Pglasgow

I would think that for slower moving projectiles, the extra inches makes more difference. So it makes sense to me that the 26" barrel produced more than 35 fps difference.

Seems like one would lose maybe an inch in the breech and1 3/4inches in the load (pellets and 1/2 the length of the projectile). With a sabot, I figure the bullet is still accelerating through the QLA (if it has one). So the "working" barrel, where breech gases are accelerating the bullet, would be in the neighborhood of 23 1/4 for the XLR and 19 3/4. So for that load, the XLR has 18% more working barrel.

Since muzzle energy is a function of the product breech pressure and displacement in the barrel, the extra barrel translates to extra muzzle energy. But not 18% more. Given there is(barrel displacement weighted) average pressure for the first 19 3/4 inches of acceleration through the barrel, one would need to know what the pressures are (related to the former) in the final 3 1/2 inches in order to know the increase in muzzle energy.

I figure the load in the XLR is yielding 2100 fps (give er take). If so the load in the original was 1995 fps. One can relate the ratios of muzzle energy by squaring the ratio of velocities. If one does, we find that the muzzle energy of the XLR is about 10.8 % greater. This would mean that the (barrel displacement weighted) average pressure in the final 3 1/2 inches (of the XLR) is about 60% the average pressure of first 19 3/4".

I don't know if this is a reasonable expectation or not. But its in the neighborhood. My sense, based on typical pressure curves (displacement curves) is that it may be more efficient than what one would typically expect. Where maybe 45-50 percent efficiency of the percentage increase of barrel length would be expected at these muzzle velocities. Even so, the difference would only be around 25 fps (80 fps increase or almost 23 fps/inch).

Sorry for ramblin, Phil

retrieverman

I have another barrel length question. I have seen that T/C is making a Pro Hunter ML barrel that is 20 inches. I am intrigued by short barrels, but is this too short in a ML?