Question on trimming 308 brass

[guncrazy72]

Hey everyone, I picked up a RCBS trim master pro today and have a question about it. I am trying to trim 308 brass back to 2.005 but I have something odd going on that Ive yet to read about anyone else doing or talking about. After I set my trimmer up to cut to 2.005 I then deburred and chamfered the brass, it then reads longer than what it should be, 2.005. After messing around with the trimmer trying to figure it out I turned it down to cut 1.99 and THEN after I deburr and chamfer It will be the correct length of 2.005. I am using the RCBS hand tool to deburr and chamfer. Anyone have insight of this?

 

[M40_A1]

I'd say either your measuring technique is off, or your deburring tool is dull.

 

[neiltus]

Springy stuff? Tool can measure .001 accurately? What does the head of the case look like?

For me, I don't measure after I trim, but just assume that the cutter puts it all in the same place.

 

[mdmp5]

Does that trimmer have a micrometer? If not, you have to make some coarse adjustments. Measure your case, adjust a little, trim, measure again and repeat until you get the length you want.

 

[guncrazy72]

Its twice fired FGMM brass that is starting to get a little long already. I am checking with two different calipers and getting the same thing. I was able to get it to cut to 2.000 and then once I deburred and chamfered it would bring it out to the 2.005 mark. I am using a brand new RCBS deburr and chamfer tool as well. These look fine doing it this way and its at the correct length. From what Ive read it looks like itll be fine doing it this way.

 

[Toast]

I'll take a long shot, but maybe the heat from your hand and the deburring etc. and friction from the tool can cause it to increase .006? .006 isn't very long at all. Try letting one sit for a couple minutes and then measure it. Good luck.

 

[guncrazy72]

I'll take a long shot, but maybe the heat from your hand and the deburring etc. and friction from the tool can cause it to increase .006? .006 isn't very long at all. Try letting one sit for a couple minutes and then measure it. Good luck.

I will give this a shot! Thanks.

 

[mdmp5]

I'll take a long shot, but maybe the heat from your hand and the deburring etc. and friction from the tool can cause it to increase .006? .006 isn't very long at all. Try letting one sit for a couple minutes and then measure it. Good luck.

.006 is not long, but there is no way you can expand brass with heat from your hands.

 

[Mad_Charlie]

.006 is not long, but there is no way you can expand brass with heat from your hands.

Not enough to measure with a caliper, by the way, .006 is a mile as far as heat expansion is concerned.

 

[Toast]

Not enough to measure with a caliper, by the way, .006 is a mile as far as heat expansion is concerned.

Plus friction of the cutting tools? I believe you though. I took a shot in the dark.

 

[pjparker]

All I can add to the mix is that you may be measuring a slight burr thrown up by the inside and outside deburring tools. Spin the neck against some fine scotch brite or steel wool to remove any possible burrs and measure again. Anyway, a few thou one way or another won't really make much difference, as long as all your cases come out the same length.

Paul

 

[smschulz]

cut 1.99 and THEN after I deburr and chamfer It will be the correct length of 2.005.

That seems very odd that there is that much variation.
I use the RCBS Trim Mate Prep Center and I have no difference in length let alone something like a HUGE .006 difference.
Somethin' ain't right???

 

[Aimsmall55]

Get the 3 way carbide cutter. It goes on the trimmer and deburrs, chamfers and trims in about 4 seconds. It's about 54$ but after using it so long it's paid for itself and then some.

 

[guncrazy72]

So, Ive set my trimmer to cut at 2.000. After I trim my brass and still deburr and chamfer it will then be the correct 2.005. Ive tried multiple things to see if I can get it to cut what I need and it still will not. Ive cut some of my brass and will give it a try this weekend. They are all within the safe range so I should be good to go. I will be ordering the new head pretty soon.

 

[66427vette]

Have someone else measure them.

 

[delixe]

You are raising a burr with one or both of the chamfering operations.
Ignore it, max length is 2.015, the burr won't hurt a thing.

 

[stangfish]

Take a power screwdriver nut driver socket and stuff some 3m scotchbright down in there. After deburring, buff the end of the case and see what happens.

 

[Icewater]

If you have a powerful magnifying glass take a look at the edge and look for a raised burr, as mentioned before a dull cutter might just swage the brass edge

 

[Bradu]

Can you take a couple pics of it fresh off the trimmer and some after you chamfer and deburr the case? I don't know that it will help but it may shed some light on the situation.