The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Measuring case expansion for pressure indication?Go | New | Find | Notify | Tools | Reply | |
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I am familiar with the 'traditional' signs of high pressure, namely ejector marks, stiff/locked bolt, cratered/loose/blown primers, etc. I have been reading mention of measuring the case width as an additional sign of pressure. I am not familiar with this procedure. What is the procedure and what measurements am I looking for? Basically, I am getting above max listed loads (Hodgden and Nosler manuals) in my 300WSM and not showing any signs of even flattening the primer, and as I am very cautious want any additional methods to check and see if I am at max loads. Thanks! | ||
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Well, according to Barnes they say the following, but I have seen .0005 expansion alot. And it depends on the brass. I think the .0005" number is a little too cautious. If you have case head expansion of more than .0005" with a once-fired case, this is a sure sign of excessive pressure. You will have to measure your case head with a Blade Micrometer just in front of the extractor groove, or you can use a regular micrometer and measure the belt on belted cases, before and after shooting. When any of these signs appear, back down one full grain and you will have a max load for your gun. | |||
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If you can believe Dr. Ken Howell, who has probably forgotten more about reloading than 99% of the "experts", trying to estimate pressure...especially max pressures... by measuring case head expansion is not only useless but can give you a false sense of security. When you say you are getting about max listed loads over what the various manuals are telling you do you mean you are using more powder or that you are getting higher velocities? Hopefully you are aware of the value of a chronograph when working up loads. In additon you might want to read what the A-Square reloading manual says about the effects of not only using different primers and seating depths but the effects of using different lots of the same primers and powder....very informative. Bottom Line ---- measuring the amount case-head expansion is neither an accurate or reliable indication of pressures in your rifle.....why take a chance to squeeze the last 20 or 30 fps out of a load? | |||
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I disagree. One full grain isn't enough. I find 5% is a better figure. I haven't had a sticky case on an extra hot day, or any other problems, since I started following this rule. I'm not surprised. I come very close to published data by the makers of the bullets I use when I follow this rule. I believe one should rechamber for the next larger case if he needs more velocity. E | |||
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If you only get .00035-.0005 dase head expansion and check it on a really hot summer day, your loads will be safe to shoot in fall weather. Also use the chronograph and if you get some kind of wild velocity, your pressure is likely a bit wild also. | |||
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Since when did a chronograph become a scientific means of testing pressure ? I would be curious to see how much difference you would get between 2 pressure test barrels with the exact same load , How many of you use the exact same components as listed in the manual ? The case really have the same capacity ? the chamber have the same dimensions ? same freebore ? I belive there are just too many varibles to let a chrono be the last word in pressure . I am not trying to be a a$$ but I dont see how it defines pressure accurately ? I also belive that most manuals are on the conseretive side and I usually end up with a load to the conservitive side of that in search of the most accurate load . I had a contender barrel that was overloaded with a suggested starting load from sierra , I fired 1 round and then pulled apart the other 19 apart , no damage to the gun but I had a difficult time getting the brass out . | |||
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You aren't seeing any "signs of pressure" whatever that is, since the brass is of a much better quality than it was around the turn of the century when measuring brass was a way people could tell they were about to blow themselves up. If you are faster than the books, you are about to blow yourself up. Why do so many people keep posting these kinds of questions? | |||
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Quote: As an engineer I appreciate the concept of a safety factor. I am currently all of .5 grain above published loads and still getting 1 hole groups, so I was considering how much higher was practical and trying to educate myself beforehand. We ask because ya'll (this group) talks about it a lot. When you are offended/annoyed by someone asking a simple question, maybe you should just not reply.....  If we weren't the adventuresome types, we probably wouldn't be here, and what is wrong with pushing a bit? | |||
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Quote: I HAVE BEEN LOADING FOR 150 YEARS AND IF YOU DO ANYTHING I WOULDN'T DO OR THINK ANYTHING I WOULDN'T THINK, THEN YOU ARE A CRAZY DANGEROUS FOOL AND YOU ARE GOING TO BLOW YOURSELF UP! Nurse, I am ready for bed now. | |||
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It is a simple but complicated concept. 1. Start with virgin brass 2. Fireform them to your chamber using a "middle of the road" charge. 3. Take measurements around the belt or in front of the extractor groove. 4. Start working up your load while subracting before from after case nead expansion. 5. When you reach .0005" case expansion (even on one case.... no matter what the weather outside!) you're maxed. | |||
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Quotation; "It is difficult to impress reloaders w/fact.. every rifle is an individual...what proves to be a max load in one may be quite mild in another,& vice/versa" B. Hagel CDH, Using a mic on the case head is ONE of the effective methods of staying out of trouble. Like a lot of other things in life please don't take it out of context. There are many other signs of pressure. Watch the bolt lift, watch the primers both for flattening and cratering, watch the case head for brass flowing or shaving. If any one of these signs of excessive pressure appears proceed with great caution. In other words use your head. Look at the overall picture. There are a lot of guideposts to pressure and taken together they start to present a picture. Even Dr. Oehler told us that his strain guage pressure testing equipment is only another sign. The only dumb question is the one you haven't asked. Keep asking. That's how we've all learned. The published load data will generally keep you out of trouble but all rifles are different. Some will shoot more and some less. And then there are all those wildcats with no load data at all. I know i've survived years of playing with them with my eyes and hands intact by watching the pressure signs. I would be careful, though, with any rifle other than a modern bolt action. knobmtn | |||
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I have used this method for years. But, normally only on widcats that I have developed that there is no load data. On factory rifles I pretty much let the reloading manuals do my work. Like POP says. I fireform and then measure each round before and after. I bought a digital Mic that has a zero feature. So I will set it before I fire to zero. Fire the round and remeasure. The new reading is the increase. I set .0005 as the max and then back down. Two of my cases are now in LoadTech. Looking at what the software comes up with for a max and what I got by measuring each load are very close. Easily accounted for by chamber size. | |||
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Quote: Hey DB, I seem to remember you posting this somewhere before, or perhaps I read where howl said that himself.  As for me, no, howl is wrong on this issue just as he is on many others.Have you seen him post over on 24hour where "he developed a method" where he can stand about half-way down range, have a person fire a cartridge at a target and howl can tell them what speed it is going by listening to "the difference" between the shot and the impact at 100yds?  Absolutely PITIFUL!!! Had a buddy "link" me to that thread and I've not stopped laughing about it yet. Must have been last year some time if you want to look for it. Or ask howl about it.Quote: howl's doctorate in Theology just lets him down when it comes to actual Internal and External Ballistics. howl even had some of the greatest Reloading Masters of all time writing for "Handloader" when he was there - Mr. Ken Waters and Mr. Bob Hagel. Strange that howl never challanged or deleted any of their references to CHE/PRE during that time. As we all know, Mr. Waters and Mr. Hagel have ALWAYS used CHE/PRE, and even mention their Expansion values in their articles. ... So, your choice is to go with a guy who believes he can tell you the Velocity of a bullet by listening to it - howl, OR, two of the finest Reloading Masters OF ALL TIME - Mr. Ken Waters and Mr. Bob Hagel. ... Maybe his "Ear Chronograpy" will be detailed in his newest book!!! | |||
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Hot Core, Who is Ken Howell? I'm an old geezer and subscibed to Handloader and Rifle for many years but I don't recall him. I agree that measuring case head expansion is a valuable and reliable tool. I first read about the method in an article Bob Hagel authored in Handloader magazines #90 and 91 - March-April and May-June,1981.It is also described in his 1986 book,"Guns,Loads,& Hunting Tips,starting on page 291. He also described the "pressure ring method" in both of these publications. I,personally,don't care for the "pressure ring expansion" method as I don't think it is as precise as the "case head expansion" method. It also is not measured where the "bad things" happen. Hagel's method used one case, measuring before the first firing and measuring after firing.He used the same case for each subsequent increase in powder charges. I believe that each firing does some "cold-working" of the brass and this change in metallurgy can impact the expansion of subsequent firings.I use seperate cases for each level of the powder charge - in fact,I use two cases for each charge and average the results. Here's a hard-to-read bar chart of case head expansion data from a .30 cal wildcat,showing the expansion of the first firing on the bottom of the bar and the expansion of the 2nd firing of the same loads stacked on top. http://members.aol.com/manyplews/che3a Per Hagel's rule,he would have gone ahead and tried 65 grains and up,stopping where he found the level where he got significant expansion with every repeated loading.Then he would have backed up a grain or two. Me - I'm satisfied at 62 grains as it gives adequate velocity and long case life. | |||
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I measure cases during load development, but I'm hoping not to ever see expansion. If I do I think it's too late and I feel lucky not to've had a problem. The variables in brass makes this a very iffy proposition. By the time you see casehead expansion you are probably well over 70000 PSI, (Fed and Bell brass are sometimes softer) and well into danger territory. If you do see casehead expansion (really the base just ahead of the head) you need to back off a full 5% IMHO. That last 5% does not buy you much velocity, but it sure spikes the pressure, and if one other thing causes an additional rise you can be in deep trouble right NOW. I use Fed primers which are very soft, and I've learned to read them fairly well over the years. I don't know how to tell a newby to read them. The best indicator of pressure is velocity. If you are using the right powder for your rifle, you should stop when you reach the published velocity even if you don't see pressure signs. When you reach the published velocity for a given powder's max load then whether you are 2 grains heavy or light you have reached the maximum safe charge. The best safety gear you can get is a chrono. Work up slowly from 10% below published max load. Read the chrono, read your primers, read your cases. 99 times out of 100 you will reach the published velocity before you see any other signs of pressure. Stop there. If you see signs of pressure, back off 5% and stop. You usually only need to go up to pressure signs for a wildcat or to proof a rifle. D'Arcy Echols must proof all his rifles. I bought a bunch of used 458 Lott cases from him and about 20% had expanded pockets. Correlating the powder loads written on the cases with teh expanded pockets made me think he'd intentionally gone over the limit on every rifle. I wish he'd told me that before I bought the cases. JJ Hack got some of the cases from me before I knew they were expanded, and he wasn't pleased with me! Don | |||
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Quote: Hey manyplews, howl at one time was the "Editor" at Handloader. I'm not sure of the time period, but it was a good while back. A few years ago he logged on to HuntAmerica and I really looked forward to his posts. But, I soon realized that my original opinion of him was incorrect. Rather than trash him any more when he isn't here, you might be able to catch his posts at www.24hourcampfire.com and come up with your own opinion. He used to post there under the "Gunwriters Board" or something like that. ... No problem from me with Mr. Hagel's method, though I do realize it is slightly different than the way I do it. I was taught CHE/PRE by some of my Elders before I knew of Mr. Hagel's and Mr. Waters' writings. | |||
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Quote: Hey Smokin54, I agree with you. The Gunwriters had me "fooled" for a very long time about Chronographs. But, all of a sudden I had access to one and then three of them. Spent a good bit of time "learning" I'd been fooled into thinking Chronographs were the greatest reloading tool ever offered. But, I don't believe a person needs 2 "pressure barrels" to be in agreement with your excellent question. All they need is access to two rifles of the same caliber and enough of the same Lot of ammo to fire through both. I really like the portions of Reloading where it is easy for anyone to be able to easily prove these often arguable points to themselves. | |||
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Quote: The above post is the one to go by. You need to use all the information that you see. Chronographs are no panacea either. They can be wrong or go wrong just like anything else. | |||
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Quote: I've read some fantastic B.S. on various forums before, but this particular statement sure takes the cake!! For example, tell me how bettering the wimpy 7X57mm-level loads most manuals are now showing for the 7mm Rem. Mag. is going to blow anyone up! Give me a cotton-picking break! My Ruger No. 1B fires a 140-grain Nosler Partition bullet at 3400 FPS using 71 grains of old H4831 and Fed. 210 primers, and has been doing this evewr since I bought it in 1969! I'll let you know when it blows up!! There is absolutely NO WAY any loading manual publisher can tell you what's safe and what's not in YOUR INDIVIDUAL RIFLE unless you send it to them, and they develop data that's unique to that gun!! | ||
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Pure physics says that the bullet velocity is a function of the integral of the pressure on the base of the bullet. So velocity does not tell you peak pressure directly, but it does say quite a lot about the overall pressure curve. If you load enough Unique behind a 400 grain 416 Rem bullet to hit 2370 fps you will kill yourself. (This is NOT what I was recommending!) But if you are using the same powder in a proven rifle with the same barrel length, using similar production cases, bullets and primers that the manufacturer's load was developed with, then when you hit the published velocity you will have hit effectively the same peak pressure. Continuing to increase the load after you hit that velocity is dangerous and unnecessary. Using a chrono does not guarantee safety, but it does help. I agree you always do want to use every safety indicator available, at all times. The chrono, working from proven load data can keep you from routinely entering the danger zone during load development. Don | |||
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You are right, you are not about to blow yourself up. The max pressure spec of the 7mm Mag is 52,000 CUP and you are only at 55,000. No harm, no foul. If you held them to 52,000 with that powder, about 30% of them would be 55,000 or a bit more anyway. This is the thing that most handloaders don't understant....there is a nornal distribution of velocities and pressures for every load, and the SAAMI specs are based on statistics, not absolutes. The downside of going 5% hotter than spec is that there is less room for a mistake, so the loader needs to be more vigilant. In general, slow powders are more forgiving than fast ones, and the 4831family is one of the most forgiving. | |||
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A more useful way to track pressure is to punch out your spent primers by hand and mike them for diameter. Each brand has a diferent hardness and strength, so you need to stick with one. CCIs are not good as they are too hard. Winchesters and Remingtons are fine. I use Winnies and when large rifle primers grow from .210 to .213 I am in the range of factory loads. .215 is HOT. When measuring primer diameter you are really measuring the little "brim" that occurs as the primer sets back in the pocket expanding into the seating flange. This will not work if you headspace is off so check headspace before relying on this method. Now, a very interesting thing happens when you focus on primers and primer pockets and do more by hand. When you punch out a hot load's primer, you will definitely feel this as an easy punch. Soon you will learn what is too easy. Same when you seat them. Use a hand tool and feel them go in. If they are too easy, the pocket is too big. Set these aside and don't use them any more for expansion tests. They will work fine as they are and the next time use CCI primers as they are a bit larger in diameter. Just don't use them for pressure estimating. | |||
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The problem with pure physics is that the variables are impossible to measure by the average person (like me). Peak pressure is not the critical determinant of velocity, but it the critical determinant of safety! How else does a 30-378 and a 308Win in the same barrel, bullet, and PEAK pressure give 2 VERY different velocities? I don't trust chronos for pressure. Stick with me.....the bigger cases with slower powders loaded to the same MAX pressure maintain HIGHER pressures over a LONGER time. The velocity is a function of the AVERAGE pressure the bullet experiences, not the MAX. Unfortunately I can't afford direct pressure equipment, so I have to infer the best I can, hence the original question. Thus far, my engineer brain has found very few MEASURABLE pressure indicators available to me, and calipers don't lie. Thanks for the tip on primer measurements, but by that, 90% of the factory ammo I have used in my 2 rifles is overpressure. The only flat primers I have seen yet have been from factory loads in my .280 and 300WSM. | |||
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CDH, You obviously can't cross data from a 308 Win and a 30-378, as you well know. If you don't have a basis to work from the chrono by itself tells you nothing. But let's take a concrete example. You have a 308 Win and MudButter powder company has a new powder that they've published loads for. In their rifle with a 24 inch barrel and a SAAMI max chamber(56 grains of water capacity), Fed GM210M primers and Win brass with they got 2750 fps for a 168 grain SMK using 43.2 grains of MudButter 4895. They say this is a 52,800 PSI load. You have a 308 Win with a tight chamber and tight neck, 24 inch barrel, you can safely work up to their load in your rifle by starting at 38 grains and working up using the same components. When you hit 2700 fps you should stop. If your case holds 54 grains of water, this will happen at 42.3 grains of MudButter 4895. Your pressure will be slightly higher due to the smaller chamber when you stop, but not dangerously so, and certainly you will be far below any visible pressure signs. In fact, with this example your pressure would be 54,651 PSI. (Quickload numbers) The point is you knew when to stop BEFORE any pressure signs showed up. Without a chrono or a pressure gauge you can't do that. It's important to know when to stop! HTH, Don | |||
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Quote: Hey Don, I disagree with your concept and am more than willing to try and discuss this so we come to some agreement. You mention, "when you hit the published velocity", that to me implies you are going to a Powder or Bullet Manufacturers Manual to see what Velocity they got using a specific Load. Lets say it is 200gr of HotPowder in a 31-06 using a 144gr bullet with a 22" barrel which generated 5000fps at a SAFE Pressure(or they sure wouldn't have listed it). Then you seem to believe that using the same 144gr bullet in your 22" 31-06 you can just add good old HotPowder until you reach 5000fps. Situation 1: You get to 185gr of HotPowder and at the point you reach 5000fps, where you believe the Pressure in your rifle is the same as what the Component Manufacturer experienced in his rifle. And there was virtually no chance of having a Pressure Problem when you were still below 5000fps. But, if you add more HotPowder to go above 5000fps, now the Load automatically becomes "dangerous and unnecessary". Situation 2: You got to 215gr of HotPowder and finally reached 5000fps, where you believe the Pressure in your rifle is the same as what the Component Manufacturer experienced in his rifle. And there was virtually no chance of having a Pressure Problem when you were still below 5000fps. But, if you add more HotPowder to go above 5000fps, now the Load automatically becomes "dangerous and unnecessary". Is that what you think? Just want to make sure I understand your thoughts. ... If we used the terms "Manufacturing Tolerance" and "Acceptable Dimensional Variability" in respect to: 1. Chamber (all the dimensions) 2. Lead (distance to, angle, etc.) 3. Bore (surface finish, actual diameter, residue, etc.) 4. Rifling (twist rate, number of Lands and Grooves, etc.) 5. Primer (duration of burn, flame intensity, etc.) 6. Powder (burn rate, etc.) 7. Bullet (diameter, Land/Groove contact patch, etc.) 8. Crimp or no crimp (loose, tight, squashed into the bullet with a Lee Squasher, etc.) 9. Neck Tension (case neck hardening, actual contact patch length, residue, etc.) 10.Bullet jump to the Lead Do you believe all the above dimensions on the Component Manufacturers "Rifle and Load" are the same as on your "Rifle and Load"? ... We are in complete agreement on using every Pressure Detection method available to you - if it actually helps you. | |||
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Quote: Hey Sabot, Interesting concept. How do you compensate for the variability of the slight taper on the mouth of the Primer Pocket? Looks like that could make you think you have an Underload(or Overload) when there really is no problem(or visa-versa). I agree that P-FLR would be the way to go so there is ZERO Headspace, or a slight crush fit. | |||
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Hey Don, We were apparently posting at the same time. If it would help, I can go back to my last post and change the Load to the one used in your example. Let me know. | |||
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Quote: Hey eldeguello, Are you saying that Mr. Bob Hagel and Mr. Ken Waters don't know what they are talking about? | |||
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Don G, Quote: The bullet velocity should be one over the mass of the bullet times the integral of ( the pressure on the base of the bullet, minus the bullet to bore friction, minus the pressure in front of the bullet). Assume we are not cutting any magnetic flux lines with the bullet conductor [a steel barrel is a good shield]*. That pressure in front of the barrel is important on cold days, and even more important under water. *I hate it when someone ELSE gets that fussy, but it's ok when I do it  eldeguello, Quote: My extractor groove expansion measurement with dial calipers technique is independent of chamber tightness. -- A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian. | |||
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