The sound level appeared to be less when compared with other subsonic ammunition we have tested. Both rifles carried heavy, Sound Tech suppressors, which dampened muzzle rise. The difference in pint of impact is due, in part, to different recoil characteristics between the high and low velocity cartridges, and occurs whenever ammunition with substantially different energy levels are used. It should be mentioned, however, that the point of impact was roughly 14-inches below, and a bit to one side of our center if aim, as both rifles were sighted in for high-velocity, 158 grain, match ammunition. We had no trouble keeping three-shot groups inside a half-inch at 100-yares, with either rifle. Slow-fire accuracy testing was conducted under windless conditions the following morning. 308 loading.ĮBR calls this ammo 7.62mm Thumper, because it uses a heavy, moly-coated, 220 grain round-nosed, flat-based bullet. ![]() We find these velocities to be very consistent and uniform for the low-density. ![]() We expect a little variation in velocity because it is very difficult to get uniform powder measurement and placement in a case that will easily hold 50 grains of powder. The Savage rifle shot its subsonic rounds at 989, 1014, 1031 10 fps, respectively. The heavier the caliber, the greater the effect, although it seems more accentuated in subsonic loadings than in full-powered loads because there is less gas to work with. As the weapon’s bore heats up from prior firing, less and less heat is withdrawn from the propellant gas by conduction to the metal in the barrel, thus we expect succeeding shots to be faster and faster as the barrel heats. The velocities from the Remington were, in order : 991, 1019, 1023, 10 fps. The rifles were taken out individually and fired rapidly over a chronograph in 85-degree ambient temperature. Velocity testing took place by loading five cartridges in each rifle in an air-conditioned room held at 70 degrees F. The second rifle was a Savage Tactical with an aftermarket Choate, Ultimate Sniper stock, a 1 in 10-inch twist barrel and an aftermarket, Sharp Shooter trigger. The first was a standard Remington 700 Varmint rifle with a 1 in 12-inch twist barrel and a synthetic stock. 308 cartridges came in we pulled two rifles from the rack for testing. 4) If the barrel has an adequate twist rate and rifling style for the bullet length and, 5) If the silencers in question have adequate clearance within the cone of dispersion that the departing bullets will describe. 3) If inherently stable bullets, with round-noses and flat-bases, are used. 2) If the first (and possibly the second) blast baffles is/are symmetrical and axially aligned with the bore. 308, one will have the greatest likelihood for dependability and accuracy if: 1) The suppressor is fastened to its barrel with a two-point mount. ![]() I covered accuracy and instability in my three-part SAR article on silenced sniper rifles, but would like to mention a few key points again. This sample of ammunition is of special interest to us because it comes at a time when very little subsonic ammunition is available in the U.S., and where accusations of inaccuracy and instability are flying between domestic importers of foreign ammunition, and some suppressor manufacturers, each blaming the other for problems their customers may be experiencing. ![]() 308 subsonic match cartridges from Engel Ballistic Research Inc., Rt 2, Box 177C, Smithville, TX 78957 Phone 51, Fax 2652.
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