I have a spare lower sitting around, that I want to start a long range build with. Pardon my ignorance, but what are my options for a larger caliber, that will work (if any) with a standard AR15 lower. Thanks
There are upper builds or kits from .22LR through 50BMG, and a bunch in between.
22, 9mm, 45, 5.7, 5.56, 6.5, 6.8, 300BLK are ones that’ll work with mags and the current magwell.
Then there are larger caliber bolt gun conversions…
depends on what you want to do with the gun, and how much you want to spend- since you mentioned long range, 6.5 and 6.8 will be the easiest conversions and will give you a little more range.
it’ll never be a real long range system though, and if you are punching paper, standard 5.56 (built in some type of SPR config) is the best value.
I would probably go with 6.5 or 6.8, if you don’t mind me asking, which choice (with good optics) would be more effective, in relation to accuracy and stopping power from 500 through 800 meters?
Think that 6.8 is better up close then 6.5 has more energy down range , and has accuracy on its side .
Stopping power for what?
They will both hit paper at 500-800 accurately since you can get a 24" barrel for the 6.8 as well.
Use a ballistics calculator to determine the velocity at the ranges you are looking at and know whether the bullet will expan or not for stopping power.
most hunters limit the range to under 500 due to the speed.
sounds like a job for a 308 after 500
Can you actually afford to shoot 6.8 or 6.5? Can you afford to have multiple uppers, magazines, optics in order to practice with a cheaper caliber? When you start crunching the numbers, it gets pretty expensive to support multiple calibers even if you reload.
That being said, have you ever done any shooting at 500-800m? I have. You can punch paper, or shoot at anything that doesn’t move effectively with any of the major assault rifle calibers. Things change when you need a flat trajectory and a short travel time to your target. We had guys in Afghanistan making torso hits at 600m with their “puny” 5.56 rifles and the MK262 load. Seemed to work well. The .308 will be the most capable for those tasks, but even it is pushing the limit of shooting ease. I prefer to use a .270 Weatherby Magnum for that kind of shooting as it is capable of shooting an bullet with an extremely high ballistic coefficient and sectional density, while keeping that bullet above 3000fps for the first 300m. There is a reason why most US military marksmen programs use the .300 Winchester Magnum, or the .338 Lapua Magnum.
One reason why engineers at the end of the 19th century came up with the copper jacketed rifle bullet was because lead alloy rifle bullets can only be pushed so fast before the bullet melts with gas cutting and it loses accuracy. You can pound silhouettes all day long with a .45-70 hardcast bullets at 1000m, but the bullet takes a long time to get there. In every major conflict of that period soliders would engage targets at long range and never hit them unless they were standing still. They would literally see the enemy pop up from behind cover and fire a shot at them. They would return fire on the exposed enemy, and by the time the bullet reached the enemy they would have been back behind cover. There are documented cases of this during that time period, espectially in the Spanish-American war where the slower velocity .30-40 Krag rifles used by US soldiers showed poor long range performance. This was also the first war time use of a 7mm jacketed spitzer bullet in the Spanish 7x57mm which kicked our butts. 130 years later and we still haven’t adopted this ideal caliber size. The Soviets also ran into this slow travel time headache during their invasion of Afghanistan with the 7.62x39.