PDA

View Full Version : Suppression > AAC vs. AAC on the zero-shift issue.



Army Chief
19 February 2009, 08:06
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

m24shooter
19 February 2009, 08:38
I'm hoping to find out in the not-too-distant future as well.

Army Chief
21 February 2009, 02:00
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

Stickman
21 February 2009, 10:51
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.

Army Chief
21 February 2009, 11:29
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

Stickman
21 February 2009, 12:46
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. [BD]

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



http://stickman.rainierarms.com/galleries/AAC/IMG_7954%201028%20stick.jpg

Army Chief
21 February 2009, 13:05
Totally tracking now, thanks. "You don't know what you don't know" -- and sometimes I definitely don't know it. ;)

AC

Creeky73
21 February 2009, 15:46
stupid question here...do cans eventually "go bad" or lose some of their dampening abilities after a lot of rounds are put through it?

Stickman
21 February 2009, 16:18
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.

Army Chief
21 February 2009, 23:53
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

Army Chief
19 March 2009, 08:41
Resurrecting the thread to see if we can't get an answer to the question posed in post #10 (above).

AC

Stickman
19 March 2009, 09:55
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.

Army Chief
19 March 2009, 10:11
So noted, thanks. That conforms with my expectations, and could simplify things a bit if a long-term restriction were enacted.

AC

John Hwang
20 March 2009, 10:17
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.

TehLlama
22 March 2009, 18:40
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.

Ryo
24 March 2009, 01:11
So here's a 3rd party comment on the M4-2000 can on a test they did with it:
They said that once the rifle is zeroed with the can on, it would keep zero relatively well when the can is removed and placed back on multiple times. But when firing with the can off, the zero is totally different than when suppressed.

Well I don't know if that's true, but it sounds plausible.. Since I'm still waiting for my tax stamp, I can't test it yet. probably won't be able to test it for a while even if I had it since i have to travel to OR to test it out. :(

Army Chief
24 March 2009, 01:25
That would be consistent with suppressor use in general, which is why so much effort has gone into developing systems like the M.I.T.E.R., which are designed to allow the supressor to be mounted in such a way as to maintain the unsuppressed zero; otherwise, there will likely be two different zeroes for suppressed and unsuppressed operation.

Whether that difference is enough to result in a hit or a miss for your applications is dependent upon any number of variables (type of suppressor, ammunition, range/distance, target dimensions, etc.), but since these zeroes are largely repeatable, I suspect that most competent M4-2000 owners come to know what adjustments are necessary when transitioning from one mode to the next.

AC

TehLlama
25 March 2009, 19:29
Does anybody have an idea on the relationship between bullet mass and the repeatability of zero with suppressors?
I'd like to assume that heavier rounds would be more consistent, but would their accompanying lower muzzle velocity also play a role in the POI shift? - I'll read up on this, but I'm very curious about what variable are involved.

chase102798
28 April 2009, 20:10
This might be an off subject question (and since I'm new here it's my first), but how often if at all do the M4-2000 amd M4/SPR suppressors need to be cleaned. I guess what I'm wondering is can you leave it on the weapon for extended periods of time or does it need to be removed to maintain it?

Stickman
28 April 2009, 21:24
5.56 caliber cans don't need to be cleaned like their pistol caliber brethren. The .22 cans are the absolute worst.

The AAC cans are all full welded and sealed, which is a good thing.

chase102798
5 May 2009, 16:54
Oh No...I have an SWR Warlock on the way. It doesn't disassemble, so what exactly am I looking at maintenance wise? I've never owned a 22 suppressor or any other one for that matter.

Fontaine
12 July 2009, 23:47
Based on responses from other forums, people have noted that the M4-2K Mod 08 results in less than 1 MOA shift on most barrel.

This weekend I went down to Oregon for the Tri-County Gun Club practical rifle match, and the match director and a RO let me try out my suppressor on one of the stages.

The stage involved shooting a swinging steel target until it did a fully rotation. This required of course, timing, speed, and precision. If you failed to rotate the MGM steel target, then there were some standard steel tombstones to shoot at 100 yards. Hit both twice, you're done.

I decided THIS was the stage to put my suppressor on. I had not checked for zero whatsoever, so I was pretty much just winging it.

As predicted, the Mod 08 had minimal POI shift. I had no idea where the shift was, but had no problem making hits on 8" at 100 yards with my Aimpoint T-1.

The Match director had noted that some other suppressors had resulted in wild POI shifts before, so I'm pleased with my AAC can.

http://www.pbase.com/image/114903227.jpg

http://www.pbase.com/image/114903228.jpg

Fontaine
3 August 2009, 21:56
Ran this baby on the 3rd day of a Magpul Carbine 1 class.

Didn't bother zeroing it again, i just used the same zero.

Still combat effective at 1-100 yards as predicted. Also increased my effective ROF as well, the weight on the muzzle and hydraulic effect of gas on baffles definitely reduced muzzle jump

http://www.pbase.com/image/115678884.jpg

http://www.pbase.com/image/115678790.jpg

shotdown
4 August 2009, 02:35
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.

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



http://stickman.rainierarms.com/galleries/AAC/IMG_7954%201028%20stick.jpg

I'm getting ready to pick up the AAC M4-2000 Mod 08. After sighting it in, what can I use to mark the location of the can without it rubbing off?

Fontaine
4 August 2009, 16:01
I'm getting ready to pick up the AAC M4-2000 Mod 08. After sighting it in, what can I use to mark the location of the can without it rubbing off?

The M4-2000 doesn't have the MITER mounting system, you don't have witness marks to worry about. Just crank it on and go.

Glad to report the zero shift is minimal

shotdown
5 August 2009, 13:49
The M4-2000 doesn't have the MITER mounting system, you don't have witness marks to worry about. Just crank it on and go.

Glad to report the zero shift is minimal

Awesome. Thanks.

687
23 September 2010, 12:05
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. [BD]

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



http://stickman.rainierarms.com/galleries/AAC/IMG_7954%201028%20stick.jpg


That system is my next investment. MY CLEO is a great guy when it comes to these matters.