Trim length in custom chamber
- Thread starter Worker
- Start date
John Kielly
Shari's fan club
If the length of a case is such that it crushes into the throat of a rifle upon loading, then pressures are liable to be erratic & excessive & liable to cause inaccuracy, the risk of ruptures or blowups.
Case trimming specs are calculated to permit safe usage of firearms by avoiding such issues. Thus, you'll find loading manuals recommend trimming cases when they grow to a specified length. Those recommendations also include a standard minimum length to trim to. The manual I have on my computer bench doesn't have your cartridge included, but the parent .284 case is shown with an OAL of 2.170" & a trim to length of 2.160".
I can't figure any easy way to determine what case neck length you might have (other than refer to the reamer specs), but even that or a chamber cast isn't going to find you an OAL. On that basis, I'd be inclined to the theory that .005" off the end of the chamber is better than who knows what off the end of the chamber, riskwise, & trim to 2.170".
Case trimming specs are calculated to permit safe usage of firearms by avoiding such issues. Thus, you'll find loading manuals recommend trimming cases when they grow to a specified length. Those recommendations also include a standard minimum length to trim to. The manual I have on my computer bench doesn't have your cartridge included, but the parent .284 case is shown with an OAL of 2.170" & a trim to length of 2.160".
I can't figure any easy way to determine what case neck length you might have (other than refer to the reamer specs), but even that or a chamber cast isn't going to find you an OAL. On that basis, I'd be inclined to the theory that .005" off the end of the chamber is better than who knows what off the end of the chamber, riskwise, & trim to 2.170".
Bob Kingsbury
New member
You can find in the sinclair catalog a gage that will allow you to measure
a very close case length. They are not expensive. Used gently as they are
made of steel. You will have to shorten a case first. I make my own from
brass and make the diameter .001 under forward neck diameter. If
you can make one, be sure not to chamfer the end, just break the edge.
a very close case length. They are not expensive. Used gently as they are
made of steel. You will have to shorten a case first. I make my own from
brass and make the diameter .001 under forward neck diameter. If
you can make one, be sure not to chamfer the end, just break the edge.
Butch Lambert
Active member
If you knew your reamer specs, your problem would be solved.
Butch
Butch
You can even make your own gauge using a bullet and the cartridge neck if you're wicked cheap 
Like I'm
al
http://www.benchrest.com/forums/attachment.php?attachmentid=7052&d=1233285377
This pic is from an old post http://www.benchrest.com/forums/showthread.php?t=58805&highlight=6X47&page=2 where entry #48 shows the cutoff wheel used.
Like I'm
al
http://www.benchrest.com/forums/attachment.php?attachmentid=7052&d=1233285377
This pic is from an old post http://www.benchrest.com/forums/showthread.php?t=58805&highlight=6X47&page=2 where entry #48 shows the cutoff wheel used.
Trim to length
wORKER =
HOWDY !
I shoot wildcats that I form myself.
I myself always try to trim to exact case length that I chose in the initial design.
Same method for a factory case would be ( .22-250 used as example )
trim the .22-250 to 1.912" case case oal.
There's a reason why powder case trimmer ( and manual ones ) can be had, which are used to trim case oal.
Some cases don't stretch much during firing ( some barely at all ), so case oal trim for these is no big deal.
With regards,
357Mag
wORKER =
HOWDY !
I shoot wildcats that I form myself.
I myself always try to trim to exact case length that I chose in the initial design.
Same method for a factory case would be ( .22-250 used as example )
trim the .22-250 to 1.912" case case oal.
There's a reason why powder case trimmer ( and manual ones ) can be had, which are used to trim case oal.
Some cases don't stretch much during firing ( some barely at all ), so case oal trim for these is no big deal.
With regards,
357Mag
Nor Cal Mikie
Active member
Either buy or make yourself a "modified" case and plug to get the actual chamber length. Once you know that measurement, you'll know when the cases need to be trimmed. Sure saves a lot of work when you know you've still got .080 till the cases need trimming.
Bob Kingsbury
New member
You can make a quick estimation by adding a drop of candle wax to
a case with a seated bullet.Clean and dry the case first and put a drop of wax
at the bullet case mouth junction. You can readily see a difference where
the case stops and the chamber neck ends. This is a quick check only.
a case with a seated bullet.Clean and dry the case first and put a drop of wax
at the bullet case mouth junction. You can readily see a difference where
the case stops and the chamber neck ends. This is a quick check only.