Case length trimming

[Mikeinkaty]

I only load 357 magnum using mixed brass. I want the COL to be the same and I want the crimps to be the same. That don't happen when your cases are all different lengths.

Hodgdon says the trim length should be 1.285". What I'm thinking of doing is, from this point forward, to consider trimming as part of my brass prepping procedure. I.e. Deprime, clean, trim, and flare. Then to keep future prepped brass in a separate bucket. My regular bucket of brass has already been deprimed, cleaned, and flared. I'll just load from the regular bucket until it is empty. The problem is I have probably 600 rounds of untrimmed brass already loaded.

In the beginning I just never thought variations in case lengths would be a problem. Once a case is trimmed to 1.285" I don't think it will be needed again.

So, got any trimmer recommendations? It must be one that measures from the outside of the case. Not all 357 brass has the same base thickness.

The thought has occurred that maybe I'm over thinking this. Maybe just keep the COL to book and crimp to where ever the top of the case lands. Cannelure or not.

Mike

 

[Rule3]

Just use your calipers. You should measure after the brass is sized and deprimed. So keep a bucket of ones that have been done, ones that need to be done. You should only need to trim them once.

Even revolver brass like 357 I have never done any of them. There is more variance in the crimp groove width to make up for a the slight difference in case length. But some folks like to trim them,


So trim the unloaded ones now, then after shooting the loaded ones
throw them in one bucket. After those are shot, clean size and then trim if needed, and you will be all set.

They do not grow that much.

 

[TAROMAN]

I use a Forster trimmer.
Keep a "reference set" of cases to quickly set the trimmer.
All revolver cases get trimmed to the same length.
Maybe its my OCD, but I prefer uniform flare and crimp.

 

[Rule3]

Oh, I guess I misread your post. You are looking for a trimmer?? Yes. No ??

If so they all work pretty much the same.RCBS, Hornady, Forster, Lyman etc etc

You want to hand crank or want electric power.??

Just like presses it's what color you like and how much you want to spend.

 

[Mikeinkaty]

After writing this down here and going out and loading 100 rounds, I came with maybe an acceptable solution. I measured 50 cases and found that they varied 0.001" around 1.285". So, I took a 1.285" case and seated a bullet in the center of the cannelure. That produced a COL of 1.590". Using that for 100 loads caused the crimp to be somewhere in the cantelure. If one crimp doesn't feel tight enough I just reach up and tighten the adjustment 1/4 turn, crimp, and turn it back. I think that will be an acceptable compromise. Hodgdon says 1.610" for the COL. I think 1.590" will be fine. Some data books call for 1.590" anyway.

 

[cjw3]

Like Taroman, I also use a Forster trimmer. It comes with a crank handle, but you can get an adaptor for use with an electric drill. I have mine mounted on a piece of 2"x 12" lumber about 18" long. I can sit and watch TV with it in my lap and trim cases at the same time.

I also keep a trimmed case in the box with the dies for all the revolver cartridges I load so that I can easily adjust the trimmer.

I like a uniform roll crimp, so I don't mind a little extra work for better results.

 

[BZimm]

So I dug out a brand new 357 cartridge and a couple spent shells and started measuring. I think I get your point...they're all over the map! And if they're not the same length then how can you get a reliable crimp?

Ok, Ok, I'm going back to reading now.

 

[Rule3]

After writing this down here and going out and loading 100 rounds, I came with maybe an acceptable solution. I measured 50 cases and found that they varied 0.001" around 1.285". So, I took a 1.285" case and seated a bullet in the center of the cannelure. That produced a COL of 1.590". Using that for 100 loads caused the crimp to be somewhere in the cantelure. If one crimp doesn't feel tight enough I just reach up and tighten the adjustment 1/4 turn, crimp, and turn it back. I think that will be an acceptable compromise. Hodgdon says 1.610" for the COL. I think 1.590" will be fine. Some data books call for 1.590" anyway.

I never measure revolver cartridges anymore. It it has a crimp groove (lead) it is gonna fit. Stamped cannelures (FMJ) can vary, so maybe check a few of them.

 

[Mikeinkaty]

I never measure revolver cartridges anymore. It it has a crimp groove (lead) it is gonna fit. Stamped cannelures (FMJ) can vary, so maybe check a few of them.

Having a consistent COL should give more consistence pressures. Regardless of case length, the open space inside the cartridges would be the same assuming the same bullet. Assuming the bullet base is the same thickness. The only other problems would be inconsistent powder loads and the crimp. It's hard to get a consistent crimp when it varies up and down the cannelure.

What about using bullets with no cannelure and a taper crimp?

 

[forestswin]

After writing this down here and going out and loading 100 rounds, I came with maybe an acceptable solution. I measured 50 cases and found that they varied 0.001" around 1.285". So, I took a 1.285" case and seated a bullet in the center of the cannelure. That produced a COL cof 1.590". Using that for 100 loads caused the crimp to be somewhere in the cantelure. If one crimp doesn't feel tight enough I just reach up and tighten the adjustment 1/4 turn, crimp, and turn it back. I think that will be an acceptable compromise. Hodgdon says 1.610" for the COL. I think 1.590" will be fine. Some data books call for 1.590" anyway.

If you have an acceptable solution to you fine....
But + or - 0.001 length shouldn't cause you to adjust your dies.

But If you are adjusting your dies up and down .....the ammo is simply not uniform

With mixed brass and who knows how many times fired...I don't think I'd bother to trim the cases .....

Just follow Rule 3's advice......close enough

 

[ameridaddy]

1. I use a Forster trimmer I bought ~40 years ago, and with an occasional cleaning of the shaft and bore, then a drop of light oil, it's going strong with no visible wear. I found the hand crank is fast enough and enables a feel feedback I couldn't get with a drill driven setup.

2. In a cartridge with heavy bullets or high recoil, I think a consistent crimp is important for decent performance accuracy-wise and also to be sure there is no bullet setback. For this to happen without a bunch of fiddling with the crimp die, the brass needs to be a consistent length.
I've found that brass length varies more right from the factory than it changes from repeated firings. I recently measured 300 new 45 Colt cases from Starline, which is excellent brass. SAAMI brass spec is 1.265" min, 1.275" trim to length, 1.285" max. I found the mean was 1.272", .003" below the trim to length, with a range of +/- .010" around the trim to length, with only 2 brass below the SAAMI min, at 1.261", and 1.263". Arranging the cases by length, the distribution looked very much like a normal curve. I trimmed to .005" below the trim to length at 1.270", but still over the SAAMI min., and tossed the cases below that.
After that, no more in-process fiddling with the crimp die. Ahhh, happiness.

 

[growr]

For many reloaders trimming straight wall pistol casings is a total waste of time....few us can hold well enough to see any difference that .003-005 of an inch would ever yield, let alone have any significant effect on pressure changes. Even over a rest....there are so many other variables....but that is just me.....

 

[iouri]

I just went through similar procedure. Trimmed about 500 cases. Well my solution is kinda pricey - some time ago I've bought Dillon trimmer for my 223 processing; added C4HD die and shell holder raiser and then just process them on single stage. Took me a little over an hour. In process culled 5 pieces of Hornady brass that was for FTX bullet (way shorter than standard min OAL).

 

[Rule3]

These six cases where pulled at random from a bucket of clean brass. None measure or adjusted, Do you think the difference in where the crimp lines up will make any difference on how the rounds shoot?I have the data somewhere but to late to go dig it out.

If I was shooting for money medals or trophies maybe I would. Might even use the same heads stamp.

 

[Frank46]

I normally end up with 100 revolver cases as in one lot. Measure them and trim to the length of the shortest case. I have found that this gives you even crimps for each cartridge in my 100 case lot. Frank

 

[Mikeinkaty]

What are the SAMMI specs for 357 magnum brass?

 

[rwsmith]

For the reasons you mention.....

...I think it worthwhile to trim pistol brass ONCE.

SAAMI sez:

1.405" min

1.590" max

 

[Nevada Ed]

I measure my cases and if .02" or more difference is found
I may place the cases in a second container with a label, for later use.

If the cases are not over length..............
it is easier for me to just adjust my seating die for a crimp after
the bullets have been all seated to the preferred OAL for the load.

This way the crimp is perfect for all your loads, no matter what the case measures..........
and no trimming is needed.

Hear is a picture of the room on a bullet for crimping. As you
can see, there is a lot of space to get the crimp right even if
your OAL is off a little.

Good shooting.

 

[m657]

I've found my own daily personal bodily variability of POA to be far more impact on the POI regardless of OAL/trim length/etc.

A buddy with the most intense CDO I've ever seen, was a top ranked precision rifle guy. He laboriously described the steps he took for loading his rifle cases....including grouping for weight of brass & water volume, as well as .01g weight differences and concentricity in boolit. Among other mystical steps he aligned all his same-headstamp cases the same direction each loading and used only same-number-of-reloadings in each brass group, plus other factors I can not recall or really understand.

When taking up pistol competition, he applied similar qualitative metrics, laboring intently to make uniform case mouth tension, OAL identical, etc.

After 6 months he abandoned much of his extreme attention finding it in fact demonstrated ~no~ advantage in accuracy of his rounds out to 50 yards...in calibers 9/38/45 acp.

 

[Rule3]

I have finally figured out the answer to this age old question!

On some cold dreary day the bored reloader should take ALL of his handgun brass (that is all of it!) and sit down and trim every darn one of them. If that doesn't cure you then there is no hope! After trimming be sure to chafer and debug them. Then put them in the Ronco Shine A Matic to get that better than new shine on them!

They are now all trimmed and you will never have to worry about it again!!

PS: measure the width of the crimp groove on a lead bullet. How much room is there to play with? Now how much difference is there in the length of your brass and the trim to length?. Think there is enough to worry about?