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I am relatively new at handloading bottlenecked cartridges. The things i looked for for signs of high pressure are things like raised or backed out primers, hard to extract cases, flattened primers, etc. If you read Speers 14th edition as i did they say the typical signs that most attribute to high pressure loads aren't actually high pressure signs most of the time. They say flattened primers as well as backed out primers can happen from to light of a load to properly expand the case, or it could be a light load combined with too much headspace etc. My question is what should i look for to tell me high or low pressure? I have checked headspace and my cartridges are sized exactly to saami specs and are identical length as Remington core-lokt factory rounds case wise. I will get into bumping the shoulder and making fine adjustments as i gain more knowledge. | ||
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Assuming you are using an action where the cartridge case is the weak link in the shooting system..... NO....signs of pressure may be caused by things other than high pressure. However such things as sticky extraction and bolt lift are to be taken seriously and unless you're dead sure this is caused by another factor, you must assume you're beyond safe pressures. Flat primers are a sign of high pressure.....but can be caused by other things too. If one is experiencing several signs of high pressure then he needs to assume that it is. None of these things are automatic.....but must be weighed by close scrutiny of the entire situation. One thing I truly believe in is primer pocket expansion....if you can't seat the next primer, you're in over the limits of your brass and that's way too much....back up at least three grains! I also take stock in CHE...(case head expansion) and keep a fine Mitutoyo blade mike just for this measurement. One must weigh the entire evidence when working up to max loads.......and by max loads I mean MAX for your shooting system /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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Wow, i never thought of primer pocket expansion, and the blade mic for head expansion is a great idea! I am glad i came to Accurate Reloading, I have gotten so much good information on here. Thanks alot, that was a very helpful post Vapodog. By the way my action is a Sako 85 Finnlight in .308. | |||
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The factory loads you have can help you get the feeling how extraction should feel in your rifle and give cases to compare with. | |||
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One thing you should always remember; Changes in case dimensions indicate that the brass is begining to fail. Good Luck! | |||
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Those "signs of high pressure" were arrived at before the era of computerized manufacturing. Tolerances varied by quite a bit (unlike modern production is supposed to be). So, if you have rifles newer than say 20 years-old or so, you can have high pressure without bolt-lift, flattened primers, etc. [see A-Square's "Any Shot You Want" book -- not original info from me]. Until you get very good at the physics part of your new hobby I wouldn't stray far from what is published for the calibers you use. Just a cautious reminder, and if you keep track of internet advice and self-reporting you will find that those who use rules-of-thumb for reloading outside the boundaries of published data (as opposed to genuine expertise) blow up guns, put holes in their body, and so on. Be safe. _______________________ | |||
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The most reliable high pressure sign that we normally can read is velocity. If the books say with x powder and y bullet you can get up to z velocity and you are getting z plus 200fps velocity, you can be sure you are doing it at higher pressures. Don't make the mistake of thinking that you can go a few to several grains of powder over what the books tell you get extra velocity and think that you aren't getting higher pressures because you don't have a sticky bolt or flattened primers......................DJ ....Remember that this is all supposed to be for fun!.................. | |||
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As Vapodog said, any one sign may be caused by another problem: a dirty chamber; a headspace problem, so you have to look at the overall situation. A Chrony is a "nice to have" first addition to your reloading bench. Aim for the exit hole | |||
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Assuming you are using a modern turnbolt rifle, the only pressure limitation is that of the brass. As one poster previously said, if the brass (in the head area) changes dimensions, then your pressures are at best unsustainable, and at worst subject to rupturing the case and leaking high pressure gas and metallic particals back into your face (as well as messing up your action). Measure the case head after firing for anything more than nominal expansion, and carefully feel for normal pressure to re-seat the primers in previously fired cases. If the primer pocket starts to lose its tension on the primer within three or four firings, then you should be reducing your charge. Along with case head/primer pocket expansion, you will often see bright marks or bolt face engravings on the case head, and possibly be experiencing sticky bolt lift. Bright marks/engravings on the case head are an immediate "no-no" and the charge must be reduced (or other cause such as bullet engaging the lands addressed). "Reading" primers (other than under controlled conditions) is largely an excercize in futility. Pressures that are not great enough to deform the case head are often excessive for use in automatics, levers, and pumps and can result in locking up the action (or even damaging it). That is why you must be somewhat more cautious when loading for guns with these actions. | |||
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Thanks for all the feedback. I didn't think of velocities for guageing problems as they arrise, but i will be getting a chronograph. I see they have one at cabelas that reads from 22-7000 fps for 119.00, It's a pro-chrono. Does anyone have this unit? Would it be adequate?I don't forsee ever needing more than 7000fps, maybe 4000 since most loads are 3000ish or less. I've only used them till now for my bow speeds at the range. | |||
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I've clocked as high as 4,300 FPS shooting a 64 grain .224 bullet out of a .300 H&H cartridge and using a sabot.....a helluva lot of IMR-3031 behind it. 7000 FPS is way more than adequate for today's needs! I use a shooting crony and have no complaints with it at all! /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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Trying to look at any one sign and making a judgement is difficult. Be like your DR making a major decision just cause you said your head hurt. I have a Master Beta Chrony works for everything I need ti to do. As usual just my $.02 Paul K | |||
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If you shoot federal red box,they will show primers that back out and some that are hammered. It does not mean that they are to hot.They sometimes need to form to your chamber.They are the only ones that I have ever seen do that. The chrno whatever one you get can be a usefull tool as well as case measurements. | |||
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Stonecreek, I certainly agree that "feeling" the finger pressure during the primer re-seating process is very helpful in gaging PSI. I note you believe that "loosening" prockets within 3 to 4 reloadings is an indication of too much pressure, but I ask why do you say 3 to 4. And, can I get you to dilate a bit on what is significant "loosening?" I have my criteria, which I'd like to share, but after you weigh in on this important subject. Regards, AIU | |||
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Hey IceMan, I'll have to disagree with DJ on this. Velocity tells you absolutely nothing at all about Pressure. Due to the variations in Chambers, Bores and Components, there is no way a person can randomly select a Velocity from a Manual, compare it to whatever a chronograph reads and come to a "valid" conclusion about what the Pressure is doing. The only thing a chronograph will do is measure Velocity, and sometimes don't even do that well. Vapo mentioned CHE and I fully support his statement. In fact, you might find some useful tips concerning CHE & PRE in that post. I also agree that Primer Pockets can tell you a lot about how the Pressure is affecting the specific Lot of cases being used. But unless a person uses CHE & PRE, they find out about the Pressure after trashing a bunch of cases. Best of luck to you. | |||
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Would the chamber/bore/component thing be consistent for a given rifle across a variety of loads? What I mean is that if one chronos a selection of factory ammo compares the actual velocity with the stated velocity and applies the same sort of differential to their homeloads, for which the data comes from a manual with printed expected velocities, would that be a useful guide to the pressure threshold for that load? | |||
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I didn't read djpaintles post that way Hot Core. I interpret his post this way.....(I'll use different words) Lets assume we're loading a .270 Winchester and 130 C&C bullets and we know the factory loads claim 3,100 FPS for this load. We also know SAAMI max pressures are 65,000 PSI and that factories such as Win and Rem and Hornady etc can measure this in fairly expensive pressure barrels. We also know that the factories will load to higher velocities if they can as long as they don't exceed SAAMI pressure (evidence Hornady light magnum) Factories compete for sales all the time and if any of them can improve on performance and maintain SAAMI pressures they will do exactly that.....it's a reason to buy their ammo over the competition. For these reasons (along with the knowlege that they can access the very best powders available for their products).....It's quite reasonable that if you are loading said rounds then it's extremely unlikely that you can reach 3,100 FPS and have much less than 60,000 PSI.....it's a reasonable statement. The wrinkle here is that the actual pressure one may be incurring could be quite a bit higher than the SAAMI max of 65,000. In other words....while velocity don't tell us pressure.....it is a bit of evidence that the reloader just might be at or quite exceeding the factory pressures. The factories (professional loaders) aren't able to go over 3,100 FPS with their best technology then it's likely that we can't either. (at SAAMI pressures) Once again.....if one has confidence in his chrony (mine has never failed me) and he's nearing the Max published by the factory loads, he has evidence that he just might be at or some amount exceeding the factory pressures....and we can reasonablt assume the factories load somewhat less than SAAMI (legal resons) and we can also reasonably assume that factory loads are normally slightly slower than published. For a reloader to say....."There...I'm safe.....it's at factory velocity" is a horrible misunderstanding of the data and dead false. However this is a two tailed story....for a reloader to say that when (and if) he reaches factory velocity (it may never be achievd) he says that it means nothing....he's dead wrong again.....it's one (of many) signs that one may in fact be reaching pressures of max factory loads. I rest my case your honor! /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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Although Velocity doesn`t tell pressure it can give us a hint at about where it is. If one gets a load from a reputable manual that tells him X amount of a certain powder under a specific bullet, when lite with brand A primers gives 4000 fps, we can be pretty certain that if our loads with the same conponents gives 4000 fps, give or take say 25/50 fps we are probable very near the same pressures as the developers of the books data were. Change the bullet, powder primer or case and the accuracy of the velocity/pressure relation isn`t as trustworthy anymore. I believe this is HCs gripe with the method, then again maybe not...... ------------------------------------ The trouble with the Internet is that it's replacing masturbation as a leisure activity. ~Patrick Murray "Why shouldn`t truth be stranger then fiction? Fiction after all has to make sense." (Samual Clemens) "Saepe errans, numquam dubitans --Frequently in error, never in doubt". | |||
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Ok, so i opened a can here didn't i? So if i am understanding everyone correctly, i should use Case Head expansion,primer signs and primer pocket leakage and expansion as the basis of my conclusion on pressure and combined with a chrony to evaluate my pressure situation, Correct? I believe i have enough valuable information to move forward with my new hobby. Thank you guys for your great information. If anyone has some more valuable info for me i'm all ears. | |||
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Also, consider getting Quick Load - the best internal ballistics program on the market. Not perfect, but a good estimator of PSI and velocity when using a specific caliber, bullet, powder, OAL, barrel length, powder charge, etc. One can learn much from using QL. Regards, AIU | |||
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and the point is????? /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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This thread is all about:
and this is off topic:
Start a new thread if you wish to discuss something different. /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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 So far this is the most emotionally free thread on pressure indication that I've seen on AR. It also contains a lot of good well presented info that will benefit more than just novice reloaders.  rogerOld age is a high price to pay for maturity!!! Some never pay and some pay and never reap the reward. Wisdom comes with age! Sometimes age comes alone.. | |||
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/////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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Good data here. I like to be able to access several methods to warn against excessive pressure BEFORE I get there. Get as many as you can. Blade mic, chrono, QuickLoad are all good. Please read through this thread carefully and keep in mind that any of the methods can indicate excessive pressure but not all of them will every time. I have seen that CHE/PRE are very accurate and repeatable as is EGE (extractor groove expansion) and they parallel primer pocket expansion. Also, please do not go under the assumption that you need to see ALL of the signs before you back off. | |||
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Hey Vapo, The 270Win is an interesting choice. I do not remember folks whining and crying about factory ammo velocity for them the way that I've seen them do for the promotional 30-06 ammo. It has been a very long time since I wasted any time at all with a Chronograph. Back then, a lot of factory stuff was rather anemic, but part of that could have been due to the rifles. I know this will disappoint a lot of folks, but I'll accept you are correct. I'm a bit confused here, because it is seldom that I pick up a factory Rem, Fed. or Win cartridge that I do not shake it close to my ears. Normally I can hear and feel Powder moving around inside. Since I use mostly lightly compressed Loads, and often they (used to) just barely meet quoted Factory Ammo Velocity, I find it difficult to imagine less Powder getting more Velocity at a sane Pressure. I realize Hornady has access to some Powders that I do not have access to. And it has been a good while since I've shaken one of their Cartridges, but I seem to remember "nothing moving" inside the Case. I just can't imagine Rem, Fed and Win doing that across their entire line of Cartridges. That is my concern for the Beginners and Rookies. Back many years ago, I had the opportunity to shoot a lot of 308Win and 30-06 rifles across Chronographs using the same Factory Ammo. The typical variation could vary +/-200fps, with a few being +/-300fps, and a few were relatively close. So the problem (as I see it) is how would a Beginner/Rookie know if his specific rifle is Slow, Fast or perhaps right on, so that Velocity would have any value? Sounds reasonable to me. When "your/my Ballistics Hero" (alf) can't even grasp it, how would it be possible for a Beginner/Rookie to understand the ambiguity? Perhaps alf can straighten you out!      | |||
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100% correct. Velocity higher than expected is an early pressure sign. If your getting more velocity at a given barrel length than you expect, there is a good reason. Unless you have sophisticated pressure measuring equipment, and the knowledge to correctly use/interpret it, a chronograph is the best way for reloaders to get an indirect measure of pressure under the curve. Assuming people are using appropriate burn speed powders for the case to begin with, then velocity will appropriately reflect relative peak pressures. This is far better than using measurements that are highly dependant on the qualities of the brass and chamber. Wes | |||
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And we're off and running. The poor guy asked about empirical pressure signs and is getting the history of creation. For a newbie, don't you think this is somewhat excessive? I agree, start another thread so's those of us that couldn't care less about your pee and che and see pissing contest can avoid it. Geeeeeez  Aim for the exit hole | |||
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This is your discussion technique? Alf, I have a science background and understand what you are getting at. Keep fighting the good fight.  | |||
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Perhaps if the differential between expected and actual velocity was worked out from firing factory ammo in the rifle and applying the same differential to the velocities in the load manual? ie. 30-06 federal 150gr stated velocity 2910fps, actual average in my rifle 2800fps max load 51 gr H4895 150 gr stated velocity 3009 fps (manufacturer's online load data) Actual average velocity 2840 fps Sample size was 10 rounds of each. What do you think Hotcore? | |||
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Looks like the ballistics guru has shown he knows much less than he lets on. It is basic ballistics that an increase in velocity corresponds with an increase in pressure. So to say that velocity tells you absolutely nothing at all about pressure is incongruous. It is also well known to most with even a rudimentary knowledge of ballistics that given appropriate loads powders with faster burning rates can produce more velocity with less powder than powders with relatively slower burning rates. You learn something new everyday whether you want to or not. | |||
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One crevat, Vel tells you something about the "average" pressure (work under the curve), but not about the peak pressure. | |||
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This is a basically correct statement however for those that haven't had the benefit of a course in integral calculus it means very little. Pressure and the length of time the pressure works on the bullet is the key to velocity. It's why burn rate is so important.....the burn must be matched as closely as possible to the volume expansion as the bullet moves down the barrel. One can actually get better velocity in some cases by playing the correct "burn rate card" than by playing the "pressure card" While some may think this is off topic, I believe this is basic data for a new reloader. Choosing powders of the correct burn rate is critical....but easy to do as the loading manuals list appropriate powders. I'd not recommend use of any powder not listed for use in any credible loading manual......and yes....this includes blue dot loads! /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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Bingo! I think this is where a lot of confusion comes from. However, the area under the sharp peak pressure zone in a pressure curve contributes a grossly disproportionate amount of the total area (velocity) under the pressure curve. This is even more true in very short barrels/pistols. For this reason, velocity is a pretty good indicator of peak pressure assuming an appropriate burning speed powder is used. Bottom Line: For the average reloader, I think that velocity is the best indicator of pressure assuming that someone is using an appropriately slow powder for the case/bullet combo and comparing their chrono readings to published pressure tested data. Other "pressure indicators" are too dependent on other variables of the brass/chamber/bolt face, etc. For a beginner, or someone without a chronograph, I would not stray outside of published data as almost all of the time, the published data will be safe in your firearm. Wes | |||
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Matching factory ammo FPS is Not a good indicator of pressure. Some factory ammo has special powder that produces extra velocities that are not available to the handloader with safe pressures. One caliber is the 204 Ruger. Hornady Superformannce ammo loadings now use special powder not available to the public. If you try to match there factory velocities, you will be running over presssure. See American Rifleman magizine 1/2010 issure, page 54. Hornady charts. | |||
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You can substitute C-4 or some similar high explosive for gunpowder to test the hypothesis that pressure and velocity are somehow proportional. The C-4 will likely blow a chunk out of the chamber, perhaps without even dislodging the bullet from the mouth of the case. In this extreme example XXX,XXX psi yields zero fps. To use a more reasonable example, a dozen grains (or some such amout) of Bulleye will generate chamber pressures of, say, 60,000 psi in a .300 Winchester, and will yield a velocity of something like 1500 fps. A charge of 70 grains of 4831 will generate the same chamber pressure, but will yield a velocity of 3,000 fps. If you increased the Bulleye to generate the same velocity as the 4831 -- well, you couldn't do it without blowing the rear end out of the brass. Clearly, pressure and velocity are not directly related in this instance. To a lesser degree, the same is true of two otherwise "suitable" powders in your .300 magnum. IMR 4350 might generate the desired 3,000 fps, but being on the "fast" side it might do so at the expense of pressures which deform the brass case head. At the same time, a greater mass of IMR 7828 might yield 3,000 fps at relatively mild, sustainable pressures. In this instance we have less powder (and potential chemical energy) generating more pressure, while more powder (and chemical energy) generates less pressure, but both yield the same bullet velocity and energy. All of this said, I DO find a chronograph to be an indispensable tool in reloading. When utilizing the same powder, there is a relationship between velocity and pressure (although not necessarily linear). Using a chronograph you are able to detect velocity spikes which typically also indicate pressure spikes, meaning that you have reached a tipping point with a powder charge. Also, if velocities are signficantly lower than expected, or higher than expected, it provides a clue to look for other, more dependable, pressure indications. But if one takes the simplistic attitude that "the book says a .30-06 will get 2750 fps with a 180 grain bullet using IMR 4064", then simply keep adding IMR 4064 until you reach 2750 fps, you actually know nothing about the pressures you are generating and might well be on the verge of blowing primers, depending on the cut of your chamber, the volume of your brass, the actual diameter of your barrel, the hardness of your bullet jacket, and a dozen or two other factors. | |||
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Stonecreek, I'm wondering if I can get you to address my question. Regards, AIU | |||
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