Hi all, it's been a while since I posted (damn almost a decade) so please forgive me if I'm stepping on post etiquette or if this is in the wrong place.
I'm getting back into loading cast boolits for my 1980 336 (20in barrel, iron sights, microgroove rifling, slugs at .357).
I worked up a load using lil' gun powder and a factory cast bullet (hunters supply 207gr gas check). I added hornady gas checks and size them in a lee sizer that I gave a light buff job to about .3585.
I worked up from quick load data with a COAL of 2.335" starting at 25gr and ended up at around 27.5gr, 75% case capacity. Groups at 25 were around 5" and at 50 around 8", shooting VERY high from what I'm used to with factory 200gr jacketed. 100 yard groups weren't on paper. At 50 yards they seemed on the verge of keyholing. Groups were 6" high from point of aim.
Assuming that lil gun is too fast (based on other threads) I tried AR-Comp, which is much slower. All other load numbers are the same. The groups were much better, around 2" at both 25 and 50. I didn't try at 100. POI was 8" lower than the previous load despite being 100fps faster, which I found odd.
My question is: What's the theory behind lil' gun being such a poor performer? Why do they seem barely stabilized? And why did AR comp shift the POI so much, and the bullets are now stable? Is there something going on with a sharp detonation vs a gentle push?
Thank you for your consideration.