I'm new here, don't know if this is the right place. Im sure this question has been asked before. But, Here goes: I work at a PD, with limited budget of course, we have some M16A1s and I'd like to make them more user friendly for our SWAT team. I'm looking at a DD 10.3 barrel, swap upper to flat top, carbine length gas tube, low pro gas block, swap to McFarland gas ring, carbine length buffer tube and spring and buffer, telescoping stock and a new flash suppressor. I'm planning on using the current BCG. What significant issues will I run in to? I'd appreciate your thoughts.

Negative on that one.

Why not just call DD and see if you can get a LE rate on a few complete MK18 uppers instead of piecing together a system?

That will probably eliminate a bunch of your potential issues right there.  You'll need to swap the buffer springs when you swap the tubes, and you should probably run H2 buffers.

I'd also suggest just getting complete uppers from someone, be it DD or another quality manufacturer like LMT.

Not sure I'd start with H2 buffers with 10.5" barrels.  Personally I'd recommend 11.5" barrels although they are less common nowadays.

11.5 uppers with new stock kits. Easy fix. If you buy them all at once you will probably get a decent deal.

I'm in the same situation, brother. My SO wouldn't pay for complete uppers (less BCG) nor barrels and individual parts to make them 11.5". We got a couple barrels and M4 stock kits from JT Distributing, but that was it per the budget. DD was my first choice as well.



We did finally just locate some M4 barrels through the 1033/RTD program. I couldn't find any shorter barrels on there. These were $20 each and we're getting 18 of them. Hopefully they will pass inspection.



I'm planning to use new carbine extractor springs.



Give me a shout if you need anything. I'm our armorer and Colt certified on the M16 family.

Buy complete mk18 or similar short barrel uppers, as mentioned Daniel defense is a good source. As for the lower receiver, take of the stock and replace with a telescoping carbine stock with mil spec buffer tube. Replace buffer spring with carbine length and get H1 buffers to use with the short barrel.

H1 buffers?  Really?  The DD MK18 uppers are overgassed as it is.  When I ran a H1 on my MK18 upper and M16 lower, I got crazy amounts of bolt bounce.  The H2 buffer corrected it.

Well its better than a carbine weight buffer and the H1 worked fine on my mk18. if you need heavier go for it but usually the thinking is start low and work up in weights.

Newer DD Mk18 barrels have significantly smaller gas ports.