HELP - Case length deviations

[thefitter]

Trying to figure out where my case length deviations are coming from.

.308

New Lapua brass

Fire formed twice

Bump shoulder .002

Re size neck .006 in 3 steps

Trim in Giraud Trimmer

Now 10 cases processed EXACTLY the same show these OAL:

2.0080
2.0080
2.0080
2.0080
2.0085
2.0085
2.0105
2.0115
2.0120
2.0120

I know the Giraud Trimmer indexes of the shoulder so I measured all from base to shoulder and they are all the same.

I am using a Forster Bushing Bump die.

I am totally lost. Where are these deviations coming from?

Thanks

 

[Innovative]

If your measurements are correct, I recommend reviewing your technique for operating the case trimmer.

 

[expiper]

Check you maeasurments......I dont know how you culd "trim" them THAT long.!!!!.....Roger

 

[watercam]

Make sure you are holding them into the trimmer long enough! If they are listed in order perhaps you are unintentionally pulling them out too soon. I have been guilty of just that...

 

[thefitter]

The Giraud is pretty simple to use, insert... half turn...done. It's spring loaded and I'm pushing all the way in each time. I will check the shell holder for debris. They are not listed in order of trimming but in numerical order.

 

[artbosco]

Try using a F/L bushing die, and indexing off the case head, and then see what you get.

 

[infantrytrophy]

One likely cause is variations in the case head to shoulder length, despite the "careful" sizing.

Even with new brass, there will be variations in this "case headspace" length. My experience has been that this is especially prominent in cases with a narrow-angled shoulder (.308 and .223). Other contributing factors are variations in the brass (alloy composition, annealing variances, thickness) and sizing issues. Note that you can vary the amount of shoulder setback quite a bit by using different amounts of case lube for each case. Test this yourself - lube up a few cases with only a small amount of lube, the lube a few with a larger amount of lube, then size them. You will see significant differences in the case head to shoulder length.

You indicated that you have fired the brass (at least) twice. That might explain everything. Variations in the brass (mentioned above) will start to show up, and each piece of brass might have differing amounts of springback after sizing. That will result in differing case head to shoulder length, thereby different OAL's since the Giraud indexes on the shoulder.

If you think that you need an extreme degree of precision in case length, you might try annealing the cases after two firings. Then try sizing samples of annealed and non-annealed cases to see if annealing reduces the variation in OAL.

I noticed that you measured the OAL to the nearest ten thousandth, or at least to the nearest .0005. I don't think that you can measure the case head to shoulder length that precisely, but you should be able to measure to the nearest .001 with a Hornady case headspace gauge. When you measure the case head to shoulder length, is there a variation among the cases? If yes, does that variation correlate with with variation in the OAL of the cases? If it is, then the OAL variation is in fact due to variation in the case head to shoulder length after sizing.

If no, then the variation is due to the trimming step with the Giraud trimmer. Are you using the same pressure to insert each case as it bottoms out? Are you holding the cases exactly perpendicular? I have noticed that there is some "play" in the Giraud's spring-loaded shell holder - it is possible to insert the cases at an angle rather than exactly perpendicular.


Taking a different tack, why do you need the case OAL measurements to be that precise? As long as your longest case length is less that the corresponding portion of your chamber, it probably doesn't matter that some of your cases are up to .004 shorter than others. Reading between the lines, your use of .308 cases and your interest in extreme precision might mean that you are a Palma or F/TR shooter and need consistent neck tension. Do you think that variations in the length of the case necks might result in differing neck tension for each case? My guess would be that other factors would overwhelm this effect - factors like differing neck wall thickness (unless you turn the necks) or differing "springback" after sizing.

Randy

 

[jonbearman]

I have 2 graceys and if you do it right,I get .002 variation.Big deal.No 2 cases size exactly the same.There are so many variables in case thickness to brass composition to hardness. Trim em and shoot em. Right roger? You are being way to picky. I would worry more about annealing and having the money for more bullets and powder.LOL Dont worry,it wont affect your shooting,I dont think any of us shoot so good that we would notice.Keep in mind about spring back of the case which does alter the datum.

 

[necchi]

Bearman's right .030 ain't a whole lot, but darn it, ya pay for good equipment it should at least work!!
Call the folks that make it and ask what's going on, could be the tool, could be the way it's being used.

FWIW, the LEE sytem I use with their little cutter head and caliber specific rods give me exactly the same size trim on every case, simple, no time spent setting up, just stick it in there and spin.
The whole Lee set up cost's under $30 for several calibers,, ???

 

[markm87]

Bearman's right .030 ain't a whole lot, but darn it, ya pay for good equipment it should at least work!!

Giraud is good equipment for bulk processing. In my opinion... If exact case lengths are what the guy is after, he should use a Wilson Case trimmer which indexes off the head.

 

[KevinThomas]

thefitter,

Why not just run them back to 2.000" even and forget about it? I've seen a lot of guys really getting obsessive about case length and minor trim length variations lately, and it's misplaced concern. Case trimming is primarily a safety issue. Making sure that the cases aren't extending into the chamber far enough that they're "crimping" and unable to release the bullet upon firing. Beyond that, a few thousandths variation won't make a bit of difference in accuracy. Neck tension won't be altered to any measurable degree (that I've ever been able to discern, anyway), and so long as you're not crimping, it won't make a bit of difference in terms of accuracy, velocity or pressure. Agreed, if you're crimping, case length variations can effect the degree of crimp that's applied. But for 99% of our reloading, this is wasted time. trim it back to 2.000" even (give or take a few thou) and don't worry about it!

There are things to be obsessive about, and others you can relax on a bit. This is one of the latter.

Incidentally, I use a Giraud myself for the vast majority of my own match ammo, and wouldn't even want to think about using anything else.

 

[thefitter]

One likely cause is variations in the case head to shoulder length, despite the "careful" sizing.

Even with new brass, there will be variations in this "case headspace" length. My experience has been that this is especially prominent in cases with a narrow-angled shoulder (.308 and .223). Other contributing factors are variations in the brass (alloy composition, annealing variances, thickness) and sizing issues. Note that you can vary the amount of shoulder setback quite a bit by using different amounts of case lube for each case. Test this yourself - lube up a few cases with only a small amount of lube, the lube a few with a larger amount of lube, then size them. You will see significant differences in the case head to shoulder length.

You indicated that you have fired the brass (at least) twice. That might explain everything. Variations in the brass (mentioned above) will start to show up, and each piece of brass might have differing amounts of springback after sizing. That will result in differing case head to shoulder length, thereby different OAL's since the Giraud indexes on the shoulder.

If you think that you need an extreme degree of precision in case length, you might try annealing the cases after two firings. Then try sizing samples of annealed and non-annealed cases to see if annealing reduces the variation in OAL.

I noticed that you measured the OAL to the nearest ten thousandth, or at least to the nearest .0005. I don't think that you can measure the case head to shoulder length that precisely, but you should be able to measure to the nearest .001 with a Hornady case headspace gauge. When you measure the case head to shoulder length, is there a variation among the cases? If yes, does that variation correlate with with variation in the OAL of the cases? If it is, then the OAL variation is in fact due to variation in the case head to shoulder length after sizing.

I measured case to shoulder several times and I'm pretty consistent in my technique. No variation in base to shoulder.

If no, then the variation is due to the trimming step with the Giraud trimmer. Are you using the same pressure to insert each case as it bottoms out? Are you holding the cases exactly perpendicular? I have noticed that there is some "play" in the Giraud's spring-loaded shell holder - it is possible to insert the cases at an angle rather than exactly perpendicular.

I feel that my technique with the Giraud is also pretty consistent.

Taking a different tack, why do you need the case OAL measurements to be that precise? As long as your longest case length is less that the corresponding portion of your chamber, it probably doesn't matter that some of your cases are up to .004 shorter than others. Reading between the lines, your use of .308 cases and your interest in extreme precision might mean that you are a Palma or F/TR shooter and need consistent neck tension. Do you think that variations in the length of the case necks might result in differing neck tension for each case? My guess would be that other factors would overwhelm this effect - factors like differing neck wall thickness (unless you turn the necks) or differing "springback" after sizing.

I want everything to be as consistent as possible. Yes I turn necks and yes I feel that neck length will effect neck tension.

Thanks for your input I appreciate it.


Randy

 

[Innovative]

thefitter .......

Measure your cases from the shoulder to the case mouth. Then trim those cases back to 2.005" and measure them all again. "Measuring" will show where your problem is. Check out the Digital Headspace Gauge. It removes a lot of the guesswork from reloading.

 

[in2deep]

If by chance you were doing ladder tests or playing around with powder charges and these cases had differing amounts of powder charge that can cause a major difference in how they get smashed down back to size in the die as the stouter loads move the brass alot more especially after only a couple firings while the brass is undergoing it's initial hardening.

Conversely if some have lighter loads they may not have expanded fully yet and are sized less in the die than the blown out ones.
After a couple more firings the brass will stop changing and become more stable (less springback) and your numbers should stabilize too or if your an annealer that should eventually help too but if none of that works I would look at your dies and maybe bumping shoulders separately from the body isn't the best scenario for you. Try the body die after the neck die (or vice versa) to see if that helps as the order makes a difference.

I use F/L dies that do the neck at the same time and cases usually don't vary much over 1 thou. once it settles down after the first few firings and I'm a duffer. Bullet seating depth is more critical anyways and will wash out with the seater automatically so don't fret.

 

[thefitter]

If by chance you were doing ladder tests or playing around with powder charges and these cases had differing amounts of powder charge that can cause a major difference in how they get smashed down back to size in the die as the stouter loads move the brass alot more especially after only a couple firings while the brass is undergoing it's initial hardening.

Conversely if some have lighter loads they may not have expanded fully yet and are sized less in the die than the blown out ones.
After a couple more firings the brass will stop changing and become more stable (less springback) and your numbers should stabilize too or if your an annealer that should eventually help too but if none of that works I would look at your dies and maybe bumping shoulders separately from the body isn't the best scenario for you. Try the body die after the neck die (or vice versa) to see if that helps as the order makes a difference.

I use F/L dies that do the neck at the same time and cases usually don't vary much over 1 thou. once it settles down after the first few firings and I'm a duffer. Bullet seating depth is more critical anyways and will wash out with the seater automatically so don't fret.

Holy crap! That is exactly what I was doing with these cases. I am very very impressed!

This is what is so engaging about this hobby, learning something new everyday.

Thanks!!

 

[in2deep]

That's why your better off to use a dozen expendable cases for ladders and finding max loads (that really plays havoc with your brass).
Honestly that brass will always act strange from now on as it is all stretched differently and you can even feel it when sizing cases the press force will be noticable.
After 15 firings I can still feel the difference in my brass that I screwed up doing ladder tests but you can't tell it when shooting and it's still as accurate as ever.

 

[thefitter]

That's why your better off to use a dozen expendable cases for ladders and finding max loads (that really plays havoc with your brass).
Honestly that brass will always act strange from now on as it is all stretched differently and you can even feel it when sizing cases the press force will be noticable.
After 15 firings I can still feel the difference in my brass that I screwed up doing ladder tests but you can't tell it when shooting and it's still as accurate as ever.

It does not even out? What about after firing the same charge weight in all of them?

 

[in2deep]

The worst ones seem to be those used to determine max loads and the web got stretched out on several of them and the primer pockets got real loose. Maybe you didn't abuse your brass as bad as I did and even so they will neutralize a little after more firings or annealing. Heck it was hard to cam the press over on some of mine they fit so tight in the die and almost got stuck and you could see the dreaded ring around the base but they are still ticking after 15 firings- gotta love that Lapua brass even a dummy like me can't hurt it Lol..

But like I said don't sweat it they shoot just as good as my lots of brass that were treated better it's just that I can still feel subtle differences when f/l sizing and seating primers and it reminds me not to do that any more.

 

[mw0248]

I had the same problem with new win brass in 243; supposed to be 2.045, and they all mic'd out to about 2.038;
I used my Lee case trimmer (hand model), and sized them all to 2.036, and set my seating die to be 2.635 OAL, for my max chamber OAL in my x-bolt of 2.695; works perfectly;

 

[Leaddog]

Trying to figure out where my case length deviations are coming from.

.308

New Lapua brass

Fire formed twice

Bump shoulder .002

Re size neck .006 in 3 steps

Trim in Giraud Trimmer

Now 10 cases processed EXACTLY the same show these OAL:

2.0080
2.0080
2.0080
2.0080
2.0085
2.0085
2.0105
2.0115
2.0120
2.0120

I know the Giraud Trimmer indexes of the shoulder so I measured all from base to shoulder and they are all the same.

I am using a Forster Bushing Bump die.

I am totally lost. Where are these deviations coming from?

Thanks

I may be able to help. I had the same problem and Doug asked me if there was some slight sticking in the case holder when using. I said there was and he said it was because of using a bushing die and/or neck die. He asked me to send a few empty cases to him and he would machine the case holder out some to accommodate my cases. He did it and now all my trimmed cases are the same or within .001. Give Doug a call or write him. He will fix your problem.