How do you look for signs of over pressure, without a Chrono?


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WhoKnowsWho
February 26, 2004, 03:22 AM
Just wondering if people rely only on reading primers, or notice the sound or slide speed. 'Cause it's strange with my Winchester brass reloads, it seems the primer always is flattened, no matter what the load, and since it seems there are no total truths in reloading, I have to look at everything about the brass to see if anything is wrong (flowing into the extractor channel, etc.) I suppose the most reliable way is with a Chronograph?

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redneck2
February 26, 2004, 07:12 AM
with an auto is to see how far the brass ejects. Kinda an indicator but at best probably a poor one

Pistols are supposed to operate at a low enough pressure level that "typical" signs are pretty much useless until well after the danger zone is reached. The one exception I can think of is Glock. If the brass starts to bulge and not blow out, you're on the very edge.

You can get factory rebuilt Shooting Chrony's for about $45-50.

stans
February 26, 2004, 07:19 AM
The chronograph is a big help, but you can still get into trouble. It is hard to get into trouble with the 45 ACP, even with Bullseye, by the time you hit pressure problems, the chrono is likely to read 900 + fps with 230 grain loads, so you know you are over spec. But with cartridges like 9mm, 40 S&W and 10mm, it can get a little muddy. These cartridges do better with medium burning rate powders, so if someone uses Bullseye, they will see pressure signs long before velocity reaches the recommended maximums seen in reloading books.

I see slightly flattened primers all the time, even with factory 45 ACP, so that is not the best sign. If you see primer flow into the firing pin hole, definitely too hot! If the primer is totally flattened and looks like a mould of the breech face, too hot! Bulging brass may be a pressure sign or a sign of the type of barrel in which the ammo was fired. Glocks are known to have little support for the case head and web, so bulged Glock brass is normal. Slide velocity is a function of bullet velocity, you can work up rounds that are pressure safe, but bullet velocity is going to be pretty high and so will slide velocity, so that is not a great indicator of pressure.

If you follow the recipe's in the reloading books and stay just under their maximum loads, you will probably never have pressure problems.

Paul "Fitz" Jones
February 26, 2004, 11:17 AM
Well aside from reading primers I would turn off the lights in the police range where I was the instructor and reloader and send a round down range in the dark and if there was a basketball sized ball of flame that came from the end of the barrel I figured that it was a pretty hot load. I did that with some super hot loads for a hideout under the armpit .380 after some highway patrol officers were disarmed and killed in Southern California in the 70's.

Fitz

30Cal
February 26, 2004, 01:01 PM
Ken Water's book "Pet Loads" has a good discussion on watching for pressure signs up front (first chapter). He measures the difference in diameter just above the case rim between new and fired factory ammo and uses that change as a baseline for comparison to his handloads. There's more to it and it's worth the read.

Primer stuff doesn't necessarily mean much and is very dependent on the cartridge, the primer and the firearm used. It's still a good idea to keep an eye on them, but flattening isn't necessarily bad. I use primer signs as a cue to scrutinize the load and look for other indications that I'm approaching a limit.

Ty

WhoKnowsWho
February 26, 2004, 04:28 PM
and if there was a basketball sized ball of flame that came from the end of the barrel I figured that it was a pretty hot load

I had a pretty good basketball size ball of flame with some test loads of 40 S&W with Blue Dot, closest thing to a flamethrower I have had. I think those loads would work better in a longer barrel... there were no signs of overpressure though.

TooTaxed
February 27, 2004, 11:02 PM
The "basketball of flame" merely means a lot of the powder isn't being completely consumed while the bullet is still in the gun barrel...very common even with standard loads in short-barrelled guns. That's simply wasted powder. Used to get a huge blast of flame with the Swedish carbines using standard ammo.

You probably need to change to a faster-burning powder...but watch pressures!

tex_n_cal
March 3, 2004, 03:12 AM
Another vote for Ken Waters' Pet Loads

The safe pressure is influenced by the strength of the gun, and Waters discusses those issues in great detail.

cheygriz
March 4, 2004, 09:30 PM
A very quick and easy method that has worked well for me for the last 40 years is case life.

If I can reload the case 5 or more times without primer pocket loosening, or splits, I know that I'm not overpressure.

On auto pistols, the distance the case is ejected is another pretty good sign. I look for flattened primers, bulged case heads etc, but the case life has been my most reliable indicator.

redneck2
March 5, 2004, 06:40 AM
has pretty much indicated that Water's case head expansion is questionable at best. When he did those tests, inexpensive and accurate pressure testing equipment and chronos were not available. He did the best he could with what he had.

Expansion varies considerably with chamber sizes, brand and quality of brass. Testing with some of his loads showed them to be significantly above acceptable pressure limits.

As above, if you have a .45-70 and start filling the case with Bullseye until you get desired velocity, pressure spikes will certainly be too high.

Only way that I know of is to use a powder of the correct burn range and chrono

tex_n_cal
March 5, 2004, 09:59 PM
redneck2 said:

has pretty much indicated that Water's case head expansion is questionable at best. When he did those tests, inexpensive and accurate pressure testing equipment and chronos were not available. He did the best he could with what he had.

Waters stated that his case expansion measurements give relative indications, and indeed that's what they are. He never claimed that .xxxx measured = xx,xxx psi in a given caliber.

In your basic bolt action rifle or Ruger single action, the gun is much stronger than the case. If one is satisfied with the factory load performance, shoot some of them, and check the pressure ring on the fired case. When your loads match them, you should be getting velocities reasonably close, as well. This method does assume that you're using a reasonable powder choice - as you said, trying to get max velocities with Bullseye in a .45-70 is one silly example of doing it wrong - the pressure will hit max long before you match factory load performance.

Assuming that I am using a strong action, and proper powders, I will load up until I either see inaccuracy, or I begin to see the start of solid web expansion in the case head. THAT is time to back off, regardless of how brave you are, how strong the gun is, what the chrono or the load manual tells you.

Expansion varies considerably with chamber sizes, brand and quality of brass. Testing with some of his loads showed them to be significantly above acceptable pressure limits.

Again, he used expansion for relative measurement. If you fire factory ammo, then reload the same cases in the same gun, you're getting a good relative pressure reading.

The notions of "acceptable" pressure have varied a lot in the last 30 years. What was a fine load for a lot of guns has indeed dropped over the years. Part of that has been discussed in some of the better handloading magazines. Modern ballisticians do statistical analysis on loads, to assure that none of a batch is statistically predicted to exceed SAAMI pressures. In many case they have found that the average load must be reduced to assure that safety requirement( i.e. lawyer - proofing) is met. It is also true that brass has gotten thicker than it was 30 ywears ago. There is no way I would accept a load from 30 years ago and try it without working up carefully. I personally haven't tried the home pressure testing equipment. I probably should, it might be amusing.:evil:

Judgement is of course required when you are loading for a gun of lesser strength, or trying to load to a particular power level. A chrono, and case expansion are all good tools. Chronos are just plain fun, anyway, and you might just find a batch of factory ammo that doesn't meet expectations. I once had a box of factory .25-06 that clocked 300 fps less than claimed!

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