I am wondering which factor will lead to more accurate long distance rifle loads. Is it focusing on the seating depth or the type and amount of powder I use? Looking for guidance, thanks!
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Which is more important for accuracy powder amount or bullet seating depth
- Thread starter SteelPlateAssassin
- Start date
I'd think having your bullet seated about .015"-.020" off contact with the chamber throat/rifling would be ideal. Of course, you still need correct bullet weight/caliber and powder requirements. You will find different sweet spots for every gun, so you'll have to run some test shots til you get your desired outcome.
Thanks for the reply! That would lead to another question, is there a way to know how far off from the rifling I am? Any techniques? Thanks!
dhuze
NES Member
BTSDOG
NES Member
I use a RCBS "PRECISION MIC" in .308 for my M1A, and seat the round .001 off of the rifling for good long range accuracy. Although at this length you have to single load, as the round is too long for the magazine...
I will toss this out there,
Consistency is a huge factor also the actual distance you set as long distance will play a big roll.
Example I run a cast load out of my 1903a3 out to 200 yards that's only 16 grains of 2400 with a 160 cast flat nose bullet .
A whopping 1600fps or so. Its a "mile" off the lands and I shoot my best scores with that load at 200 yards.
Also depending on what your shooting. I tried running some 223 77grain bullets closer to the lands and found no increase in accuracy vs just running them at mag length.
The 80 grain bullets I have been playing with are improving with each time out and I'm right around .008" off touching lands.
So figure on how and what you shooting. If your running from a mag your limited to mag length that will function and not jam into the lands
Consistency is a huge factor also the actual distance you set as long distance will play a big roll.
Example I run a cast load out of my 1903a3 out to 200 yards that's only 16 grains of 2400 with a 160 cast flat nose bullet .
A whopping 1600fps or so. Its a "mile" off the lands and I shoot my best scores with that load at 200 yards.
Also depending on what your shooting. I tried running some 223 77grain bullets closer to the lands and found no increase in accuracy vs just running them at mag length.
The 80 grain bullets I have been playing with are improving with each time out and I'm right around .008" off touching lands.
So figure on how and what you shooting. If your running from a mag your limited to mag length that will function and not jam into the lands
Not all powders burn the same, some are slower, some are faster. Stick with the ones listed in the manuals. Your rifle will shoot better with some than others. Only by running controlled tests can you determine what charge weight gives the best accuracy.
Then there are bullets. Some are more forgiving than others of jump and each rifle is unique in what it likes. Even primers have an effect.
Bottom line is, you have to control all the variables and experiment, meaning you must be precise in both charge weight and seating depth, along with a lot of other things.
Then there are bullets. Some are more forgiving than others of jump and each rifle is unique in what it likes. Even primers have an effect.
Bottom line is, you have to control all the variables and experiment, meaning you must be precise in both charge weight and seating depth, along with a lot of other things.
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The Hornady Bullet Comparator and Headspace gauge are a must. You can make your own overall gauge. This will allow you to establish your baseline, have repeat ability and consistency. I keep master cases with the specs written on them with a sharpie as a reference.
I have a 308 and 5.56 that are respectively .050 and .030 off the lands that shoot .625 and .375 at 100 yds.
The right powder is a must also.
I have a 308 and 5.56 that are respectively .050 and .030 off the lands that shoot .625 and .375 at 100 yds.
The right powder is a must also.
This is an interesting question with a bunch of excellent replies. Here are some more thoughts:
If you are at the point of tuning your load for precision, here is a Quickload example for variation of OAL and powder charge while everything else in the load equation stays the same. Looking at just the velocity result, for this example:
Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
+00.0 100 40.05 2767 2382 53274 8338 100.0 1.329
-20 thousandths
+00.0 101 40.05 2774 2394 53945 8311 100.0 1.322
+20 thousandths
+00.0 99 40.05 2760 2369 52630 8363 100.0 1.335
+0.1 grain
+00.0 100 40.15 2773 2392 53704 8346 100.0 1.324
-0.1 grain
+00.0 100 39.95 2761 2371 52846 8329 100.0 1.333
Notice, with this particular round, a 1/10th change in grains is practically equivalent to a 20 thousandth change in seating depth for velocity (this is not a rule as it only applies only to this round but there will be something similar for other rounds).
For this particular round, that would be about a 4 inch difference in drop at 1K yards for a step change from nominal. That would be excellent if practically achievable.
But, this is only a portion of the story. Different rifles, chambering, barrel length/stiffness, and projectiles will have sweet spots for the distance to the lands (jump) along with optimal barrel time (whip). One can certainly estimate based on calculations and the anecdotal results of others but to eek out an increasingly precise round (and accurate across temperature) for your platform you'll need to measure and experiment for a variety of factors including OAL and charge weight.
Some have suggested starting with tuning of the charge weight in order to find a barrel node (barrel time) that is accurate, first. Then, adjusting the jump to incrementally improve precision. Or, the other way around. Experiment by varying only one or the other at a time. Pick one and start there.
However doing this without a whole lot of frustration requires the ability to measure the various attributes accurately. And, to do so in a repeatable manner. This will be limited by the tools you have available. That is true for everyone.
For instance, if the accuracy of your measurement tool is +/- 20 thousandths while your scale is +/- 0.1 grain, there is a potential for a worst case spread between +/-24 inches at 1K (for this example). So, possibly a couple of MOA variation. And, this is with everything else being precisely the same.
This is not intended to be discouraging, at all. But, more to point out that this seems to be something of a rabbit hole. Seating depth and charge weight are both important but just as important, if not more, is the ability to consistently repeat each stage of the reloading process. Measurement error/tolerances will dictate the lower limit of precision in the end. Something to keep this in mind as one digs deeper into reloading.
Also, check out Precision Rifle Reloading Class Scheduled! - 4/29 in Littleton
If you are at the point of tuning your load for precision, here is a Quickload example for variation of OAL and powder charge while everything else in the load equation stays the same. Looking at just the velocity result, for this example:
Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
+00.0 100 40.05 2767 2382 53274 8338 100.0 1.329
-20 thousandths
+00.0 101 40.05 2774 2394 53945 8311 100.0 1.322
+20 thousandths
+00.0 99 40.05 2760 2369 52630 8363 100.0 1.335
+0.1 grain
+00.0 100 40.15 2773 2392 53704 8346 100.0 1.324
-0.1 grain
+00.0 100 39.95 2761 2371 52846 8329 100.0 1.333
Notice, with this particular round, a 1/10th change in grains is practically equivalent to a 20 thousandth change in seating depth for velocity (this is not a rule as it only applies only to this round but there will be something similar for other rounds).
For this particular round, that would be about a 4 inch difference in drop at 1K yards for a step change from nominal. That would be excellent if practically achievable.
But, this is only a portion of the story. Different rifles, chambering, barrel length/stiffness, and projectiles will have sweet spots for the distance to the lands (jump) along with optimal barrel time (whip). One can certainly estimate based on calculations and the anecdotal results of others but to eek out an increasingly precise round (and accurate across temperature) for your platform you'll need to measure and experiment for a variety of factors including OAL and charge weight.
Some have suggested starting with tuning of the charge weight in order to find a barrel node (barrel time) that is accurate, first. Then, adjusting the jump to incrementally improve precision. Or, the other way around. Experiment by varying only one or the other at a time. Pick one and start there.
However doing this without a whole lot of frustration requires the ability to measure the various attributes accurately. And, to do so in a repeatable manner. This will be limited by the tools you have available. That is true for everyone.
For instance, if the accuracy of your measurement tool is +/- 20 thousandths while your scale is +/- 0.1 grain, there is a potential for a worst case spread between +/-24 inches at 1K (for this example). So, possibly a couple of MOA variation. And, this is with everything else being precisely the same.
This is not intended to be discouraging, at all. But, more to point out that this seems to be something of a rabbit hole. Seating depth and charge weight are both important but just as important, if not more, is the ability to consistently repeat each stage of the reloading process. Measurement error/tolerances will dictate the lower limit of precision in the end. Something to keep this in mind as one digs deeper into reloading.
Also, check out Precision Rifle Reloading Class Scheduled! - 4/29 in Littleton
Thank you all for the answers! I'll have some experimenting to do this spring!
Took me a while to come around on testing.
My skills and equipment needed to improve before I actually could see changes in my accuracy down range.
I abandoned OCW method early on only to revisit it years later when my guns,ammo and reloading skills improved.
I'm just breaking sub moa now with some AR loads.
I have seen larger shifts in accuracy with powder vs seating depth but honestly lost interest as my range time gets less and less with age and growing kids.
gerrycaruso
NES Member
Look on Berger's website. They claim that best accuracy does not necessarily come from seating as long as possible. In working up a load for a bolt gun in .223, best accuracy came with the shortest O.A.L.
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It depends. Most projectiles designed for 223 are tangent or hybrid shapes that don't really "care" all that much about seating depth and can jump a lot with no significant difference in accuracy.
There are also projectiles that have a secant shape where seating depth matters a lot. For example Berger VLDs seem to like to be seated right on the lands, and the groups will open up more and more as you back them off.
(EDIT: This isn't just a 223 thing. Most rifle projectiles regardless of caliber have tangent shapes.)
xtry51
NES Member
I reload all my ammo towards the maximum standard mag specs for rifle. Personally I keep them as close to .005" under max OAL for the average. I'm pretty anal about my vharge weights. +/-.2gr max for all rifle loads.
