i have always built my own. i'm a high-volume shooter- i've been shooting less than ever before these last couple years, since the economy has been crap and work has been less than ideal, and i'm down to about 8,000 rounds a year. i've had years where i fired in excess of 15,000 rounds, through 2 or 3 different weapons. wasn't that long ago you could get xm193 for $0.16/round, and wolf for $0.08/round...
when i started building in the previous century, the parts options were pretty slim. we didn't have LMT, Sabre, KAC, BCM, daniel defense, etc, etc... we had Quality Parts Inc, Colt, and you could special order Armalite parts from a couple clearing houses, but we mostly used un-branded gunshow parts and ordered through Shotgun News- no clue what we were getting, and quality was terrible. but we'd modify parts in possibly/necessary- filing, polishing, fitting, etc, and they were really cheap, so buying extras didn't hurt too bad. the standard method was to build it up, see what failures you got, and adjust from there. once you corrected all the problems, "broke" it "in," you would have a rock solid gun, which you could then sell for twice what you had in it. we very quickly learned that QPI (quality parts inc) and Colt parts were more likely to be correct and less likely to break.. colt parts were usually three times as much as un-branded parts, and QPI parts were pretty much right in the middle- so my first half dozen ARs were probably 65% QPI guns, 20% Colt, with un-brands filling the rest. Bushmaster sprang up out of the QPI success, and for a while, became the gold standard. we LOVED QPI/Bushmaster parts. unfortunately, the times have since left Bushmaster in the dust- the technology has continued to improve, but they haven't embraced it, so nowdays i wouldn't buy anything but LPKs from those guys (and since they're over-priced, i wouldn't even do that). over the years, as the technical side has grown and more/better manufacturers have popped up, the selection is vastly improved, to the point where there are almost as many quality parts for barely any more money than crap parts- so there's pretty much no excuse to have crap parts in your gun. back in the day, you had to lap your bolts just to get them to lock up- now, you can buy the best bolt on the market for $10 more than the worst. why would anyone ever buy a delton bolt??
knowing where we're coming from, what's been a problem, whats been changed to address it, and what still needs to be done- the AR15/M16 platform is about as reliable a weapon platform as you're going to find. if you build using good parts or buy from a good manufacturer, your odds of having problems are very low. these days, my guns generally operate with a failure rate so low that it's basically non-existent. if i'm doing really custom stuff, it can take a little bit of effort to time the action- takes going to the range with different buffer weights, sometimes even opening up a gas port. but i've yet to find one that wasn't 100% after one or two fixes.
quality parts, thorough cleaning (yes- cleaning is actually important), and heavy lubrication. your gun WILL run.
when i started building in the previous century, the parts options were pretty slim. we didn't have LMT, Sabre, KAC, BCM, daniel defense, etc, etc... we had Quality Parts Inc, Colt, and you could special order Armalite parts from a couple clearing houses, but we mostly used un-branded gunshow parts and ordered through Shotgun News- no clue what we were getting, and quality was terrible. but we'd modify parts in possibly/necessary- filing, polishing, fitting, etc, and they were really cheap, so buying extras didn't hurt too bad. the standard method was to build it up, see what failures you got, and adjust from there. once you corrected all the problems, "broke" it "in," you would have a rock solid gun, which you could then sell for twice what you had in it. we very quickly learned that QPI (quality parts inc) and Colt parts were more likely to be correct and less likely to break.. colt parts were usually three times as much as un-branded parts, and QPI parts were pretty much right in the middle- so my first half dozen ARs were probably 65% QPI guns, 20% Colt, with un-brands filling the rest. Bushmaster sprang up out of the QPI success, and for a while, became the gold standard. we LOVED QPI/Bushmaster parts. unfortunately, the times have since left Bushmaster in the dust- the technology has continued to improve, but they haven't embraced it, so nowdays i wouldn't buy anything but LPKs from those guys (and since they're over-priced, i wouldn't even do that). over the years, as the technical side has grown and more/better manufacturers have popped up, the selection is vastly improved, to the point where there are almost as many quality parts for barely any more money than crap parts- so there's pretty much no excuse to have crap parts in your gun. back in the day, you had to lap your bolts just to get them to lock up- now, you can buy the best bolt on the market for $10 more than the worst. why would anyone ever buy a delton bolt??
knowing where we're coming from, what's been a problem, whats been changed to address it, and what still needs to be done- the AR15/M16 platform is about as reliable a weapon platform as you're going to find. if you build using good parts or buy from a good manufacturer, your odds of having problems are very low. these days, my guns generally operate with a failure rate so low that it's basically non-existent. if i'm doing really custom stuff, it can take a little bit of effort to time the action- takes going to the range with different buffer weights, sometimes even opening up a gas port. but i've yet to find one that wasn't 100% after one or two fixes.
quality parts, thorough cleaning (yes- cleaning is actually important), and heavy lubrication. your gun WILL run.