I've used quite a few of them at one point or another and worked for two that at one time were considered the haloed favorites.
The junk ones have long since passed. Those companies didn't last long. If your shopping and order one today you'll likely have to wait a bit. This only means that demand is high. Shooters are a demanding bunch with an eye for detail. The fact that the companies are this busy only means that the product is meeting the muster.
Buy with confidence and temper it by buying what's most appropriate for the application.
The "is my action tighter than your action" debate is often heated and passionately discussed. There's truth in it, but I wouldn't allow it to be the ultimate decision. A Nesika is one of the tightest tolerance actions you can buy. Great if your a BR/Palma shooter. It'd be my last choice if given a cart blanche decision on which gun to take to a tactical match, deployment to the middle east, etc.
Look for features like primary extraction, fire control timing, and the size of the loading port. I don't subscribe to a petite ejection port simply because at some point all rifles have a malfunction. If your a hunter buried in a snow drift with Q tips for gloves your going to have a hell of a time clearing a "double clutch" on an action with a small target style port. If the lowly M700 can shoot as well as it does with an open architecture port then there's no reason why a custom can't as well.
M-16 extractors, they seem to be the latest "gotta have it" addition to an action. I don't buy it though. Every one I've ever seen has lead to ejection angle problems. The cartridge bounces off the million dollar scope you just bought at best and at worst it flips right back into the port. Poison in every application. You can modify the extractor to alter the ejection angle, but then your robbing the amount of case rim purchase. What does this mean? In the event of a sticky case it raises the potential for a torn case rim.
The factory M700 extractor was designed to work the way it does for a reason. It kicks the case straight out at 3/9 o'clock. They are also quite strong and when properly fitted, they work extremely well. Just something to consider.
The best solution IMHO is the non rotating Mauser type found on control round feed Winchesters, Dakotas, Mausers, etc. It serves double duty. It's an effective breech block on the ejection port side of the receiver (awesome in the event of a case rupture as it helps prevent gun parts from embedding in your face like the neighborhood emo kid that fell face first into a bass fisherman's tackle box) Control round feeding just means the cartridge doesn't have tourettes when it bounces out of the feed lips and attempts to chamber.
A 3pos safety uses a firing pin block. Meaning its cammed to the rear and the trigger mechanism isn't loaded. Unless there is a catastrophic failure in the fire control, the gun becomes a club or kindling wood. It cannot fire. Not true with a Remington clone. There's a thousand horror stories worth of M700's that mysteriously go bang when the gun is dropped or when flipping the safety off.
Sako extractors are a great way to end up in the ER if you ever sneeze a case. Hope your wearing safety glasses. . .
-It's for reasons like this that most PH services in Africa demand that their clients be fitted with control round feed, 3 position safety style actions when hunting dangerous game with a bolt action. -Having been to some of the worst places Africa has to offer I have to think that Murphy and his little law thrives in that god forsaken place.
A mechanical ejector means no case preload when chambered. If were all going to obsess over the best way to chamber a barrel and hold minimal tolerances so that our brass lies perfectly aligned with the bore it seems like a mute argument when we have a spring loaded plunger poking the ass of the case over in left field. A mechanical ejector eliminates the debate. It also gives you the shooter the decision to either kick field goals with your brass by racking the bolt or have them drop in to a neat pile right next to you by being more conservative with your bolt manipulation.
I look for little things. Things that make my job easier. I don't like undercutting barrel tennons. The fillet left at the shoulder as result of my finishing insert's nose radius (the cutting tool that profiles the breech end of the barrel) empowers me to believe its a better way because its how racing crankshaft journals are designed. It's stronger this way. It'd be a simple operation to add a .035" wide 45* chamfer on the forward facing side of the recoil lug to clear the corner radius. To my knowledge I'm the only lug manufacturer that does this. It's not a big deal, but it's a pain in the arse when you have 20+ barreled actions a week to get through and you have to dedicate a machine to doing nothing but chamfering lugs.
I like truncated lead threads and action makers that invest the effort to chamfer/edge break the broken receiver ring threads that intersect the front scope base hole. To my knowledge there's only one guy doing this, AJ Goddard from Bighorn. (yes, I noticed buddy!) Anyone whos ever had to peel a galled tennon from an action will appreciate these little efforts to thwart disaster. I've just recently started incorporating it as part of our standard accurizing service for Remington/Winchester actions.
Materials:
Every custom maker out there is using premium grade materials. Some still suffer from lubricity issues, but by and large they all run well.
Long story short, if your in the market for a custom receiver, buy with confidence. It's a good time to be shopping for one as every one of them is doing a hell of a job. Just make your purchase on an educated decision based on what's most applicable for the job the gun is assigned to.
Good luck and hope this helps.
C.