Finally, after a 2 year search for a Sig-551/LB barrel, I scored one on GB today!!   It wasn't cheap, but now, I can finally get my pre-classic model, Sig-556 "rebuilt" into a more correct and true looking Sig-551/LB model... Something I've always wanted.  This will be a nice retirement gift to myself!!

The barrel I'm purchasing is a true Sig-551 17.5" barrel...  I was hoping for one of those U.S. made barrels since it would be easier to install, but I'm more than happy with an original version, which in the long run will be far better for this conversion since it's a true Sig barrel!!   I just hope that the installation of this barrel will not be a monster of project in itself.   Once I receive this barrel, I'll be sending all the parts and the rifle to get this work done.  Here are the parts I currently have in hand;

A) Complete stamped steel Sig-55x lower receiver w/black folding stock
B) Both a front and rear Sig-55x sights
C) B-Square Sig-55x scope mount  
D) U.S. copy of a Sig-55x bayonet lug

The only other items I'm hoping to find is a real "Brugger and Thomet" scope mount to round things out.   The B-Square mount looks and seems OK, but I've gone this far, so finding a B&T mount will just round things off...  BTW, I will be using an Aimpoint red-dot system with this rifle once all the conversion work is finally done.  

...Does anybody know if the HK's G3/HK33 grenade ring will fit in/on the Sig-55x grenade mount?  Man!! I hope so!!

As for the finish, I'm leaning towards the "Sig Grey" and the barrel, a slightly  darker grey.  I've also seen photos of Sig-551s in black as well, so what was the more common color for the military version?   I'm also hoping to have the upper receiver remarked to "SIG-551" and the serial number laser engraved on the lower as well.

Anyway, I know that this "project" will be my most expensive one to date, but at the end, it will still be far cheaper than a pre-ban Sig-550 rifle, by several thousands of dollars... Plus, I always wanted the Sig-551 over the Sig-550... With my luck, Sig-USA will offer a real Sig-551 in 2015!!

Did you get a trunnion with that Swiss barrel?

Swiss barrels won't work with the US trunnion. They need to be switched out. Not cheap to do, but others have done it.

I don't think you have anything to fear about Sig offering a "better" 551 clone in the future. I think they are most likely out of the "classic" 55X business stateside.

And have you tried gunfactory for the B&T rail? I have seen them on their website. Rolf there speaks english and they ship to the US.

Where are you sending it off to for this conversion work?

sounds like a nice rifle your building.  i was fortunate enough to shoot a friend's 551-lb , really nice shooter

Thanks for the photo 1iviper!!  That is what I'm hoping to have within the next few months!!

Man!! ...One more item needed for the conversion project... A Sig-55x barrel trunnion!!  I've came this far, so what the heck... The search for a Sig-55x trunnion is now on!!

To the Sig experts; Will either a Sig-550 or a Sig-552 trunnion work with a Sig-551 barrel and the Sig-556 upper receiver?    

Thanks for the tips!!

Per ATF, you will not be allowed to remark the upper. Serial number designates what it is. If it is ever checked, it would result in felony charges. I inquired to the ATF 2 yrs ago on behalf of a customer about doing the same thing. Definately no was their answer. By the way, if you want the paint done in Sig Grey, I have the correct Swiss arms paint. I am doing 6 Sig rifles, 3 pistols (for Sig Sauer in NH) and one AR15 for customers. I also am doing Sig Black now.

I also have all of the factory tools to do the barrel swap and rivet the wipers back after painting.

Jim, it is legal to remark a title-1 firearm. The serial number obviously cannot be altered. ATF has disallowed remarking title-2 firearms in the wake of the Rodman, Goldstein, et al fiasco of turning transferable MACs into M60s, M249s, M240s and other high dollar MGs using the MAC serial number transposed onto a post-86 guns "washed" with a few transfers back and forth to change information on the ATF forms with each transfer.

There are HK smiths remarking title-1 9x series guns on a routine basis.

Yeah I've personally seen tons of restamped HK's. Heck, a guy I know has one. A SP89 that was restamped MP5K and was converted to an SBR. As I understand it you just can't touch the serial number and the name / location of the manufacturer.

So you're the one who got it! I was bidding as well. Holy smokes that was a high price! Congratulations, those are nice barrels. For that price I am tempted to sell mine (not really).

Just so you are aware, that barrel will NOT fit a 556 receiver unless you have someone swap out a Swiss trunion. With the costs of doing this, you are better off buying a 553 pistol, then have the barrel installed into the pistol receiver. Cannibalize your 556 for US made 922(r) compliant parts. And have the upper refinished in SIG gray. Please DO NOT butcher that barrel trying to make it fit the 556 receiver. You would be better off having a gunsmith make you a custom LB-pattern barrel made to fit the 556 receiver. Frank Hatten at Antique and Modern Arms did some of these a few years ago and they looked great.

I don't believe the G3 grenade retaining clip will work; the SIG is different. I can get some dimensions off of my retaining ring if you'd like and email you the info. Email me at joshuasurowitz (at) gmail (dot) com.

Congrats on winning that barrel, you have a relatively rare bird.




You need a 550/551/553 trunion. The 552 trunion lacks the buttress surface against which the recoil spring is compressed as the carrier and piston travel rearward.

Damn it to Hell!! Now I'm broke!!

I now have a Sig-551 barrel trunnion coming to complete this project... Now I just need to find a grenade ring within the next month or so.  Due to the cost, I can't justify using a Sig-553 pistol for the conversion...  Not too crazy about selling my HK SP-89 pistol to fund this purchase.

I guess I can recoup some of the cost AFTER the conversion by selling the 16" Sig-556 barrel, a 14.5" Sig-551 barrel and a Sig-551A1 alloy lower receiver.  I'm going to keep the Sig-556 lower and have it refinished in Sig Grey as well... I still like the fact this lower takes AR magazines and MagPul stocks.

You do know that you can get a real Swiss 551-2sp from Michael's Machine don't you?

I think the OP is following the same rabbit hole I currently am... which is the erroneous "I can build a clone from a 556 cheaper than I can buy a real 55X" logic.

In my personal experience that logic is horrendously flawed if you are a perfectionist.

Cost?

I traded a Rolex Sub for mine, which was equal to about $5500-$6000. The rifle was perfect except for a few handling marks, even had a little piece of paper with the name of the police officer it was issued to in the pistol grip compartment. With the trade I received an issue sling and 10 Swiss 30 round mags.

That's the value of well over 1/2 of my collection.

Obviously his user name is a lie.

Yes, Swiss SIG's are expensive toys, I have made up my collection of just a few high quality firearms instead of a bunch I really won't shoot that much. I have been collecting and shooting for many years and that is just how my collecting style evolved. At one time I had a collection of over 70 rifles, I was going for a WWII rifle collection.

I took the same journey back when the 556 came out. I can tell you from experience the juice ain't worth the squeeze and one is better off starting with a 553. The error is often made by believing you can build your clone cheaper than a genuine Swiss gun. That may have been the case 5 years ago, but not so today.

OP, add up all of your costs and I suspect you will find that your project is going to cost you more than a factory 553 and possibly even close to a 551-2 from Michaels Machines.

Very good points...  I will admit that I'm a perfectionist (Thanks to a 25 year career in the Army.), but to a point.  After doing the math, “I” am fine with this rifle being a clone, but close enough to what I really want… A copy of the Sig-551/LB.  With my budget, it is easier for me to throw some money here and there, but far more difficult for me to put it all down in one lump sum since “Murphy” will always be there waiting by throwing an emergency issue in my face, which will take priority.

BTW, you are 100% correct about rabbit hole thing!!!!!

As for buying one of those real Swiss 551-2sp from Michael's Machine, I thought long and hard about doing that, but decided to drive on with the conversion of my Sig-556... I'm now on the 3rd year of collecting parts for this project and to be honest, my budget hasn't felt the pinch... Expect for this month.  I have a friend who is in the same boat as me, but with the conversion of his HK SL-8 rifle into a G-36E clone.   Last summer we were talking about our "projects" and at the same time shaking our heads at all to troubles we are going through, but agreed that at the end we would have something that "we" always wanted.

If I wasn’t so focused on having a Sig-551/LB clone, I would be focusing on doing a HK SL-8 to G-36E clone project myself.

This is my first and last project on this scale.  The only thing that I have planned in the near future is to SBR several of my pre-ban 9MM carbines, after getting approval from the ATF, since the State I’m retiring to might be changing their laws regarding SBRs.

As for the resale value of this conversion project over a real Sig-551-2sp, there is no comparison at all...  This rifle will fall into the same category as my pre-ban 80s HK-91, HK-93 and HK-94, which I will NEVER part with until it’s time to meet my maker.

Over the past year or two, I’ve been down-sizing my collection to stuff I really want to keep and selling off the rest.  I’ve picked up “stuff” over the years that I really didn’t want, but couldn’t pass it up since it was offered at a great or very good price, but this “stuff” has thrown me off course.  After selling off most of the “stuff,” I’m now happier with what I have. I’m not a hoarder or anything like that, but I feel like it’s time to simplify things in my life to a few choice pieces of “things” I’ve always wanted and this Sig-551/LB clone is one of them.

Again, this will be my last major firearm project.  In a weird way, I somewhat enjoy the hunt for that “one item” I must have, but at the same time, it’s time to finish this thing up so I can move onto my next passion, classic audio and video gear!!

BTW, I really like this forum... It's almost like an "AA" meeting!!

LilMAC25,

Wait till you hit your late 40s and early 50s. I guarantee that your “collection” will be in the 10s of thousands of dollars after a 25 to 30 year period of collecting firearms!!

True, but it's more like an AA meeting at a bar where everyone has fallen off the wagon. :)

Lots of enabling.

Sounds like you have fully thought through your project and I totally understand the enjoyment of the "chase" for parts and a cool project.

The last thought I will leave you with is that a friend has several of the 551 LB clone barrels offered by CGS. If you decide against the trunion swap, drop me an email and I will put you in touch with him.

Lol. This S/N is from a softball message board. I was a bigtime Mark McGwire (Big Mac)fan, but a little guy. Hence lilMAC. 25 was his jersey #.  Hence lilMAC25.

And this.


I'd rather sell my ARs than my HK Clones and 556R.  The ONLY firearm I would hold onto longer than those is the .222 Remington 600 my grandfather passed on to me.

ETA: after giving it some thought (and carrying a few 1s), it might not be 1/2 of the value of my collection, but it's barely short.

Roughly $6K, love mine.

Mike Otte is down to less than 20 last I talked to him

I was referring to "poorman".

Oops!

Just got off the phone with MichaelsMachines...

He has 11 left.

$5500 for the "low grade" and $7500 or more for the "near mint".


As he sells these rifles, the price will go up.

Truer words...I went down the rabbit hole myself with a 556 to 550 clone. By the time I finished I was only about $2K or so short of a real deal 550. It's a nice clone but resale value is not anywhere what I put into it.

Nice project. It's a great feeling when you find those elusive parts. (Spoken as someone who's been on the search for an Stgw57 barrel for quite a while...)

If you can, just pony up for the 551-2sp swat. Those will not be imported again while the 553s will be here for a bit.
Besides, it's a piece of history with the whole Louisiana DFG owning them previously. Lock up is beautiful, trigger is great, and it's one helluva smooth shooter. Sell some other replaceable firearms if you can.

I now have the 17.5" LB barrel in my possession, along with a Sig-551 trunnion... And a spare 14.5" barrel as well.  The 551-LB barrel looks new and the 14.5" one is used, but lightly, since the rifling still looks new and free of any excess metal or finish ware... There is some minor finish ware, but it looks far better than it did in the seller's original photos.

Anyway, my next mission is to find a gunsmith that specializes in Sig rifles builds for the needed modifications...  Again, I know that this is not the most effective means of converting a Sig-556 into a Sig-551 clone, but after handling the 551-LB barrel, I'm glad that I didn't go with one of those Colorado Gun Sales U.S. made copies... Which are really nice and are good quality barrels, but it doesn't have the weight and "looks" of a real Sig 551-LB barrel... Especially, the flash suppressor, which is turned/milled to the barrel as one-piece.  The CGS, version is VERY - very close, but still slightly off.

Can anybody point me in the right direction to a gunsmith who can PROPERLY change out the trunnion and barrel, as well as welding on the rear sight assembly AND basically make this clone "look" as real as possible to a real Sig-551 rifle?  

ANOTHER question to the experts!! To keep this conversion project legal with the needed U.S. made parts, this is what I'm coming up for the U.S. made parts from the original Sig-556 rifle;

1) Upper Receiver
2) Bolt
3) Bolt Carrier
4) Charging Handle
5) Hammer
6) Trigger
7) Sear

The Hammer, Trigger and Sear will come out of my spare, U.S. made, Sig-551A1 Lower Receiver.  Also, since the both the barrel and flash suppressor are a one-piece construction, "I" think I can save on "one" U.S. made part... Please correct me if I'm wrong... PLEASE!!  If needed, I think that I can use the Sig-556's recoil system and/or pistol grip, with a minor modification... Am I missing any other U.S. made parts that can be used as well?  

Again, thanks for ALL the tips and advice!!

Your scenario presents a unique one with the trunion swap. I would say on a Swiss or unmodified 556 receiver, the trunion and receiver are a single unit due to the way they are constructed. You will be swapping a Swiss trunion into a US receiver, so I think you have to count the trunion as a foreign part. I agree that the barrel and flash hider are one part with your 551-1 LB and 551-2 short barrels.

As for a gunsmith to do the trunion swap, I think your only option is Turner Fabrications. Have you tried contacting them?

922(r) parts for your build are:

Receiver
Trunion
Barrel/Flash hider
Bolt
Bolt carrier
Gas piston
Operating rod (cocking handle)
Trigger housing
Trigger
Hammer
Sear
Buttstock
Pistol grip
Handguard
Mag body
Mag follower
Mag floorplate

That's a total of 17 parts. You need 7 US parts for compliance.

Josh,

Do you have Turner Fabrication's contact info?

Again, thanks!!

Sorry, no I do not. You should be able to do a Google search and get their contact info. I've never dealt with them. Quite frankly the reason I've not dealt with them is because I think the trunion swap is a bad idea. It requires welding the trunion just adjacent the location where the bolt lugs lock into the trunion. I did a lot of research on the topic back when the 556 was first released and it was found that the 556 receiver would not accept a Swiss barrel. Several very respected gunsmiths with whom I spoke recommended against doing this. The fact that Turner Fab is the only outfit doing trunion swaps, I believe is a clue that the juice ain't worth the squeeze.

Estes Adams may also be doing trunion swaps. Not sure on this, but you can email him at sigman (at) runbox (dot) com.

It might be a little late for this (as you've already gotten the barrel), but Frank Hatten at AMA was making 551 and 550 clones.

He was making the barrels with the flash hider machined into the end as on the Swiss 550's and 551's.
He wasn't doing the threading on the inside of the flash hider/muzzle, but externally I believe they were pretty much the same dimensions as the Swiss rifles.

It might be worth giving him a call (just another option)

Sorry, did not read it right. Forgot that form 1 allows that. Removing the trunnion is not a fun or cheap job. Who ever is doing it would have to have some custom jigs to be sure that it all lines up after welded together. If I had the time ((hahahahaha) I would make an all steel, super duty jig that could hold it all straight. Maybe one day. I am so busy with Sig refinish work. Now have 8 rifles and 4 pistols in for Sig grey, and 3 rifles for Sig black.

Maybe someone already responded with this but

Estes Adams can install a Swiss barrel without yes WITHOUT the trunion

He did my 556 to 553 conversion pistol

I think it cost me 130.00 for him to do

He does awesome work by the way...

interesting

And that's what I originally thought...

But I had my friend send his rifle out first

Estes uses a grade 8 bolt and stamp fits the barrel into the 8 bolt, pins it and indexes the barrel

It's very interesting to see the process...but it works and is accurate at least as far as a 9" pistol goes

I highly recommend his work. If you don't have $500.00 lying around it's the way to go!

I am not going to do it to my early JS serial 556 just because I may hold out for a 553 pistol

And the early JS are becoming a rarity.

I too have an early JS prefix 556 rifle.  I was later told that it has more original Swiss parts than the later rifles.  I have indetified the gas block by its Swiss stamp marks, the bolt and carrier have serial numbers that do not match the reciever or each other, so I assume Swiss?  What other features and or build components do the early rifles have?  I am glad to hear that Estes Adams does good work, as I just sent him a different 556 to have the Swiss rail welded on.

Well that is interesting. BUT for the love of all that is holy, I would hope the OP will not destroy a rare Swiss barrel with this install method.  Any chance you can post photos of the mods Estes performs to install the barrel this way? Did you have a 552/553 barrel installed?

I had him install a 552 barrel with a 553 gas system.

As for the parts count everything on the EARLIEST is all Swiss minus

*US parts include:

The barrel

Upper receiver / unsure if these are Swiss with US welded non auto trunion

"Early JSXXXXXX seem to have poor welds"

Upper rail/ 4 torx bolts

Takedown pins

Lower receiver

Magazine release

Trigger guard/pins

Castle nut

Buffer tube

Stock/ Israeli

Hand guards / Israeli

Flash hider/ crush washer

Pistol grip/ floor plate door

*Swiss parts include :" at least on mine" from the factory

Bolt, serialized

Bolt carrier, serialized

Gas tube/ valve

Triple roll pins

Piston/ spring

Charging handle" angled"

Gas block

Safety selector

Hammer/ internals

NOTE: I am not sure about the trigger itself or the upper minus the reunion being Swiss???

This explains why they were over $2400.00 to begin with

I believe the trunion was Swiss on the early JS 556s. It is not clear whether Exeter brought in fully machined trunions or unfinished castings, then machined them in the US. The early triggers and sears looked identical to their Swiss counterparts, save for the finish. Again, not sure if the unfinished parts were imported then finished in Exeter.

Why they decided to use such crap-tastic Israeli furniture is beyond me. Are you certain the pistol grips are made in the US and not Israel?

Throw one or two transferables in the mix and then it starts adding up fast.

I've reached out to Estes and will be sending everything out to him sometime in mid/late May for the conversion work.  Finally collected all the small parts, to include the barrel's grenade tension ring... Almost there!!

I've reached out to AMA earlier this year after hearing that they might be doing a run of Sig-550/551 barrels, but never heard back from them... "If" they should offer a quality made Sig-550 barrel within the next year, I "might" think about a Sig-550 clone project.... If my second Sig-556 doesn't sell... Which was going to help fund a Steyr AUG purchase.