TM M4A1 vs TM M733: handguard/RIS issues

[Skruface]

Okey dokie folkies,

I have a TM M733 that I am trying to "update". :hammer:

I have swapped the upper reciever for an M4A1 flat-top, and have installed a G&G M733 1-piece outer barrel and Nitro top rail. The problem I am having is mounting the TM RIS I have.

It seems like the RIS is not long enough. The Delta ring does not hold the bottom "panel" of the RIS tight enough to stop it from falling off at the slightest touch of the D-ring. Or, maybe it's the collar for the handguard that's attached to the front sight that's too short to hold the panel in place.

I suspect that the problem is the outer barrel - I think that the front sight placement on the M733 barrel might be farther from the D-ring on the 733 than on the M4A1, creating the extra space that allows the bottom panel of the RIS to fall out. I also found (during my research) a comment that the M733 handguard was marginally longer than the M4A1, further supporting this theory. I do not have an M4 outer barrel on hand to compare/measure, though.

Does anyone have an outer barrel from both an M4A1 and an M733 that could measure the distance between the D-ring and the front sight for me? If they are different, the problem is solved. If they are the same, then the issue is the D-ring and/or front collar, and the problem is still solved.

Any help is appreciated.

[KEVORKIAN]

Thanks again for the age verification this weekend ! I'm glad that's been taken care of ! Anyways...I have a stock TM m733 but I'm not sure where exactly I should be measuring from.

[Skruface]

Hey Kevin.

Actually, I need the measurement for the M4 barrel....I can measure the M733 myself.

[ILLusion]

From my experience, Marui M4A1 outer barrels are slightly shorter than any other brand.

I don't have a Marui M4 o.b. on hand to measure, but I'm willing to bet that the collar to delta ring length is shorter for the M4A1 than it is for your M733

[trufret]

They are infact different. When I put a C8 body on my 733 i also changed out the barrel for a guarder m4 barrel and found that my 733 grips no longer fit. I had to pick up a pair of m4 length grips and a new grip cap on the front sight to attach them properly. unless your really good at modding i'd suggest finding an m4 length barrel for the ris or go the more expensive route and try and find an ris to fit a 733 barrel.

[ILLusion]

Another confirmation on the length differences:

I remember when I used to work with a lot of Guarder 2003 version steel outer barrels that had the "Vari-Length" feature. The vari-length design allowed the end of the outer barrel to slide in and out to adjust appropriately for various handguard lengths. At the time, it was designed around Tokyo Marui, but being as how Marui M4A1 outer barrels (and thus, grips) had shorter lengths, the Vari-length design was created to accomodate the trend at the time - which is, to allow installation of real steel parts such as handguards/RAS on to the guns by lengthening the outer barrel.