Ground-up MP5 build

[THT]

I'm considering building an MP5 and found flat receivers ready to be bent and welded for under $100. Has anyone had any experience with these?

http://www.robertrtg.com/mp5flat.html

[NeoWeird]

I have personally held these flats and several other competitors flats at the same time to compare them. From what I remember these particular flats use less stamping steps than some of the better flats and the result is less defined edges in some areas as well as stress and stretch fractures in some of the sharper corners. The less defined edges are purely cosmetic and the fractures are an easy fix for someone with the ability and equipment to bring the receiver up from a flat to a full receiver; plus most flats, even H&K flats, will form similar fractures in the bending process.

The final conclusion I came to was that they would be more then adequate for a good build if someone was willing to take the extra time to address the minor issues they came with.

I have no first hand experience however with how they actually bend to actually comment on that aspect of a build invloving these flats.

[THT]

Are there any additional complications if building a 10mm rather than a 9mm?

[ar15barrels]

Are there any additional complications if building a 10mm rather than a 9mm?

Finding the parts kit.

[THT]

Finding the parts kit.

hkparts.net has them. Pricey, but they have them.

[bridgeport]

Building HK types is very doable, it just depends on your ability to execute the required skills.... bending and forming sheet metal, welding sheet metal and welding the various fittings to the sheet metal, while keeping everything straight and plumb. My advice would be, buy a couple of the less expensive
flats and give it a whirl, that way you can begin the learning curve and see
where exactly you stand with the whole thing. Of course you would need a parts set to play with and that will cost you. I would suggest staying with
9mm rather than .40 or 10.... as the parts and such are much easier to find,
and less expensive than the latter. Seriously though, it takes time to learn to dial in an HK type build if for no other reason than understanding how to negate the effect of heat distortion from the welding. Even a "good" weldor
would need to evaluate the relationships of the parts and take perhaps a few practice passes to hone the task specific skills pulled from the craftsmans quiver, if you get what I mean, and welding is just one of the many things you will want to get right.
We have likely all seen home builds of one type or another done poorly
whether it be a TC muzzleloader kit, or a first off AK flat build for a newbie,
and this is understandable.... its just that with an HK build there is more money at stake in the parts, and more mojo required to complete the build NICELY.
So as I said before, buy a couple of the RTG plates and work with them, do some research on the others as well as the building process, and have at it.

[HotRails]

Kinda OT here but Ive always had the feeling that the MP5 design has a lot less tolerance for imperfections than the AK design when building from a flat. Can anyone who has actually done one of these from a flat share their impressions?

[bridgeport]

Hotrails, you are not OT... you are correct. Communicating the kinks and details of building though, is not easily done. For example, if you were involved at some stage with a build, a specific part of that operation could be
detailed and explained, because you would have some background and process to work with, but just to straight out explain the kinks and details of a complete build would take a small book. I detailed some of the skills required in my previous post, and that as well as some research over at
HK pro forum... would make a good place to start. Let me also add this.... If you or anybody reading this post has an Idea to do a build, I strongly support
that, as learning and doing are the only way to gain knowledge and experience. I have always found myself more willing to help some one who has taken the risk to try and do something, as this shows a certain commitment to learning and sacrifice of both time and money to gain the required knowlege. Otherwise
you might as well just pay somebody to do a build for you, or just buy a finished rifle from a dealer. that being said, my experience is, Yes, it is doable,
it does take skill and knowledge, it is more difficult than an AK type build, and requires more attention to detail, like an AK, it requires an understanding of the applicable rules and regulations and procedures for doing a legal semi auto build here in the golden state, parts are relatively expensive (compared to an AK), but if you get it
all together right and it runs like it should, the accomplishment will speak for itself.

[HotRails]

Hotrails, you are not OT... you are correct. Communicating the kinks and details of building though, is not easily done. For example, if you were involved at some stage with a build, a specific part of that operation could be
detailed and explained, because you would have some background and process to work with, but just to straight out explain the kinks and details of a complete build would take a small book. I detailed some of the skills required in my previous post, and that as well as some research over at
HK pro forum... would make a good place to start. Let me also add this.... If you or anybody reading this post has an Idea to do a build, I strongly support
that, as learning and doing are the only way to gain knowledge and experience. I have always found myself more willing to help some one who has taken the risk to try and do something, as this shows a certain commitment to learning and sacrifice of both time and money to gain the required knowlege. Otherwise
you might as well just pay somebody to do a build for you, or just buy a finished rifle from a dealer. that being said, my experience is, Yes, it is doable,
it does take skill and knowledge, it is more difficult than an AK type build, and requires more attention to detail, like an AK, it requires an understanding of the applicable rules and regulations and procedures for doing a legal semi auto build here in the golden state, parts are relatively expensive (compared to an AK), but if you get it
all together right and it runs like it should, the accomplishment will speak for itself.

pm sent

[xibunkrlilkidsx]

does the same details go for a g3/hk91 build? i can do all the welding myself its the bending portion of it that gets me. is there a jig of some sort for all this? cuz i have access to large presses, yay for being a welding student and on the good side of the teachers.

[THT]

Yes, there are jigs to properly bend the flats. They're expensive so you'd want to see if there's anyone local who would let you borrow theirs.

[bridgeport]

Xibun, The metal is thicker with the G3 plate. The key is in keeping the bend
to correct "roundness" which can be achieved by bending around a rod of the correct size and the necking the crease or bottom of the upper round to achieve the right effect. If you have access to an original HK91, you can see perfectly (and measure) exactly what this should look like. The RTG G3 plates
require the rails to be flat formed for proper fit as the rails are round bottomed from the manufacturer. Think of the carrier as your internal guide/anvil, as this will act as your central reference point... fit should be close, movement should be free.

[HotRails]

Yes, there are jigs to properly bend the flats. They're expensive so you'd want to see if there's anyone local who would let you borrow theirs.

I had heard that there was one being passed around from person to person but it ultimately turned up missing. These builds are a lot less common than AK builds too. :\ Thats another reason why I really am begining to want to do one!

[sava6e]

so look there was a thread about cetme/g3/hk91 builds a lil while ago, im not goign to search for it, ive built a few of those, they take a lot of patience, time and understandign of general mechanics, things wont work smoothly, and you must figure out why, what is causing it, and is it the fault of the receiver, or can you mod the part to work. in general they look badass, def turns heads out at the range, but a lot of risk is involved, you may wind up with a firearm that doesnt work and then your tearing it apart or giving up and selling the parts off cheap just to get out of the predicament. there is a lot of information out there, i woudl advise research research and more research before you take the plunge, and tollerences for these id say is so little there might as well be none, nothing liek an ak type rifle

[bridgeport]

Modifications must also be made to the fire control group and housing, in order to do a legal semi auto build. That alone is enough to put some people off.