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Safety, what is more important? - Lemonaid - 03-26-2020
The basic question is what is more important for safety, measured velocity or the max amount of powder listed?
In my case I used Nosler's max loading for RL 15 at 30.0 for their bullets at 2.245 oal at Max velocity of 2520 from a 24" BBL.
I found a load for my RAP using Barnes 120 match burners at 29.3 grains of RL 15 at 2.290" oal. Velocity 2480 from a 22" BBL.
Accuracy is excellent, SD very good. I was happy.
Then I see Barnes Load data for RL 15 and the 120 Match burner is 27.0 at 2.200 oal, Velocity 2511 from a 24" BBL.
So my best load is 2.3 grains over "book" max but velocity is not over max. (close though).
If you had a load that was under book max for grains of powder but over max velocity would you say safe or unsafe?
If you have a load that is over book max for grains of powder (I do) but under max velocity is it safe or unsafe?
No over pressure signs on the brass both Hornady and Lapua, cci 450 primers., bolt lift was normal.
Safety, what is more important? - BobinNC - 03-26-2020
Your powder lot, your brass, and your chamber are NOT the same as those used for the "book". Never is, never was. Book loads are only a rough guideline and YMMV. The only measure of real safety is the "performance" of load in YOUR rifle. Performance means pressure signs like case head expansion, velocity, primer flattening or worse.
In 45 years of reloading, I've blown primers with a book starting load (it was a Custom 240 Weatherby without the factory freebored chamber). And I ran a load a 7 full grains over "book" max (and still didn't get to Max book velocity, but ran out of case capacity to load more. Factory Sako 9.3x62 rifle).
Every load I ever made for my rifles was always test to visible MAX pressure, while watching the chrono of course. Which means I sometimes when over "book" MAX, and sometimes I never reached "book" Max (load or velocity), without bad pressure signs with a particular load that made me stop right there, right now. I've also only had one round ever that had to be hammered out of a chamber, after smoke came flooding out of the action, and that was with a factory Federal 35 Whelen. Bad lot of ammo, and gun and ammo were replaced by Federal.
In any event I never stopped adding powder to a case just because some book said "beyond here be dragons". The totality of the load has to be taken into account. Velocity, accuracy, case life, barrel life, muzzle blast, muzzle flash, et al are all factors that a serious reloader takes into account. That extra 50 FPS is a poor goal to be chasing.
Of course I didn't start reloading that way. I was very cautious. In the 1970's there were no chronographs you could buy( and there were none that were affordable until the 1990's). In the 1980's I was heavily into wildcats. Wildcats had little to no reloading data. No min's no max's but boy was that fun.
Some of my cats were:
30-338
250 Savage Imp.
7x57 Improved
263 Spence (6.5x57 wildcat)
6.5-06
350 G&H Magnum
.416 Taylor
458 Lott
And of course there were a bunch of factory rounds with scarce load data back when i first had them, like:
7x64
9.3x62
7mm Dakota
404 Dakota
Be safe and have fun
And of course IMHO and YMMV
Safety, what is more important? - tdbru - 03-26-2020
Lemonaid,
BobinNC is pretty spot on. each loading manual presents the data it took with the pressure barrel and sporter barrel they happened to have on hand when they were taking data. of course there were the associated production tolerances of each. if i recall, the SAAMI dimensional specs for pressure test barrels/chambers runs on the tight side. but the reloading manuals guys or gals also probably look at pressure variation for each round, along with LOT to LOT variation of the same canister powder, primers, bullets, cases. as much as they can, and adjust what they publish as max load such that the max pressure variations they saw across all the variation they measured with that particular listed max charge didn't exceed SAAMI spec max pressure limit. i have noticed the same thing that some "starting" loads looked more like max or over max in my particular rifle with it's unique dimensions along with the specific lot of canister powder, primer lot, brass lot, and bullet lot i happened to be using at the time. and like BobinNC i also have gotten to book "max" and still had sooty case necks, no flattening at all of the primers, etc. doesn't mean i didn't have the SAAMI spec max pressure. i have no way to measure. but the rifle and brass didn't act like it. A-Square published a reloading manual where they did call out what LOT number for the powder they used. i think they did that for primers too, and brass. but can't remember for sure. so if your case extraction is easy, primers are not flat, no ejector hole marks on the case bases and primer pockets are staying tight for 5+ reloads, and bolt lift is easy, you may not be getting into max pressure situations. or you might be. without being able to measure pressure you just don't know. i seem to recall reading an article once that mentioned that in match rifles, where all tolerances are taken out, actions blueprinted, and brass is fireformed to chambers etc, you don't start seeing pressure signs on the brass until you are in the 75K CUP region. but since i can't remember where i read that, take it with a grain of salt. the front of most reloading manuals have pretty complete descriptions of pressure issues, signs to watch for, and why, without actual pressure measuring equipment (either a pressure barrel for CUP or a calibrated Piezo strain gauge for PSI) you really don't know for sure were you are pressure wise. watch velocity as you do ladder tests and look for the node where you get best groups. deer can't tell the difference between 2450 fps and 2500 fps. but a tight grouping rifle gives you the confidence to place the bullet exactly where you want to place it, and in general well placed bullets are more effective on deer than an extra 50 fps or so and not being as well placed. when we handload, we assume the risk for our efforts. factories use pressure measuring equipment to mitigate risk. or should be. Sounds like Federal had QC issues with BobinNC's particular lot of 35 Whelen ammo. also the same weight bullet from each manufacturer may have different bearing length, different anneal on the bullet jacket, different jacket thickness, different jacket material, different core composition and hardness etc. which leads to different engraving forces, different barrel friction, etc. being that you're using a Ruger bolt action, and Ruger tends to build a lot of margin into their designs, or they use to, and you're presently not having any issues, from a safety point of view you're probably fine. keep track of if the primer pockets stay tight for more than 5 reloads and if they do, you're most likely ok.
-tdbru
Safety, what is more important? - Lemonaid - 03-26-2020
I am very appreciative of the well thought out responses. Thanks! My thinking is that the velocity measurement is a better indicator of danger than the strict published "book" grain amounts, taking into account danger signals from the brass and the firearm.
If my conclusion is in error, please elaborate on how/what/why it is so.
I am trying very hard not to blow my face off!
Safety, what is more important? - FLshooter - 03-26-2020
Reloading books for me or a guide on where to start. Like Bob said theyre not using the same barrel and your chamber pressure is not the same as theirs. No pressure signs on the brass or primers,bolt opens easily after the shot and you are happy w/results.go with it.
Safety, what is more important? - grayfox - 03-26-2020
The topic of "safety" necessarily translates directly to the pressures that occur in the barrel during the shot, since pressure is what a) propels your bullet and b) blows your action/barrel up if too high.
Each barrel is truly unique, in addition each steel is unique and each set of metallic grain structures is unique. That being said, it is reasonable, with adequate QC, to set a more or less standard over-pressure limit, as well as the yield limits and rupture limits. Your barrel load limit needs to yield MVs/pressures that are less than all of these, obviously!
Pretty much everything we can measure is some kind of proxy for measuring chamber pressure. I too have run out of case volume, and seen insane MV's from a so-called "normal" non-max load. The hot load sequence came from using book load data in my 308 but in Hornady, vice other (I think Win?) brass.
Bottom line I would say is you need to take a data-driven, observation based, informed, all-of-the-above approach to looking at safe loads. Which will doubtless vary from barrel to barrel, brass to brass, powder lot to powder lot, and so on.
My starting ladders are my way of establishing powder/brass/primer/bullet/barrel combo and performance. If MV or case appearance, heck- recoil kick even, if any of these give me indications then I know I'm approaching the limit.
Safety, what is more important? - grayfox - 03-26-2020
ps, I would characterize book data as (as we are all beginning to hear more about in this C-virus deal) "anecdotal" evidence, the (as-described above) results of one set of controlled measurements in one case -- well, maybe a few cases, but certainly not an exhaustive amount - nor a statistically-validated number - of tests. Therefore and in recognition of barrel-to-barrel uniqueness, definitely ymmv.
Safety, what is more important? - 1Shot - 03-26-2020
Like has been said above 41 years ago when I started hand loading chronograph's were cost prohibitive to own. But also the load data that was put out was also MUCH heaver on the powder than most today. I have and old Speer manual that the max loads are scary and some like in 30-06 you would have trouble getting that much powder into a case. That is where the "watching for pressure signs" came from. We had no idea of what velocity we were getting but we could see if primers were flattening and we could see if a case head was growing and we could feel in bolt and leaver actions if action was stiff on ejection. We could feel when sizing the case if it was hard to do pressure was too high. We could feel when seating a new primer if the pocket was loose and know pressure was too high on previous load. I also have some wildcats and had to use these things to work up loads for them.
Today loading data is pretty conservative compared to many of my loads in some weapons but then there are some like my custom 264 Win mag which has a chamber on the tight side that I can't get within a about 2 grs. of a max load without running into pressure but having a chronograph now I can see that I am getting the velocity that data says I would get with 2 more grains of that powder. So it is load to what YOUR weapon wants to digest.
My load of IMR 8208 is quite a bit more for the Speer 120 Gold Dot than Speer's data list and my velocity is a bit more than what their max load states they got. But when I load their max load and even taking into account the velocity loss of my 20" barrel compared to their 24" barrel I was WAY low on velocity. One thing I have learned over the years is that when doing a load work up you will usually find a load, node these days, for great accuracy before you run into high pressure. If you are going to be using your 6.5 Grendel for hunting and will not be shooting over 300ish yards the game will not know if the bullet was running 2600 fps or 2400 fps. Accuracy kills.
Safety, what is more important? - FRB6.5 - 03-26-2020
One point I didn't see mentioned directly that ties into case capacity; the relative burn speed tables for powder are not universally true across cartridges. Powder B may in fact be faster burning than powder A in a particular cartridge.
The overall combination of factors in YOUR firearm need to be evaluated. Lot of great advice given above.
Safety, what is more important? - tdbru - 03-26-2020
just as a technical note, part of the difference between load values from 40 years ago published stuff and today, is 40 years ago, all pressures were measured with the copper crusher pressure barrel measurement (Copper Units of Pressure or CUP). Nowadays, most producers are using Piezo strain gauges that are calibrated and measure directly in PSI. squishing the copper slugs was more of an average max chamber pressure as the slugs don't compress instantly. to get a certain amount of compression you need x amount of pressure for y amount of time. inertia in the ram etc. the piezo gauges, on the other hand, react very fast in the nanoseconds, so you can see the instantaneous change of pressure and catch true peak pressures with more precision than before. so some loads that appeared to compress the copper pellet as much as the tarrage table said 50K pounds did in the lab, might have actually had a 75K PSI spike peak pressure, but was so short in duration that the pellet ram and pellet didn't react to that peak in time before the pressure had already dropped. and so now the producers are saying, with the current higher precision measurement capabilities, oops, that old load actually exceeded 65K PSI, albeit very shortly, we need to drop that charge down a bit in our manual.... or something along those lines... obviously not a quote but you get the idea. also might have to do with the particular lot or lots of the canister powder they had on hand compared to 40 years ago too..... that's why it's not a bad thing to accumulate new data manuals through the years.
-tdbru
Safety, what is more important? - Rosecrans1 - 03-27-2020
There is another difference between load values from 40 years ago and what is published today.
There wasn't a lawyer behind every tree back then.
Safety is always primary. Everything stated in these posts above are true and well thought out. In hand loading, overall observation of every variable is important to safety and a chronograph should be in every handloader's tool set.
Safety, what is more important? - Klem - 03-27-2020
tdbru,
A very thoughtful post.
Safety, what is more important? - BobinNC - 03-28-2020
Lemonaid Wrote:I am very appreciative of the well thought out responses. Thanks! My thinking is that the velocity measurement is a better indicator of danger than the strict published "book" grain amounts, taking into account danger signals from the brass and the firearm.
If my conclusion is in error, please elaborate on how/what/why it is so.
I am trying very hard not to blow my face off!
Lemonaid,
As a follow on to what I said above., your reply generated some more thoughts.
One, if you start low (using the minimum starting load published, or a Max load minus 10%) and work up in .3 grain increments (for cases under 60 grains of powder capacity; .5 grains for cases over 60 grains) it's very hard to blow your face off, ever.
Two, never, ever, use somebody's pet loads as starting point. Always work up from below.
Three, where starting loads differ always choose to start at the lower one. Where MAX loads differ, always choose to work up to the higher one. Unless you see obvious pressure signs, then stop.
Fourth, using velocity as a pressure guide is OK, but also not always reliable or infallible. Your chamber, and barrel your length are critical in making or not making a particular velocity threshold.
Fifth, SAAMI Max pressures are often based on the original rifle a round was offered in rather than on the best, and strongest current rifle now available.
For example:
30-06 Max Pressure 60k PSI
270 Winchester Max Pressure 65K PSI
The two cases are structurally identical. But the 30-06 Max's were based on weak 03 Springfield's and Winchester Model 95's. A modern 30-06 (a Rem 700 for example) can take as much pressure as a 270 Win (in a Rem 700) can.
A similar relationship exists with the 6.5 Grendel. A bolt action like the Howa Mini can take more pressure (and deliver more velocity) than an AR 15 can, but SAAMI Max is based on an AR15's strength not that of the Howa. How much more?? I don't know, but certainly more.
Again, IMHO and YMMV
Safety, what is more important? - Lemonaid - 03-29-2020
Is there a formula or rule of thumb for the increase or decrease in velocity/pressure from bullet seating depth?
For example a load with a 120 grain bullet that generates 2500 fps seated at 2.200 OAL, what will it be if seated at 2.290 ? (bullet in not touching lands in both cases).
Safety, what is more important? - Klem - 03-29-2020
Lemonaid Wrote:Is there a formula or rule of thumb for the increase or decrease in velocity/pressure from bullet seating depth?
For example a load with a 120 grain bullet that generates 2500 fps seated at 2.200 OAL, what will it be if seated at 2.290 ? (bullet in not touching lands in both cases).
This is the essence of what an internal ballistics program like Quickload does. If you can get the algorithm out of them I will be surprised.
Safety, what is more important? - Lemonaid - 03-29-2020
Klem, I thought enough people had done testing for accuracy using bullet jump from the lands in .005 or .010 increments and measuring velocity that there would be a rough rule of thumb worked out. When allowed to go to the range again I will do a couple tests and see if there is good enough data get a general idea of what's what.
Safety, what is more important? - grayfox - 03-29-2020
I have seen a few ideas presented on this but there is no direct formula that I know of. First thing to consider is, it is not the max pressure per se, that drives MV, it is the total area under a (Pressure*area) vs distance (down the barrel) curve, the force acting through a distance= energy(work) performed, which leads to acceleration and then final velocity of the mass. (Max pressure figures in to yield strength, or breaking your action.) Of course, some of the working energy of the powder burn is lost to friction in the barrel and to heat, and torque (and engraving force) on the bullet from the twisting of the lands. So one barrel will have a different MV profile for a given load, than a second barrel, even if from the same mfr.
In general, one developed theory calculates that muzzle velocity is proportional to 1/4 of the peak pressure, but there are a lot of other factors in that equation too... I may try to locate that paper tomorrow and post it if I can find it again.
Second thing is that, as far as I have done, no bullet variance of COAL should be normally tried more than say 0.030-0.040" or so length, especially for non-competitive, non-ocd shooters like us. So the example of going from 2.200 to 2.290, IMO, is not a realistic "Fr'instance" -- maybe more like 2.240-2.280 might be a viable delta. In another forum one of the shooters there did a pretty exhaustive study of their bullets, powders, MV, and factored in some coal variations too. He found that the extra coal length didn't appreciably allow for a faster bullet but might in some cases lower the max pressure by 1000 or 2000 psi (he also found that it might allow a person to use a less-dense powder at a charge with that extra volume, whereas the smaller volume wouldn't allow him to load up that far, but X grs or powder usually equaled Y MV) ... this would imply that, for typical powder charge ranges, a given grainage of powder would have a certain fairly constant amount of kinetic energy to impart to the bullet for the range of COAL's you'd normally have; thus changing coal might allow the work to be accomplished with a slightly lower max pressure but the total area under the curve would be pretty much the same. This of course does not apply if you seat so far out as to jam the bullet into the lands -- that changes things dramatically!!
What the extra coal might do is to keep you from challenging the physical strength of your action, ie, the 52 ksi limits of the AR-15 bolt, lugs and lockup in the Grr, and thus limit the stress they feel during that shot.
Anyway, I hope I've been helpful, there are others on here with more experience I'm sure.
The biggest thing you can get from MV is from a ladder of the load up a range of powder weights, and observe the MV changes from one charge to the next. Bear in mind that, for a single load at each charge, there will be some deviation away from a straight linear relationship due to MV variances when you are off of a node... but a spread can give you a more or less linear approximation. What to look for is a sudden drop in delta MV or actual MV as you increase load... this can tell you you've probably reached a max for your barrel.
When doing these kinds of ladders I try to keep the delta powder charge to 1% or slightly less of case volume... so for the Grendel increase the powder in 0.2-0.3 gr increments. Then you'll be able to extrapolate a charge/MV curve for your examination. 0.1 gr delta's won't in general give you any statistically valid deviations since the MV variance can be at much smaller than the SD of that load (for several shots at that load). For a load charge that would have an SD of 10-12, a 9 ft/s increase (that you think you see) for that 0.1 gr increase is probably lost in the weeds so to speak.
Edit to add: no formulas out in the public domain, that is, there is Quickload and they have their math internally, so like Klem says, you do have that.
Safety, what is more important? - grayfox - 03-29-2020
You could do your own plot of the load data from Sierra, Hornady or Nosler, since they have starting, intermediate and top-end loads and MV's. I believe if you do you would see a pretty much linear relationship between their powder loads and listed charges. It's not perfect but pretty close. This might give you a feel for what their test barrel sees. Reality should be somewhere close to that. I think.
Edit to add: I found that paper, the link is posted here. They show their derivation of what they use about 1/2 way doen the page.
http://closefocusresearch.com/calculating-barrel-pressure-and-projectile-velocity-gun-systems
Safety, what is more important? - Lemonaid - 03-29-2020
Some great things to think on, Thanks! Now what accounts for velocity decreases even though more powder was added at accuracy nodes?
Safety, what is more important? - Klem - 03-29-2020
As you know a jump of 0.5mm or 20-thou is considered a reasonable minimum, unless you are wanting to push the bullet against the lands which some bench-resters do (and suffer for it if they are required to unload before firing).
In an AR I doubt if you will see any noticeable change in precision (group size) by shortening the OAL further than the max the mag will allow. There will be differences in pressure as you change the OAL and of course you will need to manage this. At mag length, guys are already experiencing quite long jumps so again, I cannot see making is shorter and therefore an even longer jump is helpful. Plus, shorter means less powder which again is unhelpful in an already 'slow' calibre. The exception here are short, fat bullets like the 95VMax which require a compromise between shank grip and jump. This is the one bullet I don't load to mag length. Everything else is mag length.
A bolt gun is of course different.