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Discussion Starter · #1 ·
Ive bent a few mp5 flats both lsc and sw and all of them passed the carrier drop test nicely. I bent my 93 sw flat the same way i did the mp5's and the carrier is really tight seems like the part of the flat in the center where its flat the crease never rounded fully and the carroer is getting hung up on it. Anyone else run into this problem?
 

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no personal experience but I wonder if the lack of a properly stamped top rib might be to blame? How have you run any layout dye inside the receiver to attempt to see exactly where it's dragging/rubbing? Is the flat already welded up tight?
 

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Discussion Starter · #3 ·
Its not welded up yet. I just held it together withh a bolt through the mag hole and rear grip push pin hole to see where i was at. No need for lay out fluid you can see where it hits. I should of took pictures i left for work this morning and wont be back until the weekend. I dont think it has anything to do with the top rib. Maybe the spacing on the rails on my jig is to big and not flattening the material for the cocking the way it should. You can see two lines of raised metal about 45 degrees up from centerline of the cocking rail. Hope this makes sense kinda difficult to explain without pics
 

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SW flats will make a good receiver as long as you do your part. The top rib is one of those operations that occur when the flat is rolled. LSC 9mm flats are more desirable because they've included the top rib and radiused the curve onto their flat.

How did you roll your flat? Did you cut off the tabs on your 223 flat prior to rolling or did you leave them on and rolled? The reason I ask is the tabs will cause the radius to have two have two pressure points. I cut off the tabs then roll. Your flat should be lined up straight as possible, then welded together. You can do the straightening at this point, don't try to straighten your flat until it is welded together. You will need a backing bar and a die/jig to get the correct radius for the bolt carrier to fit.

9mm builds are a little more forgiving for the limited home builder because the flats are smaller and do not require as much forcde to straighten. The bolt carrier dimensions are smaller so a slightly crooked receiver radius is bearable. The .223 flats require a little more finess and tooling to get right.
 

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Discussion Starter · #5 ·
SW flats will make a good receiver as long as you do your part. The top rib is one of those operations that occur when the flat is rolled. LSC 9mm flats are more desirable because they've included the top rib and radiused the curve onto their flat.

How did you roll your flat? Did you cut off the tabs on your 223 flat prior to rolling or did you leave them on and rolled? The reason I ask is the tabs will cause the radius to have two have two pressure points. I cut off the tabs then roll. Your flat should be lined up straight as possible, then welded together. You can do the straightening at this point, don't try to straighten your flat until it is welded together. You will need a backing bar and a die/jig to get the correct radius for the bolt carrier to fit.

9mm builds are a little more forgiving for the limited home builder because the flats are smaller and do not require as much forcde to straighten. The bolt carrier dimensions are smaller so a slightly crooked receiver radius is bearable. The .223 flats require a little more finess and tooling to get right.
I left the tabs on. I was sitting here thinking that might be part of my problem. I put a 1/4 inch cut in each side of the tab so there was not as much connection to the main flat body in hopes it would form rounder. but i used the tabs to attach the flat to the 20mm rod with a bolt. Im thinking now the solid attachment made the material bind and not form correctly as i started pressing. So you dont use dowels or anything? Just center with calipers and go?
 

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.790"-.800"
 
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