The 6BR Improved UBL -- A New Wildcat on the Prowl
Now you can have it all with 107s--speed, accuracy and no-turn convenience.
In the picture above, the cartridge lineup (left to right) shows:
1. Standard 6mm BR Lapua case
2. Fire-formed 6BR Improved UBL
3. 6BR with neck expanded to 6.5mm, partially sized back down to 6mm to form false shoulder, ready to fire-form with Sierra 107 Match-King
4. Formed 6BR Improved UBL with Sierra 107 Match-King.
You've all heard about the 6 BRX and the 6 Dasher, but I've been campaining yet another wildcat developed up North by Grant Ubl, hence the "UBL" in the cartridge designation. In reviewing the performance of the other 6BR wildcats, the 6 Improved UBL seems to match or exceed all the others in velocity, and it's showing great accuracy, even with no-turn necks. As advised by Grant Ubl, I'm using only Lapua brass. Grant asked Dave Kiff to grind a reamer with a .274" neck diameter, the only change from Dennis Flaharty's chamber, which had a .272" neck--supposedly large enough to eliminate the need for neck turning. However, Grant found he needed to turn necks with the lot of Lapua he had, so went with the larger neck. With the most recent lots of Lapua brass you're getting in the States, a .272" should suffice, and maybe even a .271".
Randy Gregory at Accuracy Unlimited, in Medford, Wisconsin, removed the Krieger 6.5x55 barrel on my Nesika K, then fitted and chambered a Krieger 6mm 8-twist std. Palma contour barrel, then made a set of custom dies--including a full-length sizer w/o a neck expander button, and a Forster/Bonanza Ultra Micrometer seater with the sliding chamber reamed to accept the improved case. The FL die produces around .002" neck tension, and the combination of Randy's work on the chamber and dies, along with Lapua brass, has resulted in loaded rounds with very little runout (TIR). Out of the last 50rds. I loaded, 12 had zero TIR--didn't even wiggle the needle of the dial indicator on a Sinclair concentricity checker. Three rounds had right at .003" TIR, and the rest were from .001"-.002". The .003" rounds are marked with a magic marker slash across the caseheads, and will be used as sighters.Load Testing -- Add Moly, More Varget and Bingo, 4" Groups at 600 yards
Initially, I was a bit disappointed in the 600-yard performance. Accuracy with fire-forming loads consisting of bare 107 SMKs seated over 32.5grs of Varget with Rem 7-1/2 primers. The 107s were seated to jump around .015"-.020". However, that load produced well-formed cases, with sharp shoulders. After firing approximately 50rds of bare 107s, I switched to moly'd bullets, and upped the charge to 33grs. For some reason--the change in the load or the barrel breaking-in, or a combination--the last 10-shot group I shot off the bench with a scope measured 4.3" center to center. Discount one round that was slightly out of the group (first shot out of a clean/cold barrel?), and the rest measure 3.55". Not too shabby for fire-forming loads; certainly good enough for shooting club 600yd any/any matches in good conditions.
[Editor's Note: for comparison sake, a 4.041" 10-shot Group took top honors in Light Gun at the most recent Sacramento NBRSA 600-yard match. So with very limited development, Dennis' Wildcat is capable of winning.
]Shooting the 6 UBL in Competition -- The Scenars Shine
The velocity averaged 2898 fps out of my 30" barrel, with an ES of 27fps and a SD of 9. As expected, accuracy and velocity both improved with loads in formed cases. I settled on 34.2grs of Varget with Sierra 107 MKs and Lapua Scenar 105s, while Berger and JLK 105 VLDs get 34.4grs. The Sierra 107s averaged 3005fps, with an ES of 14; SD of 5. JLKs clocked 3037fps; ES was 16, with a SD of 6. I haven't chrono'd Berger or Lapua 105s with the full charge as yet, but they shot very well during a 3x600 at the Colorado Rifle Club's range near Byers, Colorado last month. I had some elevation problems with the 107 SMKs during the first match, and wound up with an unimpressive 193-7x. However, the Lapua 105s performed real well in the 2nd match--right up until the 20th shot for record. I felt the flags were showing a big change, and instead of waiting it out, or making the adjustment using the scope's windage knob, I held off--and the rifle put that last Scenar right where I was holding--mid 9-ring. That's the breaks I guess. Wound up with a 199-13x.Now for the Bergers -- And They Find the X-Ring
I had both Berger and JLKs remaining, and finally decided to shoot the Bergers in the third match. I couldn't seem to get comfortable in my position during prep, and instead of sitting upright and starting over again, I continued to squirm around and fight it. At one point during the second string, I got so wound up that I slipped forward just as I broke a shot, which resulted in an 8 at 11:00. However, eight of the last 10 shots were Xs, so I wound up with a 194-11x. I decided there was nothing wrong with shooting Lapua 105s, at least at 600 yards, so bought another 1200 of them.
The plan so far is to shoot the Lapuas at 600 yards, and use VLDs at 1000. I'm looking forward to the opportunity to shoot several 3x1000s out at Byers next season. Given decent conditions, it's a great way to compare bullets and/or loads. I don't plan to buy any more bullets until I've learned more about how the Lapuas compare to Berger & JLK VLDs at 1000yds.Dennis Selfridge
aka - 'Flatlander'