That's where I'm at too. Unless you are using the same test barrel and have all the same variables as the published results, then you will not likely get the same results, and if every theory as to what it should be with different variables panned out, you wouldn't need the chronograph. Aside from all the typical pressure signs, if your load was over pressure, your groups would probably start to widen, and your velocity deviations would probably spread,
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Weird .308 load question
- Thread starter Greg500sw
- Start date
That's where I'm at too. Unless you are using the same test barrel and have all the same variables as the published results, then you will not likely get the same results, and if every theory as to what it should be with different variables panned out, you wouldn't need the chronograph. Aside from all the typical pressure signs, if your load was over pressure, your groups would probably start to widen, and your velocity deviations would probably spread,
You might be seeing weirdness due to the magnum primers. You're going to see a loss of velocity anyway. How much depends on who you ask.
One of the gun rags did a test years ago by cutting one inch off a barrel at a time. Result was about 100 FPS per inch, but that gets argued, repeatedly, on forums.
"...average of 2626..." Not likely. Hodgdon's MAX for a 175 is 2647 fps with more powder out of a 24" barrel. Ain't gonna happen with a 17" barrel.
41.5 of H4895 is 1.5 over minimum for a 180 or a 175. 2.821" is 21 thou over the Max OAL for .308. However, since nothing bad is going on, I wouldn't worry too much about it. Falls under Rule Number One. It works, don't fix it.
One of the gun rags did a test years ago by cutting one inch off a barrel at a time. Result was about 100 FPS per inch, but that gets argued, repeatedly, on forums.
"...average of 2626..." Not likely. Hodgdon's MAX for a 175 is 2647 fps with more powder out of a 24" barrel. Ain't gonna happen with a 17" barrel.
41.5 of H4895 is 1.5 over minimum for a 180 or a 175. 2.821" is 21 thou over the Max OAL for .308. However, since nothing bad is going on, I wouldn't worry too much about it. Falls under Rule Number One. It works, don't fix it.
http://rifleshooter.com/2014/12/308...ato-barrel-length-versus-velocity-28-to-16-5/
He tested several bullets in 308. Like always, it ain't gospel, but it is an actual test in the caliber being discussed. Theory is always useful, actual testing can be used to "calibrate" theoretical.
He tested several bullets in 308. Like always, it ain't gospel, but it is an actual test in the caliber being discussed. Theory is always useful, actual testing can be used to "calibrate" theoretical.
It certainly is inexact, but perhaps preferable to assume it is a safe pressure if his primers don't flatten, and the case doesn't stick?
Perhaps it is a sign of our modern age, perhaps not, but many people look at reloading data as a precise formula, and expect precisely the same results when they do it, despite the fact that they are not, and cannot be using the exact same components.
Everything varies some from production lot to lot. Primers, cases, powder, bullets all vary somewhat. Great care and effort goes into keeping the variances as small as practical, but still exist, and under the right conditions can stack up.
All the different factors combine, and yours isn't going to be exactly the same as mine, or the test data. I'm from a different age when we judged pressures on observed results in OUR guns with our components. Some will say I'm wrong, numbers don't lie, etc., XXk psi or cup or what ever system you are using to measure is "high pressure" and unsafe...but in my experience, what the numbers say doesn't matter as much as what your gun and ammo say.
If you don't get pressure signs, like flattened, cratered primers, if you don't get sticky extraction, then I don't think you have high pressure, for your particular combination of components and firearm.
And the other side of the coin is also true. If you ARE getting pressure signs, no matter if the "book" says pressure is ok, if you are getting them, then the pressure is NOT ok, for your specific combination of factors.
And, remember, if you DO choose to go beyond listed max limits, it is entirely YOUR responsibility, and only YOUR responsibility.
"If you don't get pressure signs, like flattened, cratered primers, if you don't get sticky extraction, then I don't think you have high pressure, for your particular combination of components and firearm."
Going to one of those who politely , and strongly disagree. By the time you get flattened primers and sticky extraction, you are likely considerably over pressure. Of course they may be other factors causing these indicators. Shame a lot of reloading manuals haven't rewritten their reading pressure signs over the decades.
It would appear greater access to actual pressure testing equipment has long dispelled these common assumptions. Way back when, a lot of the manuals actually used these techniques to publish reloading data. For almost all reloaders , it was the common way to gage top pressure.
Seems to have been a fair amount of articles over the years where they used these signs, then pressure tested the loads, they were considerable over pressure.
Of course it is someone's own responsibility, till they start posting the magical velocity's achieved with their own magic formulas and some neophyte believes them.
Going to one of those who politely , and strongly disagree. By the time you get flattened primers and sticky extraction, you are likely considerably over pressure. Of course they may be other factors causing these indicators. Shame a lot of reloading manuals haven't rewritten their reading pressure signs over the decades.
It would appear greater access to actual pressure testing equipment has long dispelled these common assumptions. Way back when, a lot of the manuals actually used these techniques to publish reloading data. For almost all reloaders , it was the common way to gage top pressure.
Seems to have been a fair amount of articles over the years where they used these signs, then pressure tested the loads, they were considerable over pressure.
Of course it is someone's own responsibility, till they start posting the magical velocity's achieved with their own magic formulas and some neophyte believes them.
Well, thank you for all the replies.
Oddly enough it must be pretty close velocity wise to 2626.
Plugged the data into JBM ballistics and went out and shot some steel. Ended up getting first round hits from 400 to 700 on 18x18 steel plates, then missed at 800 because of a bad wind call. (Wind was gusting from 10-35 mph at random gotta love eastern WA in the spring)
After seeing the targets, the 400, and 500 were dead on with the data, 600 was about 1/2 mil low, 700 was dead on, and 800 was about 3/4 mil low. Definitely going to keep shooting this load, because every 3 shot group was well under 1/2 MOA, and at 600 all three were touching, but I have to give a little credit to luck for that. This is going to be my new long range coyote killing load for sure.
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Oddly enough it must be pretty close velocity wise to 2626.
Plugged the data into JBM ballistics and went out and shot some steel. Ended up getting first round hits from 400 to 700 on 18x18 steel plates, then missed at 800 because of a bad wind call. (Wind was gusting from 10-35 mph at random gotta love eastern WA in the spring)
After seeing the targets, the 400, and 500 were dead on with the data, 600 was about 1/2 mil low, 700 was dead on, and 800 was about 3/4 mil low. Definitely going to keep shooting this load, because every 3 shot group was well under 1/2 MOA, and at 600 all three were touching, but I have to give a little credit to luck for that. This is going to be my new long range coyote killing load for sure.
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That's an amazing performance for such a short barrel, any chance you can try that load in a rifle with a longer barrel? Just curious to get a little more data to see if it's your rifle or the powder that's the major factor.
Jimro
Yeah, sometime this week I plan to try it in my 24" gas gun and I'll see if I can swipe my dads Ruger American and try it in it's 22" barrel.
I'm from a different age when we judged pressures on observed results in OUR guns with our components.
Your statement makes me feel old and is the way I was taught to work up a load. This is back in the day of copper units of pressure, or CUP, rather than PSI. Everything printed is an average for what they were using and since we can't duplicate that we start low and work up safely.
My other observation is mentioned above but I would like to add to it. How do you know your chronograph is right? I use my chronograph but I also check actual results by sighting in at 100 yard and shooting 5-10 shots at 300 yards with no holdover. The amount of average drop tells me my "real world" velocity. I've seen some big differences by doing this and have learned not to trust everything bullet companies (related to their BC claims) and chronographs tell me.
Pressure, and how it is viewed today is one of my pet peeves.
In general, tis the attitude that new pressure measurement, being more precise, shows the old loads to actually be higher pressures than what we thought they were at the time, and since they show higher than the "limits" we were UNSAFE, is what bugs me most.
What I see, often is people taking the "old" limit numbers, applying the new pressure readings, and finding them over max, so you MUST reduce the load to meet the "max" limits, to be "safe".
For example, (and for example only), let's say your old listed max pressure limit was 30,000 (forget converting different measuring units for a moment)
based on what you read in the books, your favorite load should be giving you 29,500, "safe" below the 30K max limit, right?
Now, modern measuring shows that what you thought was a 29,500 is actually a 35,000 level load. EEK! Way above the 30K max limit!!!
Note that the now "too hot" load worked for decades in your gun, in my gun, and in tens of thousands of other people's guns, did not show pressure signs of any kind, but it now "too hot" to be safe!
So since they don't change (upgrade??) the limit numbers, they say to down load the ammo to meet the (original) limit numbers, while using pressure numbers taken with the "new" accurate systems.
My point is, no matter what numbers you use, if it was safe then (proven in field use) then it is just as safe now.
In general, tis the attitude that new pressure measurement, being more precise, shows the old loads to actually be higher pressures than what we thought they were at the time, and since they show higher than the "limits" we were UNSAFE, is what bugs me most.
What I see, often is people taking the "old" limit numbers, applying the new pressure readings, and finding them over max, so you MUST reduce the load to meet the "max" limits, to be "safe".
For example, (and for example only), let's say your old listed max pressure limit was 30,000 (forget converting different measuring units for a moment)
based on what you read in the books, your favorite load should be giving you 29,500, "safe" below the 30K max limit, right?
Now, modern measuring shows that what you thought was a 29,500 is actually a 35,000 level load. EEK! Way above the 30K max limit!!!
Note that the now "too hot" load worked for decades in your gun, in my gun, and in tens of thousands of other people's guns, did not show pressure signs of any kind, but it now "too hot" to be safe!
So since they don't change (upgrade??) the limit numbers, they say to down load the ammo to meet the (original) limit numbers, while using pressure numbers taken with the "new" accurate systems.
My point is, no matter what numbers you use, if it was safe then (proven in field use) then it is just as safe now.