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Shell collapsing (Read 12363 times)

cheatin_charlie Senior Forum Member Offline Posts: 429 Location: ohio Joined: Jan 10^th, 2009	Shell collapsing Nov 15^th, 2016 at 6:44pm	Print Post
	I was test firing a rifle for a friend and was breech seating lead bullets. The throat was messed up from previous owner and I wanted to seat the bullets ahead of the bad throat. Rifle was 32/40 and seated bullets way ahead of the shell. Rifle shot really well but cases were collapsing from the pressure of firing. I annealed and expanded some cases to try to get them to seal but after a few shots same results. Was using 14.5 to 15g of 4227 and 185g bullets. What do you think caused this? Anybody have prior experience? I have some ideas to try but thought I'd ask here first. The joy of trying to overcome somebody else mess. Thanks


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rgchristensen Frequent Elocutionist Online Posts: 1190 Joined: Jan 2^nd, 2014	Re: Shell collapsing Reply #1 - Nov 15^th, 2016 at 6:53pm	Print Post
	The shell collapse is caused by a reflected pressure wave from the base of the bullet. Keeping any wads off the powder by 1/8" will help, as will a slight flare of the case mouth, so it drags going in. What happens is that a pressure wave is caused by expanding gases reflecting from the base of the bullet. The highest pressure has already exited the case allowing it to spring back a bit, so when the pressure wave reflects back, part of the high pressure gas flows around the OUTSIDE of the neck of the case. After the wave passes back thru the neck, the pressure drops again, and the high pressure gas between the case neck and chamber collapses the case. This is a common occurrence when breech-seating, especially with a card wad seated on the powder. CHRIS RGChristensen


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cheatin_charlie Senior Forum Member Offline Posts: 429 Location: ohio Joined: Jan 10^th, 2009	Re: Shell collapsing Reply #2 - Nov 15^th, 2016 at 7:07pm	Print Post
	rgchristensen wrote on Nov 15^th, 2016 at 6:53pm: The shell collapse is caused by a reflected pressure wave from the base of the bullet. Keeping any wads off the powder by 1/8" will help, as will a slight flare of the case mouth, so it drags going in. What happens is that a pressure wave is caused by expanding gases reflecting from the base of the bullet. The highest pressure has already exited the case allowing it to spring back a bit, so when the pressure wave reflects back, part of the high pressure gas flows around the OUTSIDE of the neck of the case. After the wave passes back thru the neck, the pressure drops again, and the high pressure gas between the case neck and chamber collapses the case. This is a common occurrence when breech-seating, especially with a card wad seated on the powder. CHRIS RGChristensen This is a good explanation of what is happening. I was not using any wads at all. So there must be a maximum distance a bullet can be seated in front of the case to avoid this. Never had a problem with up to .062 in front of case. I will go back to the range and try different distances and hope I can find a sweet spot where rifle shoots well and the case doesn't collapse.


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bnice Frequent Elocutionist Offline Posts: 1964 Location: Iowa Joined: Nov 30^th, 2006	Re: Shell collapsing Reply #3 - Nov 15^th, 2016 at 7:55pm	Print Post
	I have seated a lot further then that without issue and seated a wad on the powder. But I flair my case to help seal. without that I have collapsed cases as the gas blows back by the case and easily distorts the case. Do you have a lot of powder residue as well on outside of the case?


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cheatin_charlie Senior Forum Member Offline Posts: 429 Location: ohio Joined: Jan 10^th, 2009	Re: Shell collapsing Reply #4 - Nov 15^th, 2016 at 8:22pm	Print Post
	bnice wrote on Nov 15^th, 2016 at 7:55pm: I have seated a lot further then that without issue and seated a wad on the powder. But I flair my case to help seal. without that I have collapsed cases as the gas blows back by the case and easily distorts the case. Do you have a lot of powder residue as well on outside of the case? Yes I have some. I will flair my case next time. What is the farthest you have seated a bullet ahead of the case without problems?


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Schuetzenmiester Frequent Elocutionist Offline Posts: 6707 Location: Cool Wet Side of WA Joined: Apr 27^th, 2008	Re: Shell collapsing Reply #5 - Nov 15^th, 2016 at 9:00pm	Print Post
	Try a floral foam wad at the case mouth. Solved collapsing in my 25 Hornet.

	"some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence
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JS47 Frequent Elocutionist Offline Posts: 1265 Location: Arizona Joined: Oct 12^th, 2012	Re: Shell collapsing Reply #6 - Nov 15^th, 2016 at 10:53pm	Print Post
	I was having the same problem with my 38-55 when breech seating. Someone on the forum suggested flaring the case mouth to a tight fit in the chamber and it solved the problem. JS


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bnice Frequent Elocutionist Offline Posts: 1964 Location: Iowa Joined: Nov 30^th, 2006	Re: Shell collapsing Reply #7 - Nov 16^th, 2016 at 8:28am	Print Post
	I have a 32 ms that I seat +.2 out. I know a friend who is further due to a long throat. 38-55 shooters using short brass have same situation. Flare the mouth enough that you feel it drag with some resistance as you push it in.
	« Last Edit: Nov 16^th, 2016 at 8:35am by bnice »

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40_Rod Frequent Elocutionist Offline Extremism in the persuit of accuracy is not a vice Posts: 4285 Location: Knoxville, TN Joined: Apr 20^th, 2004	Re: Shell collapsing Reply #8 - Nov 16^th, 2016 at 8:43am	Print Post
	There are two ways to fix the problem. The first is to flair the case mouth so that you can feel it scrape about the last ¼” or so as you load the cartridge. The second way is to drop your charge and put a wad at the case mouth, now tip the case to orient the powder to the mouth end of the case. You may have to up the charge a little to get back to the velocities you had before but this does work. 40 Rod


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cheatin_charlie Senior Forum Member Offline Posts: 429 Location: ohio Joined: Jan 10^th, 2009	Re: Shell collapsing Reply #9 - Nov 16^th, 2016 at 9:52am	Print Post
	How thick is the floral foam wad to use at the case mouth?


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frnkeore Frequent Elocutionist Offline Posts: 7665 Location: Central Point, OR 97502 Joined: Jun 16^th, 2010	Re: Shell collapsing Reply #10 - Nov 16^th, 2016 at 10:57am	Print Post
	You didn't say how far forward of the case that your BSing your bullet. One thing to remember about BSing, is that it INCREASES the the case volume. Most BSed bullets are about 1/16 ahead of the case and that increases the case size over fixed ammo by as much as 1/2" or so (i.e. a 2 5/8 long case). Increased case capacity lowers pressure and with the burn rate powders that we use, when we reach a certain pressure range, the neck will relax enough for the powder gases to get behind it and collapse the neck. That said, what I would do, if you have a strong action, is increase the powder charge by at least .5 gr, to see if that corrects the problem. I've shot 16.1 gr of 4227, with competitive accuracy in my 32/40's and have gotten 1/2" 5 shot groups @ 100 with 16.5 gr. Frank

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John Boy Ex Member	Re: Shell collapsing Reply #11 - Nov 16^th, 2016 at 12:15pm	Print Post
	4227 being a fast bring magnum pistol powder - Suggestions: * As stated, flare the case mouth * Put a pinch of cotton at the mouth of the case only to prevent powder spilling into the chamber when seating the case * Then ... Muzzle Up ... to settle the powder against the flash hole. More consistent velocity and pressure curve


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Schuetzenmiester Frequent Elocutionist Offline Posts: 6707 Location: Cool Wet Side of WA Joined: Apr 27^th, 2008	Re: Shell collapsing Reply #12 - Nov 16^th, 2016 at 12:33pm	Print Post
	Interesting phenomenon. My 25 still collapsed nearly every case with the mouth expanded and pressures getting into sticky extraction range. It did it with both #9 and 4227.

	"some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence
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calledflyer Frequent Elocutionist Offline Posts: 3988 Joined: Mar 9^th, 2015	Re: Shell collapsing Reply #13 - Nov 16^th, 2016 at 12:45pm	Print Post
	So, how come this almost never is heard from with fixed loads that have light (read:short) bullets that clear a case neck as they enter a lead? Seems that at that point the conditions would be/might be identical to the ones I get when breech seating. I have never folded up a case either way, but if I go real low, or to a poor powder, as I have done now and then, I get a little smoke on the necks. Always keep the case neck dragging the chamber, fixed or loose ammo. And, for what it's worth your charges don't seem too high to me either, if it's a good stout rifle.


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cheatin_charlie Senior Forum Member Offline Posts: 429 Location: ohio Joined: Jan 10^th, 2009	Re: Shell collapsing Reply #14 - Nov 16^th, 2016 at 12:48pm	Print Post
	The rifle is a Hi Wall with Nieder firing pin conversion. Next time out will up powder to achieve about 1450 fps where the Barnett bullet shoots good in my rifle. With the bullet seated out I thought it would be the same as having a longer case but never anticipated the case collapsing. I achieved 2 -5 shot groups at 100 yd. under 5/8" so I know the barrel is ok just need to get case in good shape. I managed 13 shots before the case let go. The weather looks good here in Ohio for the next couple of days so hope to get back out. Do you think 1/4" floral foam wad at case mouth is in the ball park or should I go thinner?


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