IMHO, velocity flat spots are not statistically significant and meaningless for load development. Evaluate your POI for tight groups. Then look at your SD if needed.
6.5 PRC Powder Charge/Velocity Ladder Test. No Flat Spot
- Thread starter gregmark24
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gregmark24
Well-Known Member
Yes. Go into the bullet section, and look at the details for "initial pressure". In that window, you'll find normal vs magnum primers. If you select magnum primers, you'll see muzzle velocities increase around 50 fps.
gregmark24
Well-Known Member
Thanks for all of your replies. We have been under the assumption to just fire and ignore velocities and POI of new brass. Then, pick a seating depth for the once-fired, and work up powder charges (three rounds per charge), looking for velocity flat spots. I did 0.3 gn increments, and found mine around 2800 fps in the lower half of the book's recommended loads. Once the flat spot is found, load that charge and do different seating depths, looking a target POI. However, we decided to look at both velocity and target results for our different powder charges.
I could swear....I saw a video last year where the Hornady guys shot hundreds of rounds at each powder charge increment and concluded that there were no nodes...
To summarize the comments received above for powder charges vs flat spots: flat spots don't always happen and don't mean anything, look for low vertical dispersions at nearby charges, do finer powder charge increments around those better vertical dispersons (like 0.2 to 0.3 gn), pay more attention to vertical dispersion at 400-600 yards, chuck the lower half of the bullet mfgr's recommended charge range (although, the lower half worked well on my 243 for both a flat spot and the best vertical dispersion--about 2800 fps), increase powder charge to or past max looking for pressure signs, then back off 0.5 to 1.5 gn, and do 0.2 gn increments around that area.
GRT has worked well for both of us as a velocity point of reference. Worth noting is that under the bullet selection, you can open up the initial pressure section and there are three areas to choose from: caliber/projectile/primer types. For primers, standard and magnum. Magnum primers will give you a higher initial pressure and higher muzzle velocity.
I could swear....I saw a video last year where the Hornady guys shot hundreds of rounds at each powder charge increment and concluded that there were no nodes...
To summarize the comments received above for powder charges vs flat spots: flat spots don't always happen and don't mean anything, look for low vertical dispersions at nearby charges, do finer powder charge increments around those better vertical dispersons (like 0.2 to 0.3 gn), pay more attention to vertical dispersion at 400-600 yards, chuck the lower half of the bullet mfgr's recommended charge range (although, the lower half worked well on my 243 for both a flat spot and the best vertical dispersion--about 2800 fps), increase powder charge to or past max looking for pressure signs, then back off 0.5 to 1.5 gn, and do 0.2 gn increments around that area.
GRT has worked well for both of us as a velocity point of reference. Worth noting is that under the bullet selection, you can open up the initial pressure section and there are three areas to choose from: caliber/projectile/primer types. For primers, standard and magnum. Magnum primers will give you a higher initial pressure and higher muzzle velocity.
Phil Rizzo
Well-Known Member
Man I'm glad I don't need all this technology and procedure, or haven't so far anyhow.
I find a decent seating depth during barrel break-in, the do a pressure ladder with a few chosen powders. Maybe fine tune seating depth in the end.
when it repeats a few times it's good enough for me.
If I had a camera system on target I might do 3 shots at each level on the ladder.
I find a decent seating depth during barrel break-in, the do a pressure ladder with a few chosen powders. Maybe fine tune seating depth in the end.
when it repeats a few times it's good enough for me.
If I had a camera system on target I might do 3 shots at each level on the ladder.
gregmark24
Well-Known Member
Found the Hornady velocity node discussion with large group sizes. Gets started around 5 minutes in.
Hornady Ruins Load Development
I've just listened to a podcast from Hornady that pretty much ruins everything I've read on load development. The big findings for me are "velocity nodes" are a myth that wash out when you increase the sample size from 3-5 shots (statistically not significant) to 35 shots (statistically...
bushcraftusa.com
Leaf Litter
Well-Known Member
Velocity "nodes" or "flat spots" don't exist. Their existence was the result of a bunch of uneducated people attempting to analyze incomplete data from poorly designed experiments. Translation: most shooters ain't think good.
Find your max load by looking for pressure signs, then look for an accurate load at or below max by shooting various charges in groups of 5 or more. Once you find a desirable (accurate) charge, you can adjust seating depth for optimal accuracy. Do all of this as close to the environmental conditions you will experience hunting or match shooting as possible. If you're planning a late season hunt where it's 5 degrees, don't do load development in the summer when it's 95
Find your max load by looking for pressure signs, then look for an accurate load at or below max by shooting various charges in groups of 5 or more. Once you find a desirable (accurate) charge, you can adjust seating depth for optimal accuracy. Do all of this as close to the environmental conditions you will experience hunting or match shooting as possible. If you're planning a late season hunt where it's 5 degrees, don't do load development in the summer when it's 95
Phil Rizzo
Well-Known Member
Velocity flat spots don't exist with slightly different powder charges??
BrentM
Well-Known Member
You can load the lower end if you wish. However, you are giving up potentially higher speeds and just as accurate loads. Fill rate in a case does have an affect on performance too. If you are fine shooting 2800 out of a prc so be it. It has the potential of running 3000, you just have to decide if you want a creedmoor or a PRC is all. That's not anyone's call but yours.
As far as new brass....... I always get data and a good load for new brass. I have no desire to waste 6000 grains of powder, 100 bullets, and 100 primers just forming brass. I have run new brass on a new barrel and had very good success shooting to 1000. I just know at some point brass and barrel will change and I will need to tweak my load a little. Usually it's minor.
VarmintBob
Well-Known Member
Since there is no known scientific reason for a "velocity flat spot" to exist, it is no surprise that you would not find one shooting a series of stepped loads. But there is such a thing as a precision node where group size will be smaller. These correspond to certain velocities with a given set of components and equipment and they can be predicted with internal ballistic tools.
The "nodes" and "flat spots" people see in velocity are just statistical nose resulting from small sample sizes. That can be said about a lot of things people look at when reloading. Pick the charge that gives the velocity you want and go from there.
Justice1327
Well-Known Member
Thank you. I have used GRT for about a year and didn't know that was in there.
BrentM
Well-Known Member
I disagree with those saying it has no merit. How much merit might be the debate. I have used the satterlee method successfully for a couple years on multiple projects and have not been disappointed yet. My last project I took data over a larger sample, 75 rounds, and it has been the go to load for 2 rifles and 1500 rounds between the 2. Both PRC's. Agree or not with Scott, you have to start somewhere, and this method has been used by a lot people successfully. The idea is to simply identify an area the powder charge has wide bandwith for smaller variation in velocity. It gives a guy a solid place to start IMO. I'd rather burn 30 or less rounds on this method than the pile of ammo I used to burn messing with OCW and scatter ladders. IMO those are huge PIA and this method has me dialed in on a load very quickly.
Phil Rizzo
Well-Known Member
Dang I wish somebody had told me this 30+ years ago when I just started producing high performing accurate loads.
To be fair I only use slow to extremely slow powders in a range of .257-.308 calibers. And "overbore" at that. No slow pokes.
And when the velo curve starts to flatten, I'm getting close to maximum, and also very close to where top accuracy is normally found.
Who gives a flip about statistics/sample sizes or anything else if the desired results are discovered this way consistently and end up repeating?
I've always assumed the velo flattened out because in a given case size only so much of a certain propellant, usually a high fill percentage or compressed, can fit and burn effectively.
Might have it all wrong but it's what I've seen over and over and over again.
And again and again.
Anybody can get lucky a few times, but I'm talking a lot of rifles. I help a local custom builder tune his new creations frequently.
To be fair I only use slow to extremely slow powders in a range of .257-.308 calibers. And "overbore" at that. No slow pokes.
And when the velo curve starts to flatten, I'm getting close to maximum, and also very close to where top accuracy is normally found.
Who gives a flip about statistics/sample sizes or anything else if the desired results are discovered this way consistently and end up repeating?
I've always assumed the velo flattened out because in a given case size only so much of a certain propellant, usually a high fill percentage or compressed, can fit and burn effectively.
Might have it all wrong but it's what I've seen over and over and over again.
And again and again.
Anybody can get lucky a few times, but I'm talking a lot of rifles. I help a local custom builder tune his new creations frequently.
QuietTexan
Well-Known Member
I'm mean, that's a pretty bold statement with absolutely nothing given to back it up. You should definitely call Scott Satterlee and Cal Zandt to tell them their statistics are flawed.
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