Crosman Town & Country 107

[45flint]

Early this morning I did a few test shots with RWS Hobby's 11.9 gr in the T&C 108. As expected they give higher velocities, but lower energy output.
Wearing a t-shirt instead of a the thick fleece vest of yesterday evening, I noticed exactly what BB Pelletier describes in his article on the T&C:

I noticed a puff of air around my right hand every time the rifle fired, which I initially blamed on the recent resealing job my test rifle had gotten before the test. Then, I examined the bolt lockup more closely and discovered that the real problem was a loose bolt seal. No matter how hard I closed the bolt, that steep cam slot invited it to spring back just enough to exhaust some air. The problem was solved by manually holding the bolt closed with the thumb of my shooting hand as I pulled the trigger. There was still a small puff of air, but it was greatly diminished from what it had been. A real fanatic might have used some automotive valve-grinding compound to hand-lap the front of the bolt into the rear of the barrel; but this wasn’t my rifle, so I left it at that.

DTFletcher has written some advice regarding this problem on the American Vintage Airguns forum.
But this air escaping from the wrong side of the pellet might explain why my 108 is relatively low on power compared to 45's.
Have you noticed this puff of air, 45flint?

I do think you are probably onto the issue. I know I read BB Pelletier review many times and if you look at his rifle it is really well used and not in great shape, even missing the barrel spacer. I have never felt any air puff out on firing and my lockup is pretty secure. My rifle though used is in very good original shape. But since you asked the question I thought I would further test it by laying a tissue over the top of the breech and yes it hopped a small bit (1/4 inch) with some oil on the tissue when I fired with 6 pumps. So my breech is not totally locked up either. I suspect that it just locks up better than yours and Pelletier’s? I could put some of my newly acquired damping grease around the probe and see if I get a total seal? I will try that this afternoon. This could explain why a professional reseal only went so far to give you your performance. I doubt any pro on a reseal would rework a breach seal that is metal to metal. Crosman like Sheridan would soon add a O ring to the probe to fix this potential issue.

By the way I tested Hobbys in my rifle the other day as well and like you I saw a very modest increase in speed. I think common wisdom is heavier pellets are better in pneumatics: seemed to hold true. In my spring powered gun they can really make a difference.