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M4 receiver dimensions

polycounter lvl 7
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joeriv polycounter lvl 7
Didn't really want to make a thread for this, but well, I am kinda stuck on this. (and I do feel silly not being able to figure this out).

Situation:

I am currently doing a blockout of a M4
the receivers are based off the bushmaster version, if that matters.
The handguard is a la rue tactical one.

I personally felt like my top & lower receiver were a bit to narrow, and after some googling for dimensions I found the one cad drawing that is floating around.

And the problem isn't in the handguard, I have matched that up with some pictures, and doing anything there to change the width of the rail results in a obvious scale issue.

(don't mind things outside of this, still have quite a bit to fix here and there, but those are easily solved)

But here I run into issues.

Comparison width
comp2j.jpg
comparisonm.jpg

1) The less wide original version, the rails of the receiver and the handguard match up nicely in terms of width, but the receiver itself should be to small.

2) The (what should be) the accurate version in terms of width.
Here the rails don't match up, the part of the receiver where the rail is on top is as wide as the widest point on the rails on the handguard.

large3u.jpg

So, doing anything to make the rails match up just brings the receiver back to the less wide version.

Replies

  • AlecMoody
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    AlecMoody ngon master
    A lot of the pictures you find online are going to be airsoft guns which tend to be a little fatter since they need to fit a motor into the grip. Also, unless you can verify the source of the cad model I wouldn't stress about matching dimensions. Even if it is accurate, a small error along the length of the model will translate into a large proportional difference for the width.

    To my eyes the thin version looks more correct (too thin in a few places) but it has been a few years since I have held a real one.
  • Oniram
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    Oniram polycounter lvl 17
    what i like to use as an indicator for size when it comes to these things is cylinders. instead of trying to guess and check on the width of things, ill use cylindrical shapes in references because from whatever angle, the radius wont change. so in your case.. here's what ive done before.

    gp-wp02_3_mark.jpg

    so if working from a side view reference (which id hope), just make some cylinders that fit within your bounds of the gun, and go off of those. hope it helps .
  • joeriv
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    joeriv polycounter lvl 7
    Okay thanks, I kinda had this idea in my head that maybe I misenterpreted some reference wrong, or I was overlooking something.

    But I guess it's just some smaller scale issues at different places coming together to create that issue.
    (actual receiver width a bit to wide here and there in the last version, translating to the top receiver, maybe the handguard being a bit to small or so), gonna check everyhting again.
  • JonathanLambert
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    JonathanLambert polycounter lvl 6
    I have a few of these laying around if you need a pic of a particular angle. Also, there are 3d solidworks and cad models floating around on the web that you could use for comparison.
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