Overcharged? . . . Yikes!

Bullet Setback?

Zeke:
I don't know that I understand what bullet setback is or how it could cause this. Talk to me please!
Prof Young
 
Setback: The volume of the cartridge combustion chamber has an influence on pressure.
Smaller volume = higher pressure.
Seating depth locates the bullet base,which determines that volume.

Except for it can occur during the feeding cycle the bullet is pushed deeper into the case going from the magazine into the feed ramp and then into the chamber. Its more likely,even expected,there will be some setback during multiple loading/unloading sequences associated with carrying.

Monitor cartridge length of your carry ammo.

For various reasons,its possible to have inadequate neck tension holding the bullet. This.and/or rough feeding can result in the bullet getting "set back" significantly.
A significant (dangerous) pressure increase can result.
 
Prof Young- The reason i keep asking is that have had 2 instances where the mag was blown out grip of a pistol. In the first was trying to develop a 185 plus p velocity for 45 acp using Rem brass. Back then, the only commonly available factory load to me was Remington's version. This was the first learning experience of what bullet setback was, it's possible effects and once fired Rem brass's use with jacketed load.

The second time was with a full power .40 load in a BHP, which are known for exceptionally stiff recoil spring. Again with Rem brass and standard velocity jacketed loads.

In either case there was no physical damage to the pistol, but all loads now get a function test with loading a dummy round from full slide lock back using slide release and measuring col before and after. Am very careful of what i use Rem .40 and 45 acp brass for, and it ain't with full power/pressure jacketed loads.

Frankly, without any metallurgy background or knowledge of what psi a 1911 can take, would expect more damage from a double charge of fast powder like tite group.

None the less am grateful you weren't hurt.
 
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DonP said:
Why didn't the barrel blow?
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The 60K range seems high, but this is a very fast powder so that high pressure existed only within the thicker chamber portion of the barrel. If you look at blow-ups in Hatcher's Notebook, he had a Springfield barrel he turned down to 1/16" thick over the chamber that still held together just fine firing three regular 30-06 ball rounds. Would have been whippy as all get out. He then put a "blue pill" load in that was 75 kCUP (probably over 110,000 psi according to Brownell's correlation in that cartridge) and that finally blew it open. Steel is amazingly strong stuff.


Prof. Young,

Based on Quickload, here's what bullet setback shrinking the powder's initial burning space does in theory:

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I call that theoretical because it happens sometimes and not others. Fast powder is more susceptible to it. Very often, though, the pressure from the primer is great enough to move the bullet forward before the powder burn gets fully underway. In that instance, high pressure is avoided. It just isn't something you can rely on to happen consistently, so bullet setback is to be avoided. The thin-wall Remington cases are particularly prone to becoming too springy to resize properly and to then fail to hold on to a bullet well, making setback easier to have happen.
 
Final thoughts . . .

Zeke and all:

I now think I understand set back. The loads in question had about 1/2 a crimp (Meaning I set the crimp die half a twist after it touched the case) so I don't think they could have "setback" but it's clearly possible.

I dismantled the gun again and measured the barrel. I appears to be about two hundreds of an inch wider at the muzzle than it is at the end of the chamber. I'm guessing it's always been that way. Reassembled the gun and ran some light reloads through the gun and it all ran fine.

Oh, and I should note that the grips are now cracked, but not broken. I noticed that on the first dismantle.

I'm think this was an overcharge, but may have not been a full double charge. Given the turret press and the Lee auto drum powder measure it's possible to get a partial charge with a partial pull on the press lever. Meaning I charged the case and then got sloppy with another partial pull.

As I scoured my memory, I have a vague recollection of sitting down to pick up where I left off, weighting the powder throw, and coming up with 5.8 instead of 5.2. IF my memory is correct, this would mean that during of my previous loading session I'd loaded multiple bullets with 5.8. (Duh, that should have occurred to me a the time, so maybe my memory is faulty.) However I took all of those apart and weighed the powder, as noted above. Most I got was 5.4 and there were only two of those. Hmmmmmm . . .

In the final analysis, I got lucky that it wasn't worse. I've learned a lot and have reviewed and renewed my safety measures. So . . . carry on.

Life is good.
Prof Young
 
I use a lot of Tightgroup & while I never double loaded I have had a squib that slipped through & while it didn't cause any issues other than having to drive a bullet out of the barrel a second shot could have been just as bad.
This happened on my progressive press & I knew I had to do something to insure it would never occur again. I had a digital inspection camera in my garage & mounted it on the press to quickly get a visual into the case before placing a bullet. No issues since & I have caught a few before they became an issue.
vBjcZKMl.jpg


https://www.harborfreight.com/plumbing/plumbing-tools/inspection-cameras/high-resolution-digital-inspection-camera-with-recorder-61838.html
 
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Schlitz , I mark my auto drum like that as well to know when it's opened or closed . I also mark the rotor so when it rotates I can see it making it's full rotation .

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Note - to see it while actually loading , I need to place that arm thing of the auto drum in between my dies . It fits but barely , this in effect turns the powder measure 180* from what you normally would have it .

kzIOyA.jpg


If you really want to crank it up and you size first and prime off press you can double up the powder measures and seating dies . I do this for my 223/5.56 plinking loads . It speeds things up for me because I often size and prime my rifle cases ahead of loading and store in bags for later . I just need to charge and seat bullet then . It took a bit to get them both throwing the same-ish charge and the hoppers touch and sit a tad crocked but it works well for me . You still need to check your charges like any other loading .

OFQY4Y.jpg
 
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I’m curious, are you using the auto advance feature? As long as you’re making full strokes with the lever this should pretty much preclude an accidental double charge. I know some people disable this feature and sort of use this press as a single stage, which I just don’t understand. To me one of the most attractive features of the Lee turret is how safe it is to use because of the ability to minimize if not eliminate the possibility of an accidental double charge.
 
I had an unusual overcharge during a .223 session. I use a hand-made block with a paddle handle that holds 30 rounds, a RCBS powder measure, and 26.0 gr of CFE-223, which is roughly at least an 80% fill for a 55gr FMJ bullet.

The measure is extremely accurate with that powder; 90 of 100 rounds are exactly 26.0 with the remaining 10 being 26.1gr (I weighed every one before seating).

During one of the loading cycles, the powder poured all over the place as I dumped it into one of the cases. Did I fail to advance that case in sequence? I emptied the case and recharged it. The powder dumped all over again. I emptied the case and inspected it. Inside the case was a glob of corn cob media glued together by the polishing media.

That is the first time in 44 years that the media blocked any case for me, not counting primer pocket holes. Apparently, I didn't allow enough time for the polish to circulate through the corn cob media before I added the cases to be cleaned. There is always a first time for everything.
 
I do not recommend titegroup. IN fact, I think its one of the worst powders one can buy. Super dirty, and its too dense, too fast. N320 I would recommend or Sport Pistol. If you cant get those and want economical, bullseye is better than TG for sure. I am sorry this happened to you. I wish you peace and safety in future.
 
Thought I was done with this thread, but . . . .

Well I thought I was done with this thread but I have to add one more factor. I discovered that my scale was not calibrated correctly. It was weighting lite, but at the 5 grain level I don't know how lite.

Anyway this failure may have been the perfect storm, I got careless, the scale was lite, the powder is one that may go unnoticed if there is an over charge etc.

Added to the new safety practice is to calibrate the scale at the start of each reloading session.

Life is good.
Prof Young
 
Good plan. Some folks run a check weight every ten rounds, but that's only applicable to electronic scales. On a balance beam it would force you to change the beam weight positions which increases your chance of getting the setting wrong when you return them. For a balance beam you do better to clip a piece of wire to match your intended load and then drop it on the scale every once in awhile to confirm it reads the weight of the charge you want.
 
Good plan. Some folks run a check weight every ten rounds,
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Yep , check weights are your friend . I even made a .5gr and a .7gr weights for the set . This allows me to do .2 - .5 and .7gr checks as well . My scale also has .1 dash marks on it so if my charge weight is 5.8 I can use the .7gr weight along with the 5gr weight and zero the scale at .1 below the intended 5.8gr . This keeps me from needing to move the beam weight position .

I always start out zeroing my scale to the intended charge , never to lets say 100gr and call it gtg for a 5gr charge . Always to what ever weight I plan to use . I then can drop those in the pan every so often through out the loading process to confirm I'm still zeroed .

Lets say I'm loading on the Lee CTP . I first zero my scale to the intended charge weight . I then set up my auto drop to throw that intended weight . Once that's all set up I'll start loading and actually weigh one throw every 10 to 20 throws . I generally don't go more then 15 but sometimes when I'm dialed in and everything is working good I'll go as many as 20 throws before I weigh a charge . During that same session every 50 or so rounds I'll actually check weight the scale it self to be sure it's still zeroed to the intended charge . My Redding beam scale does seem to drift sometimes and that is usually to a lighter charge . Only by .1gr sometimes .2gr , I just rezero to the check weight and keep on trucking .
 
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