I have wanted a 783 pre-fit barrel in 7.62x39 for a while, and couldn't find anyone currently chambering in this caliber t my specifications. Well, X-Caliber is the only that could, so I decided to place an order. I went with a 416R SS, 20" with 11* crown, in the Remington Magnum profile, chambered in 7.62x39, with a .308 groove diameter, as I planned to handload for this rifle exclusively with .308 projectiles.
The next afternoon, I received a phone call from X-Caliber stating that my .308" groove diameter was not doable do to SAAMI safety concerns, and because they didn't have the correct pilot for the 7.62x39 reamer they had. I was told they would do it, but could not in order to meet the 5 week lead time. I conceded that it wasn't doable and settled on the standard .310" groove diameter. Boy, am I glad I did.
The rifle arrived in three weeks if I remember correctly, and I proceeded to install it that following weekend. This was not my first 783 barrel swap, so this was standard fare for me. If you decide to do this same swap, use Clymer SAAMI spec go/no go gauges.
Let me say this. The barrel arrived in excellent shape and was above my expectations. The chambering engraving is a bit far back, and is almost completely hidden by the barrel nut, but for me this isn't an issue. For some it might be. The profile is spot on for a Remington 783 and fit like a glove, in the factory stock. The matte finish I ordered contrasts with the matte Remington finish perfectly. The first five rounds down the pipe were Winchester 123 gr FMJ brass, and they printed under an inch at 100 yards. I was using a Simmons 8 point 4-12x40 scope that is usable but not super clear. So, that's saying something. I have done no break-in procedure, and was able to get these kinds of groups. Even my 76 year old neighbor shot this rifle and was impressed.
My handloads are 125 gr Sierra Pro Hunter .311" projectiles, and I was able to tune this round to 2408 fps, once-fired Winchester brass, printing .865" at 100 yards. I couldn't be happier with this barrel. It truly exceeded any expectations I had, and I'm very happy with my purchase. I'm seriously thinking of barreling a .223 783 in .204 Ruger with an X-Caliber barrel. Yes they're that good folks. This is my new deer rifle from now on. Don't hesitate to order a barrel from this great company. You'll not be disappointed