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DPMS LR-308 Accuracy Questions

Discussion in 'Rifle Discussion' started by Joe Link, Aug 24, 2008.

  1. Joe Link

    Joe Link Portland, OR Well-Known Member Staff Member Lifetime Supporter 2015 Volunteer 2016 Volunteer

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    I'd like to get a couple AR's before the election (true concern or not, it's a great excuse!) and I'm thinking of picking up a DPMS LR-308 with the 24" barrel and hopefully building it for 1000+ yard stuff. I've read these rifles are sub-MOA out of the box, but I'm curious to know if they have the potential to have comparable accuracy to a bolt action rifle. I ask this because I've also been thinking of building a bolt action rifle and it'd be really nice if one of these could do it all, especially considering that for the price I could get an M4 and a cheap AK.
     
  2. sweetbeard

    sweetbeard Beavertown OreGUN! New Member

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    I must say unless your going Hi-Power Bolt action for 1k yards then Dpms lower and cheap AK
     
  3. fromotoc

    fromotoc Downtown Portland, OR Member

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    If accuracy is all your looking for, a bolt action is the way to go. If you are 1000 yards away from someone/animal/thing and taking shots, you have alot of time to work the action, and a couple 5 round magazine is all you need. For the price, I would go with a remington 700 or something in that realm. Fishermans sometimes has good deals on used bolt actions, they had a savage .300 WSM bolt for around $300 a month or two ago. I think that might have been new, but I am not sure.
     
  4. JumpWing

    JumpWing NK WA Member

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    In the world of accuracy, the best bolt action will out-perform the best semiauto.

    Having said that, the best semiautos are still extremely formidable (and accurate) weapons. People who choose them over bolt actions usually do so because of higher capacity and faster follow-up shots. The .308 is an excellent multipurpose round that does a pretty good job of balancing cost and performance. Make sure the rifle you get is chambered for 7.62 NATO, though, and not just .308. People mistakenly consider these two rounds to be interchangeable, but they have slightly different measurements (thousandths of an inch) and the 7.62 operates at a higher pressure level.

    People sometimes fire the 7.62 out of a rifle chambered for .308 and get away with it, but it's not recommended. No point in taking the risk.
     
  5. stitchclimber

    stitchclimber St. Louis Active Member

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    I thought the pressures were the other way around for the .308 and 7.62
     
  6. OFADAN

    OFADAN Brownsville, OR Well-Known Member

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    Joey,

    At the Academy we have both bolt guns and an LR308 for LR work. We currently have a custom LR308 on order from DPMS being built to military and LEO specs in order to work with those particular customers. By the way I just spoke with our rep at DPMS a couple weeks ago and he said they are 36,000 rifles behind production because of the election which translates into a 14 to 16 month backlog - the deepest they've ever seen. So you'd better get your name on the list if you want one anytime in the near future.

    Anyway, the LR308 is a capable of sub MOA as the one at OFA will shoot 3/8" groups at 100 yards all day long and we have used it out to 1200 yards along with bolt guns. If you want a pure target gun then a bolt is going to be inheritently more accurate but if you're looking for something a wee bit more tactical (holds more rounds, can be reloaded quicker, less manipulation, faster follow up shots, less muzzle signature due to flash sup.) then the LR308 with the right reloads and "know-how" is a might good choice. The LR308 we use easily rings the 6" steel at 600 to 800 yards under various conditions with ridiculus ease.

    It all depends upon your mission needs.

    A LR308 is going to set you back easily $1200 or more depending upon options without glass...whereas a good bolt will be $800 sans glass. Glass, mounts, trigger jobs, magazines, Duracoat, etc will start adding costs.

    The key is determine your mission objectives first and then select the best tool for the job contingent upon your budget and mission profile.
     
  7. PhysicsGuy

    PhysicsGuy Corvallis, OR Resident Science Nut

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    The perfect 1000 yard bolt gun would be a 700p in .308 or .300 win mag with a leupold mark 4, and a lot of ammo/reloads and practice! And a laser rangefinder would be a nice addition.
     
  8. PhysicsGuy

    PhysicsGuy Corvallis, OR Resident Science Nut

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  9. JumpWing

    JumpWing NK WA Member

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    No, the 7.62x51mm (also referred to as "7.62 NATO") operates at a higher pressure; the military 5.56mm is also higher than the .223 civilian version. Civilians sometimes get the short end of the stick with regard to weapons/ammo. Some people will argue that it makes no difference or that they've been "doing it for years with no problem," but, like I said, why risk it?
     
  10. FreedomAdvocate

    FreedomAdvocate Itasca, IL New Member

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    Actually this is incorrect. This is not the reason you should not fire 7.62 in a DPMS LR-308 barrel chambered for 308. I know this is an old thread but it is misleading to anyone who does a search of this topic on the web. According to SAAMI Specifications 7.62 NATO runs at 50000 PSI but 308 Winchester has a pressure of 62000 PSI. The reason why you should not fire 7.62 NATO in a DPMS LR-308 chambered for 308 is the length of some 7.62 NATO rounds are 0.005 mm longer than the length of the .308 round and DPMS designed the chamber of the 308 barrel to have less head space than the chamber of 7.62 NATO barrel in order to make it a tighter fit for better accuracy. With other manufacturers of semi auto 308 rifles like Armalite, there is no problem with firing 7.62 NATO out of a rifle chambered for 308. Also if you do some research on the M14, it is not safe to fire 308 Winchester in it because the higher pressure of the 308 round may cause an explosion inside the barrel ruining the rifle and causing injury and possibly death. By the way, 24 inch bull barrels that DPMS manufactures are not available in 7.62 NATO. The 7.62 NATO rounds are meant to be fired out of a rifle with a shorter barrel.
     
  11. madcratebuilder

    madcratebuilder Ardenwald, OR Well-Known Member

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    One of the most pernicious of “urban legends” is that there is a significant difference in the pressures between the 7.62x51mm NATO cartridge and the 308 Winchester cartridge. The misinformation indicates that using the commercial offering in a military weapon will visit death and destruction of biblical proportions upon the miscreant who would attempt such a thing.

    The real problem is the confusion between the old and the new methods of pressure testing. The old pressure testing method used for the 7.62 NATO cartridge started out life in the 1950s and is still published today in the US Army Technical Manuals. The figures are based on the copper crusher method in CUP, but are published as PSI. The new method is the piezoelectric strain gauge transducer method; it is the same technology used today to show an automobile’s oil pressure. The piezoelectric strain gauge transducer pressure method is a direct pressure reading based on an absolute standard, where the older copper crusher method a conversion based on a relative measure and a conversion chart. And this is why you see the difference in the pressure readings, but the older 52,000 CUP is equal to 62,000 PSI (piezoelectric transducer method). Today, these two methods are called CUP and PSI and the readings are different, but 52,000 CUP equals 62,000 PSI and both are the same pressure, similar to the way 60 MPH equals 100 KPH.

    The pressure difference between the two rounds is insignificant, the real problem is commercial ammunition has thinner cases that were not designed to shoot in military chambers BUT we do it all the time anyway and this why you see more case head separations on commercial cases fired in military chambers.

    The M118 special long range round is loaded to 52,000 CUP (all other U.S. 7.62mm are 50,000 CUP) which would be equal to the pressure levels of commercial ammunition, this means actually there is no pressure difference between the .308 and 7.62 NATO for the M118 cartridge. No accurate conversion between copper crusher and true pressure exists, but approximations can be made. In all the conversions outlined above, pressures are in thousands of PSI (KPSI). Expect errors of several KPSI, or about 15%, with such formulas. Many factors determine how much the indicated pressure reading from a crusher misses the true pressure, and the error varies among cartridges and even among different loads for one cartridge. The conversions might be accurate enough for many practical purposes. So, to sum everything up, the pressure difference between the 308 Winchester and the 7.62x51mm NATO is less than 2,000 PSI which is statistically insignificant.