Spare AR-15

Discussion in 'AR-15 Discussion' started by bkt, Nov 8, 2010.

  1. bkt

    bkt New Member

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    It's not certain yet, but I think a friend is going to give me/sell cheap an AR-15.

    I'm soliciting suggestions on what to do with it. Getting a new upper is the obvious choice...but I'm not sure what to go with. Something that will really reach out there would be nice...been thinking about a .50 upper.

    What would you do and why?
     
  2. Dillinger

    Dillinger New Member

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    Ooooooh! I love projects! :D

    Which .50 upper are you thinking about?

    Do you plan on reloading? Or buying off the shelf?

    How far out do you want to reach and with what kind of power?
     

  3. freddy-b

    freddy-b New Member

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    I hope you are on my side when SHTF. :D
     
  4. Dillinger

    Dillinger New Member

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    As long as you are member here, you are good to go. :p
     
  5. bkt

    bkt New Member

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    Not sure yet. The Bohica and Watson's caught my eye. A bolt-action is fine...no need for mags. Looking at a BMG.

    Off the shelf.

    A couple hundred light-years would be nice, but I'll settle for 600-1000 yards.

    That brings glass into the equation, but we can wait on that for now.

    I'm not interested in 5.45x39 or 7.62x39. The 6.5 Grendel and 6.8 SPC might have potential. But if I'm gonna go broke on ammo, it might as well be something fargin' heavy...the .450 or .50 or in that neighborhood.

    So I guess the theme is "stupid long range with unquestionable knock-down power".

    No, I have no application for this. But why should that stop me?

    (Yes, freddy, I'm on your side.)
     
  6. Squirrel_Slayer

    Squirrel_Slayer New Member

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    I don't think the .50 Beowulf is a very good long range round, but I may be mistaken. I would consider some of the uppers in .300 OSSM or 6.5 Grendel.
     
  7. Dillinger

    Dillinger New Member

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    .50 BMG?? Oooooohhhhh, I just really have a problem with that application personally on that poor little aluminum lower. I know what everyone is saying, that it's been tested and you can replace the aluminum pins and blah, blah, blah....

    And the end of the day, you have two pins going through an all aluminum lower holding on to what is basically a platform for a small caliber missile being launched. Not a recipe that I would condone to those I love. :eek:

    Problem with the .450 and .50 caliber rounds is that they are not "long range" - they are medium range HEAVY knockdown types of rounds. And you are going to go broke buying ammo for them....

    EDIT: http://www.alexanderarms.com/beowulf_ballistics.pdf

    6.8 SPC has gone through a couple of changes, I was just reading some stuff on that today for Duner. The new rounds are pretty good, but once again they are more of a medium range round with the potential to go further, but it's more of a moonshot trajectory.

    Since the AR has a flat top receiver, that means you are going to need to add a scope with MASSIVE adjustments for elevation or add a new base with 20MOA built in which is going to pick your head up higher off the stock to be able to see through the glass.

    The Grendel is a great round for range, and it will hit with some power, but you are going to most likely be reloading to get what you want for performance and then you are back to going broke getting set up for it unless you know a guy....
     
    Last edited: Nov 8, 2010
  8. Squirrel_Slayer

    Squirrel_Slayer New Member

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    You are going to go broke loading for the Grendeal regardless because I think the only company that makes brass for that round at this point is Lapua, and we are talking over 100 bucks for a bag of fifty. My pops has an AR with a Grendel upper. Nice rifle, super accurate, has a recoil about like a 20 guage shot gun, but I wouldn't read into al the hype about this being such a great 1000 yard caliber. The accuracy really does kind of go into the crapper much past 600 yards. Even though balistically, they surpass the .308 at 600 yards in terms of speed and energy. Don't ask how this works, but I have seen it first hand and shot the rifle at these ranges. Olympic Arms does make some uppers with some wild calibers though, for a decent price, but you are going to have to hand load for them.
     
  9. orangello

    orangello New Member

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    Not for range, but for some oddness & fun: Did you see the .410 shotty uppers the other day? One of the vendors is offering them. I don't trust DI or particularly want an AR-platform, but one chambered for shotgun shells would be interesting (and probably quite funny on a group hunt). :D

    With some of those funky HD rounds for the "Judge", the .410 AR could probably be a pretty good home defense firearm as well.

    http://www.firearmstalk.com/forums/f53/safir-arms-410-ar-15-a2-upper-mag-469-99-a-34009/
     
    Last edited: Nov 8, 2010
  10. bkt

    bkt New Member

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    Well...I've been wondering about that. Sure, the two pins hold the upper to the lower in a vertical concern, but the recoil is directed mostly back with the back part of the upper against the stock/recoil plug portion of the lower.

    There's a helluva lot more stress. But it's not only on those two pins. Whether or not it's safe is another matter. Got any links providing material evidence that a BMG is a really bad idea for an AR? I'm willing to accept your word as gospel on this, but I'm curious is all.

    :D Understood. I'm not opposed to reloading, but I don't have the equipment for a Grendel yet. That can be fixed.
     
  11. Squirrel_Slayer

    Squirrel_Slayer New Member

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    ZEL Tactilite .416 Barret AR upper, goes for around 2,200.00. There you go. Nearly all of the force from the recoil goes into the buttstock and then your shoulder, I wouldn't think that the upper will chew through lowers. All the lower does on one of these big bore conversions is house the hammer and trigger mechanism along with the pistol grip. You nearly strip all of the regular guts out. No need for any magazine release garbage, can't use a magazine. And all of the buffer tube stuff comes out because the rifle is now a bolt action. Run a buffer tube and fill it with some lead to deaden some of the recoil and I think the lower should live just fine. In theory...
     
  12. bkt

    bkt New Member

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    Pricey but very cool. Thanks!
     
  13. Dillinger

    Dillinger New Member

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    bkt - I don't have any evidence to support my position to be flat out honest. :eek:

    We ordered one of the bolt action style uppers into the shop about 2 years ago. We fitted it to a stock A2 lower, with the fixed plastic stock and we sat it on the counter.

    At the same time we had a 33" long 1.5" diameter bull barrel benchrest .50BMG that was in for some fine tuning before B.R. Season sitting on a wood stock with a 4" wide tracking base that probably weighed in the 50# category.

    I looked at those two guns and just sat there for a minute thinking it through in my mind's eye.

    When that big bastard round gets touched off on the benchrest gun, the whole thing is going to slide backwards on the tracking sled to help ease the recoil. The action was this monster hex design and it was mated up to the wood stock with some serious action screws, along with the back of the receiver being deep inside the "meat" of that wood stock.

    And then we had a 30-something inch, monster steel upper with this big friggin tank style break on it mounted to an aluminum AR lower by two pins and that big assed action was sitting behind some plastic in the form of a stock.

    Now, what a lot folks don't know, or don't think about, is that there are several factors that happen when a round goes off.

    First is the initial back pressure from the explosion of the gunpowder. Everyone expects that.

    But almost immediately after that, there is a SERIOUS amount of torque that is applied in the form of that bullet being propelled at force into a set of lands and grooves that cause it to start rifling.

    That is the same type of torque as when you are drilling something and as you get to the end of the cut and the drill bit binds up and the drill wants to jump out of your hand and take your arm with it. :eek:

    That is not lateral, front to back, pressure or force. That is a twisting, turning, wanting to spin that upper receiver like a top, sort of pressure.

    And that pressure is being countered by a couple of pins that go through a piece of aluminum. :rolleyes::eek:

    Now, I am sure people a lot smarter than me probably graduated from MIT and looked at all these forces and compared specs and weights and measures and potential until the cows came home.

    But I personally just don't think that is a recipe that I would want to trust.

    Your Mileage WILL vary I am sure. This is just one lowly shop rats opinion.

    JD
     
  14. Squirrel_Slayer

    Squirrel_Slayer New Member

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    J.D.-I didn't even think of the torque the whole rifle undergoes when the bullet hits the rifling. What is your opinion on how this will effect the lower assembly if the bipod is mounted to the hand guard, and the operator fires the rifle without a death grip on the pistol grip. Wouldn't most of the torsional force be transferred to the hand guard?
     
  15. Dillinger

    Dillinger New Member

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    To be honest, I don't know. As I said, this is the opinion of one lowly little shop rat. I don't even have my apprentice card signed off in all categories yet... LOL :p

    In your example above, the 24" .416 barrel has a 1:11 twist, so the bullet will make a little over 2 complete revolutions in the barrel before it launches.

    These barrels are Right Hand, or clockwise, twist to the rifling. That means that pressure exerted on the barrel first is going to be fighting not to spin with the direction of the round.

    Extrapolate that out and you get the following:

    Barrel wants to spin, can't. Barrel is free floated to the receiver, so any pressure to any handguard is going to be negated until.... The Barrel tries to spin in the receiver & can't.

    At the point the torque is on the action, it can direct energy along the free float tube to the bipod, but it will sooner transfer torque to the lower receiver from the upper receiver where the energy is stored.

    I am no math whiz or a scientist. There is a gal here, Sebbie, who is though and I will PM her to weigh in on this issue.

    But in my mind, that pressure is going to reach those two pins in the aluminum faster than it is going to reach the bipod, and with more force as it will be closer to the source of the initial explosion.....
     
  16. Squirrel_Slayer

    Squirrel_Slayer New Member

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    That sounds to be very educated extrapalations to me. Used my word of the day right there. It's because of all of the reasons you have listed here, I think I would stay away from AR big bore conversions. I think if you want a .50BMG, you should go out and buy one. Having that empty mag well is dorky in my opinion. There are alot of other options out there for the AR15 platform that have quite a bit of punch and can cover some serious yardage.
     
  17. Dillinger

    Dillinger New Member

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    It's not high on my list of things to build, but down the list a ways there is this idea I have for a serious AR-10 that will chamber and shoot something like the .270 or .30-06 out of a magazine and be semi auto in nature.

    I know that COBB has their MCR, but it's more of an AR shape than a real AR platform.

    It's an idea I have rolling around that might have to have some R & D done on it in the next couple of years.

    A .30-06, magazine fed system that could achieve sub moa accuracy and still be broken down to fit in a backpack?? Now THAT would be a Battle Rifle. :D
     
  18. Squirrel_Slayer

    Squirrel_Slayer New Member

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    You can build a .300 WSSM AR15 and the ballistics are better than that of a .30-06, I think. I was looking into building one of those but then the little woman talked me into building her an AR, so my project got put on the back burner for a while.
     
  19. JonM

    JonM Moderator

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    i know this was posted in a different thread but i think it applies here as well. remember this is a semi and the action absorbs a great deal of the recoil forces. just from watching this and knowing how much a semi auto can damp a rounds recoil forces i wouldnt want to slap a 50 or any other bolt fed large bore round on a ar lower.

    [ame=http://www.youtube.com/watch?v=s5pVya7eask]YouTube - high-speed video of scope and barrel flexing on a 50BMG[/ame]
     
  20. bkt

    bkt New Member

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    I don't doubt for a minute that the AR platform for a BMG is under-engineered. It's arguably not the perfect tool for the job. Since I won't be flinging more than 100 (if that) rounds downrange, though, is it unsuitable?

    But I'm intrigued by Squirrel's suggestions, so the BMG might be moot anyway.