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How does a lower affect accuracy?

BAMAAKBAMAAK Senior MemberPosts: 4,484 Senior Member
I have a Ruger AR 556. It's pretty accurate out to 200 yds, the furthest I shoot. I also have a fairly cheap polymer lower. I swapped the Ruger upper onto the polymer lower for fun and could not hit squat. The trigger is actually a little lighter and the lower is tight, no play anywhere. What can affect the accuracy that much? Flexing plastic?

I was shooting well, was hitting 100 yds 6 or 7 times in a row with my 9mm carbine so I wasn't having a bad day.
"He only earns his freedom and his life Who takes them every day by storm."

-- Johann Wolfgang von Goethe, German writer and politician

Replies

  • timctimc Senior Member Posts: 6,684 Senior Member
    I would say flex I. The polymer lower that you don't have with the aluminum lower. Don't know what else it could be.
    timc - formerly known as timc on the last G&A forum and timc on the G&A forum before that and the G&A forum before that.....
    AKA: Former Founding Member
  • tennmiketennmike Senior Member Posts: 27,398 Senior Member
    One thing that can affect an AR as far as accuracy is the fit between the upper and lower receivers. If the fit is tight, the groups should be better. Loose fit between upper and lower lets upper receiver wobble around during the firing sequence from trigger pull to the bullet exiting the muzzle. I'd check the fit of the upper and polymer lower for wobblicity (wobblicity is a technical term for sloppy/loose fit :tooth:).
      I refuse to answer that question on the grounds that I don't know the answer”
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  • Diver43Diver43 Senior Member Posts: 10,922 Senior Member
    I actually had this conversation with a gentleman that builds ARs for a living.
    Yesterday I purchased a JP trigger for my AR and when installing it, the pin would not fit through the hammer. It was out of spec and he replaced it without hesitation. We discussed building a .300 Blackout for me.

    Anyways I asked about the lightweight polymer lowers. Without hesitation he said they are inaccurate and he doesn't build then anymore. We discussed the why nots and bottom line was that although technology has come a long way, there is enough flex in the lower that groups will open up from hardly noticeable to more than an inch at 100 yards. Just cant the consistency with plastic as you get with metal.
    Logistics cannot win a war, but its absence or inadequacy can cause defeat. FM100-5
  • bullsi1911bullsi1911 Moderator Posts: 11,155 Senior Member
    Plus, the trigger pack is in the lower. A cheaper trigger in the Poly lower will be harder to get good groups with.
    To make something simple is a thousand times more difficult than to make something complex.
    -Mikhail Kalashnikov
  • JasonMPDJasonMPD Senior Member Posts: 6,557 Senior Member
    Diver43 wrote: »
    I actually had this conversation with a gentleman that builds ARs for a living.
    Yesterday I purchased a JP trigger for my AR and when installing it, the pin would not fit through the hammer. It was out of spec and he replaced it without hesitation. We discussed building a .300 Blackout for me.

    Anyways I asked about the lightweight polymer lowers. Without hesitation he said they are inaccurate and he doesn't build then anymore. We discussed the why nots and bottom line was that although technology has come a long way, there is enough flex in the lower that groups will open up from hardly noticeable to more than an inch at 100 yards. Just cant the consistency with plastic as you get with metal.

    I'll add that an AR15 performs a butt load of mechanical functions during a cycling phase. A good portion of that occurs in the lower--the buffer and spring being a large component factor.

    Consider that during ignition, there is a tremendous amount of bolt thrust which inevitably sends a hyper-sonic (literally 20,000+ fps) shockwave through the system and some of than energy ends up in the buffer spring. If the lower isn't rigid and offers flex, all sorts of harmonic and unharmonic garbage can make the upper move.
    “There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves.” – Will Rogers
  • JeeperJeeper Senior Member Posts: 2,954 Senior Member
    Diver43 wrote: »
    I actually had this conversation with a gentleman that builds ARs for a living.
    Yesterday I purchased a JP trigger for my AR and when installing it, the pin would not fit through the hammer. It was out of spec and he replaced it without hesitation. We discussed building a .300 Blackout for me.

    Anyways I asked about the lightweight polymer lowers. Without hesitation he said they are inaccurate and he doesn't build then anymore. We discussed the why nots and bottom line was that although technology has come a long way, there is enough flex in the lower that groups will open up from hardly noticeable to more than an inch at 100 yards. Just cant the consistency with plastic as you get with metal.

    Bullhonky. I have a New Frontier lower that shoots dime sized groups, even with a sucky trigger.

    Maybe not all of them do, but mine does.


    Luis
    Wielding the Hammer of Thor first requires you to lift and carry the Hammer of Thor. - Bigslug
  • Diver43Diver43 Senior Member Posts: 10,922 Senior Member
    Jeeper wrote: »
    Bullhonky. I have a New Frontier lower that shoots dime sized groups, even with a sucky trigger.

    Maybe not all of them do, but mine does.


    Luis

    Great to hear another view point. I had thought about purchasing a polymer lower for another build when I felt like it.

    Seems like you got one of the good ones, that's for sure, guess that is where the part about hardly noticeable to more than an inch comes in. Guess it is a consistency issue or something. Heck I cant even shoot dimes size groups with the best of guns, so I would never notice.
    Logistics cannot win a war, but its absence or inadequacy can cause defeat. FM100-5
  • DoctorWhoDoctorWho Senior Member Posts: 9,496 Senior Member
    An analysis of grouping and extreme spread, stringing and other anomalies would prove most useful, I think weight has more to do than rigidity issues, the bolt carrier locks up internally the barrel, recoil is transmitted along a straight line into the buffer a and buffer spring and buffer tube assembly, more observation is required.
    Receiver waggle does not adversely affect accuracy.
    "There is some evil in all of us, Doctor, even you, the Valeyard is an amalgamation of the darker sides of your nature, somewhere between your twelfth and final incarnation, and I may say, you do not improve with age. Founding member of the G&A forum since 1996
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