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PASHOOTER
April 04, 2017, 14:40
I purchased a new 10.5" upper for my SBR that was advertised as a M4 profile. The upper I received has a very heavy barrel to the gas block then steps down to .750 diameter. Did the M4 specs change ? I have 2 other M4s both with a standard profile under the handguards.

John A
April 04, 2017, 14:51
M4 barrel profile is supposed to denote the notch for the M203 launcher just forward of the front sight post.

See photo below:

http://media.defenceindustrydaily.com/images/ORD_M203_on_M4_Carbine_lg.jpg


What you have, probably just has an M4 barrel extension to help aid feeding, but technically, it cannot be an M4 barrel if it's just 10 1/2 inches long.

edited because I changed the picture to one that wasn't 10 miles wide

hueyville
April 04, 2017, 17:16
11.5" is short as have seen a barrel that resembles an M4 profile. Used an 11.5" CHF melonite on my SBR cause all the math geeks say need that length as minimum to allow proper gas system operation without overgassing and stressing the rifle, espcially bolt, extractor and buffer. Suppressor is tack welded so only needed one stamp. Used a curly gas tube to lengthen gas system though many say it is wasted effort, I like adding a couple inches of gas tube, 11.5" barrel along with suppressor give plenty of dwell time after bullet passes port which still took an H4 buffer to soften rifle up. Used an ARP bolt so rifle should be durable as posssibe with an SBR design, waiting for my binary three position trigger to show up and turn it into a single stamp ammo muncher. Four little tack welds across the crush washer sure does streamline amount of paperwork and is 17" long with can. Considering making it my truck rifle so if SHTF won't deafen myself and once the binary trigger goes in will be able to pour massive fire on target.

Shot the first of my 13.5" White Oak Armament Wylde builds today. Used a flaming Pig muzzle device to bring up to legal length and may be coolest looking upper have assembled in recent months.

http://i68.tinypic.com/96yzb4.jpg

Purchased multiple of these when on clearance, think clearing another batch now, and been interested in how the 13.5" heavy barrels would shoot. Didn't have much time and had to rush at range today but with a 3.5 pound single stage trigger in Aero lower it shot real close to MOA first trip out and only carried some 62 grain lead core FMJ bargain bullets. Bet my 69 grain SMK's will shoot under MOA as best group shooting 25 total rounds five at a time was 1.2". They told me the 13.5" barrels would shoot well and didn't let me down. Need to take a picture of completed rifle but most know what a black lower with milspec carbine stock looks like. Think may twist up another 13.5" ASAP as this shot so well and got a lot of lookers at range with the curly gas and Geissele gas block so easily seen an big pig muzzle device looking like a Star Wars prop.

SAFN49
April 04, 2017, 19:10
M4 is feed ramps and profile in a 14.5" bbl.

The M4A1 profile is different but has the M4 feed ramps.

http://i36.photobucket.com/albums/e43/djm540i/govt-bg_zpsd2qchkuv.gif (http://s36.photobucket.com/user/djm540i/media/govt-bg_zpsd2qchkuv.gif.html)

PASHOOTER
April 05, 2017, 14:43
Thank guys. SAFN49 the M4A1 profile cut to 10.5" appears to be what my upper has.

hueyville
April 05, 2017, 16:50
Stick the finished "flaming pig" build here. After testing with scope to realize the W.O.A. 13.5" 1:7 Wylde barrel likely has MOA capability decided to streamline the top and add an aluminum chassis C More. Have pop up irons on way that are reputed to cowitness nicely with a C More then it will be complete. The 13.5" barrel with Noveske Flaming Pig is a hoot to shoot, especially watching the fireball roll out at twilight.

http://i65.tinypic.com/ehxelz.jpg

Have more of these barrels and next one will get a Vortex Strike Eagle 1-6x to tweak it's accuracy potential a little more and may even put one of my pile of Leupold VX1 3-9x Black Friday specials on it. Have three W.O.A. incoming barrel orders including some 24" heavy varmint barrels will have to power up the glass. Also purchased an 11.5" 1:7 twist 6.8 barrel and going to do another one stamp SBR by spot welding the can to barrel. Twist rate is supposed to be perfect with 200 grain subsonic loads.

FriendBesto
April 05, 2017, 16:55
Thank guys. SAFN49 the M4A1 profile cut to 10.5" appears to be what my upper has.

There are also two flats milled near the rear for the M203 on the fatter M4 barrels.