Revolver brass trimming

Unclenick. What's the mechanism for the straight wall brass to shrink? I looked it up and couldn't find a conclusive answer. Somehow the metal gets pushed into the brass head. Thanks.

-TL

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As I mentioned in post 16, I believe that because the chamber is tapered wider toward the breech end and the pressure is not high enough to make the brass stick to the chamber wall (necessary to stretch a case head back and cause pressure ring thinning, as happens with high power rifle loads), the whole case backs up in the chamber and is swelled out fatter at the bottom to fill out the taper and any bulge and unsupported chamber might allow. To supply brass for that fattening, the mouth is pulled down shorter. You can see this measuring the cases before and after resizing. Resizing extrudes the brass back forward, but apparently, it is unable to achieve 100% return to the original length (except that the first time you resize a once-fired new case using a carbide die, as the ring eliminates the taper in the case, so that first time it may result in a longer case that grows shorter subsequently).

My expectation is that a wider, looser chamber will cause greater shortening per load cycle than a tighter chamber does. I've never tested it, but I should. I've got an Encore pistol barrel in 45 Auto that I fitted with a strain gauge for pressure measurements, and it is a fairly tight and fully supported chamber, so my expectation is it would reduce that shortening effect.
 
So, I did some work with the Lee tool.

First, the pilot part measures 0.3515”. So, I can size first.

It was setup to trim. Some quick file work shortened it to min spec. The pilot can be loosened slightly, and adjusted with feeler gauges to a perfect setting. Threads are tight enough to hold the settings. Interesting system.
 
I like the Lee trimmer too. Use a drill on a table to hold the shell holder and it gets done much faster. I recently did 600 .5.56 cases and was much easier than I thought it would be. When I first started reloading I trimmed the 200 rounds of .357 brass I had.

I have upwards of 2,000 .357 cases currently and they will remain at the length they are at. With my 6" Dan Wesson I can shoot sub 1.5" groups using mixed brass of varying lengths. The powder is dispensed using a Lee Auto disk powder measure and the powder I used was Unique which people claim doesn't meter well. I've seen the weight vary up to .2 grains it's typically within +or- .1 grain. Loads are medium, not full power.
 
I like my Lyman universal trimmer . No special shell holders needed , all cases seem to fit just fine . If you know how the RCBS universal priming tool holds cases , the Lyman trimmer is similar but has a second quick adjustment base to lock the case in tight . I'll add that ( at least for me ) the Lyman locks the cases in tight enough to not need the pilots which is good when trimming several thousandths off a neck because the shavings get caught/stuck between the pilot and inside case mouth , making it hard to remove or scratch the insides of the necks .

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Do you guys have a link or a pic of the Lee trimmer you all are talking about ? I used a Lee trimmer when I first started and it worked ok at best . My Lyman is light years better so maybe I was using something different .
 
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Sorting the brass first will be helpful. I always start with new brass of the same headstamp. After it's been shot and reloaded however many times, I am measuring the case length with calipers to find a length that no more than 1/3 of my cases are shorter than. Cases shorter than my spec, go into the short bucket. Cases that are between my spec and 0.002" over don't get trimmed. They go into the ready-to-expand bucket. Cases that are more than 0.002" over my spec go into the trim bucket. My trim bucket usually ends up with less than 1/3 the total volume of cases.

If trimming case mouths to be uniform in the crimp, it is equally important that they be of consistent length and that they be square. Trimmers that won't trim the case mouth square aren't adding anything but brass chips to your bench. I use a Wilson trimmer with the Q-type case holder.

Brass can be trimmed after it's fire-formed in the chamber, or after resizing. I trim my handgun brass after it's been resized but before the case mouth is expanded. Shooting and resizing rifle brass tends to lengthen it. Shooting and resizing handgun brass tends not to change it much or to shorten it after many reloadings. Eventually, I'll have a lot of brass in the short bucket and I'll reset my spec to three or four thou shorter than what I'm using now and I'll be using all that brass again.
 
A lot of folks do it once to get their case lengths, and therefore the amount of crimp from a fixed crimp die position, consistent. But once done, I've never had to repeat it before mouth splits started retiring the brass.
 
Road_Clam said:
You guys trim revolver brass ?
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Have experienced revolver cases getting longer in levers when using full power loads. Especially after several firings. One time i mixed them altogether, but trimmed them to match the length of cases fired in the revolvers so crimp would be consistent. Same batch of brass. If possible, easier to keep the brass segregated.

If i was mixing several brands of fired brass, especially range pick ups, would check some for length, and consider trimming them depending on purpose.
 
In over 50 years of reloading I have never trimmed any pistol/revolver brass.
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I trim all my handgun brass once the first time I prep it . I get military once fired and range pickup brass from my local range . I've said this before somewhere and I'll bring it up here . It takes me the same amount of time to measure a piece of brass as it does to trim it . I'd rather just run everything through the trimmer removing the step of measuring them . That way there is zero questions later if there's a feeding issue if the case was to long .

I've never really paid attention to how many in lets say a 1k ct lot actually needs to be trimmed but off the top of my head I'd say more then 20% less the 40% . This is putting them back to trim to length and not to say because I trimmed "some" brass off they were to long to work . Only that 20 to 40% need some brass removed to return them to the trim to length .
 
Back when I started handgun hunting my wife and I went through a lot of ammo in magnum calibers. I shot mainly Winchester brass but also Starline. What I found was for general shooting, untrimmed and mixed cases shot just fine. Most will hold respectable accuracy.

That said, I usually still trim the brass for my hunting loads. I want to remove anything from the mix that might cause a flyer. There are enough errors induced by environmental or human errors. Consistent crimping is just in my routine. Shooting jacketed might let you slide by here and there but I've found that cast really likes to be set at the shoulders of the crimping groove.

For my bottom feeders, if they chamber they get shot. Even for my hunting pistols I just clean em up, load and shoot.
 
In handgun brass trimming or not trimming has little to no effect on accuracy.....In fact handgun brass gets SHORTER with repeated firings. You can verify that with your own cases.
 
If my revolver brass is not way out of spec, I just don’t bother to trim. If I do, I use my ancient RCBS manual trimmer.
 
The cheapest , easiest , fastest way for me is with a trim die and file .
Run the case up into the die , whatever sticks above the hardened die top ...
you file it off flat with the die . Inside and outside deburr and you done ...
No muss No fuss no measuring and when done everyone is exactly the same length .
Mine is marked Herter's .
Gary
 
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