Thread: Stupid Question. bare with me please

Originally Posted by blip

Case overall length for your rifle will be determined by either your chamber or what will fit in your mag. A rough way I do it is size a case start to seat a projectile then I load it it my rifle and close the bolt on it remove round and that will give you your max chamber length, then you can see if the round fits in your mag. That's how I do it for all my rifles without special measuring gear.

This is pretty much how I do it too, although for reference this is but a functional check as I've never found a factory rifle that I've done this with where the resulting test round would fit in that rifle's magazine... Usually you have to seat to magazine depth. It's worthwhile doing this check so you know what the difference is between mag and throat length in my estimation. Doesn't really change much though?

Originally Posted by Pommy

10 thou back from being jammed into the rifling is a good way to get a pressure spike.

Why?

Factory ammo usually has a bigger jump than 10 thou? In real world as long as the developed pressure is under the limits of containment we never know about this, and in reality most often (unless it's a heavy pill or crimped) the primer gas is enough to start the pill moving towards the leade. From what I've looked at, the highest pressure situation is starting with the pill jammed into the lands or put another way there is no 'soft' movement of the bullet so the pressure curve sharply increases until the pill starts moving and being engraved by the rifling. The bigger the gap, the longer this process takes and the slower the pressure curve increases but the start of the bullet into the rifling is more abrupt - contact rifling, engraving happens and gone basically.

As noted - we usually don't notice this happening so it's purely theoretical for most of our interest here I think as long as the pressure remains under the limits of the components to contain it. If it's outside those limits then we notice it haha.