I currently have a new 15" On Target Technologies 6mm T/CU Contender Barrel. Prior to this new OTT Barrel I had a Virgin Valley Custom Guns 15" 6mm T/CU, and have had a couple Bullberry 6mm-223 (non improved version of the 6mm T/CU) Contender Barrels and a Custom XP-100 also.
Yep I guess I have always been a fan of 6mm's. In my current 6mm T/CU I just finished working up a few loads for it (as well as breaking in the barrel). The loads I settled on use 55gr. Nosler Ballistic Tips & 80gr. Nosler Ballistic Tips. With Hodgdon's Benchmark and the 80gr. Nosler Ballistic Tips 5 shot groups from the bench at 100 yards are averaging .655" at a muzzle velocity of 2703 FPS. Again using Hodgdon's Benchmark but with 55gr. Nosler Ballistic Tips 5 shot groups from the bench at 100 yards are averaging .823" at a muzzle velocity of 3045 FPS. I am still playing with bullet seating depth to try to shrink the groups a little more.
For a Fireform Load I have been using 55gr. Nosler Ballistic Tips loaded with Alliant Blue Dot. This is a super low recoil, low noise load, but this is not a low pressure load, it is maximum. The average velocity with this load is 2758 FPS, and the cases form beautifully. 5 shot groups at 100 yards from the bench are running right at 1". This makes for a great plinking / fireform load that is loads of fun to shoot, but keep in mind it is not a low pressure load.
The 55gr. Nosler Ballistic Tip has a Ballistic Coefficient of .276, and at 3045 FPS makes for a good performing load and I feel it outperforms what I have been able to achieve with a Super 14 .223 Contender. I have taken quite a few different varmints with this bullet in the VVCG 6mm T/CU as well as a couple Coyotes. As per the 80gr. Nosler Ballistic Tip Load, I hope to take a Whitetail or two with it this fall. While I have not taken a Whitetail with the 80gr. Nosler Ballistic Tip I have taken several Whitetails with both the 6mm-223 and 6mm T/CU in the past with different 80gr. Bullets at close to this same velocity.
As for if you should trade the barrel or shoot it, that would be a tough call, but I know what I would do, but then like I said I have always liked 6mm's.
Good luck
SD Handgunner