124gr plated/rn- 3.5gr bullseye- cci500- and AOL is at 1.18 and it will not feed in my test pistol. can I tighten the aol uo to 1.045 as it shows in the manual under lead rn and not effect the c.u.p
The short answer is no. Using a powder as fast as Bullseye and reducing the COL from the book load of 1.18" to 1.045" will increase pressure and could so dramatically or catastrophically. Are you sure about that book load of 1.18"? The SAAMI
max for 9mm is 1.169"
With fast powders in the 9mm as little as 0.020" reducing in COL can result in huge pressure increases. That is why setback can be a big problem. But what determines peak pressure is seating depth. The amount of bullet in the case. So even if you have the same COL but are using a bullet with a different length the seating depth will be different. Follow the directions by BDS-THR and you will be fine.