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Old March 16, 2013, 12:44 PM   #1
HookedOnTheOutdoors
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Uneven case length after trimming

I've been stumbling around here trying to figure out how to start a new thread...looks like I found it..

I just bought an RCBS Trim Pro case trimmer and am getting trimmed cases that are uneven. I have followed the directions and have the correct shell holder and pilot installed.

When I slide the pilot toward the mouth of the case I always have to push down on the handle to let the case mouth line up. Is there a way to correct this issue?
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Old March 16, 2013, 01:35 PM   #2
jdscholer
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I don't have the Trim Pro, but I've got the old RCBS Rotory Case Trimmer, and I have the same problem.
On mine it is because the collet and case are sucked more or less deep into the clamp, depending on factors such as the diameter of the case head, and how much torque is used in tightening.
The difference in final length isn't more than a few thousandths, but I'm not wild about it.

I pretty much use the Lee method for most of my trimming anymore. It's quick, accurate, and economical. jd
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Old March 16, 2013, 02:20 PM   #3
Nathan
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Basically, it is what it is....

It seems to be related to how those types of case trimmers hold the case.

I use the Wilson which avoids that. FL sizing makes the case pretty perpendicular to the base. Then the trimmer aligns the case centerline perpendicular to the cutter. Any misalignment found measuring CL is base to body and is meaningless.

Base to body perpendicularity really cannot be corrected as it is caused by the gun.
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Old March 16, 2013, 02:20 PM   #4
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Uneven case length

My cases measure one length then another if I rotate the case in the caliper. It's like they are trimmed on an angle
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Old March 16, 2013, 04:15 PM   #5
reynolds357
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Is all the brass you are trimming same MFG and same Lot?
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Old March 16, 2013, 04:29 PM   #6
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Uneven trimmed brass

Yes. They are Remington UMC .357 SIG fired once out of my Glock
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Old March 16, 2013, 04:42 PM   #7
zeke
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1-do you mean an individual case has uneven lengths, or are some cases different lenghts than other cases, and by how much?

2-That is what the handle on the left is there for, to release the pressure so the case can line up. It needs to be fully depressed for each case.

3-the common rifle caliber pilots are sized for neck expanded rifle cases . Am not sure how the 357 sig pilot sizer/expander works, but do your cases easily fit over the pilot?

Last edited by zeke; March 16, 2013 at 08:49 PM.
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Old March 16, 2013, 04:45 PM   #8
chiefr
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I have the motorized trimpro which uses the same trimpro case trimmer. If your experiences equal mine, you will find there is a learning curve before you get the hang of it. Cases must be seated flush tight with the base and the shell plate in the right orientation. Allen screw must be tight.

I &^%$#'d up a few cases in learning how to use it. Suggest some berdan primed or junk cases and practice to get the hang of it.

I still have a Forster collet trimmer I use for minor trimming. If I have to trim more than .003, I use the trimpro as it is faster.
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Old March 16, 2013, 05:01 PM   #9
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Uneven trimmed cases

Yes. One side of the case will measure say .860. Turn the same case a little and it may meafure .858. It's like it's trimmed in an angle.

The pilot will not work with sized brass. Way to tight. I resize them in a .40 die and neck size them after trimming.

I can relate to the learning curve. I'm assuming this problem is something I am doing.

I get the mouth to line up with the pilot by slighting pressing down on the handle. It appears to me that this may be making the case lean?
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Old March 16, 2013, 07:05 PM   #10
chiefr
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The only time I have ever seen cases trimmed at an angle is when there is an uneven case head. Sometimes caused caused by a forceful ejection, weak brass, stepped on etc, and the rim is raised slighly in one spot.. Your cases may have this problem. Place on a flat surface and check to see.

If the case is tight and flush seated it should trim true unless there is a problem with your trimmer.
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Old March 16, 2013, 07:28 PM   #11
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Uneven trimmed cases

I will try some more tomorrow. Thank you for the replies.
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Old March 16, 2013, 08:53 PM   #12
zeke
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Another possibility is the cases are uneven to begin with, and may need trimmed shorter to uniform the length. Or the base of case is nicked up.

Are the cases past the max length after being sized, or are they significantly different lengths?
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Old March 17, 2013, 01:40 AM   #13
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uneven trimmed cases

The are a couple that are measuring near .870. Trim length is .860.

The thing is I have been wanting (not needing) a case trimmer for many years. I finally made the investment only to find out that most pistol cases do not need trimmed. Since the place I bought it at doesn't do refunds or exchanges, I'm kinda stuck with using it where I can. I have seen however that the SIG round should be trimmed because of its bottle neck design.

I've decided to test the affects of small pistol magnum primers subbed for small pistol primers. I pulled the bullets on 20 factory rounds, measured each case, labeled them then shot them through my chrony. I then re-measured them and that gave me my baseline. Now I am trimming each case to the recommended case length and documenting the other case dimensions. I will then load half of them with small pistol primers and half with small pistol magnums. I have already shot the load I am going to use through my chrony and found there is only about 20 feet per second or so difference in velocity. It is also well under the 7.9 gr max (7.6 gr).

Its really a mute point now that I found a supply of small pistol primers. There for a short while all I could find is small pistol magnums. Just curious at this point.
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Old March 17, 2013, 07:44 AM   #14
Nathan
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I believe that you will find this is life in the RCBS Trim Pro. It is because it holds by case head and pilot. Not a terrible design, but often not perfectly straight.

As I said before, the Wilson is better, but not perfect.

Unless it is off by 0.005" or more, it is ok. Just trim so your case is your trim length = longest length.
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Old March 17, 2013, 09:27 AM   #15
chiefr
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Your results with small pistol primers & mag primers are similar to mine; not much difference. I have not used small pistol mg primers in years.

I too have never trimmed pistol brass.

Some people do not like the trimpro because the back part wobbles. The trimpro was designed so that when the pilot enters the case mouth, the pilot squares the case perpendicular. There are those that prefer the collet type.

My first trimmer was a Forster, It is over 40 years old and works great. Like I mentioned before, I use the motorized trim pro for big jobs.
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Old March 18, 2013, 07:58 AM   #16
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Does the case have to move up or down, or side to side?

There is a screw underneath that holds the "head to the body" so to speak. Once in a while mine turns to the side a little after heavy use. I just move the handle one way or the other and it lines everything back up.

If it off up and down, maybe your shell holder isnt down all the way. Maybe it isnt letting the case get seated all the way down. Sometimes they are hard to get fully down.

I always rotate my cases 180* and hit them again quick before I take them from the trimmer just to make sure they are even all the way around.
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