A primer on the different configurations for your AR


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In the world of AR15s there are many configurations people want to build.

Some just blindly copy the configuration a cool guy has because the is abig name trainer... without really trying to understand what thier requirements are and what environment they come form ( SWAT, Personal protection, Infantry etc)

Others know exactly what they need and build themselves specific configurations.

I'll make an attempt based on shooting over 30,000 rds in the last 3.5 yrs and owning a dozen differently configured ARs as an addition to my military use of old school M16A2 and new style M4A1 over a 20 yr military career.

Please excuse my typos I will edit them out over the next few days.
This is my first cut at this and I may edit for clarity in next couple of days.

Also there is often some overlap between these configurations and shared features.
For example many Infantry builds feature free float rails these years.. (which use to be a feature only for accuratized rifles) even though they are not strictly necessary to fulfill that mission.

1) I'll start with the configuration that's easiest to explain.
The "DMR".
DMR stands for "Designated Marksman".

The term comes from the military where a smaller military unit such as a Squad (9-12 men depending on service and nation).
Such small units usually do not feature an organic sniper ( well schooled true long range shooter with a accurate gun usually of full powered caliber).
So this is a rifle with an emphasis on longer range shooting. Despite the AR (and the round) being optimized for rapid engagement of immediate threats ( which often means shorter ranges) many folks enjoy setting their rifles up for as much capability as possible at long(ish) ranges as well.

A historical example are the scoped and hand selected G3s issued to a few select shooters in German Infantry squads/platoons in the cold war (The G3 being at the time their standard infantry rifle making for commonality of ammo and magazines with their infantry rifles...... this is a common feature of a proper DMR)

DMR builds can be interesting and satisfying and are often a good fit to daytime hunting of smaller game.
The characteristics of a DMR configured AR15 are:

- Full length barrel. This usually means 20 inch, though some folks also use 18 inch barrels. The barrel may be matchgrade and its quality is a tad more important than for other configurations.
As a result some folks will often drop the chrome lined feature for a meloniting or similar treatmeant.
Chrome lining is great for longevity at higher rates of fire (lower priority which a DMR) but does not help the accuracy.
Only the spendiest barrels are still accurate with chrome lining... nitriding and such treatments make it easier to get an accurate barrel because chrome lining often introduces inaccuracies. Stainless steel barrels are popular for this reason. They partially negate the need for a lining and are easier to make accurate.

-Generally to be considered a useful DMR rifle folks expect 1 minute of angle accuracy ....this means the impact of the round at 100m when shot from a fixed bench cannot be further than 1 inch from the point of aim when using matchgrade ammo.

- free float rails. Self explanatory.. this really helps accuracy and is amust for a proper DMR.

- The sights will generally be magnified and variable glass optics. This works well for deliberate long range shooting.

- Trigger.. for a true DMR build a stock and /or milspec trigger simply wont do. Rock River sells a popular and affordable 2 stage trigger for ARs and at a higher price point so does Geissele. In recent years many other trigger options have been added.
W/o a good trigger a DMR build is not complete.

- Often a Bipod is added i the front and the stock is a traditional long and fixed stock optimized for the prone (such as on classic M16s) but IMO neither is stricle neccessary to make something a DMR build

- Generally a DMR rifle will fire the standatrd infantry round (in this country thats of course 5.56/.223) but the shooter may carry mostly match grade ammo in that caliber and as a minimum will have a couple mags filled only with match grade.
He will zero his rifle on the match grade ammo not the common issue ammo, even if he carries common issue ammo as well for closer targets.

2) An Infantry build.
Modern Infantry prefer rifles that have shorter and handier barrels than the classic 20 inch. The Army has been doing this for many years with the M4 and just recently the Marines have been finally moving to the M4 as well with an official adoption of the M4 for their Infantry last year.
This configuration is sometimes known as an M4gery.

Typically you see :

- A 16 inch barrel which is shortest lenght w/o NFA process or a 14.5 inch barrel wth pinned flashhider to bring it to 16 inch or for those purists who are willing to spend the extra time/ money 14.5 inch barrel.

- Barrel will wear a flash hider.

- A Infantry configured rifle will generally have a medium or heavy (HBAR) barrel as its expected to be capable a a lot of shooting ..at higher rates of fire than sa (even if semi auto)

- The Optic will generally be a fast acquisition optic such as a reddot (aimpoint and others) or a Holographic weapons sight (such as an Eotech)

- The stock will be collapsible to adjust for different firing positions, prone, standing , to help with vehicles ingress/egress, and adjust for tight spaces or body armor.

- triggers may be milspec but lately upgraded milspec triggers with a same pull lenght as military but a tad lighter/smoother have become popular.

- generally mechanical back up sights are considered a must for an Infantry configured rifle in case the electrooptic fails.

- A weapons mounted light is popular.
- Vertical front grip also very popular (easy of carry for patrolling)

- For well equipped military other acessories that support Night vision (such as a IR laser) may also be on there but IMHO are not stricly necessary to make it an Infantry configuration.

- An Infantry rifle will be zeroed not for the shooter most accurate ammo but for whichever ammo is the most reliable or cheapset is in supply chain. For military that still often means M855 but for civilian shooters it can be anything. (For me its Wolf Military Classic 62gr HP, a reliable and accurate round at a low price.)

3) The Constant-carry-carbine

This is designed to be as light as possible and is only a very small step away from the PDW role the P90 was designed for.
No only must be it light but with minimal protruding edges ( so no BCM charging handles size "large").

- A CCC Carbine will almost invariably have a lightweight cut barrel.
- It will not have aWML ( weapons mounted light) as this adds weight
- It will generally use only one sighting system w/o backup ..such as just irons ( flip ups that stay out of the way)
- collapsible buttstock a must
- May even load with 20 rd mags to emphasize the lightness.
- Barrel preferred to be short 16 inch or less

...generall worn across the back and stay out of the way while working but always be there just-in-case.

This configuration is more rare and less popular than..

4) The "Competition" rifle. As in 3 gun or 2 gun competitions that focus on fast reacting short range fire.

- Barrel can be almost anything except long. 16. 14.5 even lower..
- often a lightweight cut
- A fast aquiring electrooptic such as an Ampoint or EOtech, often without back-up sights
- adjustable stock
- generally no weapons mounted light.
- Flash hiders replaced with muzzle brakes.
- Invariable will have upgraded charging handles, sometimes with large latches.
- Often angled front grips displace the vertical front grip on these as almost all this shooting happens using "C gripping".

5) The "SWAT" configuration.

- Adjustable stock
- Short barrel
- Weapons Mounted light
- IR laser and visible laser (usually in one unit such as with a DBAL)
- A fast acquisition electroptic.. While an infantry rifle may often run an ACOG instead of a redot or holographic sights this configuration invariably will stick to Aimpoint, EOtech and similar.
- vertical front grip almost always there.

This is popular wiht folks who start out as it looks "coolest".

I usually recommend to noobs to start with the Infantry configuration.
as for my rifles personally have configured most of my ARs as Infantry rifles , but I also have a DMR a CCC and a SWAT (ish) rifle as my Nightfighter.
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