New handloader article on "guessing pressures"

[Peter M. Eick]

I just got my new Handloader last night and read the article on "guessing pressures" Yikes!!!!!!

I know he only studied a few instances, and his techniques are different then mine but I was surprised at the results. I always thought that the pressure ring (on the body of the case, not the extraction rim) was pretty reliable and well respected. I was not expecting his conclusions. Any additional thoughts and comments?

Also, using a chrono seems to be the new prefered method, with some "ballistic insight" for lack of a better term to get a reasonable final velocity. Do you all agree with this result?

Any other thoughts and comments on this topic? It seems as if pressure determination seems to have almost a mystical aspect that few want to talk about openly.

I know I have started several threads about "exactly" how do you decide what pressure is safe and not safe, and the topic gets very murky very quick.

Just trying to get a dialog going......

[KP95DAO]

Not having read the article it is hard to comment on what he wrote. However; I have been using the "pressure ring method" for over twenty years and it has worked extremely well for me.

[buford1]

What Is the pressure ring method ?

[cheygriz]

I've been reloading since early 1965. The best method that I've found is case life.

If I can load a case only three or four times, my pressure is MAX!!!

If I can reload it more than 5 times my pressure is moderate.

Having said that, I would say that selecting the slowest burning powder practical for a given caliber and bullet weight, and chronographing your loads is the best way to "guesstimate" pressure. If your velocity is very close to the "book" then your pressure is very close as well.

Again, once you think you've found your max load, use the case life method.

[Peter M. Eick]

Having read his article and then spent some time on the range today chrono-ing a bunch of loads. I had time to think about it. I was shooting 45acp and 38 special. Pressure rings were running about 3/4's of what the factory loads do and extraction was very easy out of the Python. Velocities were running in the 800 to 830 fps for the 45 and right at 800 for the 38 specials. In this particular case, given the two sets of data, I would venture to say that these are resonable to mild loads. It is just interesting to see how a bit of information (the new article) gives me pause to re-think, re-evaluate and then continue testing.

By the way, I was using 5.5 grns aa2imp, 230 berry fmj, starline brass and 1.272 col for the 45's and the average sd out of the Baer was only 7 fps. Nice powder for 45's. The python was a bit "wilder" with sd of 11 fps with 4.3 grns of 231 on a 158 lead swc, cci500 primers, starline brass 1.462 col.

[Cheapo]

I'm still using primer signs compared with factory loads using the same primer.

Wish I still had those .40 S&W 180-gr loads with WW-231 that got the "smiley face" crease when fired from a Glock . A few cases remain undisposed, but they've all been decapped...

I'll still back off *if* the velocity is higher than the load data I should be getting from that barrel length.

[Guy B. Meredith]

Peter,

What was the velocity on the .38 spl? I use 158 gr West Coast copper plated bullets, WSP and Starline brass crimped at the cannelure and get results way different than the reloading manual.

Usually the velocity is way under manual, but when I made assumptions on that one time I got a surprise in some magnum loads.

On the .38 spl I have been using 4.8 gr AA#2 for about 850 fps from a 6" 686+ and a 5" 627, ES about 100 fps, SD about 27. The same load does 900 fps in a 4" M66 with ES 25 fps and SD less than 8. 4.6 gr drops down to 850 fps, don't know ES or SD.

I am getting about 850 fps with 6.4 gr AA#2 with the 100 fps ES and over 25 SD.

[bk40]

Hi Peter,

I have not read the article... but, info I have gathered from others on judging pressure using a chrono goes as follows:

- velocity gains will fall off and may actually decrease when you have reached max pressure or gone (far) beyond it.

I have never really attempted to judge pressure in handguns (I'd hate to know what pressures my IPSC Super load pushed ;-). Normally I load my handguns within published data or just slightly beyond. I do use the pressure ring method in my bolt rifle loads. I feel fairly confident in my results using this method in addition to judging primers, ease of bolt opening...etc.

IMO judging chamber pressure w/o the correct equipment is a (semi-learned) guessing game. Learn about all the possible pressure signs, use a chrono and most importantly, use your head and best judgement.

ps- also, when testing max loads, do so at the hottest temperature you plan on shooting them.

[john kilgore]

I read the article: It still pays to do "all" the checks !!!!
What with the lot to lot variations on all components, you can't just rely on a single factor.

Like the article said, each cartridge and firearm are often a rule into themselves.
I've got a custom Mauser '98 that gives cratered firing pin marks on the primers with the lightest charge, and ditto for loads that are well above most loading manuals. However, this rifle has a longer than usual throat in the chamber and the bolt was polished and faced down in an attempt to eliminate the pit at the firing pin hole. The only way to tell if you are at or near max is to "mike" the case heads. Then, you are at the mercy of the hardness of the particular batch of brass you are using. The data in all the manuals are a starting point as I've found that the max for this rifle is somewhere in the range given for the .257 RCBS IMP. even though this rifle has a standard chamber though be it with a long throat. Different rifles I've loaded for in this caliber are just as much individuals as this rifle is.

No single pressure factor works all the time, except for the transducers and crushers, and then they are techique dependent !!!!

A pressure indication on a .38spl on the case head expansion would indicate 3x to 4x above the SAAMI max.
For different cartridges, it takes different indicators to tell if you are at or above max. It is different for the .38spl and .45acp (low pressure cart.) than for 9mm or .38super (high pressure cart.).
It is also different for 7mm Mag's and 243 wcf (v-high pressure cart.) than for .30-30 or .45/70 (low pressure rifle cart.)

Reloading is as much as an "ART" as it is "SCIENCE" and must be treated as such ----- with a degree of caution !!!

[larryw]

Repeating Buford1's question: what Is the pressure ring method ?

thanks,
LW

[Peter M. Eick]

Guy,

The 38 special load I was using in a 6" python:
Starline brass trimmed to 1.140, 2nd firing, LaserCast 158 grn SWC, cci500 primers, 4.0 grns 231, 1.462COL. My 35p gave me the following on 20 shot strings: 845+, 805-, 40s, 821m, 11sd.

Same load with 4.3 grns 231, 897+, 851-, 46s, 872m, 11sd for 20 shots.

I rounded a bit on my prior posts and mixed the info from my 4.0 and 4.3 loads. I will endevor to be more precise in the future.

On the question of pressure rings. Please do a search because others have described it much better then I. In a nutshell it is a pressure detection method based upon the case expansion as measured across the rim, body and taper of the case depending upon which school you use. These measurements are all calibrated to factory expansion in your gun, so you are working by comparison. This is a brutally short description of a sophisticated technique. Please read up on it in the search pages or in the Speer/Seirra manuals.

Thanks for the other comments. I thought it was very interesting article. It is one to re-read a few times.

[larryw]

Peter, I did a search and only came up with the numbers to use for measurement, not the where's/how's/why's. Thanks for the summary and for the pointer to the Speer manual, always figured it was good for more than simply load data.