Trimming revolver brass

R

Real Gun

New member
I trim my brass with the intent of getting a consistent crimp but have just discovered that the brass shrinks during firing and lengthens during sizing. That is important in determining when to measure and trim. I now decap and size in prepping rimmed revolver brass. Only after that do I check the case length and trim to my desired length. Brass I have measured and trimmed before will have to all be redone, because fired brass is going to load longer than it is before sizing, and brass segregated for shorter length may size out right on nominal...probably where it originated.


I came upon this realization with a batch of tumbled 45 Colt, which I was pretty sure had been loaded in spec but now too short, measured after cleaning. The only glitch came when finding the trimmer buttons on my Hornady trimmer were tight when presented with sized brass, so In some cases, certainly 45 Colt, I had to use the button guide for the next smaller caliber, my 44-40 setup. I suppose I could trim brass that was expanded but not flared.

That's my current story.
 
I learned about that the same way when I started loading handgun rounds a long time ago. I had trimmed about 300 .357 mag brass and trimmed them before resizing them. Luckily I trimmed them long. Then tried to run them through a progressive set up for the shorter length.

Didn't go well and I had to resize them all and trim them all over again. That took all the fun out of it.
 
I have found it necessary to trim some of my pilots. I use crocus cloth to gently work them to correct diameter.
 
Chuck case trimmer in drill, lock trigger back and use crocus cloth 1500 grit.....less than 45 sec; measure often.
 
Always trim after resizing. That being said, the only revolver brass I trim is my precious .38 Special wadcutter brass, and that only to prevent splits in the case mouth.

Don
 
I read the "always trim after resizing" stuff but the necks won't slip over the pilot , so I trim then size....no big deal.
After 50 years I discovered with straight sided pistol ammo there's no need to do all that measuring and trimming after the first initial get them all nearly the same length trim...
After that you just wasting your precious time.
 
After 50 years I discovered with straight sided pistol ammo there's no need to do all that measuring and trimming after the first initial get them all nearly the same length trim...
After that you just wasting your precious time.
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That would be okay if no one else's brass creeps into your rotation. I shoot cowboy, so rifle brass is picked off the ground and could potentially be anyone's returned to me. I measure everything and sort head stamps. I am pretty particular about the appearance of my roll crimps.
 
I read the "always trim after resizing" stuff but the necks won't slip over the pilot , so I trim then size....no big deal.
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If I did it that way, I would expect the brass to grow after sizing, probably .005 or so. I would have to anticipate that in the desired trim length when trimming before sizing. What I did is adjust an expander so it didn't bell. I was using a case feeder, and the press had only a sizer and expander mounted. This evening I did all my unloaded/fired 357 brass and ended with length categories .005 longer than I had been using but which were actually what was being reloaded after sizing. So now I have to load with the sizer die removed. That certainly will make cycling the press easier without that resistance. I don't size new, unprimed brass, so that works too without the sizer with decapper.
 
For over 40 years I have sized and then trimmed. If the pilot was too big I simply polished it down. In my early years I did this with a drill and sandpaper on a file if the pilot was hardened. Just lightly clamped the drill motor in a vise. Nowadays I own a small machine shop.

"one size fits all" doesn't, and many times you just have to "adjust" things.
 
For over 35 years I have NEVER trimmed pistol brass. Have never had an issue with 38s, 357, 32acp, 32swl, 45acp or 9mm. Don't intend to add that boring chore into the mix now.
 
This isn't about what you might think of trimming revolver brass. It is about things to consider when you do. Please don't feel the need to pee on the campfire.
 
I've never had to trim a pistol case. Rifle case's stretch on sizing because the neck get's pulled back over the expander button.
 
Note that I only referred to revolver brass, i.e. when needing a quality roll crimp. It has never occurred to me to trim semi-auto brass or any other brass that headspaces on the case mouth. However, feeding issues would be cause to check with a gauge or barrel chamber. Checking brass alone with a gauge, never mind the bullet, would be more valid and representative after sizing.
 
I occasionally trim my revolver brass, mostly to equalize the lengths for a more uniform crimp. But some do grow, depending on the caliber and load, and do require trimming to keep them in spec.

I trim after sizing, reducing the trimmer pilot OD as needed.
 
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I guess I'm a "real life" reloader as I don't pay a lot of attention to theory or forum "intelligence", I do/use what works for me, in real life. If I were to trim straight sided cases, I would do it as the last case forming/processing step, besides deburring. I have never found the "trim to insure consistent crimping" theory to apply in real life, or with any measurable effects on handloads (consistent velocity or accuracy). When I was shooting a lot, my untrimmed .44 Magnum ammo gave me -2" groups at 50' (indoor range) and many 2-2 1/2 inch groups at 20-25 yards (outdoors at an unimproved range). If one wants to trim revolver/straight walled brass then they should trim, but I'd suggest after sizing...
 
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Trimming brass:

Trimming brass: I crimp pistol rounds, I am the fan of having cases that are the same length and I adjust my dies ever time I use them.

So I made a case measuring tool that can not be commercial enough to interest reloaders. I have too many pistol cases to frim so I sort by length when I load.

F. Guffey
 
As a broad rule of thumb, cases fired at less than approximately 30,000 psi (varies with the case design) don't usually grow, and a lot of them that are much below that pressure can actually shrink with each reloading cycle. The growth mechanism requires them to stick to the chamber by friction harder than the force caused by pressure on the head has to be pushed to stretch the brass at the pressure ring, where it is thick enough not to expand enough to stick to the chamber. I followed the surviving cases of one lot of .45 Auto brass I had through 50 reloads, and they ended up 0.025" shorter than when they started out as new cases, all without trimming. The brass would just back up in the chamber and get wider and shorter and resizing would not quite bring it back 100%.

How wide and short a case is and how much it will grow with resizing can vary depending on the chamber it was fired in and the thickness and hardness off the brass and the pressure that was reached. Cases don't all change shape the exact same amount during firing. As a result, trimming after resizing is the only way to know they will not change length before being reloaded, and that helps with crimping consistency.
 
I always trim after sizing , why would you trim first then size which would change the length. To get the proper roll crimp on revolver cases the length must be the same . I have had the pilot on the cutter feel pretty tight probably do to case thickness , try some dry lube inside the necks , I see no harm in shaving down the pilot then polish .
 
I always trim after sizing , why would you trim first then size which would change the length. To get the proper roll crimp on revolver cases the length must be the same . I have had the pilot on the cutter feel pretty tight probably do to case thickness , try some dry lube inside the necks , I see no harm in shaving down the pilot then polish .
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Since I sized on a progressive, I included an expander set to not flare, so the pilot fit is no longer an issue. Other than seating, that also presents the cases with the two greatest stresses that could effect length before trimming.

BTW trimming before sizing happens when you haven't yet realized that brass grows during sizing and shrinks at some point before reloading, particularly possible when you don't reload for necked cartridges in rifles and are not mindful of different factors in play there. In other words, ignorance becomes wisdom at some point.
 
I always trim after sizing , why would you trim first then size which would change the length. To get the proper roll crimp on revolver cases the length must be the same . I have had the pilot on the cutter feel pretty tight probably do to case thickness , try some dry lube inside the necks , I see no harm in shaving down the pilot then polish.
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Yes, it all seems so logical, doesn't it? To get a uniform roll crimp on a straight walled revolver case, all of the cases MUST be the same length. I found this out a long, long time ago, when some case mouths barely crimped at all, while others rolled clear up under the crimping ledge in the die and distorted when I forced the ram through its stroke.

Hmmm...said I. What ever could be the problem? Then, I had a revelation! Why, all of these cases must need to be the same length! I had a new and profound understanding of physics. I was proud of myself. I began to resize and then trim, and life was good.

:D
 
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