Quote:
Originally Posted by elkhunter11
The small capacity cartridges are definitely more sensitive to small variations in powder charge, a change in the primer, or to differences in jump to the lands. The tolerances in chambers and throats mean a lot more in load using from 9 to 13 grains of powder, than in a case burning 70 -80 grains of powder. And if one chamber is at minimum toleranceces for diameter and length, with a short throat, it will produce more pressure with the same load than a max spec chamber with a long throat. In the small cases, the tolerances become significant, regardless of what some people will have you believe. As well, the Lil Gun loads are more sensitive to small changes than the CFE-BLK loads, because they use less powder to produce the same pressure. I had no issues with Lil Gun, because I started low and worked up charges, but I plan on using CFE-BLK, because it will produce similar velocities while being less sensitive to small variations, and I like the fact that copper fouling is pretty much a non factor with the CFE powders.
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I think that we are all in agreement that small capacity cartridges are more sensitive to changes in primers, jump to the lands and differences in chamber/throat dimensions which must fall within the Saami Tolerances I mentioned.
Something we have not discussed is slight differences in bore/lands dimensions which is likely why CZ rifles usually run more pressure/Velocity/grain of powder than others. I had a 17 HMR, in a CZ, that got more velocity than a Savage with factory ammo. In fact I witnessed a case head separation in the CZ, with factory ammo, on a hot day in the gopher patch. My 17 cal. J. Dewey rod was tight in the CZ but worked fine in the Savage.
Fast burning/temp sensitive powders are also much more volatile than the slower ones which are much more forgiving. As an example Lil Gun is shown to generate 35 fps/1,200 PSI/0.1grain while CFE BLK generates 25 fps/800 PSI/0.1 grain according to Hodgdon's data. As well LilGun has a really high Nito glycerin content which I believe makes it more unstable under varying conditions. Another possibility is that the reduced load density sets up a situation where detonation comes into play with LilGun in the 17HH.
I did suggest that seating to manufacturers OAL would have bullets seated 0.080 - to over 0.100" in a 17 HH chamber. The 0.015" tolerance in FB/throat length will not have a significant impact on pressures in this case. The fact that all 17 HH minimum Saami Chambers have a 1 degree 30 Minute throat angle, 0.0502" FB and a 0.0859" throat +0.015" for Max Saami chamber seems to escape you. I have been trying to teach you this for longer than I care to mention but somehow ignorance always seems to prevail and you keep taking jabs at me??
