Thinking on how twist rate affects pressure and the possibility of attaining more/less velocity, I built three rifles to do some testing over a three year period, a 22/250 AI with a 1-15 twist, a 223 with a 1-9 twist, and a 22 PPC with a 1-9 twist.

I wanted to see just how fast I could push a Berger 22 caliber 65g HP with extreme accuracy, and how the 1-9 twists would enable the bullets to blow up better on p. dogs.

On the 22/250 AI with the 1-15 twist, I worked up a load in the 27" Hart Barrel with the 65's at 3700 fps that shot very tiny groups. This bullet was so effective on those large coyotes it was hard to believe. Too bad berger quit making this bullet. This load would blow bobcats and foxes half in two. I got this info from a fellow hunter that had a rifle built in the same way, he painted air planes for a living and I thought sure as heck that he had sniffed too much paint. He was spot on in his loads.

Concerning the 223 and the 22 PPC with the 9" twists,I built the 223 on trued 700 action, McMillen Hunter class benchrest stock with a 27" Hart barrel MHV Barrel. On the 22PPC I had 24" Hart #7 contour barrel Put on a Sako A-1 Action in a McMillen Sako Varmint stock.

I had several other custom 223's of the same design but with a 1-14 twist, and at least 3 other 22 PPC's in Benchrest rifles with 1-14 twist rates, all these rifle's barrels were cut with the same reamer that had .0005 over bullet dia throats and zero freebore, with 1 1/2* leade angles.

During the testing of the 223 with the 1-9 twist, I noticed that the sweet spot in accuracy that was easily attainable at the higher node in the 1-14 twist was not attainable in the 1-9 twist without super hard extraction and opening up the primer pockets in the IMI brass that is super tough. Also, the range of powder weight in the 1-9 twist that would shoot tiny groups was very small, indicating that as temp and barometric pressure changes that so would the load's accuracy potential.

With all the 22 PPC's that I had, the 1-9" twist was very picky on what it liked to shoot bug holes with. A 22PPC with a 1-14 twist is one of the most "user friendly" cartridges a guy can play with. No doubt that the 1-9 twist was no where near as user friendly as the 1-14 twists, due to pressure spikes.

This is way off topic of a 257 Weatherby, but thought that it may be interesting at how twist rates affect pressures to some of you.