Mini review of the Wold A1 (Taiwan T91) upper
Upper was installed on a generic forged lower with BCM PNT trigger and H3 buffer in standard carbine military type tube. Upper was cleaned and lubed before shooting. Extractor was replaced with Smith Ent. hardchromed extractor and BCM extractor spring w/o-ring. POF roller cam pin installed before shooting as I wasnted to see if it would prevent upper receiver wear. I did check a chromed AR15 firing pin for fit before taking it out and the pin did fit and had protrusion within 0.002" of the original pin. The rifle was run with the OEM firing pin.
Highpoints:
1) Functioned 100% with the H3 buffer when running Brown Bear 55gr, IWI M193, ADI SS109, Hornandy 55gr JHPs, and Fiochhi 40gr JHPs. Total of 220 rounds fired with the only stoppages being FTFeed from one magazine that has had previous FTF problems.
2) Ejection was consistantly at 4 o'clock with all ammo types tested, with some light brass marks behind the ejection port.
3) Recoil was mild and the handguards didn't get excessivly hot after firing 60 rounds of controlled pairs.
Lowpoints:
1) The ejection port door spring loaded stud broke (stud and spring were ejected) during firing and weren't found. The ejection port door and door spring are not of the AR15 type. Instead of a C clip, the door spring has one deformed coil that rests in a notch in the door pivot pin. The door was easily replaced with a spare with the OEM spring and pin being reused.
2) The handguards have a gap to clear the military type gas block with bayonet lug and picatinny rail. The LE type T91 doesn't have these there is exposed barrel at the front of the handguard. It's a possible burn point if the barrel's hot and you're not wearing gloves.
3) Buffer tube wear was evident after 220 rounds fired. At this point I don't know if the wear will stabilize or not.
4) The original exttractor spring was made of thin steel and visably deformed. I didn't even try shooting it with that one before replacing it with the SE extractor and BCM extractor spring w/oring.
Observations:
1) The gas system is pretty cleverly designed to be nearly soldier proof. The gas system componets can only be assembled on the stepped op rod in the right order yet can be easily removed for cleaning. Using the gas tube sleeve is genius. It allows the moving parts to be protected from dirt, lets you pull all the moving parts at once, and guides the moving parts. A 475-480 cal. bore brush fits nicely in the gas tube sleeve for cleaning powder fouling. The cupped piston face does collect fouling but it's unknown how self limiting this will be. The piston face and gas tube are easy enough to access for cleaning, if you're picky.
1a) It would have been nice if the removable gas tube and piston head were hardchromed for resistance to gas erosion and corrosion. As is you're going to be relying on user manitance and lube to keep it from rusting.
2) The upper is pretty close to a standard upper w/o a shell deflector. The biggest diference I see is the steel piece that's rivited to the front of the upper's rail that provides support for the op rod. The 2nd difference is that the upper is using a non-standard barrel nut. You'll need a different wrench for the barrel nut if you want to pull the barrel.
3) Accuraacy. I can't really speak about accuray yet since I was shooting from closer than 50 yards mostly for function testing and rough zero. I didn't see anything that was making me worry though.
4) The POF roller cam didn't prevent all wear in the upper receiver.
Gas system details:
Under the handguard is the outer sleeve that contains the operating rod and springs. Also visible is one of the two gas vents. The opening of the gas vent is blocked by the piston except when cycling
https://i.imgur.com/2k6vshu.jpg
Detail of how the op rod interfaces with the upper receiver.
https://i.imgur.com/ZcLnXnU.jpg
Detail of the steel receiver reinforcement that's riveted to the upper. Also, that's not a standard AR type barrel nut.
https://i.imgur.com/q7j9zKw.jpg
https://i.imgur.com/eqvc56G.jpg
Gas system and op rod removed from upper.
https://i.imgur.com/4X9iQ46.jpg
Gas system field stripped.
https://i.imgur.com/L7FLpuJ.jpg
Cupped face of the gas piston.
https://i.imgur.com/IsYcdRY.jpg
Gas tube/gas cylinder.
https://i.imgur.com/NHgABcq.jpg
https://i.imgur.com/Ide774r.jpg
Cam pin wear inside the upper. This upper was only fired with the POF roller cam pin installed and it still shows typical cam pin wear.
https://i.imgur.com/tWoEit7.jpg
Buffer tube wear. This is at 450 rounds fired. I don't know at this point if the wear has stabilized or will continue to get worse.
https://i.imgur.com/YZyH1nF.jpg
Bolt carrier details. The wear on the hump that's hit by the op rod is finish wear to the parkerizing, it hasn't displaced any steel. Also note the bolt carrier has sand cuts.
https://i.imgur.com/Q5DOcpL.jpg
https://i.imgur.com/lQ5bddC.jpg
https://i.imgur.com/iDoOmTQ.jpg
Wear to the bolt is also just to the finish.
https://i.imgur.com/X4Trdq5.jpg
https://i.imgur.com/dboqi95.jpg
https://i.imgur.com/rnnZWLA.jpg
And lastly, I did find a matching rear BUIS for the low front sight height. As it turns out a HK 416 type rear BUIS ( https://www.hkparts.net/shop/pc/view...&idcategory=60) will cowitness with a Aimpoint at absolute (for a normal flat top AR) height. The front sight is close to flush and the rear as plenty of elevation adjustment remaining.
https://i.imgur.com/EBUiB0O.jpg
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