Inconsistent trim lengths
- Thread starter Chernobyl
- Start date
Ledd Slinger
Silver $$ Contributor
I only trim cases after FL sizing. Fired cases can have too many dimensional inconsistencies.
Ledd Slinger
Silver $$ Contributor
I have had issues with more expensive trimmers as well. Ive had the Wilson, Redding, Forster, etc...I gave up on trying new trimmers and went back to what I first started with, the RCBS Trimpro. I have multiple Trimpros now and they aren't expensive or anything fancy but the simple fact is they work, are easy to adjust, and they are consistent. Always have been.
I remove the handles and chuck the cutter shaft up in my cordless drill make things go faster. Lube the cutter shaft with 'Hobo Oil'. All case trim lengths are within .001"
Dusty Stevens
Shiner
The case holder has nothing to do with trim lengths. You can let it fall in or beat it in with a hammer itll trim the same length. Try cutting the brass then rotating the case holder a bit and keep trimming. If your bolt face isnt square this will get them all the same.
I have my father in laws Wilson trimmer that he bought in the early 60's.I don't see how any other trimmer could be any more precise. I never see more than .0005 variation if that.
I'm thinking out loud here, so bear with me as I work though this because I fail to see the wisdom of using a cutting tool that references the case base to establish neck length relative to shoulder (datum).
I know it's convenient to measure OAL of the cartridge case by referencing the case base to mouth dimension however, that dimension is irrelevant to proper fit of the case neck in the chamber since the chamber uses the shoulder as a stop (belted cases the exception). By measuring the case base to datum (headspace) and subtracting from OAL, we can arrive at the dimension of shoulder to mouth, and therefor how much gap there is between the case mouth and chamber end. This tells us the likelihood of carbon ring development, or in a worse case, pinching a bullet if the neck extends into the throat. But this dimension is impossible to know, even if looking at a print for the simple reason that no standard exists for tooling used to measure case base to datum "headspace".
So for example one can set back the shoulder by some extreme amount, cut the OAL per spec and still end up with the likelihood of a pinched bullet and possible over pressure event.
However there does exist tooling to measure case shoulder to end of chamber dimensions, some sold in stores, some home made. But they seem to be a rarity, more than a standard tool in hand loading.
I cut all my cartridge case mouths to length using a cutter that references the shoulder, such as the Worlds Finest Trimmer or the Worlds Cheapest Trimmer because they are accurate, fast and produce a consistent dimension between the case shoulder and case mouth. A personal preference perhaps, and depends upon correct sizing of the case beforehand to do its job properly. I use the chamber as a go, no-go gage for correct cartridge fit by measuring a piece of brass that chambers with a stiff bolt drop.
So unless we perform a chamber cast before installing a new barrel, or buying a chamber length tool for each chambering we shoot, are we just guessing that we're doing it correctly? Do we spend good money on tooling that really is only producing random sized cases?
I hope this didn't read as being too pedestrian. I tend to overanalyze, especially when my head feels like it's about to explode from a migraine.
I'll go take a pill, come back later and perhaps edit the post.
I know it's convenient to measure OAL of the cartridge case by referencing the case base to mouth dimension however, that dimension is irrelevant to proper fit of the case neck in the chamber since the chamber uses the shoulder as a stop (belted cases the exception). By measuring the case base to datum (headspace) and subtracting from OAL, we can arrive at the dimension of shoulder to mouth, and therefor how much gap there is between the case mouth and chamber end. This tells us the likelihood of carbon ring development, or in a worse case, pinching a bullet if the neck extends into the throat. But this dimension is impossible to know, even if looking at a print for the simple reason that no standard exists for tooling used to measure case base to datum "headspace".
So for example one can set back the shoulder by some extreme amount, cut the OAL per spec and still end up with the likelihood of a pinched bullet and possible over pressure event.
However there does exist tooling to measure case shoulder to end of chamber dimensions, some sold in stores, some home made. But they seem to be a rarity, more than a standard tool in hand loading.
I cut all my cartridge case mouths to length using a cutter that references the shoulder, such as the Worlds Finest Trimmer or the Worlds Cheapest Trimmer because they are accurate, fast and produce a consistent dimension between the case shoulder and case mouth. A personal preference perhaps, and depends upon correct sizing of the case beforehand to do its job properly. I use the chamber as a go, no-go gage for correct cartridge fit by measuring a piece of brass that chambers with a stiff bolt drop.
So unless we perform a chamber cast before installing a new barrel, or buying a chamber length tool for each chambering we shoot, are we just guessing that we're doing it correctly? Do we spend good money on tooling that really is only producing random sized cases?
I hope this didn't read as being too pedestrian. I tend to overanalyze, especially when my head feels like it's about to explode from a migraine.
I'll go take a pill, come back later and perhaps edit the post.
i use the Wilson and hand hold the shellholder. what i found
by applying hand pressure it varies with each case and i get varying lengths. difference between .002 not extreme but not good enough.
Fix
I turn the shellholder 180degress and trim again this has reduced varying lengths to less than .001.
Upgrade.
I got REALLY tired with the hand crank, sinclair sells a carbide cutter which you can connect to a power drill. Much more consistent and faster.
I don't see the carbide cutter, found an adaptor for OEM cutter
https://www.brownells.com/reloading...paign=itwine&utm_content=749-002-495&psize=96
all the best
Trevor
by applying hand pressure it varies with each case and i get varying lengths. difference between .002 not extreme but not good enough.
Fix
I turn the shellholder 180degress and trim again this has reduced varying lengths to less than .001.
Upgrade.
I got REALLY tired with the hand crank, sinclair sells a carbide cutter which you can connect to a power drill. Much more consistent and faster.
I don't see the carbide cutter, found an adaptor for OEM cutter
https://www.brownells.com/reloading...paign=itwine&utm_content=749-002-495&psize=96
all the best
Trevor
Last edited:
A Wilson case gage helps determine when to trim as well as headspace.
I use hand pressure as well, haven’t noticed any difference in length after trimming, perhaps I’ll check them again.
No micro adjust either I insert a measured case adjust the cutter to touch while holding a feeler gauge at the handle stop to set the amount I wish to trim off and tighten the set screw.
Just me of course
J
I use hand pressure as well, haven’t noticed any difference in length after trimming, perhaps I’ll check them again.
No micro adjust either I insert a measured case adjust the cutter to touch while holding a feeler gauge at the handle stop to set the amount I wish to trim off and tighten the set screw.
Just me of course
J
Any time I see someone refer to consistent hand pressure being used, it cannot be precise, except possibly for a life long machinist.
I have the Wilson and have found that if there is the slightest inward hand pressure on the crank handle, it is going to trim more off. It isn't much and I don't let it bother me anymore. Are there any machines with a 100% hard stop that is not adversely affected by variable hand pressure?
I have the Wilson and have found that if there is the slightest inward hand pressure on the crank handle, it is going to trim more off. It isn't much and I don't let it bother me anymore. Are there any machines with a 100% hard stop that is not adversely affected by variable hand pressure?
Hand pressure puts pressure on the cutter edges. Material deflects when the thin sharp edge hits it.
Like a lathe. Cut too fast and deep and the surface suffers. Carbide cutters cut with less pressure than tool steel.
Stone grinding puts less pressure on the surface because it is spread out.
Then you are faced with stone dressing and grit capture in soft metals.
Ease off the pressure towards the end of cut. Let the cutter do the work.
Like a lathe. Cut too fast and deep and the surface suffers. Carbide cutters cut with less pressure than tool steel.
Stone grinding puts less pressure on the surface because it is spread out.
Then you are faced with stone dressing and grit capture in soft metals.
Ease off the pressure towards the end of cut. Let the cutter do the work.
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