About to start reloading for a new rifle/cartridge combo - 260 Remington. Wanting to measure pressures as I go along. Have long paid attention to primer craters, ease of extraction on fired case, and pressure signs on rear of case. Would like to step up my pressure detecting proficiency a notch, and already have a digital micrometer.

My question is have others successfully used micrometers for this purpose (measure case head expansion) that were not blade micrometers? Or, do I really need a blade micrometer to measure in the .0005 range?

Thanks!

I take it you want to watch the pressure ring expansion?
I`m not a big fan of this procedure but I`ll admit it has some value. You need a mic that reads 0.0001" to do it properly. There is a poster around here somewhere that`s sure to pop in and explain the whole thing to ya. I won`t mention any names.....Hot Core.

I like a blade mic for the purpose and have learned that the expansion is simply a piece of data to be used along with a lot of other data to help estimate pressure.

The information isn't as valuable as I previously thought it was, That said, I still measure it.

HT,

I used the pressure ring method for many years, but have become convinced that it is of no real use. With the advent of pressure testing devices within the range of normal shooters, well, at least well-heeled normal shooters, enough data has been collected to conclude that pressure ring measurement is not a reliable indication of pressure. Neither is looking at the primers or judging pressure from the bolt lift.

I think that the choices boil down to using one of the piezo-electric devices or sticking closely to what the books publish. There are some notable exceptions regarding old cartridges for which data is kept low because of older firearms that are chambered in these classics; 45-70, 9.3x62, 7x57, and even 30-06.

However, when experimenting with these rounds above posted limits, one should be very circumspect, and refer where possible to data from reliable individuals who have done pressure testing with what I'll refer to as +P loads for these classics.

In sum, I'd not recommend the pressure ring method of arriving at pressures, and stick within the published limits in reloading manuals. If you want to see how those are in your rifle, take five cases, start below the max and work up. When (and if) you get to the max, take five new cases and fire the max five times and then section one case. Then fire the remain four, and section another case, etc. You will get a real world picture of the pressure effect on you cases, the weakest part of the pressure containment system.

Having established a max, you can then choose to back off some and preserve your brass longer, or shoot it between five and ten times before trashing it, assuming the necks don't split or the primer pockets don't loosen up too much. Kudude

quote:

Originally posted by H T:
...My question is have others successfully used micrometers for this purpose (measure case head expansion) that were not blade micrometers?...

Hey HT, Yes indeed, many multiple thousands of reloaders have used both Case Head Expansion(CHE) and Pressure Ring Expansion(PRE) with excellent results ever since the first enclosed metallic cases were available for the public.

You can measure CHE on your 260Rem with a regular 0.0001" capable Micrometer(Round Anvils), but it requires that you File down the "Rim" in two spots across from each other on 15-18 cases. You do this so you can reach past the Rim width and measure the beginning of the Case just past the extraction groove.

The Thin Blade Micrometers are able to reach this point to measure CHE without interference from the Rim on the 260Rem.

Until you get a set of Thin Blade 0.0001" capable Micrometers, you can just go with PRE. That works just fine "if done properly" and works on ANY and ALL metallic cases in existance.

Having 0.0005" capability is not accurate enough to do it properly, you must have 0.0001" capable Micrometers or you are wasting your time. Fortunately you can get regular Micrometers through www.wideners.com at a reasonable price. Also check Pawn Shops, cause I got my 0.0001" capable Thin Blade Mitutoyo Mics at one.
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There is without a doubt that CHE/PRE are the very best ways to "compare" Pressure with a Factory Load used as a Benchmark Standard. Because they provide you with First Hand information directly from the case. No other non-destructive Method in existance does that.

The Home Strain Gauge System(HSGS) is an interesting device. The people selling them expect you to do a lot of things to get them set-up properly that is difficult to accomplish outside an actual Test Lab. And the information of getting them "Calibrated" is always good for a few laughs.

You can follow their Instructions and "guess" at critical dimensions, but then the accuracy of any Data from them is based on "guesses" - or is colloquially known as - Full-of-Beans.

The very best thing I've seen come from the HSGS is "stimulating the economy", by a transfer of your $$$$.00 into other people's pockets.
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Rather than continuing to irritate people that have the HSGSs, if you want a Microsoft "Word" File on how to properly use CHE/PRE, just PM me with your email address.

Thanks, Gentlemen. I will digest what you have shared with me and go from there. Rifle arrives in late April, and I will begin working up long range target and hunting loads. Should be fun.

Mostly I believe that staying within published velocities = staying within accepted pressures. And I think if you want more velocity than standard for that cartridge, move up to another (and faster) case. Don't try to stretch the one you have into something it never was.

But .... it still nags at me to know what's going on. So I'll continue to explore this topic.

Much appreciate the answers.

I do it the old fashioned way. I don't measure cases, since the measurement can be greaty influenced by the chamber dimensions.

I rely on the old fashioned appearances:

Are the primer pockets flattened?
Are the primers pierced?
Are the case heads embossed with the tooling marks of the bolts face?
Are there tell-tale signs of head seperation?
Are there stress points in the case?
Is there difficulty operating the bolt?
Is there difficuty in the extraction/ejection of the fired case?

My favorite load for the .260 remington is:

120 grain Sierra HPBT
Remington brass
W-760 From 39.0 grains to 45.0 grains in 0.3 grains stpes
Remington 9-1/2 Primer

Case expansion measures a real condition. You are straining the brass beyond it's yeild point. At that point a sane will pause to reflect on his actions.
Good luck!

quote:

Originally posted by ricciardelli:
I rely on the old fashioned appearances:

Are the primer pockets flattened?
Are the primers pierced?
Are the case heads embossed with the tooling marks of the bolts face?
Are there tell-tale signs of head seperation?
Are there stress points in the case?
Is there difficulty operating the bolt?
Is there difficuty in the extraction/ejection of the fired case?

Certainly any of those symptoms could be a practical problem, but they are not a reliable indication of pressure.

For example, one of my lever guns will pierce primers with some reduced loads but not with max loads. The pierced primers are due to a sloppy firing pin fit, a very common condition on lever guns.

On the other hand, one of my bolt guns will show none of those symptoms at 70,000 psi.

As John Barness has written, a chronograph is the average guy's best indication of pressure with ordinary bullets and CCI or Federal primers. It's certainly not perfect, but it works well most of the time.

Barness has also written a couple of articles ridiculing CHE. But what does he know, other than the fact that he has access to Western Powder Co's lab for checking his work?

Have you thought about getting a chronograph? They aren't that expensive and with a chronograph you will be able to infer pressure from velocity (and see how velocity changes with heavier powder loads), measure standard deviation, etc., etc., etc.

I think it is the best tool for developing handloads.

quote:

Originally posted by popenmann:
...As John Barness has written, a chronograph is the average guy's best indication of pressure...

Here is a link to an interesting discussion on Chronographs & Pressure written by a fellow that frequents this site.

As I've mentioned in previous threads, Chronographs can be very mis-leading, and if you comprehend the above, it would be difficult to argue the point.

quote:

Barness has also written a couple of articles ridiculing CHE. But what does he know, other than the fact that he has access to Western Powder Co's lab for checking his work?

One of the last Handloader magazines I got before my subscription was due to run out had an article by barsness "ridiculing" CHE just as popenmann said. It was a bit difficult to see where he had the problem from the small amount of information in the article. Seemed to reflect badly on barsness to have such a poor understanding of the concept.

Previous writers in Handloader like Ken Waters, Bob Hagel and Gary Sutton seemed to do right well with both CHE and PRE.
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Having access to "Western Powder Co's lab" simply means they can Test Loads in their Test Barrels which has little to do with a regular Factory Rifle barrel. So, I don't see what significance that has on anything, unless barsness was Testing Ammo to see if it met SAAMI Specs.

HT,

Here's a couple of real world experiences that may help you decide for yourself about measuring CHE.

About 3 years back, Black Hills ammo started loading special purpose 5.56mm ammo for SOCOM units. It's called Mk 262 and in it's varying Mod's may use the Hornady 75's, Nosler or Sierra 77 gr match bullets. The terminal ballistic effects are quite a bit more effective and at further distances than the NATO 62 gr SS109 round distributed to our troops. A distributor in Georgia worked a deal to obtain some of this ammo from Black Hills on the condition of a sizable order, paid for, "upfront". All this went on over at AR15.com. I placed my order, paying "upfront" and waited...and waited....and waited! Finally decided to pull out, took my refund; something like $500+ for 500 rounds and instead decided to develop my own MK 262. Since this round was using NATO over SAAMI spec pressures, caution needed to take place. A SAAMI spec 75-77 gr bullet from a 16" barrel runs around 2600-2650 fps. NATO spec pushes that to about 2750 fps. The BH MK 262's were, surely developed in a NATO spec chamber w/ longer leade. My Rock River Arms uses a Wilde length leade; shorter than NATO but longer than SAAMI.

First, I had to set some parameters. Safety needed to be 1st followed by velocity then accuracy. Since this was to be my EOTWAWKI round("End Of The World As We Know It"), components needed to be readily available and cheap. I settled on the grossly available (to me) LC brass, vintage 1991 and more recent. Shoulders were set back .002" with my Forster BR FL seater die.

NATO spec calls for a cannelure around the bullet so it may be crimped in place, thus avoiding an over pressure situation if a bullet were jamed down into the case in full auto or some other tense situation. The canneulure has also been proven to aid in fragmentation. I rolled my own cannelures with the awesome CH4 tool.

NATO spec primers are of course crimped, something I had no control over though I hear cases are availble commercially with crimped primers in place but to my knowledge CCI primers were used. Running such high pressures, a primer thick enough to avoid piercing was in order. I settled on the older WSR primers that have the nickel plating in place. A had a new case of 5000 on hand. With more than 1000 NATO spec home brewed rounds through my RRA, I've yet to see a since piercing.

Even as close as I live to my favorite shooting spots, I still wanted to devlop my loads at the range. I hate running back and forth to the house, either needing more rounds or having to pull bullets from rounds which are too hot. I ran powders which were conducive to accurate charging via "throwing" with my Harrell's Premium powder meter. I ran W748, Varget, H4895, R15 and TAC.

Through various souces of research I settled on an average of .001" as max CHE at the point just forward of the extractor groove. .001" will definately give more than SAAMI spec pressures. I use a Starett micrometer which will measure to .0001".

Off to the range I went with prepped cases, powder, bullets with cannelures already rolled on and a Forster Ultra Seater die with preset readings for the various bullets. I use an Ohler M33 Chronograph set w/ a 5' spacing and the center of the 5' spacing set 10' from the muzzle.

I start at the suggested loads so I can get an idea of where the pressures are and where their going. I watch all the usual case signs for high pressure but pay especially close attention to my chronograph and CHE. As I'm increasing powder by about 2 clicks on my Harrell's powder meter I can see the CHE measurements increasing steadily. At first it's only .0001" then .0002" and so and so on until I'm seeing .001". I call that or just under, max for that combination. Once I get home, I set the meter to that particular setting to see how much powder the meter is actually throwing. I even hit 2780 fps with both H4895 and TAC. Deciding to add extra caution, I backed off to 2750 fps and called it good. I then compared accuracy and settled on the H4895. I'm about 3 gr over any book max. W748 didn't even get close to the velocity goal. I can't get enough Varget into the case to hit my target velocity. I've heard that Black Hills uses TAC for their MK 262 loads....good choice!

That's only one story.

I recently ran a test based purely on accuracy with a Rem 700 in 30-06, Nosler 180 Ballistic Tips seated to touch the lands and H4895. I'm getting sub 1/2 MOA with loads that are a good 3 gr over book max but I keep my CHE expansion to .0006"....within SAAMI max!

Good luck.

Big Al

Hot Core:

I would agree with the article you posted (as presented).....that chronographs can be misleading, especially when you change multiple varibles. In that case, you don't know what you are measuring.

I still think chronographs are a useful reloading tool for inferring pressure (again that doesn't mean that you can actually measure the pressure with a chronograph). You also must keep everything constant (i.e., OAL, brass, bullet, primer, same powder lot, crimp, no-crimp, weather conditions, etc.) except the powder charge weight. If you start changing more than one variable (as was the case in the article that you presented) then you can't be sure what actually caused the change in velocity (was it the primer, the bullet, and so on). Most people agree that there is a definite relationship between velocity and pressure.

You also need to load a series of loads with the same componets and increase the charge weight at some increment to establish a trend line to infer anything. You also need to compare the measured velocity (here is where you need the chronograph) against some known velocity/pressure relationship (usually find this in a reloading book) to start inferring the pressure.

In addition to all this, you still need to pay attention to the primer, primer pocket, case head, signs of difficult extraction, etc to develop safe handloads.

quote:

Originally posted by MHC_TX:
...Most people agree that there is a definite relationship between velocity and pressure.

Hey MHC, I can agree with that as a stand alone statement. The problem I see is a Beginner taking that concept and doing some extrapolating on it. All of a sudden you see someone who "thinks" they understand what is going on and draws the wrong conclusion.

The guy that wrote the above Link to "Chronographs & Pressure" sems to have researched it rather well before mentioning it to me.

quote:

You also need to compare the measured velocity (here is where you need the chronograph) against some known velocity/pressure relationship (usually find this in a reloading book) to start inferring the pressure.

Are you talking about a Load shown in say a Hodgdon Manual? If so, the same Load used in a different rifle is not likely to have the exact same Velocity/Pressure Relationship as their rifle.

Where that can be a problem is when someone begins a series of Loads "thinking they are SAFE" as long as the Velocity is below what is shown in the Manual. Maybe they are and maybe they aren't. Just another reason why chronographs can be mis-leading.

If you (or anyone) can gain access to multiple rifles chambered for the same cartridge, it would be easy to see. If you belong to a Private Range, Gun Club or such stuff, you might be able to get a few people to bring in say 5-10 30-06s. Load 40 cartridges with a mid-range Load and shoot 4-shots in each rifle while chronographing. You will quickly see the problem.

In fact, you can probably see it with 2-3 rifles if you and a couple of buddies have rifles chambered for the same cartridge.

quote:

In addition to all this, you still need to pay attention to the primer, primer pocket, case head, signs of difficult extraction, etc to develop safe handloads.

Absolutely AGREE!!!

Hot Core:

I agree ....different rifles will generally give different velocities for the same load (I have seen it with two of my 30/06's). That's why handloading manuels always recommend reducing a load below the listed max and working back up (looking for signs of pressure).

I still contend that a chronograph is a useful tool, due to the pressure/velocity relationship. The hard part (or where people can get confused and I think this is your point) is the relationship between pressure and velocity isn't a linear relationship and it is here where people can get into trouble by blindly using a chronograph.


H T

sorry for hi-jacking your thread!!

Hey MHC, Totally in AGREEMENT with you!!!

You are correct that a chronograph "can be" a useful tool. And your statement, "the relationship between pressure and velocity isn't a linear relationship and it is here where people can get into trouble by blindly using a chronograph." is right on the nose.

Those are the exact kinds of things that can get a Beginner "into trouble" when someone who really doesn't understand tells that Beginner all he needs is a chronograph to stay out of trouble.

It always amazes me at how many people do not really understand about chronographs. And I've yet to see the potential for mis-leading a reloader explained in ANY of their Manuals. Pitiful!

Best of luck to you.