The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Soot on fire formed brass, but not on new brass- 7RM??Go | New | Find | Notify | Tools | Reply | |
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| One of Us |
I reloaded new FL sized brass working with Retumbo powder and the 175 SMK bullet I got great accuracy and a full gas seal with 70 grains of retumbo. I neck sized the once fired brass with the same load and bullet and when I shot these fire formed cartridges I was getting black soot on the entire neck and about 1/3 of the way down the shoulder. Curious as to why this happened with the formed and neck sized only brass and did not occur with the new-FL sized brass? All components, bullet, powder, charge, primer was the same? Any Ideas? | ||
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Moderator |
It sounds like your neck sizer squeezes the neck a little tighter than needed. I'd guess that if you FL sized a case and put a micrometer on the neck, then neck sized one and miked that one too, the neck sized case would be smaller. I've never used retumbo, but I believe it is a rather slow powder? So either the charge needs to be upped or a faster powder to be used to get rid of the soot. for every hour in front of the computer you should have 3 hours outside | |||
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one of us |
I use Retumbo in 7 RM with 175 Part. 68 gr gets me 2934. I have not had your problem so I would do as Mark advised and try re-adjusting my die. I use a Lee Collet.Neck size dies should not move the shoulder/body at all and it appears to be happening to you. You might also try partial FL sizing. | |||
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| one of us |
It sounds like you had a mix up in your loads. Maybe less Retumbo than you think. Sounds like much reduced pressure or poor ignition for some reason. | |||
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| One of Us |
I agree with the other gentlemen. Either you had a very reduced load and didn't know it or that neck was sized too far down. Whatever it was, your brass case did not seal to the chamber upon firing, thus the soot. | |||
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| one of us |
Less pressure in the reloads is the most likely cause. New brass case capacity vs. once fired necksized brass case capacity. You may be surprized as to how much difference there may be. The extra capicity in the "fire formed" neck sized case, all other things being the same, translates into less chamber pressure for the reload. Couple that with a slightly work hardened case neck. This can lead to the "sooty" cases you describe. muck | |||
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I measured a FL sized neck and a neck sized only neck- they were the same diameter. I was at the range yesterday and I worked up the loads and I had the same soot all the way up. I tried a couple of different powders as well, same thing. The loads are definately hot enough to get a seal. As far as neck tension goes when I seat a bullet and measure the neck sized brass with no bullet I have one and one half thou neck tension. (working up to slightly over 3000 fps w/ the 175 SMK) What I have done now is adjusted my neck die so that it leaves a small amount above the shoulder junction unsized. The kicker to all of this is the gun shoots shoots lights out and I get very consistent velocity ( single didget ES for most loads with Retumbo)Working up with Retumbo to see if this problem will go away I shot a .22" 3 shot group and a .26" 3 shot group! Could this eventually etch the chamber from the escaping gas? If I do not correct it? | |||
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| one of us |
All the explanations make logical sense but I had the same problem today after using a neck sizer yesterday. Last night I did verify that the FL sizes down .003 more than the neck sizer. With the neck sized ones I had .003 tension and soot on the shoulder. With the FL sized ones I had .006 tension and no soot on the shoulder. Thinking about what you guys have said my thoughts are that the pressure may be slightly higher on the tighter neck tension and the lower volume of the FL size. Looks like next week I will try a little hotter charge on the neck size only and see if the problem( soot on shoulder) goes away. Not really a problem because it shoots good. | |||
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| One of Us |
Slow powder can cause neck "sooting". The bullet exits the case before full pressure is reached. Not a problem. Good Luck! | |||
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| one of us |
I was using almost a max load of IMR 4895 which I think does not fall into the slow range. I will try again this weekend and see what happens. | |||
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One of Us |
I don't mean this to sound "flip", so please don't take it that way. Sounds pretty likely to me that you need to use a smaller diameter neck sizing die or bushing. The greater neck tension allows the powder to build-up pressure a bit more before releasing the bullet. There's a fair chance you wouldn't need a hotter load if the neck tension on the fire-formed and neck sized brass was a bit stronger (tighter). That's one of the several reasons that many folks prefer to buy "bushing-type" dies when they buy neck-sizers. My country gal's just a moonshiner's daughter, but I love her still. | |||
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I hear you on this. I use a SAAMI spec. Redding neck die. I wass giong to try a Lee Collet die and turn the Mandrel down to increase tension. BTW, I an seating my bullet .010 into the lands. What is happening does not make much sense in my case. I get .0015 neck tension with my set-up, I think I want around .002 as a minimum. Andy. | |||
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.[/QUOTE] I hear you on this. I use a SAAMI spec. Redding neck die. I wass giong to try a Lee Collet die and turn the Mandrel down to increase tension. BTW, I an seating my bullet .010 into the lands. What is happening does not make much sense in my case. I get .0015 neck tension with my set-up, I think I want around .002 as a minimum. Andy.[/QUOTE] That should work well to increase tension. Even easier might be to just chuck up the expander ball from your Redding die and polish one or two thou off of it with some Crocus Cloth. You can always buy another expander ball for cheap, should you want to go back to a bigger one My country gal's just a moonshiner's daughter, but I love her still. | |||
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| One of Us |
Andy - I know you say your current loading shoots like a house on fire, so am not going to recommend you permanently change it. Just as an experiment, though, you might want to try the ame fire-formed brass, same load, but with the bullet seated .005 or so OFF the lands. Probably won't be as accurate, but just might do away with the smoking of the case necks. Here's the hypothesis: The bullet jammed into the lands is not going to start to move as quickly as one which isn't jammed into lands. Will, for a moment or so, act as a barrel "plug". So, as pressure begins to build, where's it and the ejecta gonna go? Answer is "anywhere it can". That might potentially be down the outside of the case neck and the shoulder. If a bit is between the case and the chamber, it might temporarily delay a good expanded case-seal from occuring. I know, both of your brass "sets" are probably loaded that way with bulets into the lands. So you'd probably just be finding out that with less neck tension you can't seat into the lands without getting smoky necks. For same accuracy you'd likely still have to increase tension so you could seat out to where that accuracy occurs without amoking your cases. Anyway, it might be something interesting to know....... Heaven knows when it might be handy info to have, if ever. My country gal's just a moonshiner's daughter, but I love her still. | |||
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What you are saying makes good since to me but I was not using a bushing die. Just a neck sizer and a FL sizer. My measurements tell me I get .003 tension with the neck sizer and .006 on the FL ones. | |||
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Alberta Canuck, Funny you mention that about backing off the lands. When ever I develop a load I always start at a low powder charge .010-.015 into the lands and work up from there. Once I find the most accurate 3 shot group I See how it does for 5. From there I pull off of the lands for 3 shot groups until it starts to open up. I will find out if it makes a difference. | |||
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The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Soot on fire formed brass, but not on new brass- 7RM??
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