RRA Entry Tactical Inspection - 09/09

AR/M4 AR Technical Discussion
1

Highlights from an initial acceptance inspection of an officer’s Rock River Arms carbine.

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Manufacturer: Rock River Arms
Type: Carbine
Model: “Entry Tactical”, p/n AR1253X
Serial Number: AC2004###

Lower Receiver:

 RRA OEM two-stage match trigger, semi-automatic fire control group. Selector is the larger star-profile type. Mil dim trigger, hammer, pivot, and takedown pins. Drain hole in magazine fence. Hex bolt in grip screw. Grip is rubber Hogue-type, RRA branded. Aluminum trigger guard. Minimal mold/seam/material artifacts. Balance unremarkable.

Buttstock Group:

 Commercial dim 6-position receiver extension. End of extension cut at an angle. Buttstock lightweight plastic, very loose fit. Receiver extension (castle) nut unstaked. Standard carbine buffer, correct weight.  Balance unremarkable.

Upper Receiver:

 Railed upper receiver. Rail slots addressed (T-numbers). Detachable RRA A2-type carry handle supplied. Extended feedramps cut post-anonidizing, and remain unfinished. Cuts are even and may be machined. Balance unremarkable.

Bolt Carrier Group:

 Bolt unmarked. Extractor spring assembly includes 4-coil spring with black insert. Carrier key bears small rectangular indents for staking with no material intrusion on carrier key screws. Key screws were removed without any resistance. Bolt carrier includes shrouded firing pin and semi-auto rear tang. Balance unremarkable.

Barrel Assembly:

 16” barrel. Marked “202/P” under hand guards. Coding indicates barrel is 4140 chrome-moly steel, unlined, R4 profile. M4-type step on barrel. Twist is undetermined but as high confidence of 1/9. Heavy profile under hand guards. A2-type flash hider installed and timed correctly. Forged traditional front sight assembly with “F” marking on left side. Sling swivel installed with rivet. Side-mount sling swivel assembly installed. Front sight base installed with straight pins. Carbine-length gas system (~7”). Handguards are full M4-dim, plastic, with dual heat shields.

Gauging:

 Passes pertinent gauges. 

 Chamber checked with Michiguns Ltd “.223/5.56?” gauge. Gauge spins freely, with only slightest of hesitation upon removal. Mark-up shows first contact on gauge shoulder. Balance unremarkable.

Other:

 None

Function Testing / Live Fire:

 Officer reports 700-800 rounds successfully fired in static slow-fire exercises. Officer reports no problems. Verification of compatibility with specified training and duty ammunition pending.

Required corrections: 

 Replace supplied fire control group with standard single-stage fire control group. Stake carrier key screws. Stake receiver extension nut to receiver end-plate. Replace grip screw with slotted screw.

Recommendations:

 Conditional approval.

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2

Other Discussion:

This carbine has a couple of unique attributes. It is a recent purchase and allegedly very recent production. This sample included hand guards with dual heat shields. Others seen are typically single shields. This is also the first RRA I’ve seen pass Ned’s 5.56mm chamber gauge, despite manufacturers claims of that chambering.

The fit of the buttstock to the receiver extension on these guns seems to get worse, not better. An aftermarket replacement is forthcoming.

This is yet another sample that would be a bit handier with a lighter profiled barrel.

3

Very similar to what I found with the AR1255X purchased mid '09, except that the AR1255X has a chrome lined barrel and mine had the single heat shield.

Changed out handguards, replaced commercial tube and stock with mil-spec MOE, staked as needed and it is a decent shooter. It has become my Franken-gun that I test parts and experiment with before they go on my “better” guns.

4

What do you mean by “balance unremarkable?”

5

Other observations that might be made of that subgroup weren’t signficant enough to mention.

6

Pardon my ignorance - but why is a regular slotted screw preferred over a hex head for the pistol grip?

7

No reason other than the fact that standard screwdrivers are easier to obtain and use.

8

I thought it was also because hex screws are easier to over-torque. Same with 1911 grip screws.

My Tango Down battlegrip came supplied with a hex screw.

9

Yup. Found worldwide, and improvised easily.

10

Try to find a hex head in the field. I switched almost all of ours in Iraq from hex to Colt standard flat tip.

11

That makes sense - thanks for clearing it up guys. Hell, I have a hard enough time finding a hex head in my garage most days, but that’s a different story…