Off Billet
What are the things to look for when choosing an AR15 for target/varmint hunting?
I enjoy target shooting in my backyard, where i have a safe 100 yards with backstop, in the countryside, and some day i would like to go prairie dog hunting. I already have very nice .17HMR and .223 bolt-actions, and currently have been saving to purchase a nice AR15 for this. The .223 performs ballistically and economically for what i want to do, but I am not very familiar with the AR15 rifles.
What are the accuracy upgrades done to this rifle, available from the makers? What upgrades can be done by the owner without gunsmithing? What is a good length of barrel, for a gun that won’t be carried around in the field out of a case? What are the different receiver styles that i see on the guns? Some are original looking, others streamlined billet. Advantages? What is a very good yet affordable trigger upgrade to get a very clean breaking pull with almost zero travel (like a Tikka T3)?
Can i buy another cheap barrel / top receiver off the net without FFL to swap for plinking?
Accuracy upgrades include (but are not limited to)…
- Free-floating the barrel with special handguards.
- Installing a match-grade barrel with a chamber that is tighter than 5.56NATO specification, (examples are the “Wylde” chamber and the .223 Remington specification chamber).
- Increasing the length of the barrel beyond 20 inches.
- Increasing the thickness of the barrel profile.
- Having the barrel ‘fluted’.
- Having the barrel cryogenically stress relieved.
- Using alternative stocks, pistol-grips and handguards.
The upper receiver types fall into three major categories:
- The A1 style looks like the M-16 A1 rifle from the 1960′s. The rear sight does not have elevation adjustment. Elevation adjustments are made with the front sight.
- The A2 style looks like the M-16 A2 rifle. The rear sight can be adjusted for elevation and windage.
- The ‘Flat-top’ style looks like the carrying handle was removed and a slotted rail was machined for mounting scopes and other accessories.
(The A3 style is a ‘Flat-top’ with a carrying handle accessory included with the rifle. The carrying handle is removable and equipped with a rear sight which is adjustable for windage and elevation.)
Yes, you can purchase a different Upper Receiver to mount onto a Lower Receiver.
The Lower Receiver is the part which requires an FFL Dealer to facilitate the purchase.
Some AR-15 manufacturers’ Lower Receivers are built to specifications which differ from ‘standard’ for a variety of reasons. Ensure the upper and lower receivers are compatible before purchasing.
Similarly, the ‘Take-down Pins’ may be of a different size, depending upon the manufacturer. There are parts available to solve some of these compatibility issues, but due diligence is required.
Some of what you ask is beyond my expertise, so I’ll let other people answer your question about trigger upgrades.
I suggest visiting the link below, browsing the AR-15 forums and following links to the major manufacturers for additional information.
I enjoy shooting my Bushmaster. Good luck with your shopping experience. 
