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  1. #1
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    Thinking of building another upper...

    I am considering building another upper...

    Here is what I am thinking...but I would like input as needed particularly on the performance differences and maybe a few components. There are a few comments/questions thrown in here below.

    As you all know I am a CMT fanboy but more than that I like the upper/lower to match. No reason why, just OCD I guess.

    I have a 10.5 upper with and SLR solo lite m lok handguard on it. I am getting pretty familiar with it for the most part. I have an aimpoint T2 on that one.

    On my other rifle I have a 16" Rainier barrel and again a solo lite m lok handguard and that one runs a Vortex 1-4x Viper PST.

    I am thinking of getting a 12.5 AR performance barrel and another CMT upper reciever (not sure which one) and building a 12.5 upper that I can swap out from time to time.

    In the process of this I am thinking I could put my 1-4x on the 12.5" upper and get a longer optic for my 16" gun, particularly since it's used more for target shooting and trying to be a precision rig. Nothing is decided yet and I have a lot going on so it might have to be on hold for a bit but the plan is the plan.

    I am not sure what are my other options for a handguard that would look good. Don't get me wrong, I love SLR, and CMT but I am totally open to trying other things, especially ones that are proven. The only criteria is that it looks good matched with a CMT upper (since that is what my SBR'ed lower is), that it is M Lok, and that it be more quality/top end.

    A note on 'quality/top end'... I do not give a single rat's ass about and will not pay more for something because some internet hero put his autograph on it... what I am talking about is good bang for good buck. The balance in between those two matters to me. I am not really looking to make a fashion statement per se or to be the cool kid at the gun range (if I ever went to a gun range) but I do want quality that will pair well together with a CMT upper receiver.

    I would also think 10 or 11'' would be about right because I do want to have the suppressor fit. I understand those ARP 12.5 are cut slightly longer to accommodate a slightly longer rail.

    My other real question would be the performance difference between a 10.5 vs a 12.5. With my 10.5 and the T2 I can tag my small steel easily at 100 yards and that is what I intended when I built it. I wanted a 100y and in gun. The handling on it seems to be pretty awesome too. The only downside is with no suppressor on it that sucker is LOUD.

    The 12.5 vs the 10.5 though, what kind of performance difference could I expect? I am specifically talking about effective terminal ballistics here. Obviously it will generate more velocity and won't be nearly as picky for terminal ballistics at greater ranges... but what say you?

    The idea here is to have 3 entirely different set ups that are specific tools for their specific set up. The 12.5 upper would split the difference between the 10.5 and the 16"...
    Last edited by alamo5000; 5 March 2016 at 07:01.

  2. #2
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    On the 10.5 I am pretty much figuring on buying a bunch of Nosler 77gr bullets and have that be my go to for that one. Within 100 yards I most certainly would not want to get hit with it. Out to about 50 yards and it's a done deal as far as terminal ballistics go. Then I really love the T2. It's my first ever non cheap chinese knock off red dot... which is part of the reason I didn't do a lot of red dots before. But suffice it to say I have more than been schooled and have more than seen the light on the whole red dot thing now.

    But before I jump in to building a 12.5 upper I would like to know performance differences and based around terminal ballistics and so on and so forth THEN apply the optic of choice. It's just a guess that the 1-4 would do the trick, but my hunch is that would be right up the alley. Maybe.

    As far as the hand guard goes I am more or less willing to expand my horizons. If I need to I can get another SLR and be happy with it.

  3. #3
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    During some range testing a few years ago, we chrono'ed loads in several barrel lengths. Most of the work was done with 6.8, but we did do some 55 grain ball in the 5.56 - no heavy bullets on that trip for the 5.56. Every bullet reacts differently, but we found the 55 grainer's gained 68.75 FPS per inch going from 10.5 to 12.5, or 137.5 FPS for that two inch difference. You could run some ballistic calc's on that to see what the energy difference is, but not really sure how much help that would be since you will be using 77 grains. Wish I had more data for you, but those were real-world numbers in Florida about 236 feet above sea level. I know this isn't much help, but thought I would put it out, just in case. If you have chrono data from your 10" using the 77 grain bullets, you might extrapolate using plus 100 FPS (as a SWAG) to see what ball park you would be in.
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  4. #4
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    Quote Originally Posted by alamo5000 View Post
    As far as the hand guard goes I am more or less willing to expand my horizons. If I need to I can get another SLR and be happy with it.
    Strike Industries Megafins XL 11" may be worth looking at. I've personally never used their handguards. You seem to be a little bit aesthetically driven (as am I), and I think it would match up with a CMT upper fairly nicely. Just a thought!
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  5. #5
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    Out of a 10.5 with 55gr rounds I average around 2600fps. I think 77gr was 2200 fps or so. That was just an estimate based on my memory. At those barrel lengths though velocity gain won't be linear I don't think. I think the initial jump from 10.5 to 12.5 might yield larger net results. Basically though I want to think through the whole thing to figure out what I will end up with before I fork out the dough.

    When I started out I was torn between a 12.5 and a 10.5 so basically I just had to build the damn thing. The beauty of it though is now I can have both at a relatively minimal cost. At least that's what I keep telling myself

    If I decide to make the changes though I will also need a third optic because I don't want to be constantly trying to trade those out. That is assuming that I will put the 1-4 on a 12.5 upper.

    EDIT: I found some threads online that say with a 77gr bullet and a 12.5 barrel I would be between 2400-2500 fps. There is no guarantee that I would use 77gr bullets but I would give it a try. I would think the velocity range for a 75-77 grain load in a 12.5 is around that ballpark.
    Last edited by alamo5000; 5 March 2016 at 08:40.

  6. #6
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    Quote Originally Posted by EO3 View Post
    Strike Industries Megafins XL 11" may be worth looking at. I've personally never used their handguards. You seem to be a little bit aesthetically driven (as am I), and I think it would match up with a CMT upper fairly nicely. Just a thought!
    Yes and no. I learned a long time ago that if you buy quality stuff once it makes a difference up the road in a whole bunch of different scenarios.

    Plus I don't want my guns looking like crap

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    On a side note I would be totally open to trying different uppers and lower combos. I COULD have a house full of CMT but if I find something that piques my interest I could be persuaded to give it a try.

    I personally dislike uncertainty as many of you know. So once I get on something I like then I am pretty loyal to it.

    I don't like seeing all kinds of cool flashy stuff in magazines or whatever then you go buy one only to go 'meh'.

    I don't know... just call me particular. It doesn't matter what it is. Not just guns. It could be anything... going to a new 'hot place to eat dinner' or whatever... you go in sit down and the service sucks and the food is 'meh'... but you get charged fad pricing for it...

    Before I fork out money for big purchases I want to know that whatever it is or whoever it is walks the walk that they try to talk.

  8. #8
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    Based on the rough estimate of 2500 fps I plugged in some numbers to the hornady ballistics calculator for a 77gr load.

    From reading Molon's posts and other stuff if I was using Nosler 77gr they would still fragment at 250-300 yards.

    I would think I could make it hit out to 500 yards if I needed to as well. Based on those numbers that's only a 15moa hold over at 500 yards...

    This is what I though so I think that would be a good job for a 1-4x optic...unless there are other options.

  9. #9
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    A quality 12.5" barrel and some match ammo that it likes will get out to 500y with no problem (assuming you can see the target). And for what it's worth, your 10.5 should be able to exceed 200y easy all day long.

  10. #10
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    Quote Originally Posted by gatordev View Post
    A quality 12.5" barrel and some match ammo that it likes will get out to 500y with no problem (assuming you can see the target). And for what it's worth, your 10.5 should be able to exceed 200y easy all day long.
    Oh I am certain the 10.5 would have no problem getting out to 200 yards. With a 1x Aimpoint T2 I can score head shots on my little steel target... which equates to a 4"x4" square plate at 100 yards. Problem being no zoom or magnifier...but I did it back to back to back a few times so it's possible for sure. I hit that standing with no rest.

    On that though I didn't build the 10.5 for distance or to 'go out there'... it's my little blaster and that sucker is FUN to shoot! LOL

    I am deciding though if I want to build a 12.5 upper or not.

    I have 5.56/223 precision side kind of down fairly decent. I am sub moa with that thing and I can go out pretty far. With the 10.5 the handling and shooting is seriously fun and I can stand and shoot, shoot off handed or do any of that stuff a lot easier.

    Now I am not sure if I should or shouldn't try to build an upper that is half way in between those. I wonder if there is wisdom in doing that from a 'intended purpose' standpoint.

    The 12.5 wouldn't really be intended to go out that far but if I wanted to plink on steel plates at 500 yards its nice to know I could.

  11. #11
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    A suppressed precision 12.5 SBR with a 1-4x optic on it...hmmm... I wonder....

  12. #12
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    Quote Originally Posted by alamo5000 View Post
    \
    Now I am not sure if I should or shouldn't try to build an upper that is half way in between those. I wonder if there is wisdom in doing that from a 'intended purpose' standpoint.
    FWIW, I built a 12.5" gun with the intent purpose of it being an all-around competition and class gun that was light. As it would turn out, I haven't run it in a class yet, but I have run it repeatedly in a local 2-gun match I shoot where the courses of fire range from up close out to 200+ yards. I have been very happy with how the form factor has behaved and it has been a great shooter over the last 2 years since I built it. Really the only complaint I have is that with a can, I get some decent POI shift, but it's a government profile barrel, so that's not really unexpected...and besides, it's still minute of man with a RDS out to 200y.

  13. #13
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    If you're planning on running it with a dedicated suppressor, take a look at Sionics. They have an 11.5" bbl with a reduced gas port specifically for people who are only running a suppressed system.

  14. #14
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    I'm doing something similar: Razor 1-6 on suppressed 11.5" MCX.

    I say go for it. :)
    Will - Owner of Arisaka LLC - http://www.arisakadefense.com

  15. #15
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    Alamo....you make my head hurt sometimes and I thought I was bad/OCD on my thinking and such.. lol..good stuff though

    My question is besides a want, that 10.5" should do very well for what your wanting.. But if you need more reinforcement , sure build a 12.5..lol

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