Flat top AR-15 now CMP EIC and NRA Service Rifle Legal!


Steve Smith
May 16, 2004, 03:57 PM
The 2004 CMP Competitions rulebook is out on their website. The most significant rifle rule change is the clarification of which M16 variants are considered service rifles.
From the rule book:

6.2.3 U.S. Rifle, Caliber 5.56mm, M16

The rifle must be an M16A2 or M16A4 rifle that was issued by the U.S. Armed Forces or a commercial rifle of the same type and caliber. M16 rifles must be chambered for the 5.56mm cartridge and comply with the following specific requirements:

(1) Modification to make automatic fire impossible without removing, replacing or altering parts is allowed.

(2) Magazines of the standard service 20 or 30 round box magazine dimensions must be attached during the firing of all courses and in all positions. A dummy magazine with a ramp for single shot loading may be used, provided this magazine has the same external configuration and dimensions as the standard service 20 round magazine. Dimensions for M14 and commercial equivalent rifles
Ref. Maximum allowable dimensions

(1) Depth immediately behind stock ferrule 3 ¼”
(2) Depth at front end of trigger housing bedding pads 4”
(3) Depth at front toe of pistol grip 6 1/8”
(4) Depth at toe of stock 8"
(5) Distance from rear of magazine (inserted and locked) across top of
magazine release to toe of pistol grip
Not less than
6 1/4"
(6) Width at front end of trigger housing bedding pads 2 ½”
(7) Total length from tip of suppressor to butt plate 45"
(8) Stock width immediately behind stock ferrule 2"
(9) Stock width at rear of stock 2 1/2"
(10) Stock width at front and rear of the receiver 2 1/2"
(11) Stock depth immediately behind front stock ferrule 1 3/4"
(12) Stock depth where tips of trigger housing bedding pads rest 2"
(13) Stock depth from toe of pistol grip to comb of stock 4 1/2"
(14) Stock depth at butt plate 5 1/2"
(15) Total length from stock ferrule 33 1/2" with
butt plate,
min. 32 1/2")

(3) The rear sight aperture may have a hood no longer than 0.70". The rear sight aperture may have a fixed, non-adjustable aperture insert. A corrective lens may be inserted in the rear sight hood.

(4) Rear sight windage and elevation adjustments may be modified to allow finer adjustments. The front sight blade may be fixed or lockable.

(5) To stabilize the rear sight assembly, it may be fitted with one or more pins extending down into the receiver or with stabilizing projections extending forward no more than 5/16” into the top groove of the carrying handle.

(6) The flash suppressor and bayonet lug may be removed (or the rifle manufactured without a flash suppressor or bayonet lug) to comply with current law. Barrel length must not exceed 20 inches. If the rifle was manufactured without a flash suppressor, the barrel may not be threaded to take one.

(7) A screw may be inserted in the back radius of the pistol grip where it joins the lower receiver. This screw may extend into the rear lock-down lug of the upper receiver for the purpose of securing the upper and lower receivers. The screw head will not protrude above the original surface of the receiver. Both ends of the original takedown pin must remain in place so that the original outside configuration is not changed.

(8) Upper receivers may not be changed during the firing of any match.

(9) An external device may be attached to prevent selector lever movement to the auto position.

(10) The front sling swivel may be attached to the front ferrule of the handguard orfront tip of the “tube” (in the case of a floating barrel system) as long as it remains in the 6 o’clock position and is no more than ½ inch from the original position.

(11) The M16A1 Carbine butt stock or the commercial equivalent may be installed on an M16A2 or M16A4 rifle.

http://www.odcmp.com/Competitions/Rulebook.pdf pages 22 and 23.

This NRA rule:

3.1.3 Service Rifle- Any rifle or modified rifle not covered by NRA Rules 3.1, 3.1.1, or 3.1.2, but permitted by CMP rules are considered service rifles in NRA sanctioned competition.

makes the M16A4 a legal NRA service rifle.

If you enjoyed reading about "Flat top AR-15 now CMP EIC and NRA Service Rifle Legal!" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
May 16, 2004, 04:54 PM
Steve, didn't you mean to title this thread: "Flat top AR-15 now CMP EIC and NRA Service Rifle Legal!" :confused:

If I understand correctly, the flat top was not CMP & NRA legal before, but is now due to the recent widespread adoption of the M16A4 by the armed services. Right?

May 16, 2004, 05:15 PM
So if you're running a flattop, what kind of rear sight is acceptable for service rifle?

Steve Smith
May 16, 2004, 05:40 PM
DMK, oops! Yes, you are correct. I fixed it.

Pipsqueak, the appropriate sight would be the standard detachable carry handle.

Andrew Wyatt
May 17, 2004, 01:04 PM
so, are 16 inch barrel AR's legal?

Steve Smith
May 17, 2004, 01:09 PM
I think that the CMP was a bit hasty writing this and didn't clarify well enough. I am pretty confident that the intent is to allow the flat top receiver with the detactable carry handle, and the rest of the rules still apply, but at this time it is very vague.

May 17, 2004, 01:15 PM
Been told the flat top does not have enough "up" adjustment for 600 yards, owing to the shorter screw in the rear sight / carry handle. Does anyone have any idea if this is true or not? Thanks in advance.


Steve Smith
May 17, 2004, 07:04 PM
It is often true. You should make sure the rear sight has at least 12 minutes of elevation, but that woult be minimal. I'd want 18-20 minutes of elevation. (that 20 number is a guess as I don't have any of my rifles near me)

May 18, 2004, 09:15 AM
Thanks Steve!

I've been shooting a Colt flat top, bought in '94 because "they" were going to "ban" them, and I knew nothing about Highpower. Never cared it was classed as a Match Rifle since I only really compete with my own last, best score.

Now our club is building a 600 / 1,000 yard range (we've been shooting the 600 yard stage at reduced MR63 targets at 300), and I've been trying to decide whether to rebarrel (from 1:9 to 1:8) for the heavier bullets, or get a new upper with the right barrel. Looks like I'll have to count clicks and see how much "up" is available in this sight.

Thanks again.


May 18, 2004, 10:47 AM
I started out shooting a flattop with a removable carry handle at my local range. The guys let me bend the rules a little so I could compete. I wasn't going to win the matches anyway as a newbie. I was also told about the lack of elevation range on the "6/3" sight of the A4. After looking the design over I came up with a simple fix. I made this mod to my sight and it has worked very well.

There is a slot in the bottom of the screw that the rear sight rides on. There is a horizontal roll pin that runs through this slot. The roll pin limits the upper range of the rear sight. When the roll pin gets to the end of the slot you are out of adjustment range. This was probably intended to keep soldiers in the field from competely unscrewing the rear sight and losing little springs and ball bearings. On a civilian gun it really doesn't matter.

Remove the roll pin, and then the rear sight assembly. Using a dremel tool with a cutting wheel (or something similar) lenghthen the slot to the end of the screw. The end of the slot will be now be open. This removes the restriction on your elevation adjustment and allows you to remove your rear sight for maintenance in the future without having to remove the roll pin. It is possible that the spring inside the evelation screw (which is designed to compensate for thread lash) will lack proper tension when the rear sight is raised above its original limit. This was not the case on my sight, but it is at least a possibility. If this happens, add a couple of washers of the proper diameter on top of the spring to act as spacers. This will increase the spring tension back to its original amount.

May 18, 2004, 12:20 PM
Thanks ks_shooter! I'll take my sight apart when I have some time, and look it over. Your fix sounds logical and if I can apply it, I can keep shooting this same rifle (that I am really attached to) - maybe just re-barrel for the heavier bullets.


May 22, 2004, 02:30 AM
Rather than rebarrelling, you might want to replace the upper with a match upper such as this http://www.competitionshootingsports.com/catalogue/category33/product41

You'd be competitive at every distance with the right bullets. The wind drift of the 123 gr. 6.5mm lapua scenar is MUCH less than the 80 gr. SMK 223 bullet.


Steve Smith
May 22, 2004, 09:26 AM
Atek, that upper is a LONG way from a Service Rifle upper and the caliber MUST be .223/ 5.56 as well.

May 22, 2004, 09:36 AM
Thanks atek3! That really gives me something to think about.

As the second-cheapest man in the World (my brother being the cheapest), the $1300 price tag makes me a little dizzy. However, this upper really makes sense for my situation.

We are putting in a 600 yard range for Highpower, but also a 1,000 yard range - for which I don't think any .223 is suitable (I could be wrong, I'm not well versed in long-range shooting). I thought I'd need a purpose-built ~ .30 cal for that. This 6.5 upper would function in both roles. Thanks for the tip! Got to go engage brain and consider this some more.


May 22, 2004, 09:45 AM

Thanks for mentioning those issues. I did say I wanted to keep my flat top since it was now "Service Rifle" instead of Match Rilfle... a lot to think about.

Got to get off the compter and go do chores. Garand Match tomorrow - need my mind clear for that.


Steve Smith
May 22, 2004, 04:36 PM
Considering the 90 grain .223s are out performing match grade M1As at 1000 yards, you might be surprised!

May 23, 2004, 09:21 PM
What barrel twist is generally used for 90 grain .223 bullets? I know this is a stupid question - like, how long is a piece of string? RPM depends on velocity, which depends on powder used and other factors - but what twist are people actually using?

I've been looking at the CMP Bushmaster with a 1:8 barrel, as well as the idea of re-barreling my flat top.

Too hard to type, too hard to see the screen. Maybe more coherent in the morning. Have a good night, all.


Steve Smith
May 23, 2004, 09:28 PM
1:6.5" twist is required for the 90s. I'd suggest you stay away from that as a beginner and stick to shooting 75 AMAXes or 80 SMKs to begin with. Shooting 90s is another step.

If you enjoyed reading about "Flat top AR-15 now CMP EIC and NRA Service Rifle Legal!" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!