Most of the mid-length Armalite factory rifles I've seen have permanently attached muzzle brakes.  If you can't remove them then you can't put on the M version of the SIR.  That's just an uneducated guess though.

You can install a #58M SIR on rifles that have permanently attached muzzlebreak.

-Cap'n

Wave:
I think he is inferring that the military is looking at mid-length handguards and moving the gas block forward.

M4 would be correct  simple can't remove muzzle comp,can't remove gas block/frnt sght,so you cant remove delta rings,,,unless you cut the delta ring off then the M version SIRS should fit.

Reading between the lines, and looking at teh tea leaveas:
1.A.R.M.S. is going after a military contract.
2.A.R.M.S. is confident in the demise of the AWB and doesn't see a reason to invest in producing a C model for a market that will dry up in just about a year.

Did I pass?

Delta rings don't require the removal of the front sight assy/gas block.  The barrel is detached from the upper and the delta ring is remove that way, or dremel it off.  "M" version SIRs work w/ muzzle devices that are not removable.  And if you want a Middie upper in pre- condition talk to trheir LE/MIL sales people, they'll set you up 123.

SULACO2,
Thank you...
Delta 6

Spec Ops has adopted the Armalite mid-length gas system with the new mid-length SIR system for the new (Navy Seals) RECCE rifle using the 6.8MM cartridge.  Nomenclature is Mk 12 Rifle (RECCE)

Delta6, are you SURE of your information ??

Do you know which company will manufacture the 6.8mm cartridge ??

Do you know anything about the magazines ??   New design or modification of an existing mag ??

5sub

5sub,

Delta is pretty much right on, the new 6.8 is being manufactured by Remington and it is a 115gr bullet, I have seen the AMax tipped version and the standard FMJ.  Magazine will have to be retrofitted with new follower and it will only hold 28 rounds.  You can also buy preparatory magazines that is designed specially for the 6.8 rounds.

SMGLee, very interesting topic we have here.

I wonder if it is official that ArmaLite will supply the new weapon ??

5sub

Thanx, Mr. Lee.  

5sub:
Here is what I know and seen.
The new mags are steel.  They are longer than the current M16 mag, approx. 3/4 of an inch longer, depending on how you measure them.  All the followers I have seen are black and the hump on top is boxier, as oppose to rounded type on the M16 5.56 mag. They are appear parkerized or some sort of phosphate finish.  Retro fitted 5.56 mags work as well, just replace the follower and spring (the replacement of the spring maybe optional). They are noticably heavier than the aluminum M16 mags.  The aluminum M16 retro fit mags, as Mr. Lee stated, hold 28 rounds.  Some difficulty is encountered when trying to load the mag in a gun with the bolt and carrier forward, so, 26 or 27 may be the realistic number. There appears to be plenty of material in the follower, so maybe a slight mod could be made to add a bit more space.
The rounds that I have seen were made by two different manufacturers of which one is Remington. Some of the head stamps say 6.8 and others say .30 Remington.  
Some of the bolt and bolt carriers appear standard M16, that have been modified, and some are of new mfg.  The bolt face has been opened to accept the 6.8/30 Rem case.  The new type carriers have three holes in the cut out area as opposed to two on the M16 type carrier.  Also the gas relief hole has been moved about an 1/8 inch higher.  These mods could have been made because the primary use of this rifle will be Spec. Ops, and therefore a lot of suppressor use(this is pure, hopefully rational, speculation on my part.)  I do not know this for fact.
I have heard that PRI is selling mags and uppers for this caliber.  This maybe rumor, but I'm sure you could find out on their web site.
I'm sure there will be lots of pros and cons, and lots controversy on this caliber and rifle.  Not wanting to be left out, I'll start the ball rolling...."It's HEAVY, way HEAVY"

Delta6,
a most interesting post.  I had heard a few mumblings about the 6.8mm cartridge but had no idea that any part of our military was actually interested.

Please keep us informed.

5sub

Heavy??

Our 6.8 mm rifles weigh the same as their 5.56 mm counterparts.

Ammunition weights are obviously different, as the following comparison illustrates: 30 rounds of 5.56 mm M855 weigh about 0.8 lbs, while both 28 rounds of 6.8 mm and 20 rounds of 7.62 mm M80 weigh roughly 1 lbs.

Doc,
Thanx for the ammo weights.  Saved me time looking in my notes.  
Which rifle mod. are you using for weight comparison.  I worked with 4 different upper combo's and all were heavier than a standard M4 variant, sans all the silencer stuff.

What he means is you have to take the whole barrel off to install the military version of the SIR which is a pain in the ass for just installing a handguard.

There is another mistake you are making on this board.  You DO NOT have to remove the barrel to install the SIR military.  take a dremel tool and quarter the delta ring and just install the yoke and pop on the SIR M.  

Doc Roberts,

Excellent info again, thanks for the update.  from your measurement the 28 rounds of 6.8 weights roughly 1 lbs. compare to the 5.56 at 0.8lbs.  this in turn give the individual soldier carrying the new 6.8 system a combine weight of roughly 8 lbs ammo load out if the operator is carrying 8 magazines in his pouches.  an operator carrying the 62gr 5.56 will have a combine weight of 6.4 lbs for the eight magazines he is carrying.

I would more then gladly to carry the extra 1.6 lbs for the performance increase gain by the new 6.8 round.  I think your new 6.8 round is absolutely on target when it comes to the perfect round for the M16/AR15 system.  

One question, what are the ability of the 6.8 FMJ against hard armor, let's say compare to the 62gr M855??  Thanks for your input.