OBR 7.62 barrel length.

Discussion in 'Black Rifle Forum' started by Travclem, Oct 10, 2012.


  1. MrMurphy

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    Greg Coker kept a MOA or better group at over 1k yards (I think it was like 1,108m?) with a 16" OBR.

    Others have done similarly. The gun can do it. The shooter typically, can not.

    That said, the 20" would be better shooting a 1k than the 16". However, if he's primarily going to be a hogslayer with the occasional long shots, anything under 600 isn't all that terribly hard with one if you have a clue (which Travclem seems to) and getting into the 800+ range with any rifle is a challenge.

    I've made repeated hits on a silhouette at 500m with a FN SCAR-H using crappy German ball ammo using a 3.5X TA11, and I wasn't even trying very hard. And the OBR is more accurate.......
     

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  2. Travclem

    Travclem Badass Member
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    Excellent! I think the 16" scored enough internetz to be my next rifle.


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  3. I doubt you'll have any complaints with a 16" OBR for your use, especially since you already have a 20" bolt gun.
     
  4. For myself, if it is a rifle that I am going to be humping around and hunting with I prefer shorter and lighter. As mentioned 16" is not sweat IMO out to 800 and 1K is not out of reach. And if it was primarily a hunting rig etc, I would probably opt for the lighter LaRue.

    For more long range work with good mobility I like 18"-19" as generally with most loads you will get a good burn out of 18". I have found that using 168gr FGMM from 26" cut down in 2" increments to 18" I am still dialing about the same dope to 500. Out to 1K I am dialing roughly 7 extra mins. Of course shooting ability and reading conditions is the key. I will stretch an 18" out to 1200 with good results also.
     
  5. Travclem

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    I'm not a fan of the PredatArs pencil barrel. I do like the PredatOBR but they don't exist yet. Good info on the barrel cutting test.


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  6. Travclem

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    Just placed my order.


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  7. 200fps changes the distance where the bullet goes trans-sonic.

    If I was going to reach out there, I'd get an 18" or a 20".
     
  8. Travclem

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    Do you know by how much it changes the distance? Really too late now, I ordered the 16".


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  9. Big Bird

    Big Bird NRA Life Member

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    If you take a standard Federal Gold Medal Match load with the 175 grain bullet you will see a muzzle velocity of around 2650 fps with a 20" barrel. Trim it back to 16" and you are looking at about 2450 (I disagree with the 100 fps loss per inch--its more like 50 fps in my experience).

    If you really want an eye opener look up the numbers for a Sierra 168 Gold Medal Match load and make the velocity adjustment for the shorter barrel and look where it goes sub-sonic. I can't tell you how many times I've seen people try to shoot that load at 1,000 yards with a short barrel gun and have been in the pits and have seen the bullets keyhole. I've had more than a few people here tell me I'm full of crap when I say this. But the ballistics calculator doesn't lie. Run the numbers for yourself. The 168 grain bullet is a crappy long range bullet for different reasons as well. But the retained velocity of this bullet out of a short barrel is pitiful.

    Run the above numbers through any ballistics calculator and you will see that the 20" barrel keeps the 175 grain supersonic well out to ~1100 yards while the 16" barrel will be dropping below the supersonic barrier at ~1,000 yards. That's at sea level.

    At 500 and beyond its the wind that gets you though and velocity matters in the wind. Its not the wind you can dope that gets you. (providing you can dope wind) Its the wind that you can't predict. I've personally used windage corrections at 1,000 yards that involved 30 quarter MOA clicks of applied windage--that's more than 7 feet of wind drift...:shocked: If a small gust catches you bullet it will blow it 9-10 inches at 1,000. Again, velocity matters--and I should rephrase that to; RETAINED velocity matters most. Muzzle velocity is largely irrelevant except that it contributes to retained velocity downrange.

    I'm unimpressed with people who tell me things like I've seen people make hits with a given platform at 1,000 yards etc. How many shots did it take to make a hit? Under what conditions? Known distance range? Sighters? Hell, if I throw enough lead downrange with my Colt Single Action I'm quite certain I can make hits at 500 yards...
     
    #29 Big Bird, Oct 13, 2012
    Last edited: Oct 13, 2012
  10. Paraphrashing what big bird wrote:

    Load development has a large role to play in where (along the flight path) a bullet will go into the subsonic speeds. BC of the projectile gets a vote here.

    Environmental (particularly the density altitude and wind conditions) can wreak havoc on your attempts... Ballistic solvers are all well and good, but the bullet really tells you what's going on.

    True the ballistic solver and then you have the no-crap answer as to what is happening between the internal and external ballistics of your rifle/bullet combo.
     
  11. Big Bird

    Big Bird NRA Life Member

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    Its also been my experience in working up 1,000 yard loads that standard deviation means a lot in terms of accuracy. You take a .308 load of most any flavor with a standard deviation of between 30 and 40 FPS and you have a built in 1-1.5 MOA dispersion factor at 1,000 yards added to the mechanical accuracy of the platform. That's 10-12" load to load vertical dispersion on the target based solely on small velocity changes. I always tried to get my long range loads down to under 10 FPS Standard Deviation.
     
  12. Travclem

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    Thread Resurrection.

    Still waiting on the rifle but the suppressor is in. I think I have decided on the NF F1 3.5-15x50 with the NP-RF1 reticle and an Aimpoint T1 in a LaRue offset mount. I was going to get the H58/H59 reticle but the premium that reticle commands is the same price as the T1.

    Anyone have any experience with this particular scope?
     
  13. Matthew Courtney

    Matthew Courtney Instructor #298

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    I ended up with an 18 inch LR .308 because that is the longest rifle that I can easily handle getting in and out of my vehicles. Getting tangled up while trying to deploy a rifle is potentially a bigger issue for me than being limited to 987.2 yards. For those who enjoy 1000+ yard competitions, choose what works best for you.
     
  14. Matthew Courtney

    Matthew Courtney Instructor #298

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    Would anybody else be interested in a .260 rem AR style rifle if one of the higher quality makers built one? That would be a sweet 18 inch rifle.
     
  15. Travclem

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    I think that would be really cool for long range. The .260 flat smokes the .308 at long ranges.
     
    #35 Travclem, Nov 30, 2012
    Last edited: Nov 30, 2012
  16. MrMurphy

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    Trav I've shot that scope, on an OBR, but only at 100m.
     
  17. Travclem

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    Seems to be everyone's experience. I guess I'll just have to cough up the $2300 and try it out.:supergrin:
     
  18. Big Bird

    Big Bird NRA Life Member

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    Maybe handloaded it does. But I don't see any off the shelf ammo that will do it. All the commercial ammo I've seen is mostly 300 yard deer loads.
     
  19. TravClem, I'm very jealous. I have an AR10T that sucks and is getting a new barrel as we speak. I have no idea how much money I spent on trips to the range, load development, shipping costs to armalite for 2 new barrels before I threw the towel in and acknowledged armalite sucked. I now am paying for a bartlein to be put on it and would have been so much better off with an OBR.

    During that process I bought the 5.56 OBR in 18" It is magnificent, test group was slightly over 1/2 minute. I can consistently shoot it the same and sometimes better.

    The lesson I learned was to buy quality once and be done with it. As a fellow Texan, I'm sure you will also share an extra source of pride looking at a silhouette of Texas on the side of your rifle. Good for you.
     
  20. We call it "Buy once, cry once."
     

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