MartiniBelgian wrote on Jun 1
st, 2014 at 12:05pm:
For me, compression is not something I strive for - it merely is a consequence of loading more or less powder, or using more/thicker or less/thinner wads. I will never try for a certain amount of compression - also because it is so hard to measure correctly.
I just add more powder which will increase compression, or decrease the charge - lower compression. But there is no way you can say that a given amount of compression shoots best in a rifle. If you increase compression without changing the load or wad, you are changing bullet seating depth (bullet deeper in the case). For me, it is a 2nd-line variable, which is a consequence of more important 1st-line variables (powder volume, wad column, bullet used and seating depth).
I agree that when your using fixed ammunition in order for one variable to remain constant you need to change two variables at the same time.
The effect of compression as a sole variable wasnt clear to me until I ventured into breech seating.
I tested compression on three charge weights that showed promising groups after just being drop tubed into the case.
Using Goex
At 0 compression the cases were left with lots of black fouling residue
At a very slight compression of .050" every single load produced a vertical group. Im not entirely sure what exactly is going on there but I have some theories. Fouling in the case was slightly less but still black.
At .100" of compression the group went back to round and the fouling in the case was light reddish powder
At .150"+ of compression the fouling was a scant grey powder in a clean case.
I'm still in the process of testing up to .300" of compression but thus far I can clearly say that compression does have its own effect as an independent variable