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Thread: Company changing the barrel on my new upper due to poor accuracy.

  1. #31
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    Some things that will cause patterns instead of groups-

    -Incorrect rifling twist for the bullet. If they somehow got a blank with a twist that's too slow, the bullets will not stabilize enough to group but just enough to keep them going point first

    -Tight/Loose spots in the bore. This problem is worse when the loose spot is at the muzzle

    -Bad chamber. If oversized, the the round will not position correctly or consistently

    -Bad crown. A crown that's rough or more importantly, not square to the bore can cause the bullet to tip as it exits the muzzle

    -Voodoo curse. Sometimes a barrel emerges that simply will not shoot no matter what is tried or counter ritual is used

  2. #32
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    Quote Originally Posted by Canonshooter View Post
    Is it my lousy eyesight or do some of those holes look a bit elongated?
    Looks that way to me too, hard to say with the dark picture, looks more like the target was shot at a bit of an angle than keyholing though, as the elongated holes are all horizontal.

  3. #33
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    All the targets were shot dead on and not at an angle.
    American by birth, southern by the grace of American Van Lines

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  4. #34
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    Looks like the results my two carbon fiber Bushmasters used to produce.

    Quote Originally Posted by ghostman1960 View Post

  5. #35
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    Quote Originally Posted by rob_s View Post
    You guys that are (were) clamoring to know the manufacturer are missing the point of the thread.

    As I read his post ghostman is looking to increase his knowledgebase by asking what would cause a 3' group at 50 yards (just to be clear, this an actual, measured, "group"? How many rounds? Pictures of the target?).

    GM, since you said it's a 14.5" we can assume pinned muzzle device as well? So there's no real way for you to inspect the crown? If so, I wonder if the drill press didn't get ahead of someone and the pin got inserted too deep (yes, I know the press should have a stop on it to prevent this) or the crown somehow got damaged in the process.

    Just chalk it up to chaos theory, or so I'm told.


    Well as I said I think "they" got some bad barrels. We could list off reasons why a gun could group 3' at 50 yards but its not going to help the OP figure out why his particular gun did what it did. None of us have access to it or likely the tools needed to figure it out.


    When you get a pattern of people with the same issue the most obvious answer is that they got a run of barrels that were not made correctly, and that wouldn't be identifiable unless they shot every single one for groups. Im sure they can source it back to a particular batch, and figure it out.

  6. #36
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    Quote Originally Posted by Canonshooter View Post
    That is my guess as well. Not wanting to "chance it" when I sent mine back to BCM I requested an upgrade to their SS410 16 inch mid length with LaRue rail. They accommodated my request in a very fair and reasonable fashion, so it all ended well for me. Kudos to BCM for taking care of me.
    Quote Originally Posted by Belmont31R View Post
    Well as I said I think "they" got some bad barrels. We could list off reasons why a gun could group 3' at 50 yards but its not going to help the OP figure out why his particular gun did what it did. None of us have access to it or likely the tools needed to figure it out.


    When you get a pattern of people with the same issue the most obvious answer is that they got a run of barrels that were not made correctly, and that wouldn't be identifiable unless they shot every single one for groups. Im sure they can source it back to a particular batch, and figure it out.

    Surely they function test-fire each upper for a few rounds. How hard is it to have a lower in a fixed rest and slap a laser on the flat top to see if it groups reasonably? Don't they have a 50yd tube or something?

    Also, how many bad barrels are you aware of? Two? 20?
    Last edited by VelveteenMole; 11-09-10 at 18:21.

  7. #37
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    Quote Originally Posted by Canonshooter View Post
    Photo removed so you don't have to go through life with your panties in a bunch.
    Just sick of watching people stroke their own....... egos. Especially when they don't contribute anything of value to the discussion other then the long strokes of their.... egos.
    Mobocracy is alive and well in America.*
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  8. #38
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    Quote Originally Posted by 500grains View Post
    Looks like the results my two carbon fiber Bushmasters used to produce.
    Have a patron at my bar that has a carbon fiber Bushmaster that has that very same problem. Guess it was a result of a loose barrel that took a pretty penny to fix with a local gun smith. The guy was ready to throw the gun out when we first talked, and I was surprised that he kept it the last time we talked. I do think it is fixable though if you still have the BM guns, don't know if it is worth it though.
    Mobocracy is alive and well in America.*
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    'All of my firearms have 4 military features, a barrel, a trigger, a hammer, and a stock."
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  9. #39
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    Same problem, same company, different shooter

    Two uppers from the same company with the same problem in a relatively short period of time. Probably no need to know the manufacturer.


    Quote Originally Posted by Canonshooter View Post
    Range Report – BCM 14.5” Mid Length

    As you will read here, I have a major issue with this new upper. My goal with this post is not to bash BCM (I’m sure they will make this right) but rather to share my experience and perhaps get some insight as to what the problem may be. I intend to contact BCM as soon as I get a “sanity check” here.

    The upper is a new 14.5” mid length with a PWS FSC556. It is using a complete new BCM bolt group (ordered separately, not with the upper), an Aimpoint M2L in a BOBRO mount and a Larue BUIS. The hand guards are Cav Arms.

    The lower is a Bushmaster which I have owned and used for many years. With my old BM M4gery upper and their pinned-on “Izzy” brake, the BM rifle held under 2 MOA all day, and was capable of 1.25” groups at 100 yards from the bench with a Trijicon Mini ACOG using XM193 ammo. Recent changes to the lower include a Geissele Super Semi-Automatic Trigger, an ambidextrous safety and Grant’s Magpul Industries CTR Carbine Stock MIL-Spec Package.

    For reference, here is a photo of the completed rifle in question;



    My first shots fired at the range this morning were to get the irons sighted in at 50 yards. Target used was NRA international 50 foot. With the Aimpoint off, I fired my first 3 round group, which was reasonably centered but low and scattered. I made adjustments until the group was generally in the center of the target, but was still scattered.

    Knowing that my eyes aren’t what they used to be, I turned on the Aimpoint and made my initial adjustments based on the iron sights. I fired four more 3-shot groups, which were generally centered on the target but still scattered.

    OK, maybe I need to bear down and the poor grouping is my fault. I had been shooting off a bench, under cover with the front of the rifle supported on sandbags. I hunkered down, supported the rear of the rifle too and fired some 5-shot groups, using only the Aimpoint. Once again, I was unable to get a grouping.

    At this point I wanted to eliminate the possibility that the Aimpoint was loose or the dot was not holding zero. I shot four more 5-shot groups, using both the irons and the Aimpoint. Since I am set up for absolute co-witness, I made a few small tweaks to my iron sights so that the dot sat perfectly on top of the front post. Using the small aperture and keeping an eye on the dot in relation to the irons, I shot more groups. The dot never moved in relation to the irons – the sight picture remained rock solid and the dot did not shift off the top of the front post. This IMO eliminated the possibilty of loose sights.

    Luckily, the guy I was with is a NRA high power shooter (goes to Camp Perry every year). He had his 20” NM AR with him and some 77 grain handloads that hold sub-MOA from his rifle. I tried a 5-shot string of those too, but the results were the nearly same and remained completely unacceptable – even for a “service grade” rifle.

    Below are the best 50 yard targets of the session using my best bench rest skills and a fully supported rifle. Bottom line, this upper cannot hold 12 MOA with quality ball ammo (XM193) or 10 MOA with handloads using match bullets.





    I will be contacting BCM and ask for a replacement – unless someone here can suggest something I’m missing. What could possibly be the cause for this upper to shoot so poorly?

    BTW, the rifle functioned flawlessly, and just as smooth as been reported by other users. The SSA trigger is awesome, breaks cleanly. The rifle functioned perfectly and is a joy to shoot...other than the unusable accuracy.

    Title edited for clarity.--gotm4

  10. #40
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    Quote Originally Posted by Mac5.56 View Post
    Just sick of watching people stroke their own....... egos. Especially when they don't contribute anything of value to the discussion other then the long strokes of their.... egos.

    Actually Sherlock, it had nothing to do with ego stroking. It was simply to help illustrate that BCM makes a quality product and stands behind them - enough so that they made me a happy camper and am willing to illustrate the outcome of my dealings with them with a photo of their product.

    Maybe you need to chill a bit?

    Edit - uh oh, seacoastnh just reposted another photo of mine. I got some cold ones in the frig that I'm willing to send your way to help you deal with it (if you'd like).
    Last edited by Canonshooter; 11-09-10 at 19:16.

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