Author Topic: splain to me about case trimming BEFORE firing (Read 1603 times)

bluebayou · « **on:** February 04, 2007, 04:02:04 PM »

I have seen a couple of threads in the last month (on different websites) about how you should NOT trim to length before firing the first time. The threads talk about how the cases will "grow" more.

Basically, I see no logical reason not to trim a case to length the first go around.

If my .223 case is 1.790 at first loading then it is .030 to long. If it "grows" .030 with firing/expanding/resizing then it is 1.820. I then trim it to 1.760 and fire it a second time. Big deal.

If my .223 case is 1.790 before first loading then I trim it to 1.760. If it grows .030 with firing/expanding/resizing then it is 1.790. I then trim it to 1.760 and fire it a second time. Big deal.

Either way........I just don't understand why you wouldn't want consistent brass from the first firing. Granted that I don't necksize so is that what this is all about?

quickdtoo · « **Reply #1 on:** February 04, 2007, 04:26:59 PM »

I trim all my new brass to a nominal length so they're all the same since new brass varies quite a bit length, I find the shortest of the batch, then trim it just enough to square up the case mouth and the rest to the same length. If they aren't the same length to start with, how can bullet pull be the same and hence accuracy? At least that's my opinion, anyway.

Tim

bigjeepman · « **Reply #2 on:** February 04, 2007, 04:34:49 PM »

I'm with "quick" on this one as I trim new brass when necessary. I have stated it before on forums and have been told it was the wrong thing to do. I still cannot understand why it would make the brass grow more .... unless some very knowledgeable person has done extensive testing on this and has proved brass will grow more. I would like to read articles written on this subject if anyone knows of any. I am always willing to learn more.

beemanbeme · « **Reply #3 on:** February 05, 2007, 08:07:56 AM »

Your examples are of brass that is grossly overlength which should be trimmed to a safe length before firing. That is something I haven't found to be the rule. However, brass that is within the parameters of length doesn't need to be trimmed until after the first firing because minute differences in the dimensions of the case will cause each case to extrude to a different length. Simple enough. Why don't you try it. Trim your unfired brass to a uniform length and then fire it and measure it again. You will find differences.
There is no rule that says you can't trim before the first firing or as often as you'd like but its pretty much a wasted effort.
I just took a box of remington brass for .222 and measured some of them. They varied from 1.2589 to 1.162. All shorter than the case max as shown in Lyman's 48th. Am I gonna trim them before I fire form them? Not a chance. But once I've fired them, I will trim them all to the length of the shortest one even if that's shorter than the reccommended trim-to length.

skb2706 · « **Reply #4 on:** February 05, 2007, 09:51:31 AM »

I'm with beeman on this one. I fireform alot of different chamberings and find it pointless not to fireform the brass first as it will often shrink in the process.

Awf Hand · « **Reply #5 on:** February 05, 2007, 02:27:49 PM »

Another supporting post for the Beeman. No sense in trimming before fireforming as they all change in OAL. Depending on which tool you use, you may want to do your flash-hole uniforming before the first shot. You should have no problem if you do a primer-pocket uni. as well.

bigjeepman · « **Reply #6 on:** February 05, 2007, 02:33:58 PM »

beemanbeme ... you are saying that the "fireforming process" itself is going to change the case length more than the normal firing of previously fireformed brass. Even though I find some differences in length of once, second, or third time fired brass, these differences in length are less that brass being fireformed? If that is the case (and I am certainly not doubting your word), it makes sense to me. I have found new brass though that I just didn't feel good about fireforming without some trimming. I am not talking about 20 out of a bag of 50 but maybe 6 to 8 of them. I am finding new brass these days to appear to be more out of round, different lengths, etc than ever before.

Jerry Lester · « **Reply #7 on:** February 05, 2007, 04:40:54 PM »

I trim all my new brass before firing, and then trim it again every time I load it.

gypsyman · « **Reply #8 on:** February 05, 2007, 07:17:39 PM »

Trimming before the first firing is definetly a good thing, as that gets it close. The reason brass lenght changes from one reload to the second is this. (bottleneck cases that is) When you pull the case out of the sizing die, the expander ball pulls up thru the neck, it stretch's the neck. And since the thickness of the brass vary's from case to case, the amount of tension on the expander ball will vary. A case with a thinner brass, will not lenthen as much as a case with a thicker neck. This is why benchrest shooters most of the time, neck turn their cases. As this also means that bullet tension will be more consistant, when the round is fired. A carbide expander ball will be much easier on the brass. We keep trying peace, it usually doesn't work!!Remember-(12/7/41)(9/11/01)-gypsyman

skb2706 · « **Reply #9 on:** February 06, 2007, 04:28:38 AM »

Quote from: bigjeepman on February 05, 2007, 02:33:58 PM

beemanbeme ... you are saying that the "fireforming process" itself is going to change the case length more than the normal firing of previously fireformed brass. Even though I find some differences in length of once, second, or third time fired brass, these differences in length are less that brass being fireformed? If that is the case (and I am certainly not doubting your word), it makes sense to me. I have found new brass though that I just didn't feel good about fireforming without some trimming. I am not talking about 20 out of a bag of 50 but maybe 6 to 8 of them. I am finding new brass these days to appear to be more out of round, different lengths, etc than ever before.

Depends on how radical the fire form process is. For example I have a wildcat cartridge that I want the finished fireformed case to be 1.910". The case will start out 1.928 and after firing will be very close to the desired length. Case actually shrinks .018" as it takes on its new form. The chamber was cut custom to allow for the "improvement". Once the cases are fireformed I then can trim them all to identical length.

beemanbeme · « **Reply #10 on:** February 06, 2007, 06:46:00 AM »

BigJeep, I'm not sure I understand. Fireforming is when the brass is fired for the first time (or the first time in your chamber). To me it is the first step in load/accuracy developement. Mating the brass to your chamber. As posted, your brass will often grow shorter on the first firing due to the brass "puffing" out from its "one size fits all" diminsions to the diminsions of your chamber.

Brass growing longer is a result more of brass flowing during ignition than being pulled up by a expander ball thru a lightly lubed neck.

As I posted, a fellow can trim his brass as often and whenever he wants. I was just pointing out that if he does it before the first firing, he's just killing time.

I use my fire forming sessions as an opportunity to clean out some of the odds and ends of bullets and partial cans of powder that we all accumulate. I practice my bench technique and don't expect a lot in the way of accuracy. But if I find a case that is considerably out of the group, I mark it and if it still misbehaves on its second firing, I discard it.

bluebayou · « **Reply #11 on:** February 06, 2007, 07:25:30 AM »

I assume that you are not full length resizing if you are this critical with your brass. What is your technique if you don't mind my asking? Do you bump the shoulder every 5 loading or anything like that?

Maybe I ought to switch to necksizing. As it stands I am only full length resizing right now. I think that- in my case -trimming before first firing still makes sense. Just to maintain consistency. I cull the too short cases as spoilers similar to your fireforming use of odds/ends bullets.

bigjeepman · « **Reply #12 on:** February 06, 2007, 09:01:45 AM »

beemanbeme ...
If I confused you, I apologize. I have always understood the reasoning behind "not" trimming before fireforming is because the brass changed in length to the point of diminishing returns. In other words, brass grew during the fireforming process and was going to have to be trimmed anyway afterward. I have always just trimmed excessively long new brass before fireforming so my brass would be more uniform from the beginning. I then trimmed all my brass after fireforming and then every 4th or 5th firing after full length sizing depending on growth. I always neck size after fireforming. I am not sure I am being very clear but I understand the reasoning behind your process.

bluebayou ...
I neck-size after fireforming and noticeably get more consistant, smaller groups in my bolt guns. I do not neck-size for my Handi's as I did not see any noticeable improvements. I am not as experienced a reloader as a lot of these guys and I am just trying to better understand everyone's reloading processes.

beemanbeme · « **Reply #13 on:** February 06, 2007, 04:26:55 PM »

BB, I try to practice the K.I.S.S. principle in my reloading. It has become a dirty word to say, but I neck size with my F/L die. I first set up the die to F/L resize. That is a firm cam-over feeling when the ram tops out. After I have F/L resized, charged and fireformed my brass, I'm ready to get serious about things.

I have a flat washer about the thickness of a dime (high tech I ain't) that will fit over the threaded portion of the die. I put that on the top of the press and thread the die thru the washer into the press. The die will resize all of the neck except for a small portion at the base of the neck. After several firings, that portion will form a small donut looking ring around the neck of the case. I don't think it does any harm and may help align the case in the chamber. --as a side bar: For years and years, all of the reloading books referred to neck sizing as backing your die off a turn or two. Then some smart cookie realized they could sell another die is they said you can't neck size without a full grown neck sizing die. And, as they say, the rest was history. I have taken a .223 case to the shop, blacked it all over with magic marker and run it thru the die set up as I outlined above. The only part of the case that was touched was the neck. What does that tell you?? -- Once the brass get difficult to chamber, or if I am loading ammo that I plan on taking hunting, I remove the washer, full length resize it and start over again. That's usually when I will trim my brass to length again.
Keeping with the K.I.S.S. principle, I don't weigh brass. Actually, where the weight is is what's important or not. I just load it and shoot it. An unexplained flyer gets marked and then culled if it happens again. I set my bullet jump by dead reckoning. I seat a bullet long and coat it with magic marker. It, of course, won't chamber (maybe -I've a 7x57 that has a leade about a block long) . I reblack the bullet and set the seater down about a half turn and try again. I do this until I no longer get marks from the lands. I have measured the COL with each adjustment. When I get to the no mark measurement, I subtract that from the previous measurement and that give me a vague idea of what my bullet jump is. This is, of course, a dummy round. With a Magic marker, I write on the side of the case, what bullet, calibre, and length. I keep this in case I have to change the seater die around for another bullet. Once I have a really good load worked up, I will put a witness mark on the top of the seater die and try increasing the jump by a quarter or half turn. Some times it helps, sometimes its just a way to burn more powder. That is one of the things I do last. IMO, adjusting the bullet jump may help a good load become slightly better but I have never seen the mystical changes some folks claim. Your mileage may vary.
Sorry I ran long. See what happens when you ask me for the time. You get a history of watch making.

bluebayou · « **Reply #14 on:** February 06, 2007, 07:04:46 PM »

I appreciate your time in answering. I don't always agree with you, but I think that you are very knowledgeable.

All of you guys seem interested in more than if it goes "boom". I like knowing WHY people do what they do. Not just because "that is how you do it".

Jerry Lester · « **Reply #15 on:** February 06, 2007, 08:08:58 PM »

beemanbeme,

You made a lot of good points here on sizing. I totaly agree with almost every bit of it. One thing I have to disagree with though is that you can "always" neck, or partialy size with a full length die.

Like you, that's the way I've always done it for years. Just simply back off the shell holder a little, and all is well. Out of literally dozens of guns over the years, none ever gave me a problem with that method. I bought my Ruger 223 about 10 years ago though, and after partialy sizing 100 cases, and loading them back, I then realized that not a single one would chamber in the gun again!

I know!

I learned very hard that we need to check the cases to be sure they chamber before loading them. Funny thing is, I'd almost always checked them before that happened, but after hundreds of times, with not a single hitch, I didn't "waste" my time that session.

It turns out that this rifles chamber is considerably larger than my full length die. When I tried partial sizing with it, it slightly buldged the shoulders out, and the daggone cases would positively not chamber untill I set the die all the way down tight. I bought a neck die, and with it, they chamber just fine.

Just thought I'd throw that in on this thread in case somebody else runs into the same problem.

beemanbeme · « **Reply #16 on:** February 07, 2007, 06:42:27 AM »

Jerry, U R rite. I had that happen with a .243. My solution was to just F/L resize for it. I think the AI cases and such are more apt to need a neck sizing die. Were you brushing the insides of the neck and lightly lubing it before resizing?
BB, I think every one that reloads should try everything at least once. But they should try different stuff one at a time only after they are competent to produce basically good ammo --a baseline so to speak-- and then decide if it helps them or if its some anal, chicken-soup exercise in wasting time.

Jerry Lester · « **Reply #17 on:** February 07, 2007, 07:14:32 AM »

Quote from: beemanbeme on February 07, 2007, 06:42:27 AM

Jerry, U R rite. I had that happen with a .243. My solution was to just F/L resize for it. I think the AI cases and such are more apt to need a neck sizing die. Were you brushing the insides of the neck and lightly lubing it before resizing?

Yep, thats pretty much standard procedure for me with bottle neck calibers. This is the only one that ever gave me any troubles.

Don Fischer · « **Reply #18 on:** February 07, 2007, 07:49:54 AM »

I'm with Beeman for the most part. First difference is that I set a dime on the shell holder and tighten the die down to it. Next I measure case length AFTER re-sizing. I think Beeman also pointed out the flow when the neck is pulled back over the expander plug. I also lude inside the necks. I found that streach was greatly reduced when I inside lubed with a bit of STP on a q-tip but you really should clean that stuff out of there befor priming.

By the way, I just measured a dime in good condition, 1995, and it's .054"!

bluebayou · « **Reply #19 on:** February 07, 2007, 10:39:28 AM »

I learned the hard way about lubing inside the case necks. My first batch of 7-08 brass was trimmed (I don't know how much but it was curls of brass, not just shavings) EVERY time that I reloaded. That and my shoulder was sore after each sizing session. Little did I know that I was doing it wrong. Pays to have a mentor in the flesh to give you criticism.

Ranger J · « **Reply #20 on:** February 07, 2007, 11:17:33 AM »

I trim and resize all new brass just in case Murphy has managed to get a job at the brass factory.

RJ

beemanbeme · « **Reply #21 on:** February 07, 2007, 01:10:01 PM »

Don, I used to use a dime but I got tired of having to go up to the house and ask my wife if I could have a dime, everytime I wanted to neck size. As often as not, I'd forget and leave it in the shop and have to walk back down to get it and return it to her when I was done reloading ..............................

Actually, I did use a dime but I theorized that a dime or even one on each side of the die could possibly push it out of alignment with the ram and so I went with a fender washer that goes all the way around. Kewl huh.

Actually, I said the greater cause of case growth is caused by metal flow during firing, not by drawing the neck of a properly prepped case over the expander ball.

Yes, AFTER I have fire formed my brass, it is run thru the resizer, tumbled, and THEN trimmed to length.

After I resize my brass, its dumped in the tumbler to clean the lube off. From the action of the media, if its cleaning the outside of lube, it has to be cleaning the inside. That said, knock on wood, I've not experienced any misfires doing it this way.