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The '-1' stands for a 1" in 10" rifle twist and the 'LB' for Long Barrel, as it has a 16" barrel vs the 14" of the standard 551. The longer barrel has military applications and is meant to fire rifle grenades. It seems it was a request of the French Military for their Special Forces. Brazil's Air Force SF's also adopted the same rifle.
It is a selective fire weapon with a 4 position safety/selector including a 3 round burst capability, that re-sets itself after any number of shots are fired in any given burst. It has a rate of fire of 750rpm in either full-auto or burst mode. It has both 20 and 30 rounds magazines made in high resistance translucid plastic. The magazines may come with or without the studs to clamp them together. It seems the Swiss Special Forces, now adopting the new 552 LB/Stgw 04, requested their magazines to be made without the clamping studs as they may be a nightmare to extract/insert from/to their issue ammo pouches: 
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Quoted:
My Sig 551 LB. On the LB models, the barrel extends beyond the handguards the same length as the Sig 550 so they can launch rifle grenades as well as use the standard Stw90 bayonet. http://i65.tinypic.com/29ok9jq.jpg I has envies. |
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