- Sun Jul 26, 2020 12:59 pm
#36063
Parts shortages and shipping delays have stalled this thread much longer than planned but I can still get a solid start on it.
Most of this will apply to basically any AR setup but I will also point out some tune ups that should be left to “competition use only” and others that are more along the lines of SHTF/home defense. An AR for home/self defense? With the right ammo, yeah - it is an option but more on that later.
The general idea to keep in mind with any AR build (direct impingement or piston driven) is they are gas operated. Gas is the heart of the design and should be a major focus when you start your build or when you start tuning your factory built AR. I have seen many factory built and home built ARs that treat the gas system more like an afterthought when it should be a major focal point in the build. Just to stress the importance of the gas system, I am going to start this with two parts that will seem slightly odd...
The Barrel and Gas Block.
What? No upper receiver and lower receiver as starting point? Nope.
My starting point for an AR is always the gas system. The initial point is actually the gas block but you cannot pick the gas block without deciding what barrel you want to use because the gas block has to match the barrel diameter.
Most of us are likely using one of the standard AR profiles but it is easy to figure out if you have a pair of calipers - simply measure the diameter of the barrel near the gas port. Many government profile barrels (including SPR profile) will be .750” but if you are just ordering the barrel for the build, the specs for the barrel diameter at the gas port will always be included so you can pick your barrel and order your gas block as soon as you have chosen a barrel.
Worthy of all caps:
SPEND THE MONEY FOR AN ADJUSTABLE GAS BLOCK
There are several good ones on the market - JP, Odin, Superlative Arms (my current favorite but it may not work with some really slim free float handguards), etc.
Why spend $75-$110 or more on an adjustable gas block when you can get a low profile block for $20?
Gas runs the gun and ammo shortages have resulted in manufacturers making some odd decisions to please the average gun buyer. People expect their ARs to run cheap ammo. Cheap ammo is often underpowered compared to milspec ammo and that means less gas to make the gun cycle. In order to make their ARs run cheap ammo, many manufacturers simply increased the size of the gas port in the barrel. It’s the cheap and easy fix to make an AR run under powered ammo...but it also means the gun will be overgassed with milspec ammo as well as most warmer commercial ammo.
Why is this a big deal?
Overgassed ARs have much more recoil/muzzle rise than necessary, they will wear out parts faster due to more violent cycling and they are much more apt to damage your brass if you are a reloader. None of this is good.
An adjustable gas block will allow tuning the AR to whatever ammo you are running so that it has no more recoil than necessary to run (obviously, with a slight safety margin). Other bonuses: moving parts will last longer, brass will not take as much of a beating, you can shoot faster while still maintaining accuracy and, with the right block, the AR can even run a bit cleaner and cooler.
How much less recoil? Many may find it hard to believe but an AR shooting milspec M193 or M855 can have recoil and muzzle rise that is about like a Ruger 10/22.
Coffee break...and then some pics.
Most of this will apply to basically any AR setup but I will also point out some tune ups that should be left to “competition use only” and others that are more along the lines of SHTF/home defense. An AR for home/self defense? With the right ammo, yeah - it is an option but more on that later.
The general idea to keep in mind with any AR build (direct impingement or piston driven) is they are gas operated. Gas is the heart of the design and should be a major focus when you start your build or when you start tuning your factory built AR. I have seen many factory built and home built ARs that treat the gas system more like an afterthought when it should be a major focal point in the build. Just to stress the importance of the gas system, I am going to start this with two parts that will seem slightly odd...
The Barrel and Gas Block.
What? No upper receiver and lower receiver as starting point? Nope.
My starting point for an AR is always the gas system. The initial point is actually the gas block but you cannot pick the gas block without deciding what barrel you want to use because the gas block has to match the barrel diameter.
Most of us are likely using one of the standard AR profiles but it is easy to figure out if you have a pair of calipers - simply measure the diameter of the barrel near the gas port. Many government profile barrels (including SPR profile) will be .750” but if you are just ordering the barrel for the build, the specs for the barrel diameter at the gas port will always be included so you can pick your barrel and order your gas block as soon as you have chosen a barrel.
Worthy of all caps:
SPEND THE MONEY FOR AN ADJUSTABLE GAS BLOCK
There are several good ones on the market - JP, Odin, Superlative Arms (my current favorite but it may not work with some really slim free float handguards), etc.
Why spend $75-$110 or more on an adjustable gas block when you can get a low profile block for $20?
Gas runs the gun and ammo shortages have resulted in manufacturers making some odd decisions to please the average gun buyer. People expect their ARs to run cheap ammo. Cheap ammo is often underpowered compared to milspec ammo and that means less gas to make the gun cycle. In order to make their ARs run cheap ammo, many manufacturers simply increased the size of the gas port in the barrel. It’s the cheap and easy fix to make an AR run under powered ammo...but it also means the gun will be overgassed with milspec ammo as well as most warmer commercial ammo.
Why is this a big deal?
Overgassed ARs have much more recoil/muzzle rise than necessary, they will wear out parts faster due to more violent cycling and they are much more apt to damage your brass if you are a reloader. None of this is good.
An adjustable gas block will allow tuning the AR to whatever ammo you are running so that it has no more recoil than necessary to run (obviously, with a slight safety margin). Other bonuses: moving parts will last longer, brass will not take as much of a beating, you can shoot faster while still maintaining accuracy and, with the right block, the AR can even run a bit cleaner and cooler.
How much less recoil? Many may find it hard to believe but an AR shooting milspec M193 or M855 can have recoil and muzzle rise that is about like a Ruger 10/22.
Coffee break...and then some pics.