Service Rifle Buyer's Guide

The Service Rifle reflects the military roots of High Power rifle competition, and is intended to closely resemble the US service rifles (the current US service rifle is the M16/M4). Since the modern service rifles are not generally available to civilians, the rules allow the use of commercial equivalents (AR-15 for the M16). Certain specific modifications to the basic rifle are allowed as long as the external appearance, basic functioning, and safety features are not changed.

Rules

High Power rifle is governed by rules set forth by the sanctioning bodies. The National Rifle Association (NRA) is the oldest and best known sanctioning body but the Civilian Marksmanship Program (CMP) is beginning to play a larger role in sanctioning local club-level matches. Each body has its own rules but for the most part the rules are the same - especially the rules governing the rifles. A rifle that meets one organization's rules will also meet the other organization's rules.
This guide is not a substitute for the rules. Be sure to refer to the actual rules before purchasing a service rifle or any other gear.

What to Look For

20 inch barrel, heavy contour, with 1-8 or faster twist rifling - The rules limit barrel length to 20 inches; an AR with a 20 inch barrel is "standard". A heavy contour barrel whips and flexes less during firing and handles the heat of rapid fire better without changing point of aim. Flash hiders are permitted but are not required and do not help accuracy. A twist rate of 1-8 (the bullet spins once every eight inches it travels) or quicker is necessary to accurately shoot bullets in the 75 grain class or heavier, which is important when shooting at 600 yards.
Float tube or equivalent quadrail handguard - The use of a sling is critical to accurate shooting, and without a sling you are just wasting ammunition. The sling must be tight to be effective, and that places a lot of tension on the front sling swivel. Standard AR-15s mount the front sling swivel on the barrel; a tight sling will bend even heavy barrels enough to change the point of impact. A good competition rifle incorporates a float tube inside a standard handguard or a floating quadrail handguard that is attached only at the receiver. The front sling swivel is mounted to the float tube, and since the float tube does not contact the barrel the tension of the sling extends back to the receiver and does not change the point of aim.
Military-style sights on an A2 carry handle
Iron sights must be the type normally issued with iron-sighted M16s, with the front sight on the front sight tower and the rear in the normal position in the carry handle. Flip-up and other aftermarket sights are not allowed. Rear sight hoods and replaceable (smaller) apertures are allowed and prefered. Look for 1/2 or 1/4 minute per click sights. The front sight must be a post, and a "National Match" post is best.
Scope on an A4 receiver
Scopes have been allowed for the past several years, consistent with the military's switch to optics for combat. Scopes may be fixed or variable power but are limited to 4.5 power with a maximum objective lens diameter of 34mm. The scope should have 1/2 or 1/4 minute adjustments and "target" turrets that are marked in minutes of angle and adjustable using fingers alone (no coins or other tools). Click-adjustable turrets are preferred since they can be adjusted without looking at the turret. No single reticle style is the best, but the reticle must be fine enough to permit aiming accurately within an inch at 200 yards under all daytime lighting conditions. Lighted reticles generally offer no advantage. Acceptable scopes may range from $200 to several thousand dollars, and in general you get what you pay for in terms of clarity, function, repeatability, and reliability. Most major manufacturers make suitable scopes, and Vortex, Leupold, and Nightforce are often seen on the firing line.
Don't be tempted to mount a scope on a carry handle - not only will it be too high to meet the rules, it will be impossible to use well. Get an A4 (flat top) upper and good cantilever scope mount (normal scope rings will not mount the scope forward far enough).
.223 Rem/5.56 NATO caliber - The rules require that the rifle be chambered in 5.56 NATO/.223 Remington caliber. Most good competition barrels will have a Wilde chamber or some variation of it, which is much better than a standard military chamber.
Buttstock - The rules permit a fixed or adjustable buttstock. The buttstock cannot have an asymetric or adjustable cheek rest or buttplate. A standard A2 buttstock is inexpensive and works for most people. If you want an adjustable buttstock, look at the Magpul UBR. There is a Gen I and a Gen II UBR; the Gen I is out of production but currently available from White Oak. Many shooters prefer the Gen I but both are excellent buttstocks.
Pistol grip - Only standard A1 or A2-style pistol grips are allowed.
Trigger The rules require a curved trigger with a minimum pull weight of 4.5 pounds, and a good trigger is critical to getting the most accuracy out of any rifle. A standard AR trigger is "single stage", which has a consistent pull weight and travel from the time you start pulling to the time the rifle fires. A "two-stage" trigger has two distinct stages. Most of the weight is in the first stage; you "take up the slack" and pause. The final stage takes just a little more effort. The benefit of the two-stage trigger is that it is a 4.5 pound trigger but feels like a lighter-weight trigger. Really good triggers are fully-adjustable for first and second stage weight, sear engagement, and overtravel. Two-stage triggers that come with competition-ready rifles are generally pretty good, and are easily upgraded later. Giesselle (the Hi-speed National Match model) is a very good and popular manufacturer of very high quality triggers.
Sling - While not required by the rules, you must use a sling to make the most of your ability and the rifle's accuracy, and you will get no respect or help from the other shooters if you do not use a sling. The rules do limit the sling, if used, to be either a standard military "M1" web sling (WWII/Korea) or a M1907-style sling. The sling takes a lot of abuse and is critical - use a good one and replace it when it wears out.
Extra weight - Many shooters add weight to their rifle to balance the weight and slow down the normal movements while aiming. Lead weights that fit inside a standard A2 handguard and in the storage compartment of a standard A2 buttstock are available and can add several pounds to the rifle. Weights are available for some adjustable buttstocks and quadrails, but not all types support the addition of weight.

Don't Get

Certain popular AR-15 features are either illegal according to the rules, will hurt the accuracy of the rifle, or are just a complete waste of money.
Front Pistol Grips - don't bother with front pistol grips or other appendages. They are either illegal, unusable, or detract from the accuracy of the rifle. Handstops and palm rests of any kind are not allowed.
Flashlights/Lasers - flashlights and lasers are useless in precision shooting.
Muzzle Brakes, Compensators, Suppressors - besides being illegal in competition, muzzle brakes and compensators distract the other shooters and will make new enemies on the firing line. Suppressors are neither permitted, nor conducive to accuracy,.

Recommendations

If you have an M1 Garand or M1A already, use it and spend your initial money on a good coat, spotting scope, and scope stand. If you need to buy a rifle, get an AR-15.
If you have good eyesight (can see the front sight clearly without a lot of correction), you might consider starting out with iron sights. Not only are the rifles less expensive (no scope or mount to buy), iron sights teach good marksmanship fundamentals.
The easiest way to get started is to buy a complete National Match ("NM") AR-15 A2 (iron sights) or A4 (flat top) rifle from Rock River. If you opt for the A4, a 30mm ID Zero MOA Ultra Precision One-Piece Scope Mount from Pacific Tool and Gauge and a Crossfire II 1-4x24 scope from Vortex Optics is a good basic scope/mount option. There are many other options, but this one will take the new shooter a long way.
You can buy the upper and lower receivers separately.
The Lower Receiver Consider starting with a standard A2 fixed buttstock. Not only is it less expensive than a good adjustable buttstock, it eliminates one variable that might get in the way of learning to shoot the rifle. Look for a lower with a 2-stage, 4.5 pound trigger. Rock River and Armalite make reasonably good lowers with decent triggers. The lower receiver is the controlled part of the AR-15, so you'll need to go through a licensed firearms dealer to get it.
The Upper Receiver Look for an upper that is advertised as "National Match"/"NM" or "DCM-legal"; Look at Rock River, Armalite, or White Oak (high end). Upper receivers are not controlled, and can be purchased on line without going through a dealer.

Resources

Civilian Marksmanship Program rules: (http://thecmp.org/wp-content/uploads/2020/01/2020HighpowerRifleRules.pdf)
National Rifle Association rules: (http://rulebooks.nra.org/documents/pdf/compete/RuleBooks/HPR/hpr-book.pdf)
White Oak (https://www.whiteoakarmament.com) (uppers, parts, tools, accessories)
Rock River (https://www.rockriverarms.com) (uppers, lowers, complete rifles)
Brownells (https://www.brownells.com/) (parts, tools)
Armalite (https://www.armalite.com/) (uppers, lowers)
Geissele (https://geissele.com/) (triggers, scope mounts, quad rails)
Wisconsin Trigger Company (https://wisconsintrigger.com/) (triggers)
Creedmore Sports (https://www.creedmoorsports.com/) (accessories, parts, most gear needed for high power match shooting)
Leopold (https://www.leupold.com/) (optics)
Night Force (https://www.nightforceoptics.com/) (optics - Competition SR Fixed 4.5x24)
Vortex Optics (https://vortexoptics.com/) (optics - Crossfire II 1-4x24)
Turner Saddlery (https://turnersling.com/) (1907-style slings)
Pacific Tool and Gauge (http://pacifictoolandgauge.com/) (Scope mount)