Sig 551 Rifle Conversion!
The following blog entry was written originally on ar15.com by a Weaponcraft Customer, and he was kind enough to allow us to share it on the Weaponcraft Blog for all those Sig Rifle Fans.
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I’ve wanted a Sig 551 for many years now. So, when I was finally convinced that Sig had worked some of the “kinks” out of their process, I picked up a Sig Classic rifle. I ran about 400 rounds through it to make sure everything was working correctly, and that it was not battering the carrier as some of the earlier guns had done. Then set out to make a few changes…
First thing, the side-folding and collapsing stock had to go. it made an otherwise solid gun feel flimsy IMHO. here was my rifle about a week after I bought it:
Next, came a fix for one of the obvious differences between the 551, and the 556 – barrel length. I sent out my form 1′s, and contemplated how exactly I would get the barrel shortened. After reading around a bit, and coming across the Swiss barrel replacement instructions, I decided to just pull the barrel and send it off to ADCO (who has always delivered 110% on the work they’ve done for me).
First, after stripping the gun down, I removed the gas block. A piece of wood with a hole drilled in it, and an appropriate sized punch was all it took.
Next, I engraved three randomly placed indexing marks on the barrel and trunion so I would know where to re-torque the barrel to.
Now, for that “just pulling the barrel” part…
NO WAY!! It sounded much easier in the Swiss armorer’s instructions.
In the end, I needed a VERY large vise securely mounted to a nearly unmoveable bench, at a friend’s machine shop. I also needed a few other “tools”.
After a little heat, and a LOT of “persuasion”, I finally got it apart. The barrel went off to ADCO, the receiver went off to IDENT (had to put my “maker’s marks on), and I waited…
While the work was being done, I stripped and refinished the lower and the gas block in a gray color that looks just a bit darker than the original Swiss gray.It is a Duracoat (durabake) product called “parker”. I know some folks don’t like Duracoat, but I’ve had very good luck with the Durabake product and I’m exceedingly happy with how the lower and gas block turned out.
When I finally had my receiver and barrel back in my hands, I cleaned them both up, applied some anti-seize to the barrel “collar” and the trunion face, and thread locker to the threads, and torqued the barrel back into place via my indexing marks. two things to note here: 1) the barrel torqued back into place *substantially* easier than it came apart, and 2) it kind-of “clicked” right into alignment. Maybe it was just luck, but as I was applying the torque it slowly got firmer and then stopped dead. where it stopped was in perfect alignment with my marks. sweet!
So, I pieced the Sig together for a quick function test prior to refinishing the upper.
I’ve been shooting this thing just about every day, and it runs perfect – i’m very happy with that. Accuracy is as good or better than it was, and I couldn’t be happier with how well the gun handles.
Here was the finished gun:
