Part of being a responsible armed American is understanding your firearm, inside and out. We should all know the mechanics of operation. With that said, I often hear firearm owners talk about fitting and tolerances of their chosen firearm. However, many of us use the terms interchangeably. How many of you understand the difference between the two terms?
And by understand, I don’t mean ONLY know the definition of each. I mean “understand” how the two terms apply to firearms, let’s say…for example; AK-47 vs AR 15 platforms. Benefits and downside of Fitting and Tolerance as they apply to the two platforms?
@Patrick47, you are probably going to have to educate us on this area.
I never worked on the design of firearms, but my understanding is the AK parts are designed such that the nominal dimensions for each part still has a lot of “slop” with respect to mating parts. This in turn means that even with worst case tolerance stack-ups there is still a lot of space left for debris to work its way in and out without losing function. In other words they don’t feel like tight, precision designs, but are in fact designed to work no matter what conditions, including thermal expansion and contraction.
Excellent. You are spot on with your AK examples, as they apply directly to fitment. However, your tolerance reference doesn’t apply here. Tolerances literally means the allowable deviation from the originally specified dimensions for a manufactured part. We can probably agree that Tolerance and Fitment are closely related, however, they are distinct. For example, I purchased a nickel boron BCG for my AR that is well within the allowable deviation for this particular part. However, it didn’t cycle properly. Obviously, a fitment issue. So in this example, Tolerance and Fitment are mutually exclusive. But, more often than not, Tolerance and Fitment work together.
One of the benefits of tighter fitment is that the AR platform is more accurate than the AK platform. Another is the longer service life of the AR. Whereas, the AR platforms won’t do well in the mud, dirt, or sand. Friction rears its ugly head.
Kinda confused as to where this is going and to what end. I “fit” parts to my 1911 so that they function, the tolerances are for reliability as well as visual appeal. (ie: the gaps in the beaver tail) On current generation AR’s almost EVERYTHING is spec’d out to a particular tolerance via CNC and CAD/CAM so 99% of the parts are interchangeable and will “function” when you get down into the weeds on creating a “match grade” weapon there are more things that you can do to ensure that there is zero tolerance such as facing the upper receiver for perfect barrel fitment and alignment.
Not sure why you think you are confused Craig, because your response shows your ‘understanding’ of Tolerance and Fitment. Your understanding is confirmed in your example. That is where I was going with this request for dialogue on this subject…understanding is the “and to what end.”
