8 spc II or 6.5 grendel. (unless it's a SBR/pistol...in which case the .300 blk is pretty solid)
     

    MikeTF

    Ultimate Member
    My son is selling his 7.62 x 39 AR. I have a 6.8 SPC II AR (to be legal for hunting in VA). I've been thinking of replacing it with a 300 blk.

    Why the change? Local topography. Where I live now I won't have to take a shot any further than 200 yards, and most likely 50 - 100 yards.

    I can also suppress a 300 BLK easily, making it a great hog gun (in other states, no feral hogs here).

    I love my 6.8, but it made more sense in a different location.

    That said, I'm still kind of on the fence.
     

    Blazin

    Ultimate Member
    Jan 13, 2008
    1,333
    Leonardtown, MD
    FWIW, 6.5 Grendel uses the 7.62x39 bolt size. They are based off the exact same case. Any issue you have w/ a x39 bolt you can have w/ a Grendel bolt (and conversely, any solution for the Grendel can be used to improve the x39.)

    I respectfully disagree. The Grendel has a LOT less case taper in it than the 7.62x39. Case taper increases bolt thrust.
     

    Sticky

    Beware of Dog
    MDS Supporter
    Mar 16, 2013
    4,501
    AA Co
    Many have hit on the "common" issues with 7.62x39 in an AR. GOOD Mags are the biggest hiccup. The new PSA AR that takes AK Mags solves that problem from what I see.

    Another problem is light strikes. Firing Pin Protrusion is critical for a reliable x39 AR.

    Another problem wth AR's in 7.62x39 is the headspace spec. American 7.62x39 chamberings often use a commercial spec, where the european spec uses a spec called CIP Gauges. This somewhat piggybacks on firing pin and reliability issues.

    I believe this is one of the issues some bolt action 7.62x39 rifles from CA and the SIG 556r Rifles had with them not igniting primers reliably.
    This begs a question, while we're on the subject.... Do the 'enhanced' firing pins help with this issue?

    Pretty sure I know the correct answer, use a proper gauge and diagnose it from there, but.... many tout the enhanced/extended firing pins to help resolve light strikes.. just asking based on your experience.
     

    mac1_131

    MSI Executive Member
    MDS Supporter
    Jan 31, 2009
    3,280
    Lots of more options in terms of reloading with the AR-10. Brass, components, etc. So unless you are happy shooting junk ammo I would save up a few hundred more for the AR-10.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,818
    I have an 16" Colt 7.62x39 and it shoots fine. The magazines can be problematic, but once you get them tweaked, they run pretty good.

    Recoil is noticeably more than the 5.56, but not unpleasant.

    Ballistics are closer to the .300 BO than they are to the .308, especially in the shorter barrels. If you envision ballistics similar to a .308, you will be disappointed.

    ^^^This^^^
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    This begs a question, while we're on the subject.... Do the 'enhanced' firing pins help with this issue?

    Pretty sure I know the correct answer, use a proper gauge and diagnose it from there, but.... many tout the enhanced/extended firing pins to help resolve light strikes.. just asking based on your experience.

    Yes they help. They often just have a thinner flange to allow more protrusion.

    You can cut the tail of a Bolt Head down and simulate the same thing though
     
    Last edited:

    Boss94

    Ultimate Member
    Feb 15, 2013
    6,945
    Yes they do help a ton. on 1 of my guns I tried to cut the tail down. but in that particular 1 the firing pin shoulder near the very front hit so it was no help without using the longer pin.
     

    FlatsFlite

    Active Member
    Aug 6, 2012
    691
    King George, VA
    6.5 Grendel resized and fire formed from 7.62x39 brass w 129 SST
    7.62x39 steel case 123FMJ
    .50 Beowulf 335 HP

    All "can" use the same bolt. And the bolts are pretty reliable these days, but you can't push them. They can only handle so much bolt thrust.

    ARs in 7.62x39, have been around long enough that the bugs have been worked out and most new mags run right off the shelf. Just do your home work before you buy and buy the right parts. I have a few thousand through mine without a single failure. But I rarely dump mag after mag either.

    7.62X39s are a hoot to shoot, but no where near a .308 in performance. Neither is the 6.5 Grendel, but it is a much better choice for long range compared to the x39. Anything under 600 yards is easy to hit, but. energy for hunting is good to about 450yds anything more is not ethical on medium sized game.
     

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    TheGunnyRet

    Ultimate Member
    Mar 27, 2014
    2,234
    Falling Waters, WV
    7.62x39 out to 350yds then drops like a rock.

    7.62x51 / NATO, effective out to 600 yards, 800 yards sweet spot, 1000 yards pushing it...and it all depends on Round/Barrel Length/Action etc...

    Again, purpose and platform, or platform and purpose, that will then determine your choice, JMO

    Then you have 6.5 Grendel. 6.8 SPC, 300 BLK, 6.5CreedMoor, 458 SOCOM, 375, 7mm 08, 338 Federal, 7.62x54mm, 300 WinMag, 270, 243, the list is endless...
     

    Sthomas229

    none
    MDS Supporter
    May 7, 2009
    6,659
    Laurel, MD
    Just got a PSA 7.62 upper from High Rock, took it to the range today and it performed flawlessly. Ran 3 full mags though it, using an ACS mag and a C products mag.

    I'm happy with it.
     

    Boss94

    Ultimate Member
    Feb 15, 2013
    6,945
    D and H tactical makes a 30 rd mag that works flawlessly so far in my friends M16 with a 7.62x39 upper . There very well made !!
     

    Sthomas229

    none
    MDS Supporter
    May 7, 2009
    6,659
    Laurel, MD
    Question for you guys, as I said my rifle fired flawlessly, but is there anything I should change in a lower to keep it running that way? Different buffer or spring?

    Thanks
     

    fidelity

    piled higher and deeper
    MDS Supporter
    Aug 15, 2012
    22,400
    Frederick County
    Just got a PSA 7.62 upper from High Rock, took it to the range today and it performed flawlessly. Ran 3 full mags though it, using an ACS mag and a C products mag.

    I'm happy with it.
    Question for you guys, as I said my rifle fired flawlessly, but is there anything I should change in a lower to keep it running that way? Different buffer or spring?

    Thanks

    Ha, I was looking at that same upper at High Rock when picking up ammo and ended up walking out with a KS-47.

    As per the buffer question, if the upper is set up for carbine length gas, I would imagine whatever is recommended for 300 BLK when running carbine length gas (many run pistol of course) should work. Although it's not in front of me, the KS-47 buffer looked like a T1 when I previously inspected.


    Sent from my Nexus 5X using Tapatalk
     

    Magnumite

    Ultimate Member
    Dec 17, 2007
    6,564
    Harford County, Maryland
    I had an LR-308, full size rifle. It is a big heavy gun, obnoxious to handle in some ways, but also fun to shoot, especially offhand. I am not recoil sensitive but the recoil pushes you around when shooting off the bench, doesn't hurt, just pushes you around and effects group size. Prone not too bad. The configuration, pistol grip AR, etc. of the rifle doesn't make it as shootable in the heavier caliber, the original AR size gun wins for me. Referencing accuracy and shootability in 308, I feel more anchored and do much better with a bolt gun, nonpistol grip type stock, and the standard AR. If I were to seek a 30 caliber in the AR pattern gun again it would be in 300 Blackout. An upper in 7.62x39 would be good to shoot inexpensive factory loaded ammo in it. As far as 'messing up' a precision barrel in 7.62x39 - wouldn't bother me, I wouldn't put a premium barrel on it, blaster grade would suffice. A 'good' upper in 300 would be in the safe and would come out to play occasionally. If things got to a SHTF situation, I'd choose the .223/5.56 caliber AR.

    The 855-A1 ammo is reported to have more effective close in effectiveness than the present 855/SS109. Not sure if civilians could ever purchase it but....
     

    Bart_man

    Clinging to gun&religion
    Jan 8, 2011
    2,310
    Hazzard County
    I had an LR-308, full size rifle. It is a big heavy gun, obnoxious to handle in some ways, but also fun to shoot, especially offhand. I am not recoil sensitive but the recoil pushes you around when shooting off the bench, doesn't hurt, just pushes you around and effects group size. Prone not too bad. The configuration, pistol grip AR, etc. of the rifle doesn't make it as shootable in the heavier caliber


    I'll just leave this here

    9b7ffbdb68d8ec4136833f58d61bfc95.jpg
     

    Major03

    Ultimate Member
    Let's go back to the original question...short answer is that 7.62X39 isn't a good choice for distance shooting.

    It would be helpful to know what you mean by "shootability" and what you're looking to do other than shoot long range. Do you mean flexibility to use the weapon for many uses or a light recoiling / light weight easy to control firearm? The .308 will have a lot more powder / power behind it than the 7.692x39 so if shootability means the ability to control the weapon in rapid fire / at self defense distances...the AR-10 will be a heavier weapon to handle and will have a lot more recoil and be harder to control. Probably not the best self defense choice.

    As others have already said, there really isn't a comparison between the two in regards to accuracy. .308 / 7.62 X 51 is by far superior if you want to do precision shooting or anything 600+ yards and offers you more flexibility and options for hunting and long range precision shooting. I know it's a bummer if you have a large stockpile of 7.62x39 to start buying a new caliber...but it'll be worth it in the long run. Reloading helps to keep the costs down, and is itself a fun hobby. You have a LOT more flexibility with the .308 in regards to what type of bullets you can shoot too, especially if you reload. There are a slew of choices, from match bullets with better ballistic coefficients to hunting bullets with better expansion characteristics.

    .300 AAC Blackout is a possible option for you, but as others have said, supersonic is pretty similar to the 7.62x 39. It moves a bit slower, but since the bullets typically have a better ballistic coefficient they tend to be more accurate and hit with higher energy at longer distances. What is really convenient is that you can use the same bolt, lower and mags as a standard AR...and just buy a different upper. That way you could essentially have two rifles for less than the cost of two, just swap out uppers between 5.56 and .300 AAC BO. The .300 BO also gives you the option of shooting sub-sonic rounds as well, which makes for a soft recoiling round that is easy on the shoulder for shooting within say 100-150 yds (and then it's dropping like a mortar round). If you ever invest in a suppressor, the sub-sonic .300 AAC BO is almost Hollywood quiet.

    So there it is...I think you need to think about the primary task you're trying to achieve? Long range accuracy? Controllable weapon with more knock down energy than a 5.56 for self defense? Flexibility in regards to the type of ammo you can shoot? Or the convenience of being able to have one type of ammo to buy that can feed more than one weapon?

    Depending on the answers, the AR-10 may or may not be the right tool for the job.
     

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