Is There Room for a Little Error on Max Case Length?

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Glen

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I know, don't go over. But sometimes when I'm trimming cases, I find one that is long enough to make me think it was too long when I fired that particular round. I know it's a pressure issue, but I also wondered if there was a little room for error or fudging allowed. Now, I hate to use that word fudging when it comes to what is supposed to be precise measuring, but I wondered if there was any safety built into the system to where being a little long was not the end of the world (or the gun, or my face).
 
I've had the same thought after trimming some once fired HXP. There's no way they were not over max length before firing. I'm sure it depends on the firearm, chamber, projectile, and load, but in general I'd say there's some leeway.

Think of all the people who reload 5.56 and look confused when you ask them how often they have to trim. :D
 
There are tolerances involved for everything. It would be better to trim a case too short than have one so long the mouth is further crimped being stuffed into the lead. The latter is going to raise pressures the former, you might not even notice.
 
The specs call for "MAXIMUM" case length. It is pretty common to trim them enough shorter than maximum so that you can get more firings before they need trimming again. If you always leave them right at the maximum length you'll end up trimming every time.
 
Yes there is room for fudging. Its no different than Max COAL. Though measuring max case length allowances would require a chamber cast unless there's a better way.
 
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In regards to bottle neck cartridges. Assuming head space is correct one danger of overlong case, excess length being the neck, will place the seated bullet into the leade of the chamber. This could result in the neck being pinched and increased chamber pressure. In an auto loader, pump or lever action the round won’t chamber. In a bolt action it’s possible to chamber the round. Chamber a round and examine the bullet for signs it’s engaging the riffling.

In rimless straight wall pistol cases a long case can result in slam fires or a failure to chamber. A short case can result in the case headspacing on the extractor. Extreme results but possible. At any rate it’s just good house keeping and safety practice to monitor ones brass.
 
There usually is a bit of room for error, but it will depend on the reamer used. I was curious, so I bought the 30 cal. case length spud from Sinclair to see what the max case length is on two of my 308 bolt guns. Max. case length for 308 Win. is 2.815".

On my Remington factory rifle, the length measured was 2.845". My custom reamer 308 measured 2.840".

If you really need to know. measure it.

Maximum Cartridge overall length and maximum case length are two different measurements which have nothing to do with one another.

Maximum Cartridge length will usually give the maximum length in which the cartridge will fit into a magazine. The issue with bullet ogive engaging the rifling is another measurement that could be over or under the SAAMI maximum depending on the throat length of the chamber reamer used. Usually, factory chambers have leads that are long. Cartridge / bullet length / ogive to lands is another measurement to be considered when hand loading.
 
Many years ago now, I owned a Winchester M70 in .243. It was a tack driver, and I really enjoyed shooting it. I had developed an H4350 load for it that was a bit under listed max that always delivered sub MOA groups, and it was just easy. Then one day, I had a shot that vented through the receiver and when ejected had blown the primer. That spooked me, but after checking out the gun, I fired another that did the same thing. I was done for the day, and completely shaken by the experience.
I began to try to figure out what went wrong with my "standard" load. I took reloads apart. I reweighed charges. I measured bullets. Finally, I measured cases.
I had not paid much attention to the number of times cases had been reloaded. (error) I had not measured case length. (error) I had never done the paperclip test to check for incipient case head separation. (error)
When I did finally measure case length, I found a number of cases that were way too long. I cut a couple of them in half lengthwise and discovered the dip in case wall thickness indicative of case stretching and eventual case head separation.
Since then, I always keep track of number of reloads. I always measure case length and trim as necessary. I also don't full length resize all the time.
Bottom line: Yes, cases that are too long can an will eventually let you know, and it may very well scare the hell out of you.
Be safe.
 
Ummmmm What caliber??. Rifle or Pistol??

Th length of just the brass or the length of the loaded cartridge (to avoid mis communication COL COAL etc etc

"We seek perfection here!";)
 
I usually trim my cases around 0..015" because I don't want the case neck being pinched in the throat. You can see the clearance I have in this Sheridan cartridge case headspace gauge. It has been cut with a SAAMI minimum chamber reamer. So it is dimensionally exact to a SAAMI minimum rifle chamber.

XOHUEzE.jpg

Let that case length approach that chamber throat and you will be blowing primers! Sort of like the dog chewing on the powder cord, you will eventually figure out why you should not be doing that.
 
Yes there is usually some wiggle room on case length. The trick as Klausman has pointed out is recognizing the signs. When the case neck gets so long that it runs up on to the barrel leade (the leade is basically a milled ramp to the lands in the barrel) you’re gonna start having pressure problems. I’ve been reloading for better than 50 years. Some of the old reloading manuals instructed you to shoot the case until you start to see a “disturbance” on the case mouth. This would be caused by the case stretching to the point that the mouth of the case made contact with the leade and set up a burr on the case mouth. Problem is that not all barrels and leades are created equal. Some of the older Tikka barrels had leades that were the longest I’ve ever seen and therein lies the problem. There’s only so much room in a rifle barrel. Start imposing the case neck between the bullet and the barrel leade and the initial pressure signs may easily get over looked. For example: Is that flattened primer caused by pressure or a primer pocket that’s just a bit lose? When I shot competitively I had a friend that let his cases get so long that he actually peened a ring in the leade of a National Match M1 Grand. When you start peening nickel steel with a jacketed bullet and a brass case that should give you an idea about the pressure we’re talking about. All was well until that rifle started ripping case necks off the cases and blowing the op rod off the rifle. Cliff never was one to give up on a rifle barrel. He just trimmed his cases 10 thousands of an inch below minimum and went on to win the 30 Caliber Championship at Camp Blanding that year with that rifle. But there is the issue.

Trimming cases is my least favorite thing in reloading. That said accuracy in reloading is directly related to consistency. The more variables you can eliminate the better. I trim my cases to minimum if I only find one in a box of 50 that’s too long. I just loaded 50 rounds of 30-30 yesterday. I had a variance of 6 to 7 thousands of an inch in that box, but none of the cases exceeded the maximum length. I trimmed the entire box to 3 thousands below minimum (the length of my shortest case). Why? Consistency. Those cases all have to be crimped and I want my crimp pressure as consistent as I can get it case to case. If you’re gonna take the time to reload your ammo, take the time to make the best possible rounds that you can. Pay attention to the small details and eliminate as many of the variables as you can. It’s worth the effort.
 
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whatnickname said:
Yes there is usually some wiggle room on case length. The trick as Klausman has pointed out is recognizing the signs. When the case neck gets so long that it runs up on to the barrel leade (the leade is basically a milled ramp to the lands in the barrel) you’re gonna start having pressure problems. I’ve been reloading for better than 50 years. Some of the old reloading manuals instructed you to shoot the case until you start to see a “disturbance” on the case mouth. This would be caused by the case stretching to the point that the mouth of the case made contact with the leade and set up a burr on the case mouth. Problem is that not all barrels and leades are created equal. Some of the older Tikka barrels had leades that were the longest I’ve ever seen and therein lies the problem. There’s only so much room in a rifle barrel. Start imposing the case neck between the bullet and the barrel leade and the initial pressure signs may easily get over looked. For example: Is that flattened primer caused by pressure or a primer pocket that’s just a bit lose? When I shot competitively I had a friend that let his cases get so long that he actually peened a ring in the leade of a National Match M1 Grand. When you start peening nickel steel with a jacketed bullet and a brass case that should give you an idea about the pressure we’re talking about. All was well until that rifle started ripping case necks off the cases and blowing the op rod off the rifle. Cliff never was one to give up on a rifle barrel. He just trimmed his cases 10 thousands of an inch below minimum and went on to win the 30 Caliber Championship at Camp Blanding that year with that rifle. But there is the issue.

Trimming cases is my least favorite thing in reloading. That said accuracy in reloading is directly related to consistency. The more variables you can eliminate the better. I trim my cases to minimum if I only find one in a box of 50 that’s too long. I just loaded 50 rounds of 30-30 yesterday. I had a variance of 6 to 7 thousands of an inch in that box, but none of the cases exceeded the maximum length. I trimmed the entire box to 3 thousands below minimum (the length of my shortest case). Why? Consistency. Those cases all have to be crimped and I want my crimp pressure as consistent as I can get it case to case. If you’re gonna take the time to reload your ammo, take the time to make the best possible rounds that you can. Pay attention to the small details and eliminate as many of the variables as you can. It’s worth the effort.
Click to expand...
Wisdom of the ages. :)
The last three sentences pretty much sums it up.
 
Since the 6 Dasher is fairly new and there are no SAMMI specs, I wanted to double check how long the chamber/neck was in mine. I made a little "gauge" that would slip into a sized case with much of the neck cut off with a second diameter of .268. I meant to go .270, but missed. My chamber is supposed to be .272. Since my neck OD with a bullet seated is right at .268, .268 should be fine.

The Dasher should have a max length of 1.560 and a trim length of 1.550 from all I have read.

I chambered my little gauge in the modified case a handful of times and kept getting 1.559 +/-, so I know if I stay under that I will be OK. That means I need to trim to 1.550 so when the cases stretch on firing a little they will stay under that number. 1.550 was my plan, but this verifies that it will be good.

The pic was taken before I chambered it, so it is long here.
6 Dasher Neck Gauge Pic 1 @ 50%.JPG

Someone used to make and sell these things (No, I didn't invent them), I need to do some searching and see if they can still be bought.

IIRC, they were used with a split neck case. I'll look around the net for them.
 
That's a very easy to to check your chamber's throat length. Did not know those existed. But like you a simple task on a lathe.

Did you turn the OD to match the bullet dia? So you get a tight fit.
 
Well, I sure appreciate all the info. Yes, I was talking specifically about the case length, not OAL. Also, I was asking about both handgun and rifle. Good info. I really like this forum and the good people in it. Thanks.
 
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