A frequent subject of discussion on this forum is “Parts are Parts.” Here is my experience building my second M4. Perhaps someone can learn from my mistakes. Please note that I am not writing this to bitch and moan, but to make you laugh at me. Enjoy. 
I had a very specific plan for the upper assembly: Noveske 16” SS PG 1/7 mid-length gas bbl (borrowing a term from Grant, I’m a “barrel snob”); LaRue Tactical (LT) Stealth Upper; Taper-pinned front sight tower (FST); mil-spec shot-peened MPI bolt carrier group (BCG). I called Grant first, but he didn’t have the barrel or upper in stock, so I found another well-known internet retailer (that shall be nameless; not G&R, ADCO, Bravo Comp) that represented that he had everything in stock. He offered to have his in-house gunsmith drill the barrel for the taper pins and assemble the upper since I didn’t have the necessary jig. The retailer specifically said he had everything, including the LT Stealth upper, in stock. I didn’t ask for prices, I didn’t ask for discounts, I just gave them the credit card info.
Three weeks went by with no response. When I called he admitted that he had sold his last LT upper to someone else after he had already billed me for it. This lie was the first clue. I should have canceled the order then. Stupid me. :rolleyes:
I called Mark LaRue, and confirmed when he would be shipping uppers again. Mark is good guy. 
Nine weeks later, the parts finally arrived. I assembled the rifle and sighted it in. Maybe 60 rounds. The FST was crooked, so I had to crank the rear LT BUIS all the way to the left to find black. Not good. 
The next weekend I took the gun and the wife to Northern Utah to spend time with family over the Thanksgiving holiday. Went shooting with sons and daughters-in-law in 18° weather. Failure to feed (FTF) every single time. I figured it was the cold. So much for showing off the new ratgun.
After returning home to warmer weather, I cleaned it and oiled it with the lightest oil I had and tried again. Same problem, but less frequently. Switching lowers, and magazines (Pmag, Brownells, H&K and C Products,) made no difference at all.
I sent the upper back to the retailer, and asked him to fix the crooked FST and the FTF problem. He shipped it back to me without comment or explanation, and would not take my telephone calls. The FST was now properly oriented. I reassembled everything, but it still failed to feed too often.
I swallowed a big helping of crow, and called Grant. Starting with the cheapest fix first, he suggested a lighter spring and buffer. I ordered the parts and tried again. No improvement. I tried different ammo. I even made some really hot handloads that ruined primer pockets. The hot loads produced some improvement, but not resolution.
I figured it was a gas problem, so I removed the FST and saw that the taper-pin holes were all wrong. This could only have resulted from the retailer’s short-bus gunsmith carelessly misaligning the taper pin jig, and then deceptively foisting the sloppy work onto me. The scumbag retailer had then tried to fix the FST misalignment by hitting it with a hammer, but the two pot metal taper pins simply crumbled. By using substandard (probably Chinese-made) taper pins instead of what he billed me for, he increased his profits a couple of dollars. :mad:
Next, I checked the size of the gas port. Exactly within tolerance. Noveske does good work. I then flared the gas hole in the FST in an attempt resolve the gas port alignment problem, and reassembled it using standard quality pins purchased from Brownells. No improvement.
Desperate by now, I pulled the gas tube and found that the flared end was abraded flat on one side. Strange. The gas key was lightly staked, and the cap screws were tight, but I noticed that gas was leaking from between the key and carrier. The underside of the key was warped and covered with deep mill marks. No surprise, the inside of the key was rough as a cob, and black as a lawyer’s heart (no chrome plating). That explained the chewed-up gas tube. I reattached the gas key to the carrier, but when I torqued the cap screws, one broke off. Even the cap screws were cheap Chinese crap. Hopeless. :mad:
I don’t know who manufactured the bolt, but it was not marked with “MP.” By now I had no faith in any of the parts I had originally purchased other than the Noveske Barrel and LT upper, so I ordered a new gas tube, BCG, and other replacement parts from Grant. Some improvement, but still, frequent FTF.
The pinned FST was essential to the philosophy behind this build, but I finally surrendered to the Laws of Thermodynamics and ordered a JP A2 adjustable-gas, clamp-on, stainless steel FST (an absolutely beautiful piece of work, BTW). The rifle works perfectly now, but only after I replaced every single one of the originally-purchased parts (except the barrel and LT upper).
Now remember that I requested, was promised, and paid for, the highest-quality parts available from what is considered by many to be a reputable retailer. In fact, he used to have a banner on this forum. In your posts, some of you guys have mentioned buying stuff from him. Instead of getting what I ordered, and what I paid for, what I actually received was reject parts (except the barrel and upper) assembled by a dishonest incompetent. It took two years, and an extra $367 in parts and shipping, to get this gun working properly. Wasted time. Wasted money. Wasted ammo.
Lessons learned:
- Parts ain’t parts: Ordering and even paying for quality parts doesn’t mean you get quality parts. Buy only from reputable people like Grant, Bravo C, ADCO, Brownells, etc.
- Good parts are hard to find: Procuring quality parts is difficult enough for people that do it professionally. It’s even more difficult for amateurs like me. One-stop shopping from someone like Grant or Brownells, or buying an assembled gun from Colt or LMT or other established manufacturer that deals exclusively in quality parts, and has a huge reputation to lose, is cheaper, and quicker.
- Appearances are deceiving: What appears to be a quality part, may actually be crap. The temptation to increase profits by using sub-standard parts and incompetent labor is too strong for some retailers. Caveat emptor.
- Every man to his trade: Don’t trust a retailer to do irreversible gunsmithing work. He might ask his half-whit brother-in-law on furlough from drug-rehab to do it for him. ADCO recently did some excellent gunsmithing for me.
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A silver Lining: Being forced to study the proper specifications and manufacturing techniques of nearly every component in the AR15 system was an education. :)
For what it’s worth. Pictures below. Note that I have since replaced the LT upper which I am using in an SPR build.
Keep You Powder Dry (KYPD)
