I'm in the process of working up some hunting loads for my 220 Swift and I'm wondering just how important case length is in the overall process of obtaining the most accurate load that I can. I dont want to over trim and shorten the useful life of the brass but if it means the difference between a half inch group or a 3 tenths group then i will. I dont weigh my brass or do any neck work and I full length size. I've got Winchester, Hornady, R/P and Norma brass and I keep them separate when loading. Thanks for any help!!!
Importance of case length
- Thread starter jaytee
- Start date
Bill Norris
Back in the Day
Case length is important for safety reasons and it may be something accuracy could see if in the short range B R arena. Trimming cases to prevent them from being crimped in the chamber is a must. The case will grow especially if you are F/L re-sizing in time and at some point become longer than the chamber neck area which will cause the chamber crimp. This will increase pressure to a dangerous level. Performing a chamber cast will give you a true picture of the chamber and neck size and length.
Case length increases each time the brass is resized. If not trimmed, it can be a big problem bumping into a carbon ring, which can cause a spike in pressure. I'll trim my cases after every firing just to keep the length the same to be sure there's no change in the interference with the bullet's barring surface and neck surface and so that there's never any bumping into the carbon ring. The more the carbon ring builds, the more the probability of having a carbon ring issue. Of course, if one cleans out the carbon ring with every barrel cleaning, then that isn't likely to be an issue.
NorCalMikie
Gold $$ Contributor
Easier if you know the "measured length" of your chamber. Sinclair makes plugs to get that measurement. Got them for every caliber I shoot. 
With that measurement, you'll know when and if trimming is needed. Shoulder bump dies will also control case length . Full length dies with the neck button pull the neck longer with every up stroke. Somewhere along the line, full length or at least a body resize will need to come into play.
I've got BR brass with 20/25 resizes and still no trimming needed.
And most reamers cut to .020 longer than Max trim length.
Measure your brass and don't trim till needed.
With that measurement, you'll know when and if trimming is needed. Shoulder bump dies will also control case length . Full length dies with the neck button pull the neck longer with every up stroke. Somewhere along the line, full length or at least a body resize will need to come into play.
I've got BR brass with 20/25 resizes and still no trimming needed.
And most reamers cut to .020 longer than Max trim length.
Measure your brass and don't trim till needed.
JEFFPPC
Gold $$ Contributor
Too short will not hurt anything. Too long could get you severely injured. Few years back I trimmed some 6BRX cases way to short. This case already has a very short neck. The accuracy was not affected in the least. If you clean correctly you should have no carbon ring short or long. If you have a bore scope drill out the primer pocket so you can put the bore scope through it. Do this with the longest case you have. Now insert it in the gun, insert the bore scope thru it and you will see the end of the case and the end of the chamber. As long as the end of the case is within the chamber with a small bit of clearance you are good too that length. I find what that length is and trim to that number . Now if you trim to that number you must measure every loading and trim as needed. The advantage is it lessens the area where a carbon ring wants to form.
wow jeffppc what an awesome idea with the borescope. think ill try it.
Brownell's/Sinclair's have a chamber length tool that will give you and exact measurement as to how long the neck length is in your rifle. You'll probably need to sacrifice one case to use with this gizmo, but it will give an exact measurement on the neck length and when you need to trim cases.
JEFFPPC
Gold $$ Contributor
It is a good idea, one I can't take the credit for. A friend of mine who is a long time good shooter came up with the idea. When good shooters talk I listen then try what I learn from them out. If it helps I do it. If it doesn't I move on with my current process.
Last edited:
As others have said, case length can be a safety issue if the case become too long so it's important to monitor it.
As NorCalMikie said, a Sinclair chamber length gauge can measure the actual chamber length. Most rifles have a generous length thus you can reduce the amount of trimming necessary once you measure the length even with the Sinclair specified safety factor applied. I've reduced my trimming by about 90% since I began using this inexpensive and simple tool. Just don't forget to apply the safety margin Sinclair recommends.
As NorCalMikie said, a Sinclair chamber length gauge can measure the actual chamber length. Most rifles have a generous length thus you can reduce the amount of trimming necessary once you measure the length even with the Sinclair specified safety factor applied. I've reduced my trimming by about 90% since I began using this inexpensive and simple tool. Just don't forget to apply the safety margin Sinclair recommends.
PhilC
Silver $$ Contributor
I've used the Sinclair gauges for decades, every rifle has its own "trim to length" and ALL are longer than SAAMI "standard".
On any lot of brass I'll find the shortest and either trim the rest to it or my established trim length whichever is shorter.
If you have a Teslong bore scope just slip it through the muzzle and save a case.
On any lot of brass I'll find the shortest and either trim the rest to it or my established trim length whichever is shorter.
If you have a Teslong bore scope just slip it through the muzzle and save a case.
Ironman308
Gold $$ Contributor
My brass tends to grow inconsistently. So I measure several pieces and trim all to the shortest length. I use the same technique as Jeff to verify the brass is not too long.
Coyotefurharvester
Silver $$ Contributor
For hunting there really is no difference between .3 and .5 inch groups.
divingin
Gold $$ Contributor
If you have a Teslong bore scope just slip it through the muzzle and save a case.
I think he meant "Chamber a piece of empty brass and borescope from the muzzle" as opposed to drilling out the primer pocket on the brass and scoping from the chamber end. The borescope needs to be long enough to reach the mouth of the brass though.
257ack
Silver $$ Contributor
I can remember at a match that Wilbur Harris was shooting a shotgun pattern instead of a group. Now Wilbur was a tuff competitor and very unusual for him to have a bad group. Well, he finally figgered it was case length. I had a Wilson trimmer in my box and after he trimmed, he went back to kicking our butts
I turned inserts for my 260 and 22-250 that are the same diameter as the fired neck of the case, then turned them to the correct bullet diameter to fit in a case that has been shortened. The end is flat and they are a snug fit in the case mouth. I insert it long in the cut down case and chamber it. After carefully unchambering I measure from the base to the end of the insert. I'll take this measurement three or four times just to make sure I have a good number, then record it in my log.
divingin
Gold $$ Contributor
As an aside, for 6mm, you can use a 22Mag case with the rim turned down to your chamber neck diameter. Slip the body into your Hornady modified case, and add the Hornady OAL gauge tool and you've got a chamber length checker. I turn the rim down by chucking the 22Mag brass in a drill and lightly using a file.
JMayo
Silver $$ Contributor
I just go in the muzzel end and look.
JEFFPPC
Gold $$ Contributor
This begs a reply but I will refrain,lol.
6MMsteve
Gold $$ Contributor
if you have a bore scope you can chamber a case and chk the length with the scope to see case length issues, I'm lazy and try not to trim unless I must, but I don't shoot that much anymore, but it's a way to tell if your close to the danger zone, I see about everybody else has said the same thin
g
g
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.