Rimfire internals - Design exposition

[T-Rex]

Redesigned per suggestions.
Pretty basic.
I shortened the original endcap, as well as the blast chamber to make room for another K.

[a_canadian]

I didn't spot this while following the thread but perhaps missed it, so my apologies if that's the case. My thought is that you ought to take advantage of the external tube's volume in such a way that FRP becomes irrelevant, by cutting a path for expansion into the last stage of the K baffle stack. As I understand .22"LR dynamics, FRP happens in the initial volume after the muzzle owing to the intense heat coming into contact with a supply of fresh oxygen. Well, what if you access the larger outer volume when the bulk of that hot blast has already been dissipated? For example you could bore a series of ports through an inwardly-extended portion of the front end cap, radiating outwards at 60° from the bore, leading to a much more deeply cut (close to the end of the cap, leaving just a thin front wall) area which then scoops the remaining pressure backward into all that outer volume. If carefully drilled these sloping ports could surpass 90% of the surface of the inside false face just after the last K cone, adding little resistance to gas expansion. Of course they'd be supported by the widening triangular section between the holes as they radiate outward. Sort of like a thick K face drilled almost completely away. A rotary table ought to make cutting these with a mill bit fairly easy.

If it seems that the pressure remaining at the end cap is too low to make this worthwhile, perhaps introduce a plate midway up the K stack and bore it in a similar way, venting the relatively higher pressure into the reflex volume at a point where the first explosion has diminished in intensity sufficiently to avoid significant FRP.

[LavaRed]

I didn't spot this while following the thread but perhaps missed it, so my apologies if that's the case. My thought is that you ought to take advantage of the external tube's volume in such a way that FRP becomes irrelevant, by cutting a path for expansion into the last stage of the K baffle stack. As I understand .22"LR dynamics, FRP happens in the initial volume after the muzzle owing to the intense heat coming into contact with a supply of fresh oxygen. Well, what if you access the larger outer volume when the bulk of that hot blast has already been dissipated? For example you could bore a series of ports through an inwardly-extended portion of the front end cap, radiating outwards at 60° from the bore, leading to a much more deeply cut (close to the end of the cap, leaving just a thin front wall) area which then scoops the remaining pressure backward into all that outer volume. If carefully drilled these sloping ports could surpass 90% of the surface of the inside false face just after the last K cone, adding little resistance to gas expansion. Of course they'd be supported by the widening triangular section between the holes as they radiate outward. Sort of like a thick K face drilled almost completely away. A rotary table ought to make cutting these with a mill bit fairly easy.

If it seems that the pressure remaining at the end cap is too low to make this worthwhile, perhaps introduce a plate midway up the K stack and bore it in a similar way, venting the relatively higher pressure into the reflex volume at a point where the first explosion has diminished in intensity sufficiently to avoid significant FRP.

Holy ****! You might be on to something here!