View Full Version : Thin wall on lower
ncshooter18
01-18-16, 10:30
Got a new lower and the left FCG pocket wall looks thin. Is this within spec? Also noticed the hole where the RE threads in is uneven causing the endplate to look off center.
http://i280.photobucket.com/albums/kk179/7lf10/3EDA72C0-0816-451A-B1BA-534FDDE92E3B_zpsja7ko2kb.jpg (http://s280.photobucket.com/user/7lf10/media/3EDA72C0-0816-451A-B1BA-534FDDE92E3B_zpsja7ko2kb.jpg.html)
http://i280.photobucket.com/albums/kk179/7lf10/8E22524D-A1E0-444B-8A65-968C31AC716C_zpsv50uevth.jpg (http://s280.photobucket.com/user/7lf10/media/8E22524D-A1E0-444B-8A65-968C31AC716C_zpsv50uevth.jpg.html)
http://i280.photobucket.com/albums/kk179/7lf10/AC56303C-DA2A-4CD0-BC8B-FC06B176D1E6_zpsp332mnw7.jpg (http://s280.photobucket.com/user/7lf10/media/AC56303C-DA2A-4CD0-BC8B-FC06B176D1E6_zpsp332mnw7.jpg.html)
I don't know what the spec is off hand but I measured a Colt & BCM lower & they measured 0.090" & 0.084" respectively. My Colt's right side is wider, like yours.
ETA- I measured my Colt & the OA width is 0.885" & the pocket is 0.695".
ncshooter18
01-18-16, 18:06
It is an Aero lower. The left is around .075 and the right side around .090.
Only thing I see on the print in front of me is the inside width is .690"
I do not see any external dimension or width of the walls dimension, but will keep looking.
I have two Anderson lowers.
First lower inside is .690"
Left wall is .097"
Right wall is .100"
Second lower inside is .688"
Left wall is .094"
Right wall is .092"
Clarence
I'm surprised they don't group the forgings better than that.
Only thing I see on the print in front of me is the inside width is .690"
I do not see any external dimension or width of the walls dimension, but will keep looking.
I have two Anderson lowers.
First lower inside is .690"
Left wall is .097"
Right wall is .100"
Second lower inside is .688"
Left wall is .094"
Right wall is .092"
Clarence
The pocket is .690" wide.
The right inside wall of the pocket is supposed to be .095 +/- .003" from the inside surface of the right front lug.
The inside surface of the right front lug is supposed to be .251 +/- .002" from the center-line of the forging.
So, the pocket should be centered on the forging to around +/- .005"
The pocket also should be parallel to the center-line of the forging to .020" over 10 inches.
The forging should be .87 +/- .010 wide in that area.
That doesn't look to be a forging issue but a set-up issue.
It is an Aero lower. The left is around .075 and the right side around .090.
I have an aero with the same thing...measured.864...way too thin on the left side. My bushy measured .884. I emailed aero and they wanted pics but have not heard back
I noticed my Aero is pretty different from my MEGA and LMT. One wall is thicker than the other and the left wall is pretty thin.
Left to Right: MEGA, LMT, Aero
https://40.media.tumblr.com/1c12584f1c455c191d9951d595442e00/tumblr_o0ttiqKOqz1ux6c75o2_1280.jpg
That's the way mine is...causes safety selector to stick too far out on the left compared to my other lowers.
I have the same problem with my Aero lower. Just got it about a month ago.
Left side 0.078"
Right side 0.094"
I hope this is not an issue in the short term like affecting function or long term like the FCG holes ovaling. I was looking to use this lower for an SBR.
wolf_walker
01-21-16, 15:36
There isn't really a spec for external dems exactly that I've seen, it's based on a centerline measurement
and my conclusion is that how it comes out has to do with how sloppy the casting is and/or how good the
initial centering is done on the first cuts. Within reason, it'll not matter other than aesthetically.
I haven't seen a brand of lower yet that there was not an example somewhere of them being visually
"off center" to one degree or another. As long as the centerline is consistent and the inner cuts are in spec
for width and depth and to that centerline, it'll work. If one was cutting a raw lower and used the side wall
width as a basis for the center line(of the fcg pocket), then cut the buffertube hole based on that centerline, that hole could very
well be off. Maybe they center on the
buffertube hole and then cut the rest based on it, I've never done one from scratch like that. It's not an uncommon
thing though, don't sweat it. You can find machine drawings online and measure most of the cuts in a lower
yourself and see how far off they are if at all, the specs are fairly generous for that sorta thing. It's why we can get
away cutting 80%'s at home.
There isn't really a spec for external dems exactly that I've seen...
There is a forging drawing, the pertinent dimension was noted.
The thinnest a wall can be according to the print is .00775".
If your thinnest wall is .078", or more, you should not have a problem....
To the guy that posted his thin wall was .075", I wouldn't worry to much about it, .003", less than the thickness of a piece of paper, isn't going to cause the thing to fall apart.
wolf_walker
01-21-16, 18:17
There is a forging drawing, the pertinent dimension was noted.
The thinnest a wall can be according to the print is .00775".
If your thinnest wall is .078", or more, you should not have a problem....
To the guy that posted his thin wall was .075", I wouldn't worry to much about it, .003", less than the thickness of a piece of paper, isn't going to cause the thing to fall apart.
Cool, I don't think either of the diagrams I have show external dimensions. Got a link handy?
I have a drawing of the forging, but it belongs to someone else, I won't post it without permission.
StainlessSlide
01-21-16, 22:10
Mine is .085 left, .095 right, also an Aero bought in the last few months.
Maybe the forging is fixtured resting on the left side, and dirt or chips can get into the fixture, moving it to its right? Searching around, most fcg walls seems to be thicker on the right (but the difference is usually less than the measurements of the Aeros in this thread).
gesundheit
01-24-16, 20:24
Mine is .085 left, .095 right, also an Aero bought in the last few months.
Maybe the forging is fixtured resting on the left side,
Negative on above. The machining is what determines the left and right wall dimensions. If it is a little bit off center, one of the walls will be thinner than the other as has been the case with many of folks here. Forging a lower only creates the lower but does not influence how the FC cavity is milled out.
Negative on above. The machining is what determines the left and right wall dimensions. If it is a little bit off center, one of the walls will be thinner than the other as has been the case with many of folks here. Forging a lower only creates the lower but does not influence how the FC cavity is milled out.
If their fixture relies on one side or the other to index the forging, it will be off center if the outside measurements are different. That's why most companies will sort forgings of similar thicknesses together.
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