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shinny
09-15-2011, 05:08 PM
A few days ago I made up some 30BR brass from Lapua 6BR. I necked it up in 3 stages then turned the necks to a very precise .0093.

Loaded with 34.7g of 4198 set the bullets .005 into the lands, lubed the neck shoulder junction w/Ballistol and fired.

I then neck sized it and when checking the dimensions found the Neck Thickness had grown to .0095-.0096.

This is not the first time I have noted this condition and was wonderingf if anyone else experienced this or am I getting Senile?:confused:

mwezell
09-16-2011, 09:42 PM
Those tolerances are best kept in a controlled environment, if not a 68 degree lab. The temps here have changed dramatically over the last few days. Are you checking them inside where the temp is at least reasonably stable? These variables are often overlooked and when talking about a couple of ten thousandths, the tools we use are susceptible to change with temps. If you hold a mic too long, it'll warm and change slightly too.--Mike Ezell

shinny
09-19-2011, 09:56 AM
Mike,

Thanx for the reply.

I do not hold the ball mic and to my best recollection the temps were reasonably the same. This expansion happened after the first fire forming.

Was at a shoot over the weekend and a few other shooters said they have experienced the same oddity.

Next time will try checking under very close conditions.

Shinny

Bob Kingsbury
09-19-2011, 11:14 AM
Shinny, Brass cut at a true .0093 will never thicken to .0095 or .0096. Somewhere the turning tool has changed. Back when
turning necks became a standard thing, I made most of my own neck turners out of aluminum. They work but there are
things that need to be understood. The expansion ratio of aluminum is far greater than steel and changes around .0003
were commonplace just from hand temps. Within a year I made them from steel and have had no problems at all. No
ice water, nothing. The other item I would mention is the ball Micrometer,, it is very prone to user error. If your not
using a ball mic every day, the feel is hard to duplicate. I have been reading them for 40 years and will be the first to
admit that. A much better way is to measure a loaded round.

shinny
09-19-2011, 11:33 AM
Bob,

Thanx 4 the info. I will try measuring the loaded rounds as you suggest.

Shinny

Elkhound
09-27-2011, 03:18 AM
Hello,
I experienced too some days ago.
I found the edge of necks after shooting curved inside. If you resize your case you'll find the neck thickness .0093". It should be that your rifle chamber is not perfectly straight, so you could need a reamer for the rear part of chamber that could be conical.

Jim Borden
09-28-2011, 10:11 AM
Hello,
I experienced too some days ago.
I found the edge of necks after shooting curved inside. If you resize your case you'll find the neck thickness .0093". It should be that your rifle chamber is not perfectly straight, so you could need a reamer for the rear part of chamber that could be conical.

Be careful-sounds like your cases are actually too long for the chamber and you are getting a crimp at the mouth.

shinny
09-28-2011, 02:15 PM
Be careful-sounds like your cases are actually too long for the chamber and you are getting a crimp at the mouth.

No Jim, that isn't the case..CL is 1.550; cases are 1.520.

However, I did find the culprit. I have several 75w Flood lights shining on my work area. Seems I left the brass under one of this lights before measuring it. When I put in a unlit area for a while and re-easure all is OK, Duhhhh.:rolleyes:

Thanks 4 the input Jim. Hope all is well with you & Joan.

Shinny

Jim Borden
09-28-2011, 02:27 PM
Shinny

My comment was not about the problem you are having-I was addressing elkhound with his necks curled in at front!

Jim

shinny
09-28-2011, 02:29 PM
So sorry.......

Elkhound
09-30-2011, 03:56 PM
Be careful-sounds like your cases are actually too long for the chamber and you are getting a crimp at the mouth.
Hi Jim.
This is the my first thought. Then I measured the chamber with a gage I built by a lathe and it measures 1.720". I trimmed to 1.695 so the chamber length is not the problem. As you can see from the pictures I was quite scrupulous in measuring. At the moment I didn't find a solution.
Shinny did you measure the neck after resizing?
http://i1199.photobucket.com/albums/aa477/Elkhound2/straigthedgeafterresize.jpg
http://i1199.photobucket.com/albums/aa477/Elkhound2/beforeresize.jpg
http://i1199.photobucket.com/albums/aa477/Elkhound2/curvedadge.jpg
http://i1199.photobucket.com/albums/aa477/Elkhound2/chambergage.jpg
http://i1199.photobucket.com/albums/aa477/Elkhound2/afterresize.jpg
http://i1199.photobucket.com/albums/aa477/Elkhound2/1720measure.jpg
For the next shooting session I'll try to trim the case to lower measure to verify if the problem remain or not.
Costa

Dick Grosbier
09-30-2011, 04:38 PM
Hi Jim.
This is the my first thought. Then I measured the chamber with a gage I built by a lathe and it measures 1.720" so the chamber length is not the problem. As you can see from the pictures I was quite scrupulous in measuring. At the moment I didn't find a solution.

Elkhound,
I am not sure what chambering you are talking but at 1.520" it certainly is not a 30BR . Case mouths crimping shut typically is case is too long for chamber as Jim says. Been there done that, at a Nationals match no less, and had to borrow a case trimmer.

What chambering are you talking about, the neck looks quite long?

Dick

Elkhound
09-30-2011, 05:25 PM
Hi Dick,
I talk about my old Walther KKJ-E in 222R caliber. And the chamber is 1.720 as you can see from the pictures, not 1.520.
Thank you Jim for warning. Sure I'll check carefully case neck at the next shooting sessions and will trim the neck shorter to find out a solution.
Costa