A novice reloader question. Today, using a Ruger Precision, 6.5 Creedmoor, I tested some of my first loads. Using a chronograph (yard sale find by my wife), I shot two groups of 5 at a steady pace. Load was 120g Hornady ELD-M, 43g H 4350, seated at 2.710. The groups were .612 and .693”. However the velocities had 4 radical deviations. Six rounds ranged between 2738 ( first shot)and 2773 (7th shot). I had three rounds drop all the way to 2723 and one round jump to 2782. All charges were thrown a few kernels below 43g, then trickled up using an RCBS 1000. Cases were once fired, Hornady match and I used CCI BR-2 primers. What can cause those radical jumps? I did have some consistency problems with a Hornady seating die in a Lee Classic Breechlock press. Not enough thread purchase to keep the die steady. I don’t have this problem with Lee seating dies for .223 and .308. I did read that wimpy shoulder pressure can cause velocities to drop.
Cause for radical drop/jump in velocity
- Thread starter Old Tanker
- Start date
wedgy
Gold $$ Contributor
Take your pick but the only reliable chronos are MS , Labradar, and Ohler. Other than that you have bullet weight & bearing surface variations, case capacity, neck tension, runout, case length to name a few. How accurate is your scale ? It could be it doesn't like your load combination, you could adjust neck tension, seating depth, switch primers, clean up the flsh hole, primer pockets, etc.
First start with a good chrono though as that spread is well within the error and you will be chasing your tail.
First start with a good chrono though as that spread is well within the error and you will be chasing your tail.
wedgy
Gold $$ Contributor
Also, run you velocity spread thru a ballistics calculator to see what 50fps difference makes at the yardages you are shooting. It might not make as big a difference as you think, but it really shows up as you get out far.
https://bergerbullets.com/ballistics-calculator/
https://bergerbullets.com/ballistics-calculator/
Thank you Joe,
I don’t plan on any competitions at my age, but would like to develop loads that can do near half MOA at 300. Eventually, I would like to take it to Rock Castle, KY, a short distance away, and see if I can hit at 1000. A bucket list thing I guess. This is a lot different that hitting the giant bull at 600 in service rifle.
My yardage won’t go much beyond 300 normally but I would, eventually take it down to Rock Castle to see if I can hit at 1000. The spreads at 100 didn’t make much difference and I shot these loads a little tighter than factory. Next go around, I will be more careful with seating, maybe a new/better seating die then shoot at 300 to see if it stays near half MOA. I will try the Berger app, right now, I downloaded the free, Hornady app. Joe R, above, has me figured out. I’m staying within a budget. I don’t intend to compete. My service rifle days are long past.
Ned Ludd
Silver $$ Contributor
From your description, six shots fell within a 35 fps range (2738 to 2773 fps). One shot registered at 2723 fps, or 15 fps below the lowest of the six listed above, and an additional shot registered at 2782, or 9 fps above the highest of the six listed above. Why do you believe either of these two velocities are necessarily outliers?
Of course, it's difficult to prove one way or another without having all the values, but my instinct tells me you simply have an 8-shot extreme spread of 59 fps. Unfortunately, we typically do not shoot the optimal number of shots required for solid statistical analyses. If we did, barrel makers would be ecstatic. If you have a sufficient number of data points, you can effectively make a determination of whether a velocity value is an outlier using distribution [statistical] analysis.
Of course, we normally would like to minimize ES/SD values in the reloading process. One thing you might look with relatively little effort at is whether the cases representing lowest/highest velocities from your shot string have noticeably different volumes. Alternatively, you can weigh them if it's easier, as heavier cases generally will have smaller internal volume. When attempting to determine the cause of a particular velocity outlier, every scrap of information about the loaded rounds you can record may be useful (i.e. case volume.weight, exact charge weight, seating depth, etc.). If something is different about the outliers, that can sometimes make it easier to spot.
On the other hand, we often try to do a number of things in the reloading process to a level well beyond what might be required to prevent affecting velocity noticeably. In other words, we weigh powder to a very fine increment, seat bullets to very exacting dimensions, re-size and trim cases (possibly even sort them) so the internal volume should be fairly uniform. By doing as many steps as possible to a more exacting degree than necessary, what we are trying to accomplish is simply to eliminate these steps as as the largest, or "limiting" sources of error. The largest source(s) of error, whatever it may be in your hands, will have the largest impact on your velocity readings. Collectively, several smaller sources of error added together can have the same cumulative effect as the limiting source of error, but not this is not so common if you're fairly careful and follow good reloading practices. It's usually one or two things (limiting sources of error) that cause high ES/SD values. A list of common causes for high ES/SD might include non-uniform neck tension, charge weight variance, and choice of sub-optimal primer for the powder/cartridge/bullet weight among other things. I usually find choosing the right primer, meticulous brass preparation, and precise weighing of charges is usually sufficient to generate pretty reasonable ES/SD values. Determining the exact limiting source of error(s) can sometimes be very difficult, especially if it's not one of the common ones. A lot depends on how much time/effort you're willing to devote to the problem, but it is usually possible to isolate one variable at a time, test it, and if it's not the problem, move on to the next. It can sometimes be painful, though. I'd suggest trying the obvious steps first to minimize ES/SD to the point you can keep it under 30 fps, or so, which is not enough to be a big issue at 300 yd. In addition to consistent brass prep and charge weight delivery, if you have a different brand or two of primers, you might give them a try with your load. Sometimes switching to a different primer is all it takes. Good luck with it!
Of course, it's difficult to prove one way or another without having all the values, but my instinct tells me you simply have an 8-shot extreme spread of 59 fps. Unfortunately, we typically do not shoot the optimal number of shots required for solid statistical analyses. If we did, barrel makers would be ecstatic. If you have a sufficient number of data points, you can effectively make a determination of whether a velocity value is an outlier using distribution [statistical] analysis.
Of course, we normally would like to minimize ES/SD values in the reloading process. One thing you might look with relatively little effort at is whether the cases representing lowest/highest velocities from your shot string have noticeably different volumes. Alternatively, you can weigh them if it's easier, as heavier cases generally will have smaller internal volume. When attempting to determine the cause of a particular velocity outlier, every scrap of information about the loaded rounds you can record may be useful (i.e. case volume.weight, exact charge weight, seating depth, etc.). If something is different about the outliers, that can sometimes make it easier to spot.
On the other hand, we often try to do a number of things in the reloading process to a level well beyond what might be required to prevent affecting velocity noticeably. In other words, we weigh powder to a very fine increment, seat bullets to very exacting dimensions, re-size and trim cases (possibly even sort them) so the internal volume should be fairly uniform. By doing as many steps as possible to a more exacting degree than necessary, what we are trying to accomplish is simply to eliminate these steps as as the largest, or "limiting" sources of error. The largest source(s) of error, whatever it may be in your hands, will have the largest impact on your velocity readings. Collectively, several smaller sources of error added together can have the same cumulative effect as the limiting source of error, but not this is not so common if you're fairly careful and follow good reloading practices. It's usually one or two things (limiting sources of error) that cause high ES/SD values. A list of common causes for high ES/SD might include non-uniform neck tension, charge weight variance, and choice of sub-optimal primer for the powder/cartridge/bullet weight among other things. I usually find choosing the right primer, meticulous brass preparation, and precise weighing of charges is usually sufficient to generate pretty reasonable ES/SD values. Determining the exact limiting source of error(s) can sometimes be very difficult, especially if it's not one of the common ones. A lot depends on how much time/effort you're willing to devote to the problem, but it is usually possible to isolate one variable at a time, test it, and if it's not the problem, move on to the next. It can sometimes be painful, though. I'd suggest trying the obvious steps first to minimize ES/SD to the point you can keep it under 30 fps, or so, which is not enough to be a big issue at 300 yd. In addition to consistent brass prep and charge weight delivery, if you have a different brand or two of primers, you might give them a try with your load. Sometimes switching to a different primer is all it takes. Good luck with it!
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Not sure why except SD on all 10 was pretty high. SD is 11 on the six that are near the median. I was overall satisfied with the groups considering the first factory loads were around .7. I can tighten the groups with a little shooting skill improvement. Better breathing and a little more buttstock pressure against my shoulder. I’ve developed a few bad habits shooting off a rest. When I feel myself getting lazy, I take my lever action 45-70 out and shoot some off hand. Makes you hold the rifle.
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Dusty Stevens
Shiner
Regular chronographs can vary wildly just with light changes.
This is the same thing that I’ve been thinking. I read garage sale crono. What brand and model? I tried an F1 years back, and couldn’t get consistent readings from it. I learned not to put much faith into the info.
pirate ammo
Guaranteed to take the wind out of their sails
Yes, what you have stated is true, and then the poor soul realizes he's got to find a 2nd job to pay for it all.
You probably know me too well. I started out in Wyo hunting with a 30-30 and 30-06. Never shot anything beyond 200. I also shot NRA 3 position small bore in HS and college. A college team mate got me hooked on service rifle and I stuck with it through my Army career. At about age 55 I gave up service rifle because I got tired of the day long rotations of firing line to scoring table to target pits. After retirement, a friend and just shoot, at a local range, for fun and self gratification. He got me in to reloading. Here is why I did it. Many studies say if you learn a new hobby or past time, especially something that interests you, it helps slow down the onset of dementia. Reloading makes you think and it is fun. It is a hobby of very specific steps, for safety sake. If I get better at it, that’s a fringe benefit. No, I will never invest in a high end competition rifle, but I will watch the barrel and have a better one installed when needed. I will also periodically upgrade the loading bench. I just follow this site to see if there is something I can learn from the pros.
rwj
Gold $$ Contributor
Sun powered light screens most certainly do! I use a CED Millennium chronograph and bought the battery powered infrared sky screens... no worries now!
Dusty Stevens
Shiner
The shooting chronys can only get a good reading in my experience with the light kit up on the top and indoors. They read very consistent like that
It’s a ProChrono, at least 15 years old. Funny story. I was still shooting service rifle at the time and letting uncle sam provide ammo, so not reloading at all. Wife comes home from yard sales and says, “I bought this thing for $5, has to do with shooting. “ Knowing what it was, I stuck it on the shelf. Ten years later, this spring, I started reloading. On a whim, I pulled the chrono off the shelf, stuck a battery in it and sure enough got a ready light. It looks unused but had no diffusers. I ordered new diffusers and took it out to see what it would do. The rest you all know. It almost looks so pristine that the previous owner might have shot the diffusers on first try, boxed it up and sold it.
rwj
Gold $$ Contributor
They can also be successfully used outdoors by covering the infrared sky screens with black plastic. I like the high (42 kHz) sampling frequency...
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