Case length deviations?Giraud??

[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 <span style="text-decoration: underline">EXACTLY</span> 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

 

[former naval person]

Re: Case length deviations???

Must be in the cutting action of the Giraud. Run them through the Giraud again and see if they change.

 

[TexIndian]

Re: Case length deviations???

I have a couple Gracey trimmers and they also index off the shoulder. I've noticed that if I get in a hurry and don't hold the cases perfectly straight going into the mouth of the trimmer, I can get variations. Otherwise, I don't have a clue.

 

[blklabs]

Re: Case length deviations???

Try trimming the case and then rotate 45 degrees and run the case back in the Giraurd. I have found that sometimes it will leave a little ridge on one side and that can throw off your measurements. If that doesn't fix it then I wouldn't sweat it, you are only talking about .002" variance.

 

[bcuzisedso]

Re: Case length deviations???

I just finished trimming a batch of 223 LC brass on the Giraud and had deviations of .006 in OAL.

I tried different techniques but nothing gave consistent results...

 

[thefitter]

Re: Case length deviations???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bcuzisedso</div><div class="ubbcode-body">I just finished trimming a batch of 223 LC brass on the Giraud and had deviations of .006 in OAL.

I tried different techniques but nothing gave consistent results... </div></div>


.006 ? That sucks. But I'm glad I'm not the only one.

thanks

 

[2clicks]

Re: Case length deviations???

I just measured 20 out of a batch of 1,000 only found .001 difference. All the same Lake City headstamped brass. Seems like the case rim on a few was slightly out of square on some that measured different.

I don't see how it could be Giraud trimmers fault. As long as your giving it a twist as you complete the trimming.


Also make sure that lock ring isn't backing out from all those vibrations on the trimmer!!! I've had that happen before. Seems like your length is growing. I index with a marker on the lock ring to base now to make sure nothing moves in or out.

 

[427Cobra]

Re: Case length deviations???

The bigger question is can you or anybody else here shoot the .006 difference, that answer is F-NO, I agree on it being something in your technique, I turn my cases 360, every now and then I can tell by the sound that a case needs a little more

 

[FLIGHT762]

Re: Case length deviations???

I use a Gracey. At times, a brass chip or other build up will cause issues. I will take a Q tip and swipe the shoulder area in the shoulder area of the case holder clean. This returns the cutting to close tolerances. It's worth a try. A variance in shoulder bump can also cause can cause OAL cutting issues, since it indexes off of the shoulder.

 

[bcuzisedso]

Re: Case length deviations???

I agree with not being able to notice .006 on case length differences....heck some of the once fired FC .223 brass I was trimming today was not even long enough to touch the cutting blades.

That being said, I did notice today(as was mentioned above) that some brass "trimmings" end up in the case holder and prevent the shoulder from properly indexing and thus causing some deviations.

 

[ToxGunn]

Re: Case length deviations???

Same here - I've gotten minor variances due to the occasional small shaving keeping the brass from *really* seating in the holder. Flipping it on its back so I'm feeding the brass from above largely resolved it.

Don't forget to turn the brass when cutting.

 

[turbo54]

Re: Case length deviations???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 427Cobra</div><div class="ubbcode-body">The bigger question is can you or anybody else here shoot the .006 difference, that answer is F-NO, I agree on it being something in your technique, I turn my cases 360, every now and then I can tell by the sound that a case needs a little more </div></div>

This^^

As far as I'm concerned, as long as the case neck doesn't bottom out in the chamber, the trim-to length is good to go. 6 thou aint shit. Be happy you've got a nicely chamfered case miuth OD and ID, and move on.