The sun's still up and I had a good night's sleep and a short nap earlier.
If unlike me, you have patience, do not pull down new ammo to make reloading fodder. Yes, you will incur 1 firing wear and tear, but shooting those factory loads is worth it for the gain in powder capacity and having your cases fire formed to your rifle's chamber. You will profit from measuring just how long a particular bullet can be seated and still fit in your magazine also. In the following example, I am loading Hornady 125 SST into sized 1-fired cases with the shoulder pushed back to 1.57 measured at the datum point.
Here's the skinny:
From my initial trip out to the range a few weeks ago when the weather was actually nice for one day, it was obvious that none of the powders I was using, came close to maxing out the safe pressure and worse, coming anywhere close to what QuickLoad predicted for resulting velocity. OK, so live and learn.
During that initial calibration run, I was able to calculate a coefficient to apply to QuikLoad's Ba
characteristic for each powder I used, to make predicted results agree with the real results I achieved. That having been done, None of the maximum charges listed above, fall into a dangerous range. Most do not fall into a dangerous range even using the original default QuickLoad Ba
values which were overly optimistic.
The next time we get similar weather to the last outing, I will return to the range with some fresh loads that are the longer COL as well as closer to maximum case fill. Not right up to the limit since other factors come into play when using fire formed brass, such as elasticity. If this helps, think about cases that are smaller than the chamber during those first few milliseconds in time after the primer blows. The brass stretches so that the outside conforms with the limit of the chamber walls. That's what fire forming does, as they do not contract back down all the way after the pressure drops. While the case is stretched, the volume inside it is more than prior to ignition, so the powder fill ratio is lower and that is a contributor to pressure. Once the cases are formed, there is less stretch during the early stage of ignition and the lessening of pressure does not occur to the same extent. That equals a higher pressure spike. So, as most of us try to emphasize starting lower with a new recipe, which this in essence is, Safety is still a factor.
Generally speaking, for commonly available powders that burn in the range that this caliber can benefit from, without being too fast. The case capacity seems to be the limiting factor where velocity is concerned and bullets are light. Some of these same powders have plenty of umph when the bullet weight goes up. As was pointed out, when you get up to the 150gr bullets, you are forced to use less powder in order to seat them so that they fit in the magazine. Ditto on all copper bullets that run longer in length for the same weight as cup and lead core bullets. That has a self-limiting effect.
More on this after my next Range Day.