Looking at a Sig 551-2SP with the machined flash hider. How do you suppress this without barrel threads, was there a suppressor for this sort of barrel? Otherwise would need to have the barrel threaded.

Thanks

A Gemtech HALO will fit and work just fine as long as the diameter of the flash hider area is 22mm.



Here is how a HALO attaches:

quote:

Originally posted by MG34_Dan:
A Gemtech HALO will fit and work just fine as long as the diameter of the flash hider area is 22mm.

Hi Dan, long time no see.

The rifles standard versions have a 22mm STANAG type flash hider. However if this applies for US import versions is not clear and should be verified before purchasing it. If the flash hider has 22mm any suppressor with a STANAG interface will fit the 551 as well as any other self loader with a STANAG type muzzle.

quote:

Originally posted by OTD:

quote:

Originally posted by MG34_Dan:
A Gemtech HALO will fit and work just fine as long as the diameter of the flash hider area is 22mm.

Hi Dan, long time no see.
The rifles standard versions have a 22mm STANAG type flash hider. However if this applies for US import versions is not clear and should be verified before purchasing it. If the flash hider has 22mm any suppressor with a STANAG interface will fit the 551 as well as any other self loader with a STANAG type muzzle.

Daniel; It's nice to speak with you again. Back in the day, I spoke with Doc Dater at Gemtech and he said that many SIG 550s/551s that SIG imported were neutered for import into the US. They had their flash hiders shaved down by a couple millimeters. Those slimmed down flash hider weapons will not hold a HALO suppressor in perfect bore alignment and on a baffle strike would be inevitable.

Hi Dan. Thanks for the feedback. I was aware to have read somewhere about the needed transformations to make a SIG550 US legal. I think it was on Biggerhammer or the competetive white SIGForums from long time ago.

quote:

Originally posted by OTD:
Hi Dan. Thanks for the feedback. I was aware to have read somewhere about the needed transformations to make a SIG550 US legal. I think it was on Biggerhammer or the competetive white SIGForums from long time ago.

It's my understanding that the flash hider shaving was done to dissuade the attachment of a bayonet. Even if a 55X owner added a non-neutered gas block or attached a homemade bayonet lug, the bayonet would not cleanly fit the flash hider. I also know that the 55Xs sold directly to US law enforcement agencies have original unaltered flash hiders. Interestingly, these LE agencies can dispose of their non-automatic fire 55Xs on the civilian market when they are done with them.

Bayonet attachment might be one reason but I think it was rather the ablity to launch rifle grenades with a rifle. The barrel section in front of the gas regulator is designed as an adapter for standardized NATO rifle grenades. The inside diameter of the tail unit of such grenades have a diameter of 22mm. The 551-SB is not really capable to launch any type RG precisely with, but it is probably still possible if an FN TELGREN grenade with a telescope tail unit or a similar type was handy. I think this was the idea behind the reduction of the flashider’s diameter, else it would have been classified as a destructive device, not a self loading rilfe. In oder to make it street leagal SIG had to neuter all such features before they could import to the US.

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

If it’s a 14.3” OAL barrel the integral flash hider will be of appropriate diameter. It was 550s and the 16” OAL barrel 551s that had smaller diameter flash hider OD.