Re: Federal GM210M vs CCI BR-2 LR Primers
Never an absolute answer when it comes to reloading. Just use the items that shoot best in your rifle...PERIOD.
I use both primers and will test any rifle with both primers. My 7Mystic only shoots the Fed 210M. Other rifles, the CCI BR2.
I can say that the CCI is the milder of the two but that is greatly affected by the type of powder, cartridge pressure and barrel.
You are also likely to find differences in lots of the same component so if you find a combo that works for you, buy a bunch so you don't need to tweak all the time.
Temp has a pretty profound affect on primers just as it does many powder. Test under the conditions you are going to hunt/compete.
As to testing over the chrony, sure it is a great aid and can help to narrow down loads or catch when things get too toasty. However, no one scores our chronie, only the holes on paper. So ultimately, that is what matters.
Always keep in mind that the average chrony has a mechanical error of at least 0.1% to 0.5% (just ask the manf). At 3000fps, the error in the chrony is......3 to 15FPS plus or minus for a total ES of 6 to 30FPS.
Not so good when the measuring device has a built in error equal or larger then the amounts you are trying to measure. Just give your manf a call and ask for their reading error specs...All optical and timing devices have one.
I use the chronie alot to catch really gross errors. However, I use the target to fine tune any load/rifle.