Author: pogson
Subject: Acceptable Groups
Posted: July 10 2018 at 5:14pm
Subject: Acceptable Groups
Posted: July 10 2018 at 5:14pm
That's much better but anyone can be lucky a few times. In searching for an accurate combination one should try to minimize the worst group... ![Approve]( "Approve")
The keys to good accuracy in almost any rifle is to choose the right components and to assemble them very uniformly every time. Things that help me:
- using an electronic scale with fine resolution, accuracy and repeatability - mine takes a few minutes to settle down but turns most of my non-ancient rifles into tack-drivers,
- choose a powder that gives top velocity with a variety of bullet-weights and try a round or two from the starting load to maximum in small steps, say 0.5 to 1 grain or even less when you are close,
- try different seating depths for the bullet - many rifles have long or short throats compared to what people use in the reloading manuals - close to the start of rifling seems best for me - use a good caliper,
- use a chronograph - most rifles want each bullet to fly out the muzzle at the same speed to get the best groups - "sweet spots" can happen when the small range of variation in speed/departure time coincides with some particular point on the vibrational cycle of the barrel - sadly, temperature can also affect muzzle-velocity,
- trim cases to length every time to ensure less variance in bearing surface with the case - adjust dies carefully to avoid sizing more than necessary and anneal case necks to avoid cracking, and
- sort your cases both by head-stamp and weight.
Neck-sizing alone can cut groups in half. These other measures can do that as well. I have only one rifle that shoots commercial ammunition as well as my reloads. I don't know what's wrong with it...
For fun, I took two young friends out to the bush so they could try their brand new rifles and commercial ammunition. I took a ~100 year old rifle with no bluing and rifling that came and went down the bore. I got better groups... Of course I was only fifty years old then. I'm a little more shaky now.