Yes a simple glance at specific energy values backs that up. H. VarGet has a Heat of Explosion index of 4,050 KJ / Kg (K-Joules per kilo) putting it with all but the 'hottest' of double-based powders. It has an identical rating to Viht's N550 'high-energy' grade and is actually marginally higher than that of N560 for instance. N133 by comparison is rated at 3,630 which puts it in the lowest 10 or so ratings on this metric. (Values from QuickLOAD whose compiler obtains them from the manufacturers.) I fired thousands of 52gn match bullets / N133 through 223 in an early Remington 700VS and its throat erosion was tiny with no discernible drop in precision by the time I sold it on.
Load anything to max, or above-max, pressures and it'll burn barrel throats out.
The issue with both 133 and 135 in the 223 is that the very best bug hole accuracy is at 3600 fps with the 50g with N133 and 3500 fps with the N135 using the 55g, both bullets in 12T. My groups have been in the 1's many, many times and made me wonder why no one had ever shot this round in registered competition as it was just as accurate as the 22 pPC's that I shot in competition years ago. The 223 AI's accuracy node with N133 and the 50g is at 3850 and the N135 with the 55g is at 3650 or a tad higher.
These hot loads explain why these powders are rough on barrels in my experience,but why slow it down when those groups are so small with incredible velocity? I had rather set the barrel back or buy new barrels!
I did see fire cracking with 133 faster than H335 and 748.
I have never shot Varget in the 223 or AI since it seems to work it's best with 65g bullets and heavier.
For anyone that had any of the old AA2015, it will equal the N133 in velocity and accuracy.
6mm Bore changes the characteristics of the throat erosion of 133.
For those looking for the most temp sensitive powder for 50-55g bullets, Benchmark is where it is at. If you are looking for the longest barrel life, then H335 is King with Win 748 being a close second in the powders I have shot in the 223. H335 is simply unbelievably great in the 223 AI.
Hunting partner and I used to shoot 24K-26K rounds a year each, carried a 5 gallon bucket of ammo for each gun on the p. dog hunts, barrels on order all the time.
Anyone that has shot registered Bench Rest knows that you have to vary your loads from cool to hot weather no matter what powder you are using if you are going to shoot top end accuracy nodes, so choose your compromises carefully related to your shooting circumstances.
To put my findings in context, The results above are related to high volume shooting. Informal target shooting, slow fire results may be very different. I delegate N133 and N135 loads for special purpose loads only where extremes in speed and Accuracy are needed such as occasional shots on crows or coyote hunting.
