G&P XM177-E1 Review

By MikeG
Nov 08, 2007

History of the XM177

The XM177 was designed by Colt as a part of the CAR-15 program that aimed to create a carbine based on the M16. The main differences from the XM16 and M16A1 were that the XM177-E1 featured a 10″ barrel, a 3 position rubber coated aluminum or polymer collapsible stock, and round hand guards while the XM177-E2 had a 11.5″ barrel.

The XM177′s short barrel caused 2 problems.  First, firing 5.56x45mm with such a short barrel would produce a blinding and deafening muzzle blast.  Second, the gas port in the barrel that accepted expanding gasses from the cartridge ignition to work the action had to be closer to the muzzle.  Testing showed that due to this, the gun might not cycle reliably in some conditions.  To help compensate for these problems, Colt designed a large ‘flash and sound moderator’ to be attached to the tip of the barrel in place of a standard flash hider.  Though it did reduce these problems, it did not completely eliminate any of them.

The XM177 saw most of its use in the Vietnam war. The Army issued XM177s to infantry (it is seen frequently in photos from the war), but the Air Force was the only branch of the military to officially adopt the weapon. It was dubbed the GAU-5/A and given in small quantities to guards on airbases.

The Replica

I have been very impressed with the appearance and feel of every G&P AR I’ve handled. The XM177-E1 is no exception. It has a tight fitting body with relatively little play in the fit of the charging handle and bolt catch. The entire gun is very solid, with no movement whatsoever between the receiver, barrel and stock tube. Most of the external parts are made of an alloy and are finished with a very durable dark gray or black paint.  I don’t think the XM177 will develop the chipping paint that many other replicas have.  The barrel and hand guard retention ring appear to be made of milled aluminum and anodized. The flash and sound moderator on the muzzle is made of steel and is finished with a light parkerization. For this type of finish on steel, it is wise to apply a light coat of gun oil to avoid developing any surface rust. The plastic parts on the gun, the stock, grip and hand guards are all constructed of and finished as the parts on the XM177′s real counterpart would be.  The front sling swivel is even rubber coated to keep it from rattling against the hand guards.

The heft and balance of the gun are extremely close to that of the real thing. Especially so when a battery is inserted into the hand guards, helping to compensate for the aluminum (instead of steel) barrel.

Some of you may be wondering how this gun is different than any other short AR, or the M4A1 in particular. First, it has different trademarks. The XM177 has authentic Colt “AR-15″ trademarks. They are deeply engraved rather than a shallow image where the receiver paint has been removed by a laser, as you would see on many other manufacturer’s full metal replicas. You will also notice that it does not have the removable carry handle of the M4A1 or M16 A3/A4.

On the other side of the receiver, you will notice that the XM177 is drastically different than most other AR rifles. It has no shell deflector, no forward assist and no ‘fence’ (the raised rail that surrounds the mag release and runs under the ejection port). Many real XM177s did have a forward assist and fence, but early examples lacked them. The lack of these features is very similar to the XM16 (or M16 Vietnam, as it is known in airsoft.) In fact, G&P’s XM16 and XM177E1 are built on the same receiver.

Looking further up the receiver, we can see that the XM177 features the original ‘windage only’ rear sight. Unlike later models, this sight requires a special tool to adjust, but still has the different sized day and night apertures.

The pistol grip of the XM177 is also different; it lacks the finger nub and rear serrations seen seen on later ARs. Personally, I find this style more comfortable.  The fire selector feel is average for an airsoft AR.  It has reasonably strong detents with audible clicks at each setting.  Unfortunately,  as the selector is turned from ‘SAFE’ to ‘FULL’, there is a noticeable and uneven friction in its action.  Note that it is wise to re-secure the fire selector switch’s retention screw with a bit of Lock-Tite if you ever have the need to take the mechbox out of the gun.  Without this, over many skirmished, the selector switch will be come looser and looser with use.

The stock is standard collapsible design but is running on a 3 position stock tube, rather than the 4 or 6 position used on later rifles.  The buffer tube is also slightly shorter than M4A1s.  When its stock is fully extended, it has the same length of pull as a XM16.  I have always felt that the stocks on M16A4s and M4A1s are too long, so I prefer this.  As you can see, there is a small defect in the casting of the buffer tube.  My XM177 is the only G&P where I have noticed a defect like this.

The stock butt is heavily checkered and stays in place well when shouldered.

Moving on, we see that the hand guard retention ring is not flared, a change that was first made in the M16A2. While a flare is nearly necessary to remove the hand guards on a real AR, in the airsoft version, it makes little difference due to the relatively weak spring behind it. The lower receiver lacks the front receiver tab reinforcement of later models. Also of note is that the G&P receiver uses actual pins instead of screws (as with most other manufacturers) to keep the upper and lower together.  This makes the gun easier to disassemble, however, it is possible that the pin could start to work its way out of place with strenuous use.

The hand guards are of the early slim round style. While this makes it more difficult to fit a battery inside, it is doable. Generally, the XM177 requires a ‘V shape’ battery constructed with 4/5A or smaller cells.

Finally, we have the ‘Moderator’ muzzle device. The XM177 was the only gun to use a moderator of this particular design. I’ve got to admit, I’m a sucker for cool looking muzzle devices.  It’s often a tipping factor for deciding between two guns for me.  Not only is this one cool looking, but it is of excellent construction.  It is made from machined steel and has well defined cuts.  It is of much nicer construction than the standard cast metal flash hider.

Performance

As mentioned earlier, the gun is built with G&P upgraded parts giving it a muzzle velocity upwards of 350 feet per second (it easily shoots BBs through both sides of a Coke can.) It has a metal loading nozzle, G&P M120 motor and the gears spin on 7mm bearings. The rate of fire on a 9.6V battery is around 900 rounds per minute.

The only letdown on this gun so far is the hop-up. The adjustment wheel does not move smoothly and consistently. Even when the hop-up is turned on fully, the BBs don’t have enough backspin to maintain a level trajectory. This may just be due to over lubrication of the hop rubber, but as I have not had a chance to put many rounds through the gun, I don’t know. If G&P has a bad reputation for anything, it’s their hop-ups. While sometimes they work well, more often they do not. I’m sure the hop-up could be fixed relatively easily however. A new hop-up rubber and bucking would probably improve it greatly. Failing that, whole new hop-up units are not too expensive.  Notice in the photo below that the ejection port cover is usually sprung closed. Due to this, there’s no hokey looking fake bolt inside.

Battery

As I mentioned earlier in the review, due to its slim handguards cannot fit a standard ‘mini’ battery constructed with 2/3A cells in its foregrip.  Instead, custom V-shaped batteries are typically used in these guns.  The 9.6V NiMH V-battery shown below is one I constructed using 4/5A cells and has a capacity of 2700mAH.  As far as I am aware, this is the highest capacity NiMH battery that can fit internally to the XM177.  However, if capacity is not of the utmost importance, nunchuck-style batteries constructed from AA cells fit into the hand guards more easily.  I currently run a 9.6V 2000mAH Intellect nunchuck battery in my XM177.  I also suspect that many sizes of the new Lithium Polymer batteries would fit easily in the gun’s foregrip.

Update: Hop-UP

Earlier today, I installed a Guarder Improved Hop-up Rubber & Bucking (The clear silicone version). The improvement in performance was drastic. Before, even with the hop-up fully ‘on’ the BBs were still dropping.  Now, with the hop-up only 1/6th ‘on’, the BBs travel with a straight trajectory. Not bad for a $4 replacement part.

Now that the hop-up is working properly, I can finally gauge the accuracy of the gun. Like any other short barreled replica, it’s not extremely accurate. Firing from a crouched position, the XM177 seems to be able to make fist sized groups at 40 feet. For a short gun with no accuracy upgrades like a tight bore barrel, I’m more than happy with this performance.

Update: Mechbox & Internal Components

After skirmishing this gun several times, I finally ran into a problem.  At my last skirmish, the XM177 stripped its piston.  This gave me an excuse to disassemble the gun and open the mechbox.  I was quite impressed with what greeted me.  As you can see in the following pictures, this mechbox is highly reinforced.  It features 7mm bearings rather than plastic or steel bushings.

The XM177′s cylinder head and nozzle are both highly polished steel.

Steel gears inside are branded G&P and came well lubricated.

The spring guide is a highly polished steel reinforced version featuring bearings for torsional spring tension release.

The gears appear well shimmed. Note that the nub on the selector gear is significantly larger than normal.  You will also notice that the contour of the tappet plate where it contacts the nub is different from standard tappet plates.

Finally, on to the piston.  I have heard reports in many forums that the white G&P pistons are among the most durable, however I did not find this to be the case.  After about 4000 rounds the sector gear tore through multiple teeth on the piston.  While I’m glad that only the piston was damaged, as it is one of the cheaper and easier parts to replace, I’m frustrated that it stripped after so few rounds.  Keep in mind, I had not upgraded or even opened the gearbox until this point.  This happened with the original 340 fps spring.  I had originally intended to keep the blue piston head as it is ported and appears to be of good quality but I was unable to separate it from the piston.  I purchased a Guarder Polycarbonate Piston w/ Full Steel Teeth and a Guarder Polycarbonate Ball Bearing Piston Head as replacements since these parts have worked well in other guns I own.  After installation, the XM177 is shooting at least as well as it did when it was new.  The rate of fire seems to have increased slightly due to the lighter piston assembly.

Update – 6/13/2009

I encountered a barrel blockage while firing the XM recently and managed to strip all the teeth off of the bevel gear.  The other gears and piston remained undamaged.  I dropped in a marui replacement and the gun is as good as new.  While I was at it, I replaced the G&P steel nozzle with a standard Guarder plastic version and the original G&P spring with a Guarder SP100 irregular pitch.  It still shoots 340fps and with my 9.6V Intellect 2000mAH battery, I’ve clocked the gun at 25 rounds/sec (1500 rounds/min).

Overall

So far, my impression of the gun has been overwhelmingly positive. I feel it was well worth exchanging my Classic Army M15 SPC for this gun. Not only is the body tighter, better made and much more realistic, the gun’s performance exceeds that of the CA with exception of the hop-up. The sound of the gun is also excellent. It makes an amazingly loud muzzle crack due to the short barrel and the moderator which seems to amplify the sound.

Performance: 3/5
The poor hop-up and questionable piston durability are the only issues hampering its out of the box performance.

External Design: 5/5
This is one of the most realistic and impressive airsoft replicas you will ever handle.

Value: 4/5
For $285 shipped from Boomarms, this gun is a great deal.

Overall: 4/5
This little gun has quickly become a favorite in my collection and I would not hesitate to recommend a G&P to anyone looking for an AR style rifle.