so from what I've read older gemtech halos can work for fixed flash hider models with an OD of 22mm. Is this still the only method for using a silencer? can the 4-pos 553 gas selector be used for 551 or 550 or would they require their own specific gas selector?

are certain barrels more guaranteed to work than others (ie 551-2 sb barrel vs 551-1 sb barrel).

I would like to use a silencer with my JDI sg550p, and a 551sb variant. Didn't jdi mention some type of partnership for silencers to be made here for these or is that vaporware.

As far as I know, there is no 551SB that has a 22mm flash hider. So, despite what you may read on various forums, the older HALOs will not work on a 551SB. You aren't going to suppress your 551SB without removing the barrel and having it threaded. From what I have seen, in my experimentation, I suspect that the very few HALOs that were supposedly built for the 551 didn't really work all that well, due to the taper behind the muzzle device. An older HALO will not work on a 550 without removal of the barrel, and modification of the groove behind the flash hider slots. Either way, all this requires that you have an older HALO; if you don't already, you'd be quite lucky to find one.

The SAN 4-pos valves will not work on a 551 or 550, because the OD of the piston is smaller on the short gas system guns that those valves are designed to work with. Custom valves are doable though.

As far as I know, despite what you read, all 551SB barrels are the same, and none of them are 22mm at the flash hider.

Either of the guns you're asking about would be best-off being threaded by a competent gunsmith, if you want silencer compatibility. If you have an older HALO, you can retain some originality on the 550, by only modifying that groove. Keep in mind it has to be the HALO that is compatible with the Smith Vortex flash hiders, for the pocket to be deep enough to cover the flash hider completely.

I am unsure whether or not JDI mentioned any kind of silencer partnership. The only thing that is often cited is B&T, but even they don't have one for the 551, and aren't making rifle cans stateside yet, as far as I know.

Everything I have to say on this subject is based on experience. I have 553s, 551s, and a 553LB (same barrel profile as 550), and I have invested much time, and plenty of money, in experimenting with suppressing all of them in the best way possible. If you have more questions, I'd be happy to answer them to the best of my ability.

So if i don't want to alter barrels I pretty much have no option unless someone comes out with something that works with the internal threading..?

Correct. I think it's pretty unlikely that something utilizing the internal muzzle threads will come around. If it hasn't happened by now, I don't think it ever will. The 551 seems to have been largely replaced by the 553 and 553LB, by any organization or agency that cares to use a 550-series weapon. The 550 is obviously still in use by the Swiss armed forces, but they don't seem in a hurry to suppress infantry rifles. There is a thread somewhat similar to this a little ways down the page, in the suppressed weapons forum. The OP of that thread ended up having a barrel I didn't know about, which would actually likely work with a few available silencers. In the interest of covering all the bases, I'd encourage you to look at that thread; there's always the chance that your 550 barrel is of the same design as his 553LB's.

the internal threading is for a blank firing adaptor, not a suppressor. If you want a 551 to run suppressed, you either need to chop/thread the 14.3" barrel or you should look for a 16" 551A1, West Coast Armory/Sig 551 or a normal 556.

The 552 and 553 were designed to run suppressors...the longer iterations were not so cans were an afterthought.

I tried a newer Gemtech Halo on both my 16" 551-2 and my 550 and as KSGM has said, no dice.

my 550 barrel is a 1 piece hammerli. It definitely won't work.

In europe there are silencers available for the SG rifles that work with the internal threading, http://saimaastill.fi/portfoli...uppressor-rk-series/

and I believe sig sauer AG lists silencers for them in their catalog as well.

Ain't that some shit. I wish they had more images of those silencers. I am curious how they seal off the flash hider slots; if they do it internally or externally, and I wonder how they make up for the difference in OD between the two guns. Either they seal internally, or there is some kind of swappable piece. I can't seem to find a single image of one on a Sig rifle of any kind. Unfortunately, the chances of seeing one of those cans stateside are slim to none; if B&T hasn't decided to produce the ROTEX here yet, we're still a long way off for other fancy European rifle cans. The trouble with the Sig rifle aftermarket, is the demand isn't quite high enough to make it worth most manufacturer's while.

I think all the silencers in the AG catalog are B&T types, not necessarily intended for the 551 and 550. I'd take their catalog with a grain of salt anyway, as the one's I have seen are riddled with grammar errors, typos, and other silliness. It wouldn't surprise me if they just stuck a picture of a silencer with every weapon accessory list in there. The 553 in .300BLK has a barrel contoured for use with a dedicated reflex-type silencer. The US market will never see that can, so folks are just irritated by the barrel length and contour, and chop them down.

Well, it would appear that the b&t rotex are coming to USA soon if not now. So is that a viable option?

also, someone claiming the halo works here

https://www.m4carbine.net/arch...ex.php/t-197025.html

Likely not. They will undoubtedly prioritize production of more versatile cans. I don't know that they don't make one that uses the BFA threads, but I have never heard tell of it, if they do. Unless your barrel is profiled like the one in the OP of that other thread, you're likely out of luck unless you get it threaded.

quote:

Originally posted by krieg:
Well, it would appear that the b&t rotex are coming to USA soon if not now. So is that a viable option?

also, someone claiming the halo works here

https://www.m4carbine.net/arch...ex.php/t-197025.html

Yeah B&T was supposed to start in early 4th quarter of this year. I hope they make it happen but I'm not gonna hold my breath considering they missed that mark. I also would love to get a suppressor for my SIG 550.

quote:

Ain't that some shit. I wish they had more images of those silencers. I am curious how they seal off the flash hider slots; if they do it internally or externally, and I wonder how they make up for the difference in OD between the two guns. Either they seal internally, or there is some kind of swappable piece. I can't seem to find a single image of one on a Sig rifle of any kind.

Yeah I would love to see more on these cans just as a curiosity.

https://schiesscenter.ch/produ...-sig-stgw-90-5-56mm/

so it looks like b&t makes one for their home market...

possible to have these made here? wonder if a group buy could set this in motion. Knights did one for mp5 cans and the hkpro members.

actually, couldn't one just use the fastener from this on the rotex-V's available stateside? For suppressing a 550, would a 4 pos valve be preferable like for the 552/553

quote:

Originally posted by krieg:
so it looks like b&t makes one for their home market...

possible to have these made here? wonder if a group buy could set this in motion. Knights did one for mp5 cans and the hkpro members.

actually, couldn't one just use the fastener from this on the rotex-V's available stateside? For suppressing a 550, would a 4 pos valve be preferable like for the 552/553

Looks like a fully welded can, so probably no possibility of putting that interface on another Rotex.

All the available factory 4-position valves that I know of are for the 552/3, which is a smaller diameter piston head than the other 55X guns.

Good find all the same though. I don't know how that never came up in my searches.

the locking collar won't fit on another rotex? I can probably try to get one, I've emailed b&t usa, they probably won't respond but I'm trying..

B&T is communicative; I have corresponded with them before, concerning silencers for the Sigs. Definitely let us know what they say.

The regular Rotex uses a latch similar to the KAC NT4 and Griffin M4SD, as best I can tell. I have never handled one, but I have a Rotex FH on one of my guns. I had to open up the groove ever so slightly, and can now use it as a mount for my HALO and M4SDK. That aside, the sleeve protruding from the 550 Rotex, that covers the flash hider, and provides the threads for the collar is what is lacking on the regular Rotex. And, like I said earlier, it appears to be welded to the body, and therefore couldn't be removed and sold separately for use in adapting another Rotex.

I modified my 553LB barrel for use with an early HALO, and actually had a custom collar made to attach the same silencer without barrel modification, but it ended up failing after a while.

I knew I had this information saved somewhere. Here is a clip from an old Gemtech ad about their HALO suppressor.
"The SIG 551 delivered in the United States has an integral flash hider 21.5mm in diameter, which is not NATO spec. On special order, we can provide a variant of the HALO specifically for this weapon. Although the SIG 552 also uses a non-specification flash hider, this flash hider is threaded on and we suggest changing the flash hider to one that is 22 mm in diameter."

No one is disputing the fact that Gemtech may have previously offered a special-order version of the HALO that apparently no one ever purchased. No one has any real-life reports of this silencer, outside of seeing it in images in the HALO manual, and the excerpt from the ad you just furnished. Thank you, though, for acknowledging the fact that production HALOs don't work on the 551.

I think it's worth noting as well, that they seem to allude to the fact that the 551 HALO may work on the 552 hider, but they suggest going an alternative route anyway. In my experience with a custom HALO "closer", tightening it against that tapered rear portion of the Sig device will lead to warping of the closer, if it's not extremely overbuilt. It would be much preferred if the closer actually tightened against the silencer body itself, but with a tight-enough tolerance to not readily spin around on the gun.

I'll measure a 552 vs 551 hider, and update later.

They are definitely not implying that the special order HALO would work on a threaded 552 flash hider. The ODs are probably made to the same spec, but the 552 is shorter. The closer would bottom out on the can before it was tight on the gun.

This message has been edited. Last edited by: KSGM,

I haven't heard anything from B&T USA, but it would seem to me the best solution is if enough 550/551/ fixed flash hider owners can convince them to do a run of cans.

quote:

Originally posted by krieg:
I haven't heard anything from B&T USA, but it would seem to me the best solution is if enough 550/551/ fixed flash hider owners can convince them to do a run of cans.

B&T announced last summer that they were going to make cans here in the US. They were targeting the third quarter of 2021 for release so they appear to have missed that mark. Hopefully they will get it done soon.

Do you mean silencers that can mount on the sg550 specifically? B&T has been making stateside silencers for a little while now haven't they.