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Posted: 1 November 2008 07:06 PM |
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Someone gave me some 30.06 brass. I used a Dillon trimmer to full length size and trim. I trimmed to 2.490 and made up 28 rounds with 4831sc. After shooting, 11 of the brass were 2.485 long, and the rest were between 2.478 and 2.481 long?
How come?
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72coupe
Handloading Master
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Posted: 2 November 2008 02:16 AM |
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| The only explanation I can think of is If you trimmed after sizing and measured after firing they would be shorter.
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Parsec
HB Pro Staff
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Posted: 2 November 2008 03:17 AM |
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With the Dillon system the trimmer is actually a full length sizing die with an electric cutting head on top so you do both more or less at the same time. I also made these rounds long enough to touch just the lands.
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springer1911
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Posted: 2 November 2008 01:56 PM |
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I load a lot of 45 ACP and have noticed the cases shrinking also. I re-size the case, then measure it. I never trim a straight walled pistol case so they aren't shrinking due to trimming after re-sizing. I don't know what causes the shrinking, I just know that it isn't uncommon.
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ghrit
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Posted: 2 November 2008 08:47 PM |
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Bearing in mind that I'm not a reloader, is it possible you've full length resized, trimmed, then fired them in a chamber that is on the large side?  If so, the brass might have expanded to fill the chamber and in the process pulled the neck material back. You didn't lose metal, just moved it around.
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HB Pro Staff
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Posted: 3 November 2008 01:51 PM |
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I dunno ghrit..It's a Browning Abolt so I wouldn't have guessed it was particularly oversized.
It does make it difficult to try and take advantage of using once-fired brass to improve accuracy, and I can't help but wonder what would have happened if I trimmed them back to 2.485 like all my reloading manuals advise.
I did note on an Alaska shooting forum that one member mentioned in passing that a reduction of 10 thousands isn't uncommon in his experience.
The whole thing seems odd to me. Maybe I'll call Hornady or Sierra and see what the experts have to say.
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ghrit
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Posted: 4 November 2008 02:49 AM |
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Dunno. I suppose a chamber cast would tell that tale. I just cannot imagine brass shrinkage without some odd heat treat or alloy involvement. The amount of metal just about has to be constant. I'll defer to anyone with another idea (including Hornady and Sierra). My experience just won't cover it.
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Remote locations are cheap insurance.
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Bigdog57
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| Joined: | 30 October 2008 |
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Posted: 4 November 2008 01:56 PM |
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I'm not a metallurgist, and don't play one on TV, but here's a theory....
You size the case, stretching the brass and inducing stress in the metal.
You then load and fire the cartridge, and the heat & pressure relieve the stress, allowing the brass to rebound back to it's ideal rest state, which shows as 'shrinkage'.
Just a wild idea......
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Parsec
HB Pro Staff
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Posted: 4 November 2008 09:00 PM |
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Could be I guess.
I asked Hornady and they said some brass gets thicker and shorter, and some brass gets thinner and longer.
(Maybe we could lobby them to label the brass so we know which one we're buying!!)
I do have a couple of cases from my 6.5mm that have really thick necks so I'm sure he's right; but the odd thing is they haven't actually shrunk more than the others.
With a 30.06 the necks are pretty long to begin with so this may not be a real critical problem but I'm kinda in the market for a target rifle (never had one) and would like to sort this out before I start spending money on expensive brass and newer equipment.
Anyways...I'm going to reload and shoot them again I guess. I'm sure someone will let me know if I'm wrong about this but I don't believe this kind of thing will have any impact on the headspacing or be dangerous at all. If I continue to make the cartridges the same length (ogive to base) I'll just have a bit more case volume for the burn and a bit less neck tension for the bullet I suppose.
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swampshooter
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Posted: 6 November 2008 03:20 PM |
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| Your problem started by using scrounged up brass in the first place. Not a good way to try and save money. Just asking for problems.
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Posted: 6 November 2008 03:43 PM |
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| I never said anything about trying to save money.
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DesertMarine
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Posted: 13 November 2008 06:42 PM |
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In my experience, I have never seen brass shrink. I am not familiar with the Dillon trimmer, so I cannot comment on that. Sounds like the brass is being trimmed more than what you think, unless you check length on each case after trimming.
I use a L E Wilson case trimmer, you can see them at sinclairintl.com. I check the first 10 or so to make sure I am trimming consistently.
If I use once-fired brass, it is from new ammo, Federal, Remington, Winchester and Hornady. Normally, I buy new brass for that particular rifle, mainly Federal Match, Norma or IMC brass. I have had good results with them, normally they will stretch rather than shrink.
Good luck, hope you find a solution.
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Oddbod
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Posted: 15 November 2008 02:46 AM |
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Chambers on semi automatics are generally cut larger than for bolt actions (to reduce the force needed to chamber the round) & this may well be the reason for the decrease in case length.
I'll bet the length increases slightly next time you reload & fire those cases.
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DesertMarine
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Posted: 15 November 2008 03:29 AM |
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I looked at the Dillon trimmer on the Dillon website. If I understand it correctly, you mount the trimmer on your press, whether it is a Dillon or other type. When you resize a case it is also trimmed, whether auto or manually. I am curious as to how the trimmer is adjusted and as to how and when cases are checked for length.
Another question, when a case is trimmed, if on a progressive press, how do you deburr the case? Single stage press, no problem, take the case out and deburr and check length. Might check and ensure that your trimmer is not moving and giving different lengths. I would say that .009" to .011" loss is excessive. Generally a case will stretch no more than .002".
I still think that probably the cases are being trimmed too much, the how is the question. The how is the question: trimmer not set proberly, trimmer going out of adjustment, etc. But not being there can't be sure.
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Posted: 16 November 2008 01:44 AM |
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I cleaned and FL sized with a regular RCBS die first. Then I measured and separated out the ones that were longer than the specs allow.
I only trim on a rockchucker and leave my 550b set up for pistol reloading.
The Dillon FL sizing die that fits into the press is modified. Its threaded on the top as well as the bottom, and hollow inside. The die is screwed into the press like any other die and a case is thrust up into it as it would be on any normal sizing die. You then remove and check the case to make sure the shoulder hasn't been pushed back. If it's good you leave the die where it is, if not adjust as needed.
If the case neck has been stretched by repeated firings it will stick out into the hollowed out middle section of the die. If you've been on their web site you must have seen the big "window" that's been cut out of the middle of the die? Thats where the neck sticks out. The electric motor is then screwed down onto the top of the die with the cutting blade fitting down inside where the guts of any other die would normally be found. You screw it down onto the die until the blade just touches the top of the case. You then lower the case and screw the motor down a tiny bit more and turn it on. As the blade is spinning you then raise the case back up and it gets trimmed. You measure it for length and if necessary lower the cutter a bit more and try again. Once you have the right size you lock it place just like a die with a lock ring and trim away. I usually camfer the edges a day or two later with a Lee hand tool and often don't reload them for as much as a week or ten days after that.
Perhaps you are right: Perhaps something changed and I didn't notice ...I dunno. I confess I've never really paid a lot of attention to brass other than looking for defects after firing. But if I'm going to buy a target rifle and take this hobby a bit more seriously I need to develop a good, foolproof system for preparing brass that won't lead to any more surprises! Although the Dillon system is efficient and easy to use I think it might be advantageous to be able to trim without having to FL resize in some circumstances.
I hope I've made some sense with all this.
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DesertMarine
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Posted: 16 November 2008 02:48 AM |
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Sounds like you are doing a good job of resizing, checking, trimming and checking again. The procedures sound ok but still think something is changing, somehow. I keep wanting to ask if the Dillon die resizes while trimming but you stated that you check them afterwards. Keep thinking that the Dillon die is pushing the shoulder back some, question is how do you check the shoulder? When I set my dies to a press, I will use a case that headspace is too long and use a go headspace gauge and adjust until headspace on case is the same as go gauge. Sometimes that takes different case holders, as some are taller than others, sometimes.
For precision loads, I would change my procedures. I would resize using the Rock Chucker. With new brass, full-length the case and fire forming. After fire-forming, then neck-size until you start feeling resistance on closing the bolt, then full-length resize. Except for what you paid for the Dillon, I would say get a trimmer that benchrest shooters use. Normally, that is a manual trimmer and it is basically a small lathe. Like I said earlier, I use a LE Wilson trimmer and that gives me great results. For precision equipment I go to sinclairintl.com. I also check precision loads for runout both on the case and loaded round, sort and fire like rounds. Have you talked to Dillon and discussed what is going on? Hope you can work it out with what you use.
Precision loading can be fun but also frustrating.
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DesertMarine
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Posted: 16 November 2008 03:09 AM |
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| Forgot to add, if you go sinclairintl.com, order their catalog. Sometimes it is easier to find what you are looking for. Once you know how they are set up the site is easier. I have gotten great service from them and prices on items that you can find elsewhere are pretty competitive.
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DesertMarine
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Posted: 23 November 2008 07:56 PM |
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Kept thinking about brass shrinking, I did a check on different brand brass and this what I came up with.
.223, IMI brass, new, 25 cases checked, length 1.751"-1.760", trim to length (ttl) for .223 is 1.750".
.223, Federal Match cases, new, 25 cases checked, length 1.743-1.560", did not find any fired cases.
LC brass, once-fired (OF), 25 cases checked, 1.746-1.770" fired in Oly AR with either an upper w/24" match barrel or upper w/16" heavy barrel.
.308, Lapua brass, new, 25 cases checked, 2.006"-2.009", ttl for .308 is 2.005.
Lapua brass, OF, 20 cases checked, 2.004"-2.011, fired in either Rem 40x or Win Mod 70 Featherweight.
.300 WSM, Norma cases, new, 20 cases checked, 2.090"-2.095, TTL 2.090" fired in Rem 700 converted from 300 Win Mag to 300 WSM.
Norma cases, once-fired, 20 cases checked, 2.090-2.099.
There are some cases that are shorter than TTL but do not have the length before firing, cannot verify shrinkage. What I will do is load 20 rounds each with Federal Match and IMI new brass, record their lengths and compare after firing. Cases will be marked with new length and fired length for comparison. I'll do the same with the 300 WSM as I do not have any .308 anymore.
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runfiverun
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Posted: 24 November 2008 02:39 AM |
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i have the dillon and if you don't set it up so that your press comes to a dead halt, during the trimming process. you can give it an extra oomph and trim an extra .002-3 off the cases.
it also sizes to the minimum size. minimum.
when these are fired they can be driven forward in the chamber hitting the shoulder causng the headspace to shorten some.
kinda ironic as most semi-auto's cause cases to stretch as they are still gripping the case walls while being extracted.
i would shoot them again and measure again before i worried about it though.
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