Quoted:
M16A1 20" (lightweight profile) barrel with .625" FSB. You then have it cut down to ~13". Doing it correct is definitely not cheap. When I started my IDF project, no one offered a carbine length, .625" FSB, lightweight barrel assembly with the correct contour  (that could be cut down to the correct length). I went through a Noveske and DD barrel assembly before deciding to go with John Thomas to have it done correctly once and for all.

Here is my IDF build with the Noveske barrel. Note incorrect .750" OD gas block, and length.

https://lh3.googleusercontent.com/e1QSTjrao_IA7UUWOAnKdOmTLHG9n3iQt5oFeOkMh4gFFi_cq5znLG3FkzEtPS49EtGHZ_4ykkwivjyYz_PoINMDZNEtJtyBCxMQbSOLUI8StvpiMLml0Bibqv7smRY9gjqiNQMbK46R8ysjR338rbfMRtP5Lv9gYJ9fYXwbhiJhc-qum8BTTebXX-EXHcq7TFiDVysZvlNQUj25JvlZiMnyEXoFvImn6f-tUdRDUBTfdf1aOqOFUMcynvBRb4y-Y-mtqGjvfNOh1gT_e4CSOnUQ0U-4afKqR0pvFyOl-Ma_3_R9sdwqbYW78v0yMb72YDKPo4ck4SBP0rRdQQYIWu6euoJI6wvQmOT9MVFGLQT8iHURC94qZr87gyv5rCtD0ycMc8ROIPWEaMsof_1WST5Wbb0ILo_CJD2zx3uTR_wMBspEfEQSYXc88r4W1eBJxGgo-vu8HEchCTltsVveLIbDhrL7hFxae62SkyG0JxHX_Y5hNJ-kFQQa6eXEkh7VTWoIU9WAe1Koeyk18WkMR9hoMeoQzVLCv0gXd7PqXF7uSieyioJ-KSMXrnfruQmk22RzFQ=w1840-h1226-no

Is that carbine gas system or midlength? Did you end up SBRing the rifle?




Here is the same build after having John Thomas work on a M16A1 barrel that I sent him.


https://lh3.googleusercontent.com/TnjXZ3NeefbA3f9myav40ZnM15fnTWa2EgTnh5Sj-cPLCD4BwGeNHo77otpL5zq9cYCUQeJtX-vuJWaAOCr8_XqctDByR7hJTuTgUT1RlsfxlM3b-wnxSiQOHz2iKsRzFes8BFHmq-PleSLz-xaTjEGMyydw8S2hKUo-AjwhSHuKYEAv4SkldhRAOILzHP7KbKklNQmrk0SzlaajhxuX0hJxhufDmP_Ni6-Bq-iVJfa_evDK-SIFTqw4_uOiVvVSKYI6sgYo-MIXEUhMGqOoj32JBP0GOdmJm6va-lq5QQUNHSWQhezOZSJIWkfRbo_pi-TRWpJyPOSss2K3kqmh660q9itgZA1pZ-QSmu6tY_OeLT77JT1hkfJp4tU9eoU0wJouRgJO6848s4AvH7rVyuc9A1tEnmWZNGrgq43VFJFZcLCUTX8ppNsSXTq0IYpscS61GbRDpVWeMEgKwGhisu1xcRFBzRstmyBl0vJ_AlZkLFit99zvA0-VpQ7i4854fCg2-vMth5RxJL7CsdONmwXlLt4XbYkObG4Cn7vcllfUzsnbkGf8aXOtYnzFaG8HuzwEsg=w2048-h1365-no