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How much under the max COAL can I go? Login/Join 
Be Like Mike
Picture of CEShooter
posted
I've made it through my first ever batch of reloading and things went overall pretty smoothly, sort of.

One of the more pressing questions that I have is if I was finishing up the last round of .243 way past my bedtime and misread the calipers and the COAL of my rounds that I created is 2.610" and the max. COAL per Speer is 2.710" with a COAL as tested by them of 2.625", how do I know if I've seated the bullet too deep to safely shoot? I've heard too deep can lead to unsafe pressures but if I'm only in the lower 25% of their powder range I should have a little wiggle room correct?

The load is a Speer 90gr bullet over 36.0 grains of IMR 4895.

Should I be good to go or should I have a friend or neighbor shoot it first to makes sure it's safe for me? Big Grin


---------------
"Structural engineering is the art of moulding materials we don't understand into shapes we cannot precisely analyze, so as to withstand forces we cannot really access, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. A. R. Dykes
 
Posts: 2174 | Location: 500 Miles from the homeland | Registered: February 21, 2004Reply With QuoteReport This Post
I Deal In Lead
Picture of Flash-LB
posted Hide Post
You're perfectly safe.

Look at it from a common sense point of view. If -.010" took a load from perfectly safe to dangerous, then reloading is way too dangerous to get involved in for anybody including me.

Speer/CCI did a test where they gradually seated bullets deeper and deeper into a case until it would go no farther and it never even got pressures into the realm of a proof load.

I know people will say that they only tested one load, but I can guarantee you they wouldn't publish if they'd only done one caliber/load, it's just that it's a practical impossibility to publish all of them. Publishing one is a guide to reloaders showing what the general effect of bullet setback is. Generally, it's way overrated.

Lucky Gunner did a similar, but unscientific test where they hammered bullets back in cases and shot them up with no ill effects years ago.



And from Lucky Gunner:

Lucky Gunner Ammo
1 week ago . Public
https://instructordevelopmentj.../tag/bullet-setback/

Battered Bullets: What Impact Does Bullet Setback Have on Function?
Experiment Conducted by: +Andrew Tuohy

I have been conducting experiments relating to firearms for a number of years, some of them quite mundane and others rather unorthodox. Many of the unorthodox experiments have never come to light, either because nothing of value was learned, or because I had decided to compile their results over a long period of time before releasing the data.

One series of tests which falls into the latter category relates to what, exactly, makes guns blow up. We've all seen photos of exploded firearms and bloodied hands or faces that result from a "kaboom," or catastrophic failure of a firearm or the ammunition it fires. As a result, a lot of people exercise an overabundance of caution relating to any ammunition that "looks funny" to them - even going so far as to discard cases with tiny dents in them, for fear of causing an explosion.

While it's always a good idea to err on the side of caution when working with items that contain 1,000 times more pressure than a car tire, it's also a good idea to have an understanding of what can really cause a catastrophic failure. And my experimentation has shown to me that the common knowledge relating to this topic is entirely wrong.

Many others have performed experiments of this type in the past - my interest in the topic was piqued by a conversation with a ballistician who told me of a test performed decades ago by a famous writer. The details of the test made me immediately think, "There's no way the gun didn't blow up!" But not only did the gun not blow up, it exhibited no signs of damage.

Which brings me to the test I conducted using a Glock 22 and some Speer Gold Dot ammunition. I had observed minor bullet setback over a long period of time with this firearm/ammo combination. "Setback" is when the bullet is pushed into the case, sometimes by repeated chambering.

Armed with the common knowledge that .40 S&W was especially susceptible to pressure issues from bullet setback, and that the Glock 22 would blow up if you looked at it wrong, I set out to find exactly what amount of bullet setback would cause a catastrophic failure.

Because I was absolutely certain that the gun would blow up, I took several precautions. First, I clamped the pistol in a vise and fired it remotely using a trigger actuating device. Second, I started with the tiniest levels of bullet setback, using a reloading die to push the projectiles into the case. Third, while firing the Glock, I made sure to put an adequate barrier between myself and the firearm. I then took seven cartridges and set them back at .005" intervals, to a maximum of .035" bullet setback.

I then fired all of these cartridges. Surprisingly, the Glock didn't blow up. Using a dye penetrant designed to identify small cracks, I carefully inspected the barrel and slide. They showed no signs of damage or impending doom.

I scratched my head and tried to figure out why it hadn't turned out the way I expected. I was determined to find out the "zone of danger" for a .40 S&W Speer Gold Dot and a Glock 22 in terms of setback, so I set a few more cartridges back with the press and headed to the range - but not before I grabbed a hammer, too.

As I feared, the further-setback cartridges had no adverse effect, so I slowly looked between the hammer and some of the remaining intact cartridges. I set one cartridge, bullet up, on a smooth hard surface and delivered a solid blow to its face. The result was ugly - the hollow point deformed and the case was bulged a tiny bit, the bullet set back a significant distance.

Due to the bulged case, I had to use the hammer to "ease" the slide into battery. I crossed my fingers and stepped back, then activated the trigger.

No obvious damage.

I took another cartridge and hit it twice, then a third and hit it three times. The end result was disgusting and hardly recognizable - the cartridges were badly deformed and required a solid hit to the rear of the slide in order to chamber. And yet neither caused the firearm to blow up. I hit a few more cartridges with the hammer, but didn't have the heart to fire them - I figured the poor Glock had had enough punishment.

Back at home, I used the dye penetrant and found that the barrel and slide remained undamaged.

Why did this happen?

Well, Glock has revised the barrel since the early "unsupported chambers" which left the pistol with such a bad reputation, and they also beefed up the frame since the earliest iterations of the .40 S&W. And while certain powders, when used in .40, can cause dangerous pressure spikes, manufacturers of commercial ammunition wisely test and select powders that are not as susceptible to changes in temperature or, obviously, bullet setback.

So while I'm not saying that you should attack your ammunition with hammers, I am saying that you should not fear tiny amounts of bullet setback with commercial ammo - at least when it comes to pistol cartridges like the .40 S&W, and especially when you consider that some factory ammo has a natural variation in overall length that does not result in a dangerous condition.

What do you think? Is this something you’d like more details about? If so, let us know. If there is enough interest, we'll publish an in-depth LuckyGunner Labs post detailing more experiments related to chamber pressure.
 
Posts: 9646 | Location: Gilbert Arizona | Registered: March 21, 2013Reply With QuoteReport This Post
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