As mentioned in another thread, I've been away from group and score shooting for over ten years. Omitting 6PPC bench guns which are sort of in a special class, what is the best way to "tune" a rifle load? I'm thinking of guns that will be accurate with at least a custom barrel and chamber, properly bedded synthetic stock, and either a custom action or at least a "trued" Rem 700 or 40X. I have a chronograph and all case prep tools. My old fashioned load development method was just pick the bullet to fit the job, choose a powder with the proper burn rate, start loading a few grains off the higher end and work up. If a load looked promising, I might focus around that powder weight and try varying the seating depth. But it seems things have gotten more scientific in the last 10-15 years. I've been reading about various load tuning methods including the "ladder" and a "round robin" variation on it. What is the current thinking on tuning a load?
Tuning a rifle?
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Dusty Stevens
Hollow Point Dispenser
You still got it figured out. Forget the new stuff.
DeltaBravo
Member
Well, you know what "they" say:
You can't tune a rifle,
But you CAN tuna fish!
Happy New Year to all.
Dennis
You can't tune a rifle,
But you CAN tuna fish!
Happy New Year to all.
Dennis
M
mks
Guest
Ladder testing can be very useful, and can be applied to most variables, including powder charge, neck tension and seating depth. The concept is that, no matter how hard we try, there will be some variation in our "variables." So taking this into account, best accuracy can be found where variations have little effect on POI. For powder charge, for instance, prepare loads with 0.1 gr increments over a range of charges where you think the best window will be. (You can start with larger increments if you want, but don't go too big or you won't be able to identify the steps, which are usually only a few tenths wide.) Fire each at a different bull and measure the horizontal and vertical deviation from center. The "steps" in the "ladder" are where the the deviations remain the same for several charge increments. Always confirm by running the test at least twice, but if conditions are good, the second round will likely mirror the first. Once you have the best powder charge, do another ladder test varying seating depth using that best charge. Repeat until you have covered all the variables you want to include, varying one thing at a time.
Let's say you found the best seating depth to be different from what you used for the powder test. How do you know if the powder charge you identified is still the best? Well, you don't. If you want to find out for sure, you need to run more tests. But at some point, the accuracy of the rifle will hopefully be better than your ability to read wind flags. This is the point to call it good, and practice, practice, practice. It's really not all that much different from the old-fashioned way of just shooting groups.
Oh, and remember that the tune you found is only good for the temperature under which you tested.
Hope this helps,
Keith
Let's say you found the best seating depth to be different from what you used for the powder test. How do you know if the powder charge you identified is still the best? Well, you don't. If you want to find out for sure, you need to run more tests. But at some point, the accuracy of the rifle will hopefully be better than your ability to read wind flags. This is the point to call it good, and practice, practice, practice. It's really not all that much different from the old-fashioned way of just shooting groups.
Oh, and remember that the tune you found is only good for the temperature under which you tested.
Hope this helps,
Keith
A
abintx
Guest
What is the current thinking on tuning a load?
Find a bullet-barrel-powder-brass-primer combination that works, then fine tune with neck tension and seating depth. ... All shot over a good set of wind flags. Once you've turned tight cloverleaf groups into one hole groups then pull out the chronograph for recording historical data if so inclined.
Find a bullet-barrel-powder-brass-primer combination that works, then fine tune with neck tension and seating depth. ... All shot over a good set of wind flags. Once you've turned tight cloverleaf groups into one hole groups then pull out the chronograph for recording historical data if so inclined.
mwezell
Mike Ezell
Find a bullet-barrel-powder-brass-primer combination that works, then fine tune with neck tension and seating depth. ... All shot over a good set of wind flags. Once you've turned tight cloverleaf groups into one hole groups then pull out the chronograph for recording historical data if so inclined.
....and tuners.
M
mks
Guest
Find a bullet-barrel-powder-brass-primer combination that works, then fine tune with neck tension and seating depth. ... All shot over a good set of wind flags. Once you've turned tight cloverleaf groups into one hole groups then pull out the chronograph for recording historical data if so inclined.
You can also use the chronograph to validate that increasing powder charge correlates with increasing muzzle velocity during your ladder tests. If you have a shot with higher or lower MV than expected for the powder charge, it may not fit with the rest of the data in the ladder test and should be tossed out.
Pete Wass
Well-known member
Something we found out - -
years ago, some friends and I were trying to tune our 30 BR using H-322, shooting over a crono. What we fund was at a certain point, velocities started to go south. More isn't always better.
I use to believe I could make any kind of bullets of the proper length shoot in my rifles (30 Cal BR stuff). The barrel I have on my rifle now taught me otherwise. This one only seems to like one powder and one length bullet.
Pete
years ago, some friends and I were trying to tune our 30 BR using H-322, shooting over a crono. What we fund was at a certain point, velocities started to go south. More isn't always better.
I use to believe I could make any kind of bullets of the proper length shoot in my rifles (30 Cal BR stuff). The barrel I have on my rifle now taught me otherwise. This one only seems to like one powder and one length bullet.
Pete
A
abintx
Guest
Forget the chrono, watch the target over a good set of wind flags.
M
mks
Guest
No, the steps in the ladder correspond to ranges of powder charge AND muzzle velocity. That is the objective of the ladder test - to find a range of velocities that minimize vertical. There is usually some variability in muzzle velocity versus powder charge. When there is an odd velocity from a particular powder charge that doesn't fit the rest of the curve, it is best to try another to see if it is repeatable. But I have not found any consistency to it. It seems to be one of those random variables that is hard to eliminate.
M
mks
Guest
No, that's what tuning is about - getting shots with different MV to hit the same hole. See this article: http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm
Now the opposite is true - low MV spread should result in low vertical spread. But it is for practical purposes impossible to reduce MV spread to zero, so what to do about the remaining vertical? That's where tuning comes in. And once a rifle is tuned, it also becomes less critical to achieve low MV spread.
Dusty Stevens
Hollow Point Dispenser
Its amazing we can shoot a teen agg. Youd think not even owning a chrono and not doing ladder tests the top benchrest shooters can even hit the paper twice.