Many, unknowingly, haven't made preferable decisions that aren't at any fault of their own as they do not have or have had access to studies of the M16 FOW. Compare and contrast the 20" rifle gas 5.56 vs a slightly lower case capacity for the same bore, or a 5.56 case capacity with a slightly larger bore, think .222. The components can work in more of a harmony that requires a reduced effort, less stress on parts. The timing of events can come together much better. Increasing the 20" rifle case capacity to 5.56 from .222 takes the timing of events from close to ideal to a margin that reduces it some, but not huge.
Enter the carbine, or anything less than the 20" rifle gas sample. The timing of the events change, those changes are a reduction in time, but are not equal for all of them. That basically means that all the items the system does has lost some of the balance it could have had. The problem is how to restore, at least some of the balance when making a carbine out of a rifle that was made on the "outer edge" of operation. To help some of the timing issues sometimes gas port distance has been extended from the bolt face farther than the traditional "carbine length", that delay can improve the timing, but you can obviously see that too long can reduce the span of function. Another alternative is to try to mimic the timing during cycling of the 20" rifle gas with a balance of action weight and spring. In the balance of weight and spring, to help improve timing, a carbine would need more weight and less spring. Unfortunately, most manufacturers have gone the opposite direction using the carbine action spring with less mass, that may not be the best direction. There are timing issues that have the potential to improve the timing issues. Cam tracking in the carriers can have a huge influence on timing of certain things, the problem is that few options are available. So, to keep things in time as much as possible, knowing that it is a compromise, how would an end user bring things back into the balance, or towards it at least? There are a few commercially available items that can help get you closer timing, but it won't get you there, even in a 20" barrel, but it is much better than what is offered normally. Action weights really need to be higher in general, but there is a limit in this system as other functions like resetting the hammer and stripping a round, etc all take work and their work shouldn't detract from the operation as a system.
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