5.56x45mm 14.5" (Bushmaster M4) Upper
This is the upper receiver that came with my Bushmaster M4. Really about the only thing that is non-original about it is the forearm and the gas block.
| Caliber: | 5.56x45mm (.223 Remington) |
|---|---|
| Barrel: | Bushmaster 14.5" chrome-lined with 1:9" twist |
| Muzzle Attachment: | Izzy flash suppressor (permanently attached) |
| Forearm: | YHM Smooth Carbine |
| Main Sight: | Trijicon RX06 Reflex Site w/throw lever mount |
| Backup Sight: | YHM Flip-Up Hooded Front Sight/Gas-Block, Magpul Gen2 MBUS flip-up rear sight |
The upper receiver, barrel, bolt carrier group, and flash hider are all made by Bushmaster. It has an A3 (flat top) receiver, and an Izzy flash suppressor.
This upper fires either the 5.56x45mm NATO cartridge or the .223 Remington, the two being almost identical. This cartridge has excellent ballistics, shooting flat and accurate. In addition to home or personal defense, this weapon could be used for larger varmints and smaller game.
Optics
I now have a Trijicon RX06-23 reflex sight on this rifle. It uses a combination tritium and fiber-optic light source which is always on, requires no battery, and automatically adjusts to surrounding light levels. This version of the sight uses a 12.9 MOA triangle reticle. I hope to use the upper point of the triangle for more precise shooting.
Ammunition
For self defense, I had selected the Wilson Combat ammunition with the 65gr Sierra GameKing bullet. It is "match grade tactical ammunition" that uses the bullet I believe to be most ideally suited to my rifle for defense applications. I have tested it, and it groups well for factory ammunition. I need to stock up and have several loaded magazines ready.
Unfortunately, they stopped making it.
Hornady has released a line of Critical Defense Rifle ammunition, which uses FTX bullets. In this caliber, they have a 55 grain and a 73 grain variety. Nosler has also released an interesting 64 grain bonded bullet for defense. I have tested these in this gun, and I will think about possibly selecting one for personal defense.
55 gr. Hornady Critical Defense: I test fired a single 5-rd group, and it measured 1.454" @ 100 yds.
73 gr. Hornady Critical Defense: I test fired a single 5-rd group, and it measured 2.624" @ 100 yds. No keyholing.
64 gr. Nosler Defense: I test fired a single 5-rd group, and it measured 1.829" @ 100 yds.
How much accuracy do I really need for defensive ammunition, given that I'll be using a reflex sight with a 12.9 MOA trianglular reticle? For CQB, accuracy is not really a high priority. Maybe it would be a different story if I had a decent optic mounted on the thing. So really, I should probably choose the round I believe to be most effective (as long as they don't keyhole).
All of these choices are basically moot, since I am going to essentially retire this rifle from service as a home defense weapon.