Re: Just ordered a Rock Creek barrel
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What sort of velocity difference have you seen between the 265 ULD RBBT and the 290 ULD RBBT?
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Figure about 150 fps more for the 265 at the same pressures. I shot them both yesterday and they averaged 138 fps faster but the 290 load seemed just a bit hotter. Also the new 265's I'll try next will be shorter.
Here were the loads:
265 RBBT Bonded, 98 gr US869, Fed 215, Nos Brass, 3.6" OAL: 2827 fps
290 RBBT, 95 gr US 869, Fed 215, Nos Brass, 3.6" OAL: 2689 fps
Again, that's from a 26.7" long standard 300 RUM. Temp, 43 degrees.
In addition to the extra length, these weren't quite as slippery as the flat base 290's I tested earlier. There was slight extraction resistance on a couple of shots with each bullet indicating those loads need to be backed down a couple of grains. I'd expect a 30" barrel to give a good 100 fps more than mine at least.
The other news is these bullets turned out to be too long for my 1:9 twist. The 265's built on the shorter jacket should work for me so I'll try them next. I would expect a 1:8.3 to work fine for the 290's, but my 1:9 just can't handle them.