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Discussion Starter · #1 ·
I recently purchased a NIB P556 for a project. It's a bit of a pain to take apart, but so far it's been pretty flawless. Just a bit of finish marring on the flats of the too tight flash hider. Seems crazy that they put on a hider that wont allow gas tube removal! Anyway, I figured it may come apart easier before being fired and so far, here it is...

 

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so sexy! make sure that is legal before you assemble. Im guessing it is. sbr paperwork :D
 

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This is a project I have alot of interest in- have you or are you planning on the dissambly of the 551 lower for painting and semi modification? I am curioius to know what all that takes.
Thanks much for post this, I will be interested in following you process!
Have you sent your SBR paperwork, or are licensed to manufacture? :p
 

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Discussion Starter · #6 ·
I'm still undecided on the stock/SBR. I probably will eventually, but we'll see. Obviously the 55X trigger group is going on and it's already from a semi gun, so there's not much involved. Take off the old & put on the new.

I'm also undecided on refinishing the lower or the receiver. Parts like the mag release and trigger guard are riveted/peened in place on the 550/1. So, to refinish it correctly, I'd have to source those small parts. The receiver isn't much easier with the riveted dust covers. Plus everything is new, so it's sucks to refinish anything. Maybe I'll go with the 2 tone!

I'm not sure about the handguard either. The 552 is too short, so I'll need to have a front "plate" machined. Or, maybe use a 552 front piece and modify a handguard with 552 style vents?!? Dunno.

There's more, but in short, I'm undecided on pretty much everything, so I'm just seeing how things play out. :D
 

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I have seen an ad on a different site for getting a 551 lower correctly modified to with with a 556 upper-
I can see myself with one of those two tones perhaps in the future also! It would make for a neat firearm! :wink:
 

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Discussion Starter · #8 ·
I received the 552 handguards today. They were sold to me as original Sig 552 handguards and they may be, but they're definitely 550 handguards that are shortened and with holes drilled. I suppose Sig may do this, just like Sig USA does with the 556 and P556 handguards. Can anyone confirm? Regardless, to use on a P556, they'd require a slightly longer, custom, retaining ring than stock...


I'm still looking for a 552 handguard retaining ring as I may just modify a 550 handguard by drilling all the holes and shortening it to P556 length.

Anyway, it's coming along...
 

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Discussion Starter · #10 ·
It's going slow, but there's definite progress!

I've read all the posts about the US versus Swiss "elves" produced parts in the 556. I don't want to get into all that, but for this project, I'll say I felt it was worth the trouble and expense to use as many Swiss parts as possible. So, I purchased a NIB low serial 556 rifle with the intent of using all the Swiss parts off it on this project. For example the complete bolt group, complete gas block, a shortened operating rod, etc. It's on its way to my dealer now.

That said, my project has taken a sudden turn as I just purchased a brand new front end and complete bolt group from a Sig 552 as follows...



So, my "new" tentative plan is to lengthen the 552 op rod slightly and use the entire 552 bolt group, the 552 gas block assembly including handguard collar, with a 550 handguard modified to 552 specs. The only parts left from the P556 will be the receiver, barrel, rail and gas tube. The rest will be Sig 55X. All with original finish, green/gray lower, gas block handguard collar, front sight and the rest in black with black furniture, so it will be 2 tone.

I haven't yet explored the possibility of using the entire 552 front end with the P556 receiver. I realize the barrel threads are different and that's the first roadblock. We shall see.
 

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Which will you mod to get a fit on the bolt, the 556 receiver or the 55x bolt?
It sounds very promising and fun!
Please do keep us up on the project, I am all eyes!!! :shock:
 

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Discussion Starter · #12 ·
Well, I discovered the receiver would definitely need modifications to accept the 552 op-rod and in addition, the op-rod would need to be lengthened as well. I decided that was outside the realm of this project. So, I kept the 552 gasblock assembly, front sight, handguard collar and sold the rest.

Here's where I'm at now...



I haven't actually modified anything (yet) and everything has just been assembled together. The only NIB P556 parts left are the receiver, barrel, gas tube, valve, op rod and rail. The rest: New take-off 552 gas block assembly with hooded "night" sight and handguard collar. New take-off 550/1 lower receiver with pins, complete bolt group, and magazines.

I obtained a set of new 550 handguards and promptly cut them in half to fit for length and add 552 handguard replica holes. After that and adding a thread protector, it will be done.

Anyone in Orlando have a milling machine I can use for a couple hours?

;^)

 

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Discussion Starter · #15 ·
Thanks!

I got the last "kit" that COG Sales had and it was almost $2600 with the black grip. I wasn't happy with the price, but more importantly it was available. Even after I sell off some of the other "kit" parts, I'll still have $$$ in the lower. That said, in selling off the unused P556 parts, the unused kit parts, the unused 552 parts, and everything else related to this project, the total I have in the actual gun will be pretty reasonable. The weird part is, I was pretty Sig ignorant and had basically no interest in them until passing a P556 at a local gun show. Kudos to Sig for making a pistol.

BTW, I was serious about using a milling machine in Orlando, so if anyone has one or knows a friend, please contact me. Thanks!
 

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Discussion Starter · #16 ·
Almost done... Just need a milling machine to replicate the 552 holes and wait for the thread protector to come in.

BTW, how can Sig keep screwing it up?!? They didn't deliver the pre-production prototype with the true 552 handguard. Now, they're actually going to use a 552 handguard collar with cut down 551 handguards instead of 550 handguards? WTF? They just can't get it right.

 

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Discussion Starter · #18 ·
It's coming along. I had a custom thread protector machined for it. I was going to put a Vortex on it, but the skirt on the Vortex didn't fit over the shoulder, it butted against it. Maybe if I had the skirt machined off, but the shorter look of the thread protector is growing on me. It's a range gun anyway.

I'm keeping the 2-tone as is. I like the way it worked out with the green gasblock, sight and handguard collar. Need to either get a rear sight or take off the front and stick a laser on it.

I decided against SBRing it. Instead I'm using the stock hinge as an attachment point for a single point sling. I've drawn up a sling bushing that will keep the stock pin in place and position the webbing well. I'll have someone machine it from black nylon or delrin. Lastly, I STILL need to have the 552 pattern holes drilled in the handguard. Anyone have a mill in Orlando I can use for 5 minutes?!?


Sorry about the blurry picture...

 

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Pic of NIB project 556 stripped...

That's an awesome setup,where did you pick-up the swiss gas block,and the other swiss parts.Do you have any parts left over your getting rid of?I bet it took qiite awhile to get all that stuff rounded up.Hey and thanks for the tip on the charging handle not being in position,awhile back.I just cleaned it and was'nt aware it was'nt locked in place,good eye.Anyway nice pistol and good luck with her.
 

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Discussion Starter · #20 ·
Thanks! I've been buying parts since I got it last November, but not from any one good source. Sorry, I wish there was as it would have made things much easier. For example, I bought 2 NIB early 556 rifles, just so I could get the Swiss parts off them and part the rest out.

I have a couple parts for sale on my site... www.hkbeltfed.com

I also have a complete Swiss "kit" for a P556 upper similar to what's on my P556 except all black. It's all either new or new take-off, and all Swiss- Gas block, 552 handguard collar ("priceless" according to MFI!), 550 handguard already cut down like mine, complete bolt group, and with 2 receiver pins. I was going to post the package for sale after I drill the 552 pattern holes in the handguard. See pic. I have the 552 handguard in there just to show the hole pattern. I can include it if some is interested and I also have a complete set of new take-off Swiss trigger parts from a 556 available.

 
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