When to Trim and When to Size Bottle Necks - Troll Fodder

[engnerdan]

Since the search on this forum is about as useful as the safety on a Mosin Nagant. I will ask

This came up in conversation the other day between myself an a fellow consumer of gun powder.

When do you trim a bottle neck case before or after sizing?

I know what the F'in manual says and I know what I was taught to do and I even looks to see what Mr. Google had to say on the matter.

1. TFM - (Speer, hornady, another one) Says trim shorter than spec, then size
2. Google - Says size and then trim
3. John at GS - Trim then size
4. My pappy - Size then trim


So what is it?

[JJ]

Size then trim.

[Rodentman]

May not apply to the actual query, but when I reload 5.7 I resize and decap first, then trim. Well, I have to since I use the Lee case gauge and lock stud method. Also, resizing those buggers will usually reveal if the shoulder is torqued and then the case goes in the trash right away. And they DO need to be trimmed every use.

[Ironsight87]

I size then trim. Sometimes the case mouth isn't even round before sizing, cant imagine it would trim perfectly even.

[shooter115]

I size then trim also.

[engnerdan]

DAMN I thought for sure this would turn into a mess.

Everyone is agreeing and it logically makes sense. But why do the books say otherwise?

[rugersol]

But why do the books say otherwise?

cite, please?

[engnerdan]

But why do the books say otherwise?

cite, please?

I will be glad to when I get my hands on the books my friend has. I think I have one of them at home.

[bulletproof]

The only time I've heard of trimming before resizing would be when you're using a specialty die such as the RCBS X-Die.

[justaguy]

This should have been a poll, just to see how it pans out.

[Jbotto]

Size then trim. I started out doing it bass-ackwards to what I just mentioned, and read a bit on the subject only to realize what I was reading made more sense than what I was doing.

[usnret]

Size and trim in the same step. Dillon system.

[crbutler]

I usually full length size, trim, chamfer/deburr, polish, and then size it again. Its probably not nearly as important in what order you do it if you are just neck sizing. If its a really unusual case, I will anneal after the full length resize, but before trimming.

The only real advantage that trim/size offers you is that you can skip the chamfer and deburr process most of the time.

It also makes it so you lose control of your exact case length. In most cases that can mean a loss of accuracy.

[Countryfried Frank]

Size then trim.

[Seismic Sam]

crbutler is right - size then trim. If you trim first, and then the shoulder bump shortens the case by a variable amount depending on the pressure in the case when it's fired, case length uniformity goes right out the window. Plus if you got the shoulder bump dialed in perfectly, then trimming cases will be a task that you don't have to do very often.