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  1. #1
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    Suppression > AAC vs. AAC on the zero-shift issue.

    Haven't yet waded back into NFA waters after a 10+ year hiatus, but I'm giving serious consideration to resuming the journey by means of investing in a suppressor. Assuming we start with the AAC M4-2000 (which is my likely can of choice at this point), I'm curious how predictable zero shift is with this unit, and to what degree the difference is repeatable.

    In simpler terms, if I zero the weapon unsupressed, I understand that I can -- and should -- expect some zero shift when the suppressor is mounted. Let's assume I re-zero, and annotate the shift for future reference. All is right with the world, right?

    Now I go home, remove the supressor for cleaning, etc., and reinstall it at some point thereafter. When I return to the range, is my earlier suppressed zero going to remain valid, or am I likely to see yet another shift, because the can may or may not be precisely aligned as it was during the previous session?

    It would seem that any shift should be minimal, given that I'm installing the can on the same mount, in the same way, and presumably with the same rotation/number of turns/ratchet count, etc. Trouble is, common sense tells me that if that were true, the SPR/M4's M.I.T.E.R. system would be much less of a selling point.

    If I'm understanding all of this correctly, the M.I.T.E.R.'s strong suit is that it infuses a certain predictability (and adjustability) into the process, but if that's true, than how much of a factor are these things with the M4/2000? It's true that we are treading into the realm of the theoretical here just a bit, and it isn't my purpose to make mountains out of mole hills, but clearly there is a reason why the SPR/M4 commands a higher price and features a specific technology aimed at addressing zero shift.

    My question, then, is this: what is the real-world difference between the M4/2000 and the SPR/M4 in normal usage? Are we making much ado about nothing in this zero shift discussion, or is this something that probably should be entering into our thinking?

    AC

  2. #2
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    I'm hoping to find out in the not-too-distant future as well.

  3. #3
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    Anyone, anyone ... Bueller, Bueller?

    I'd like to sort this out before I make a final ruling on a perm pinned AAC Blackout, and at the moment I am undecided between the M4/2000 (which seems to be more readily accessible), and the SPR/M4 (which seems to have more overt potential). It is admittedly a tough call to make from a distance, though I prefer to make the decision based upon long-term capabilities, rather than near-term economics.

    Stick, you're using both, no? What say you?

    AC

  4. #4
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    Quote Originally Posted by Army Chief View Post
    It is admittedly a tough call to make from a distance, though I prefer to make the decision based upon long-term capabilities, rather than near-term economics.

    Stick, you're using both, no? What say you?

    AC
    Here is my understanding of the ratchet, and how it worked out for me. Zero the weapon with the muzzle device installed. Drop the can on, tighten it all the way down. Fire for zero. If its not correct, move the ratchet one place. Check zero, if its not correct, move the ratchet one more.... repeat as needed.

    If both cans were an option, there is not a doubt in my mind that I would go with the SPR/ M4. The way it recesses over the barrel to take up less space, MITER system, durability, and prevention of massive gas blow back into my face are the main reasons.
    Last edited by Stickman; 21 February 2009 at 11:54. Reason: spelling

  5. #5
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    Most helpful, Stick. I was tracking on some of this, but not necessarily on your last point, which is probably one of the most relevant considerations for me as a left-handed firer. I'm unlikely to use a Gas Buster, but the Switchblock, extended Blackout and SPR/M4 combination should go far in addressing the blowback problem.

    With respect to the M.I.T.E.R., once the zero/zero setting is determined, I suppose a simple painted witness mark from can to mount could help to provide a fast visual reference, just in case the ratchet count was difficult to remember. Either way, it sounds like an exceptional system.

    AC

  6. #6
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    If you look on the AAC SPR/M4 can, its numbered. I should have mentioned that earlier. Much easier to dial it in that way.

    A witness mark would be another easy way, just make sure it can take the heat.




  7. #7
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    Totally tracking now, thanks. "You don't know what you don't know" -- and sometimes I definitely don't know it.

    AC

  8. #8
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    stupid question here...do cans eventually "go bad" or lose some of their dampening abilities after a lot of rounds are put through it?

  9. #9
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    Quote Originally Posted by Creeky73 View Post
    stupid question here...do cans eventually "go bad" or lose some of their dampening abilities after a lot of rounds are put through it?
    Yes, which is why you want to get a can which is built extra well from the start. Heat and muzzle blast tend to be large parts of a cans demise. A short barreled weapon will impart much more abuse into a can than a 20" rifle. High round count usually is part of fast shooting, or full auto use, and the heat is another factor that can damage or shorten the life of a can, just like it can a barrel.

  10. #10
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    Perhaps an even more relevant question is this: when a supressor does begin to show signs of wear, can the internals be replaced without any additional NFA involvement, provided the same serial-numbered enclosure/can is used?

    Conventional wisdom would say yes, but conventional wisdom is often incompatible with Title II. Are suppressor core components SN-matched to the unit, or is this a baseless concern?

    AC

  11. #11
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    Resurrecting the thread to see if we can't get an answer to the question posed in post #10 (above).

    AC
    Stand your ground; don't fire unless fired upon, but if they mean to have a war, let it begin here. -- Captain John Parker, Lexington, 1775.

  12. #12
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    Quote Originally Posted by Army Chief View Post
    Are suppressor core components SN-matched to the unit, or is this a baseless concern?

    AC


    Components are NOT serial number on any can I've ever heard of. The outside of the can is the only thing that gets the number.

    Can can be rebuilt, but if they are heavily damaged, it may not be worth the cost. Of course if a total ban comes through, that may alter things as well.

  13. #13
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    So noted, thanks. That conforms with my expectations, and could simplify things a bit if a long-term restriction were enacted.

    AC
    Stand your ground; don't fire unless fired upon, but if they mean to have a war, let it begin here. -- Captain John Parker, Lexington, 1775.

  14. #14
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    I spoke to AAC and they said, they've never experienced anything like that wearing out. If it did, it would be a warranty issue so in either case, I think it's not something you need to worry about.

  15. #15
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    I'm just waiting on a shorter version of the AAC SPR/M4 can.

    Something akin to the OPS 14th unit (as a downscaled 16th adaptation). If I could keep OAL at a minimum with a 12.5" barrel that would be preferred, but the difference in suppression between a 12.5" Bbl with SPR/M4 isn't any better than the older PS 14th mounted on a 14.5" barrel. With use of the SEI Threaded Vortex and OPS collar, the OPS unit is comparable in price and performance, and you're getting some muzzle velocity from the added couple inches.
    And especially attractive with the 14.5"/SEI/OPS Inc setup is that it would be a single tax stamp rig, and also compatible with the M4-S unit coming out.

    In shorter iterations, the OPS with an 11.5" barrel would be competing against the M4-2k, in which case the M4-2000 wins unless you've already got host weapons for the 14/15/16th mounting system.

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