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case length - how critical?
Discussion regarding the reloading of ammunition and tuning of loads for accuracy
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twofifty
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PostPosted: Tue Feb 12, 2008 11:37 pm    Post subject: case length - how critical? Reply with quote

As you guys know, I am new to reloading, having reloaded some 200 rounds thus far using a friend's equipment. Now I have my own setup. I am mystified by this business of case length and deciding when the case has grown such that it needs trimming.

Here are the numbers:

Was measuring cases that I shot 3 times (commercial ammo shot then reloaded 2x by me to moderate velocities) in the same rifle and decided to mike the case length...

Here is how these Winchester 22-250 cases grew, from the time I started keeping notes:

1.908" to 1.915" after 1st firing, before FL resize.
1.918" is the average length after 3rd firing and FL resize.

Since SAAMI case length is 1.912", my brass is now 6 thou over on average. Hmmmm.

At what length should I trim these to the recommended trim-to length of 1.902"? When the case reaches 1.920?

I don't know the size of my chamber other than bullets are set before the lands (should have written down how much the jump is but did not).

With each reload, I set the bullet so that COL averaged at 2.450", with length varying somewhat depending on bullet length. SAAMI says that 2.350 is the max COL allowable. Hmmmm.

It seems that for my particular chamber, the optimum COL is greater than that called for by SAAMI. Is this unusual? I read somewhere that Remington chambers can be on the long side.

Finally, would the purchase of a Lyman Headspace Gauge be helpful. Apparently, these help to determine whether a round meets headspace requirements as well as case length criteria. But if the headspace gauge is sized for SAAMI spec chambers, obviously, the rounds that group well when shot from my chamber will stick out of this gauge. ?? How are headspace gauges used anyhow? Gadget or useful tool?
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1895ss
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PostPosted: Wed Feb 13, 2008 12:05 am    Post subject: Re: case length - how critical? Reply with quote

If the case is too long then you could have a problem chambering the round. Minimum case length for 22-250 brass is 1.902" and MAXIMUM length is 1.912". So if your brass is longer then 1.912", it's time to trim it back to MINIMUM length which is 1.902". I would keep my brass between those measurements Smile

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PostPosted: Wed Feb 13, 2008 12:44 am    Post subject: Re: case length - how critical? Reply with quote

Just for consistency I trim all my cases, even new ones, at the first loading and then again when they reach the SAAMI max length. I think this is especially important for loads you are crimping, including revolver. I'm thinking that it would be equally important for auto pistol loads that headspace on the case mouth but I really haven't tested that yet.

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1895ss
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PostPosted: Wed Feb 13, 2008 1:08 am    Post subject: Re: case length - how critical? Reply with quote

As long as my brass is within specs I don't trim it, but If some in a batch go over then I trim the complete batch back to minimum specs. The only rounds that I crimp are for my .45-70 and my .35 Remington and to crimp those I use a Lee Factory Crimp Die and with it the brass doesn't all have to be exactly the same length for trouble free/uniform crimping.

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SingleShotLover
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PostPosted: Wed Feb 13, 2008 7:23 am    Post subject: Re: case length - how critical? Reply with quote

Pumpkinslinger; You are correct in thinking that cartridges that headspace on their mouths require consistent lengths. When you are looking for accuracy and dependability then length becomes critical and uniformity is mandatory.

I have also found that case length makes a difference in accuracy and velocity with crimped cartridges. Maybe it's only in my guns, but crimped cartridges in my 1911s, revolvers and 45/70s all shoot better with uniform lengths which also result in more uniform velocities.

Twofifty; Case length is critical from the aspect of safety as well. Cases that are too long can cause the case neck to be constricted in the chamber throat and will cause pressures to rise dramatically.

As to your COL being longer than spec...not unusual at all. You are on the right track by checking to see what the optimum length for your particular rifle is and loading accordingly. Some chambers are simply longer than others and the best accuracy is often with the bullets set as close to the rifling as safety permits. Only by trial and error will you find that "sweet spot" for your rifle.

Headspace gauges are interesting, but not really essential for the average shooter. As long as your chamber isn't grossly over-sized causing excess headspace there is nothing to worry about. As a matter of fact, you will find that your accuracy can be improved by adjusting your standard sizing die to not move the shoulder of your fired cases back to "spec". They then fit your particular rifle as snuggly as is possible. Just smoke a case neck and shoulder and adjust your die to just touch the shoulder of a fired case. This will provide a form of neck-sizing while keeping the shoulder from moving too far forward for proper chambering. This also squeezes the case body a bit which allows for ease in chambering.

Neck-size-only or collet-type dies can do the same thing, but the shoulder can continue to grow with them and you will eventually have to full-length size to get the cartridge to chamber easily again.

Do remember that cases that are neck-sized or sized as I outlined above will probably not fit another chamber well, so if you load for several rifles using the same cartridge you will either need to adjust the die for each rifle (a real pain) or just have a set of dies dedicated for each.

Good luck and stay safe.

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mikeleduc
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PostPosted: Wed Feb 13, 2008 7:57 am    Post subject: Re: case length - how critical? Reply with quote

You should trim them now, I trim mine the minute they go over the max listed in the book. What you may want to do is get a Stoney Point (or similar) OAL gauge so you can tell how far out you can seat the bullet. The length of the case is important because because you do not want to crimp the bullet into the case when you chamber a round, that raises pressure. You also don't want your bullet touching the rifling in the barrel.
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PostPosted: Wed Feb 13, 2008 9:32 am    Post subject: Re: case length - how critical? Reply with quote

1895ss...I have found that using the Lee FCD does require the cases to be the same length within +/-.002 to get consistent crimp on my revolver cartridges...Otherwise you get a short crimp or a long crimp...Whether it makes that much difference in accuracy? ? Confused ?

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PostPosted: Wed Feb 13, 2008 12:09 pm    Post subject: Re: case length - how critical? Reply with quote

Mike, I've never noticed that it makes much difference in my .45-70.

www.leeprecision.com/c...crimp.html

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Last edited by 1895ss on Wed Feb 13, 2008 12:15 pm; edited 1 time in total
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Bushmaster
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PostPosted: Wed Feb 13, 2008 12:14 pm    Post subject: Re: case length - how critical? Reply with quote

Like I said. It might just be me (I like uniformity, Military you know), but with the smaller calibres like .38 Special and .357 magnum it does seem to make a difference as to how much crimp surface is exposed...

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PostPosted: Wed Feb 13, 2008 12:54 pm    Post subject: Re: case length - how critical? Reply with quote

twofifty

How critical????????????
If the bullet is unable to release....................... pressure rises.......................

Max length minus .010 is the standard trim length. Most reloading manuals will show these numbers.

Always measure case length AFTER it has been resized. Cases will grow in length when they are resized. This is more so with large chambers when doing a true full length resize. The brass flows the less path of resistance, the case neck.

In my testing uniform lengths when crimping does make a difference.

As far as SAAMI specs on COL, this is sometimes confusing to new reloaders.
If your gun has a magizine you'll need to go by the SAAMI spec.
If you have a single shot or are gonna load only one at a time you can extend this dimenssion until the ogive of the bullet touches the lands in the rifling. However, if touching the lands be aware of pressure. Start low and work up

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chambered221
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PostPosted: Wed Feb 13, 2008 1:10 pm    Post subject: Re: case length - how critical? Reply with quote

I knew I missed something!!!!!!!!!!!!!!!!!

Trim them anytime you want when between MIN. and MAX.

The more you reload for a gun you will get to know it better, and when to trim your cases.

I have a gun that I can usually predict each firing will grow .002

I have another gun that no matter what I do I have to trim with each reloading.

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PostPosted: Wed Feb 13, 2008 1:22 pm    Post subject: Re: case length - how critical? Reply with quote

chambered221 wrote:

In my testing uniform lengths when crimping does make a difference.

What method do you use for crimping?


Bushmaster wrote:

1895ss...I have found that using the Lee FCD does require the cases to be the same length within +/-.002 to get consistent crimp on my revolver cartridges...Otherwise you get a short crimp or a long crimp...Whether it makes that much difference in accuracy? ? Confused ?

First of all I know nothing about pistol reloading cause I don't have one.

So do you trim your cases every time you load then? Some rifle cases could stretch more then others in the same batch and you could have more then a .002 difference in case length and as such would need trimming after each firing. I sure don't as long as they're within spec, that's why I use the Lee FCD cause case length uniformity is not as critical using the Lee fcd as with other crimp methods.

www.leeprecision.com/c...crimp.html

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chambered221
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PostPosted: Wed Feb 13, 2008 1:51 pm    Post subject: Re: case length - how critical? Reply with quote

I should have mentioned that my crimp testing was only done with pistols

Most test used a Lee factory crimp die.

In some tests I had to trim cases to a uniform length other test I had enough brass from the same batch that all I did was meassure a group of x amount that were within .002 of one another.

All accuracy testing was done at 25 yards for revolvers and 30 feet for auto loading pistols.

Velocity measurements all at 8 feet with a Pact model 1 chronogragh.

To ensure best possible readings over the chrono, befor each round was fired the gun was raised to a 45 degree angle and tapped on the side to ensure all powder was at the rear of the case. ( it makes a difference also)

In the end all test showed the same, uniform crimps are better.
Some only slightly better. My 45 ACP huge!!!!!!!!!!!!!!!!
In the 45, vel spread went from about 90 FPS to under 10 FPS and groups looked a whole lot better.

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PostPosted: Wed Feb 13, 2008 1:53 pm    Post subject: Re: case length - how critical? Reply with quote

I try to keep them trimed within +/-.002" of each other...I don't worry about .30-06 which I keep within low/high specifications and 9mm X 19 which I don't even worry about. .30-30 I keep with +/-.002" for crimping reasons...Along with .38 Special, .357 magnum. .45 ACP I trim at .893" because my Colts 1911 seems to prefer .890" to .892"

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PostPosted: Wed Feb 13, 2008 2:01 pm    Post subject: Re: case length - how critical? Reply with quote

I honestly haven't done any testing on case length verses crimp etc. with my .45-70 and I haven't had my .35 rem long enough to do much with it at all. The brass for my .45-70 is all with specified length but varies more than .002 and it shoots pretty good groups. Smile

Here's a 100 yard target.



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