Why is the overall case length so important? If you are trimming the neck, isnt this just changing how far down in the neck the bullet is seated? It seems to me, and for what it is worth do not know anything about reloading,that the important measurement would be the length from the back of the case to the neck.

Educate me please!

h181, the only time I trim necks is when they grow up to max case length according to SAAMI specifications. If the case grows enough it will impinge the bullet and cause a serious over-pressure episode. My friend did exactly that with his tight chambered 300WSM ( I think all WSM are tight chambered in my limited experience with them). I find that keeping the necks as long as possible enhances accuracy but I don't go to the inconvenience of performing exacting measurements of my rifle chambers. All dimensions of the case are important especially to extended case life.

The most important measurement is the length of the case from the base to the datum line on the shoulder, which is the headspace measurement and insures that your ammunition fits your rifle's chamber.

Overall length is the distance to from the case head to the tip of the bullet and is controlled by the bullet seating die. This does a coupe of things:

It insures that your loaded rounds fit in your magazine (in a repeater).

It controls how close to the lands in the barrel the bullet is. If you get to long and jam the bullet into the lands, chamber pressure goes up quickly. If you have a long distance to the lands the pressure is lower but usually accuracy suffers.

Also if the overall length is to short and the bullet is pushed deeply into the case it reduces the cartridge powder capacity.

Get a copy of a Hornady reloading manual. It explains it very well.

quote:

Originally posted by aliveincc:
Get a copy of a Hornady reloading manual. It explains it very well.

This

The man asked about case length not overall
length. Case length in pistol cartridges effects crimping. If too long the case mmouth can enter the lead (leed) and be forced against
the bullet which is what causes the pressure
rise.

Come on guys! The OP does not have access to the Hornady Manual he is not a reloader - so I'll give a brief description. Chambers are cut in steel barrels to a specified depth. This usually leaves a 'step' at the end of the chamber where the case mouth should be. If the rifle case is longer than specified, it can jam into this step when chambered and either prevent the action from closing all the way, or it can squeeze the case mouth into the bullet, increasing chamber pressures and even causing damage to the firearm. In most rifles, a case trimmed a bit too short is not a problem.

In many handguns the only thing which keeps the case from falling too deeply into the chamber is the case mouth hitting the step. If the case is too long the action may not close. If the case is too short it may fall so deeply into the chamber that the firing pin may not hit it with enough force - resulting in a failure to fire. With rimmless handgun cartridges like the 9mm, .40S&W and .45ACP, the overall case length usually must be within a narrow specified range in order for the handgun to perform reliably. With rimmed cases, the case length needs to be within a narrow range to insure uniform crimping. Non-uniform crimping will cause erratic pressures, velocity and accuracy.

Hawkins above is kinda right about crimping with rimmed cases, but he means leade, not lead. The leade actually refers to the end of the rifling, not to the 'step' at the end of the chamber. The leade will not cause the case mouth to be crimped onto the bullet, but the 'step' will.



.

Pretty good laymen's term explanation.

What TX Nimrod said. Chamber and Cartridge info here. > SAAMI

Well, I got confused there with overall length and references to the neck. I was thinking rifle cartridges.

Thanks for all the help guys!

Sorry, I should have been more specific. I am referring to rifle cartridges. I am reloading for my 270 WSM if that makes a difference.

Overall case length becomes a problem if the cartridge length starts to exceed you actual chamber length. When this happens the chamber starts pinching/crimping the case onto the bullet. This can cause pressures to rise rather dramatically. The question that needs to be answered is how long is your actual chamber? This can be measured with some fussing around. In my experience most factory chambers are at least as long as the listed max. oal. Custom chambers should be checked.
C.G.B.

So should I seat the bullet a little less (.005 - .010) than the listed overall case length?

quote:

Originally posted by heilman181:
So should I seat the bullet a little less (.005 - .010) than the listed overall case length?

Case length has nothing to do with OAL (over all length).
Case length is just that, from the base (where the headstamp is) to the mouth (the hole you stick the bullet in). This has 3 listed lengths, Max, Trim to, and Minimum. As a rule max and min are .020" apart with the "Trim to" length being 1/2 way between the 2.

OAL is from the base to the tip of the bullet. The manual listed OAL is at or shorter than SAAMI spec (light bullets and those with very blunt noses are shorter).

Stop.
You have been given some great info,but seem to not have a good handle on the subject yet.
You need to do more reading and studying.
Better yet find a mentor.
In your last post you confused the terms case length and overall cartridge length. The depth of bullet seating is (to the most part) controlled by the OVERALL CARTRIDGE LENGTH as listed in the loading manuals.
The MAXIMUM/MINIMUM CASE LENGTH is (to the most part) independent of the CARTRIDGE OVERALL LENGTH.
Changing the seating depth can raise (or lower) the chamber pressure.
Hope this helps some.

muck

If the smaller chamber diameter in front of
the case isn't part of the lead (leed,lede..)
then what is it?, a "Taint" ?.

Quote "If the smaller chamber diameter in front of
the case isn't part of the lead (leed,lede..)
then what is it?, a "Taint" ?."

Could be---or, depending on measurement, it might be "free-bore".

quote:

Originally posted by muck:
Stop.
You have been given some great info,but seem to not have a good handle on the subject yet.
You need to do more reading and studying.
Better yet find a mentor.


muck

I have to agree with this. You are at a point where a very small misunderstanding can lead to a very sad event. Asking these questions on any forum is better than nothing but as you can see, often questions are misunderstood or even answered incorrectly by well meaning people.

quote:

Originally posted by Tailgunner:

quote:

Originally posted by heilman181:
So should I seat the bullet a little less (.005 - .010) than the listed overall case length?

Case length has nothing to do with OAL (over all length).
Case length is just that, from the base (where the headstamp is) to the mouth (the hole you stick the bullet in). This has 3 listed lengths, Max, Trim to, and Minimum. As a rule max and min are .020" apart with the "Trim to" length being 1/2 way between the 2.

OAL is from the base to the tip of the bullet. The manual listed OAL is at or shorter than SAAMI spec (light bullets and those with very blunt noses are shorter).

Sorry, I did not intend to confuse the two. I do not have my own reloading equipment. I have been using a friends with him there too. I am asking because some of the rounds that we reloaded last resulted in the bolt closing tight. They shot fine, but I am not comfortable with it so I am trying to figure out what I need to change.

Is this due to OAL or COL causing this?

Most likely neither. I'm assuming you measured the sized cases to make sure that they are under the max length, and that you kept the OAL at the manuals spec for those bullets.

Was the brass originally fired in a different rifle?

Use a magic marker and "color" one of the hard closers at the following places. Bullet, mouth and neck, shoulder and around the base. Chamber the colored round and after extracting (unfired) and examine the marking for rubbing.

Personally I'm betting on either a little shoulder rub or base rub. The cases may also be slightly out of round at the base (due to the chamber they were originally fired in)

Laymans answer:

If the case is too long it will jam in the barrel and blow up and you'll be #@&% 'd.

If the bolt is a bit too hard to close then the case has not be squeezed down enough (re-sized) or the bullet is sticking too far out.

Code 4 is probly right. You should always full lenght resize any brass that was not fired in your rifle. Once it has been fired in your rifle (this is called fire lapping) you can neck or partical resize your brass for more accurate rounds. Your friend should understand this if not you need to find someone to help both of you. Reloading is fun but guessing will get someone or worse an innocent gun hurt

quote:

Originally posted by mdvjrp93:
Code 4 is probly right. You should always full lenght resize any brass that was not fired in your rifle. Once it has been fired in your rifle (this is called fire lapping) you can neck or partical resize your brass for more accurate rounds. Your friend should understand this if not you need to find someone to help both of you. Reloading is fun but guessing will get someone or worse an innocent gun hurt

Some of the advise given is just plain wrong and leading to more confusion for not only the OP but others who may be trying to learn a thing or two. In this forum a very careful check of what you have written should be undertaken before hitting the post now button.
_______________________________________________________________________________________________________________________
TX Nimrod was as clear as need be and others are just muddying the waters of his simple and clear explanation.
Come on guys! The OP does not have access to the Hornady Manual he is not a reloader - so I'll give a brief description. Chambers are cut in steel barrels to a specified depth. This usually leaves a 'step' at the end of the chamber where the case mouth should be. If the rifle case is longer than specified, it can jam into this step when chambered and either prevent the action from closing all the way, or it can squeeze the case mouth into the bullet, increasing chamber pressures and even causing damage to the firearm. In most rifles, a case trimmed a bit too short is not a problem.

________________________________________________________________________________________________________________________


Now heilman 181 has said---

Sorry, I did not intend to confuse the two. I do not have my own reloading equipment. I have been using a friends with him there too. I am asking because some of the rounds that we reloaded last resulted in the bolt closing tight. They shot fine, but I am not comfortable with it so I am trying to figure out what I need to change.

That could be one of three areas to check. The case length the sizing of the case or the overall length of the loaded cartridge.
How experienced is the friend who is overseeing this reloading? He shoild be capable of understanding and checking each of these areas.

All brass was ONLY fired from my Tikka T3 270WSM. All brass was processed through the resizing die, but some resulted in hard both lock and the others bolted just fine. The OAL was within specs listed in reloading manuals. Now there was a different length based on bullet type and we loaded Barnes TSX 130 grain bullets. If I recall correctly, we went off the PSP length and not BT length.

The case mouth needs to be trimmed back enough so it does not contact the chamber where it reduces in diameter at the "freebore throat lead"

That is your CASE OVERALL LENGTH


The distance from the case head to the bullet tip is the CARTRIDGE OVERALL LENGTH and it must be set so that you have "free-travel clearance jump" so the bullet ogive is not into the lands

A picture really is worth a 1000 words!

THANK YOU!