Tips for getting least SD at chrono?
- Thread starter TresMon
- Start date
Adjust the powder charge and bullet seating depth. You may even have to try a different powder and bullet. And dont forget primes that can also make a diff. then there is allways neck tension. It just a matter of getting it all together. Kind of like a jigsaw puzzle with all the peices in place it works
Well, first off, pick a "most likely" powder, in other words one of the powders that has worked well for other folks doing well at matches using the same powder. Same with primers, usually any powder has a primer which it prefers and surprisingly enough, sometimes it ain't one of the "match" primers. But it's enough to start with what other folks have had success with with your chosen powder.
Start with a clean barrel and about three fouling shots. Depending one your choice of chambering go anywhere from .3 to .5 grain increments, seat the bullets so as to lightly kiss the lands and fire five shot groups making sure you keep track of which target goes with which load. The somewhere in there should be pretty good accuracy with pretty good SD/ES numbers. Pick that and do some fine tuning with finer increments of powder charge, seating depth and here is a big one, neck tension. I've found what amount of neck tension doesn't matter nearly as much as uniformity. Additionally, if you size much more than .004" under your bullet diameter the tension doesn't really change much and you'll just be over working your brass. .002" seems to work fairly well for my uses.
And here is another thought. Some rifles don't have a super sweet spot where SD/ES and 1,000 accuracy happily coincide, sometimes you get pretty good accuracy as fair numbers, or really good numbers and fair accuracy. I've had two barrels like that, stellar ES/SD and pretty good accuracy. Good enough as it's turned out once or twice.
The thing is, unless you've got a fair chunk of change and a smith handy who does top-notch work on a fast turn-around, you may just be searching for the best compromise. Velocity in the desired range, good ES/SD numbers and good accuracy. You can burn out a good barrel doing load developement before you even get to a match, or at least use up a fair share of it.
And not all loads that work at a couple of hundred or 600 will carry to 1,000 either. Develop a decent load and take it to the 1,000 yard line on a day with good conditions. See what it does then head back to testing.
Start with a clean barrel and about three fouling shots. Depending one your choice of chambering go anywhere from .3 to .5 grain increments, seat the bullets so as to lightly kiss the lands and fire five shot groups making sure you keep track of which target goes with which load. The somewhere in there should be pretty good accuracy with pretty good SD/ES numbers. Pick that and do some fine tuning with finer increments of powder charge, seating depth and here is a big one, neck tension. I've found what amount of neck tension doesn't matter nearly as much as uniformity. Additionally, if you size much more than .004" under your bullet diameter the tension doesn't really change much and you'll just be over working your brass. .002" seems to work fairly well for my uses.
And here is another thought. Some rifles don't have a super sweet spot where SD/ES and 1,000 accuracy happily coincide, sometimes you get pretty good accuracy as fair numbers, or really good numbers and fair accuracy. I've had two barrels like that, stellar ES/SD and pretty good accuracy. Good enough as it's turned out once or twice.
The thing is, unless you've got a fair chunk of change and a smith handy who does top-notch work on a fast turn-around, you may just be searching for the best compromise. Velocity in the desired range, good ES/SD numbers and good accuracy. You can burn out a good barrel doing load developement before you even get to a match, or at least use up a fair share of it.
And not all loads that work at a couple of hundred or 600 will carry to 1,000 either. Develop a decent load and take it to the 1,000 yard line on a day with good conditions. See what it does then head back to testing.
HTSmith
Silver $$ Contributor
"seat the bullets so as to lightly kiss the lands"
This is advice that I'd followed for years. Its gotten me into trouble. With the variation in bullets and reloading gear, "lightly kissing the lands" ends up being sometimes off the lands and sometimes jammed,and yes sometimes just kissing). Check it out for yourself with a Stoney Point or Sinclair nut. This can give erratic velocity and accuracy.
My advice would be either to get off the lands by at least .010" or jam into the lands by at least .010" "Just kissing" is a place I would stay away from.
This is advice that I'd followed for years. Its gotten me into trouble. With the variation in bullets and reloading gear, "lightly kissing the lands" ends up being sometimes off the lands and sometimes jammed,and yes sometimes just kissing). Check it out for yourself with a Stoney Point or Sinclair nut. This can give erratic velocity and accuracy.
My advice would be either to get off the lands by at least .010" or jam into the lands by at least .010" "Just kissing" is a place I would stay away from.
rcw3
Site $$ Sponsor
Tres
It's all a balancing act,in my opinion). You can get loads that show great chrono numbers but group poorly, and loads that shoot great groups but have bad chrono numbers and therefore string vertically in a bad way at 1000 yards. Then you can also get a lot of other stuff in between.
The trick is to find a load that not only shoots very well, but also gives good chrono numbers. The more quickly you can rule out what does not work and spend your time testing things that have the potential to work the better. It's also no good to blow out the useful life of your barrel just doing a lot of testing to try to find a good load.
Robert Whitley
It's all a balancing act,in my opinion). You can get loads that show great chrono numbers but group poorly, and loads that shoot great groups but have bad chrono numbers and therefore string vertically in a bad way at 1000 yards. Then you can also get a lot of other stuff in between.
The trick is to find a load that not only shoots very well, but also gives good chrono numbers. The more quickly you can rule out what does not work and spend your time testing things that have the potential to work the better. It's also no good to blow out the useful life of your barrel just doing a lot of testing to try to find a good load.
Robert Whitley
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