Short answer: the AR-15 is smaller, lighter and cheaper to shoot in 5.56. The AR-10 is bigger and heavier and fires .308, which hits harder at distance.
Size and weight
AR-10 parts are larger and heavier. Expect a bigger rifle with more recoil.
Ammo
5.56 is common and light. .308 is more powerful, with a heavier bullet and larger case.
Parts
Many AR-10 parts do not swap with AR-15 parts. Check each part for the platform before buying.
Use
Use an AR-15 for training, home and light-duty. Use an AR-10 for bigger game and longer range.
See the AR-15 vs AR-10 platform guide and our .308 ammo guide.
How to decide
- Distance: inside 300 yards, either works. Past that, .308 carries more energy and handles wind better.
- Game: for deer-size game, .308 is a common choice. 5.56 is better for varmints and training.
- Weight: an AR-15 can be a pound or more lighter, and recoil is milder.
- Cost: 5.56 ammunition costs less per round, so you shoot more for the money.
Parts compatibility
AR-10 receivers come in different patterns, so check that the upper, lower, bolt carrier group and magazines match each other. Magazines are not interchangeable with AR-15 magazines.
Which one first
If this is your first build, an AR-15 is the easier place to start, with more parts and information available. Choose an AR-10 when you know you need the extra power.
Keep building
Browse AR-15 parts, read the custom AR-15 build guide, or let our Palmetto, FL shop help with gunsmithing and custom AR builds.
Shop ammunition by caliber at BMTC USA, a gun shop and gunsmith in Palmetto, FL.