Originally Posted by predmaster223
I know barrels vary in speed and some seem to have earlier pressure signs. Some obvious variables include bore diameter, type of rifling, throat and lead angle but what are some lesser known reasons some won't achieve the speed before pressure? I just rechambered a 6.5cm to 6.5x284 and I hit pressure signs with 47 gr h4831 and 140 at 2600 with a 22" barrel. That's creedmoor speed. I'm not sure what's wrong. New lapua brass and 1x fired in this rifle. Tried RL 22 with same result hit pressure at like 2625 with 140s. The chamber is tight but bolt closes on new lapua brass smoothly. The chamber has been polished so after reading about the need for brass to grip the walls as it expands I'm going to add some cross hatching thoroughly clean and try again. Any other thoughts on this issue? I know I'm not going to get super speed from a 22" barrel but has to do better than a creedmoor.
The brass gripping the chamber walls is a myth. I tested even dipping a cartridge in oil. Same pressure on bolt face.
Charlie