Pistol brass of differing lengths

[NJdiverTony 27]

I was wondering if you guys with some good reloading experience can help with this question. I was reloading some 9mm and .45ACP ammo the other day and realized that my OAL was varying by a very small amount from load to load. So I was checking over my brass and found that since I have mixed brass (from different manufacturers), there is some small variation in the case lengths (+/- .007"). This is causing some of my ammo to come out with slightly different OAL's. Is this anything to worry about? The difference is pretty miniscule, but being the cautious guy that I am, I thought that I'd put the question out to you more seasoned reloaders and get your opinions. Do I need to trim my cases so they are all the same length? I have probably about 1500 empty 9mm cases... so I can't even imagine how long that would take... yikes! A friend of mine gifted me about 200 brand new 9mm cases, and these seem to be about .007" longer than the once fired factory ammo brass I have. Does new brass need to be trimmed?

 

P.S. I realize that theoretically, the small variance in case length should not have any bearing on your OAL... depending on the case length variance, the bullet should get seated either slightly deeper or shallower, but OAL should not change... but for some reason I am getting a small variance in OAL! If I group the brass that is of the same manufacturer, the OAL's of my loads match... but when comparing the loads from the different case manufacturers, side by side, there is a slight OAL difference. It really has me stumped and don't know what could be causing it.

[Pew Pew Plates 358]

case lenghth wont affect seating depth. Try loading a 380 case in your 9mm setup. it will be tough to start the bullet since the flare is set higher for 9x19, but if you seat the bullet it will be same length. your variation is just from movement in the turret and that amounts fine. dont bother trimming pistol. the reason the new stuff is longer is because a fired and unsized case is swollen. If the (acceptable) variation drives you crazy, you can always sort brass by headstamp. It will probably not eliminate your variation but maybe it will make you feel better

[NJdiverTony 27]

case lenghth wont affect seating depth. Try loading a 380 case in your 9mm setup. it will be tough to start the bullet since the flare is set higher for 9x19, but if you seat the bullet it will be same length. your variation is just from movement in the turret and that amounts fine. dont bother trimming pistol. the reason the new stuff is longer is because a fired and unsized case is swollen. If the (acceptable) variation drives you crazy, you can always sort brass by headstamp. It will probably not eliminate your variation but maybe it will make you feel better

 

Thanks, Glenn. Yeah, I contemplated sorting my brass by headstamp, but I decided that it would just take too much time. I am so anal about details and precision, so the variance in OAL was driving me nuts.

[njJoniGuy 2,133]

Thanks, Glenn. Yeah, I contemplated sorting my brass by headstamp, but I decided that it would just take too much time. I am so anal about details and precision, so the variance in OAL was driving me nuts.

You're not truly anal unless you sort by headstamp

[Pew Pew Plates 358]

You're not truly anal unless you sort by headstamp

 

 

guilty but only for target stuff (not blasting/idpa)

[Old School 611]

case lenghth wont affect seating depth. Try loading a 380 case in your 9mm setup. it will be tough to start the bullet since the flare is set higher for 9x19, but if you seat the bullet it will be same length. your variation is just from movement in the turret and that amounts fine. dont bother trimming pistol. the reason the new stuff is longer is because a fired and unsized case is swollen. If the (acceptable) variation drives you crazy, you can always sort brass by headstamp. It will probably not eliminate your variation but maybe it will make you feel better

 

 

If you are checking case length before sizing you are whistling in the wind. Case length ia only measured on a sized case, for the reasons you mentioned. Good catch Glenn!

 

And don't think all your bullets are perfect either...

[NJdiverTony 27]

If you are checking case length before sizing you are whistling in the wind. Case length ia only measured on a sized case, for the reasons you mentioned. Good catch Glenn!

 

And don't think all your bullets are perfect either...

 

OK, I'll have to check the cases out after sizing next time... just out of curiousity.

 

Oh and I know that bullets are not perfect... especially the LSWC's that I'm using for my .45 loads. They have a lot of variance in weight and length. They are Missouri Bullet Company 200gr LSWC's. The Montana Gold 124gr JHP's I'm using seem to be a bit more consistent.

[NJdiverTony 27]

So, is there a maximum acceptable variance in OAL when reloading? .01" ? More? Less?

[Old School 611]

So, is there a maximum acceptable variance in OAL when reloading? .01" ? More? Less?

 

 

For liability reasons, I don't think anyone will publish a variance.

 

Take a random sampling(you're going to collect your brass anyway) and check the primers for signs of overpressure.

 

When I'm picking up my practice spent casing I'm always looking at them.

[Pizza Bob 1,488]

You do not want your sized case length to exceed the maximum listed in your reloading manual(s). Theoretically, a rimless case headspaces on the case mouth. At maximum length it may actually be doing that. At lengths exceeding maximum it is definitely doing that and depending on how extreme the overlength is, it could actually prevent the gun going into battery.

 

In reality, as long as you are at maximum or below, it is headspacing on the extractor. Just check sized case length every now and then to make sure they haven't grown past maximum and you'll be OK.

 

Re: Variance in OA length: Glenn may be correct if you are using a turret press. Cases with thicker walls may offer more resistance during seating and the turret may flex the small variance that you're seeing. Other than that, I'm stumped, but wouldn't worry about it.

 

Adios,

 

Pizza Bob

[Old School 611]

You do not want your sized case length to exceed the maximum listed in your reloading manual(s). Theoretically, a rimless case headspaces on the case mouth. At maximum length it may actually be doing that. At lengths exceeding maximum it is definitely doing that and depending on how extreme the overlength is, it could actually prevent the gun going into battery.

 

In reality, as long as you are at maximum or below, it is headspacing on the extractor. Just check sized case length every now and then to make sure they haven't grown past maximum and you'll be OK.

 

Re: Variance in OA length: Glenn may be correct if you are using a turret press. Cases with thicker walls may offer more resistance during seating and the turret may flex the small variance that you're seeing. Other than that, I'm stumped, but wouldn't worry about it.

 

Adios,

 

Pizza Bob

 

 

Well there's a first time for everything Bob.

 

I can see the extractor holding a cartridge agaist the bolt face but I wouldn't call that headspacing on the extractor.

 

Flex in the turret causing difference in OAL? The turret is always in the same position for a given operation so turret flex should be the same and case thickness at the mouth is where we are working and the bell mouth die enters and sizes the ID of the mouth.

 

Sorry Bobby, I'm not with you on this one. I'm for bullet shape inconsistancy knockig off OAL. On jackets anyway.

[JonF 79]

Varying case length of mixed brass will have an effect not so much OAL, but the bullet seating position in the case. Since you're loading for semi-auto calibers that headspace on the case mouth, its important to develop a OAL value that works with your chamber. Guns with shorter chambers will generally have to seat deeper to avoid sticking the bullet into the rifling before its fully chambered. Since it headspaces on the case mouth, the dimension from case mouth to bullet tip will vary from the extremes of short to long brass. If you seating bullets specifically to a specific chamber as i do my CZ, i have to take in to account a sampling of case length data and seat to the lowest common denominator to avoid sticking one on a piece of short brass. You can build also a tolerance into your OAL but the deeper you seat, the more the pressure can potentially rise, especially if you're going pretty far already to account for a short chamber.

 

Case variation also affects crimp whereas longer cases will get crimped more and shorter cases crimped less for the same die setting. as long as its pretty much removing the bell, its ok though.

[Pizza Bob 1,488]

I can see the extractor holding a cartridge agaist the bolt face but I wouldn't call that headspacing on the extractor.

 

What else would you call it? Cartridges can headspaceon a belt, on the shoulder, on the rim, on the case mouth - in this instance it is headspacing on the extractor - or maybe to be more precise, the extractor groove. If the extractor is holding the cartridge against the breech, it's headspacing on the extractor. If it didn't, the firing pin would drive the case into the chamber until the case mouth contacted ridge in the chamber that on which it is supposed to headspace. If the distance was great enough, the primer may not ignite.

 

Flex in the turret causing difference in OAL? The turret is always in the same position for a given operation so turret flex should be the same and case thickness at the mouth is where we are working and the bell mouth die enters and sizes the ID of the mouth.

 

How would a variance in bullet shape affect OAL. The OAL is determined by the distance from the shellholder to the seating stem. A longer or shorter bullet would just seat deeper or shallower - OAL would be the same.

 

If a case has thicker walls it will offer more resistance to the bullet being seated. Yes, the expander button of the die is the same diameter regardless of wall thickness of the case, but as that expander button exits the case, there would be a degree of "springback" (metal has a certain amount of elasticity, or we wouldn't be able reload a case multiple times). The "springback" will result in a smaller inside case diameter and thus more resistance to bullet seating. That greater resistance may result in greater flex of the turret (wouldn't happen on a single stage press or one with a fixed tool head) thus increasing the distance from the shellholder to bullet seating stem. IIRC, we are only talking .007". I can't think of anything else that would account for the increase in OAL.

 

Adios,

 

Pizza Bob

[Socom 19]

You're not truly anal unless you sort by headstamp

 

 

i think that is the best way to keep oal near perfect in each of your hundred round make ups.. i will always and continually sort by headstamp its the SMART thing to do.. if your a real reloader

[Old School 611]

What else would you call it? Cartridges can headspaceon a belt, on the shoulder, on the rim, on the case mouth - in this instance it is headspacing on the extractor - or maybe to be more precise, the extractor groove. If the extractor is holding the cartridge against the breech, it's headspacing on the extractor. If it didn't, the firing pin would drive the case into the chamber until the case mouth contacted ridge in the chamber that on which it is supposed to headspace. If the distance was great enough, the primer may not ignite.

 

 

 

How would a variance in bullet shape affect OAL. The OAL is determined by the distance from the shellholder to the seating stem. A longer or shorter bullet would just seat deeper or shallower - OAL would be the same.

 

If a case has thicker walls it will offer more resistance to the bullet being seated. Yes, the expander button of the die is the same diameter regardless of wall thickness of the case, but as that expander button exits the case, there would be a degree of "springback" (metal has a certain amount of elasticity, or we wouldn't be able reload a case multiple times). The "springback" will result in a smaller inside case diameter and thus more resistance to bullet seating. That greater resistance may result in greater flex of the turret (wouldn't happen on a single stage press or one with a fixed tool head) thus increasing the distance from the shellholder to bullet seating stem. IIRC, we are only talking .007". I can't think of anything else that would account for the increase in OAL.

 

Adios,

 

Pizza Bob

 

 

Will respond tomorrow before wine.

[Shocker 151]

How are you measuring your OAL? If its with a caliper maybe YOU'RE the reason for variance (tipped ctg, pushing the jaws too hard)?

 

Maybe your primer is not seated flush or below?

[Vlad G 345]

Flex in the turret causing difference in OAL? The turret is always in the same position for a given operation so turret flex should be the same and case thickness at the mouth is where we are working and the bell mouth die enters and sizes the ID of the mouth.

 

Well not every turret is solid. For example the Dillon 550 tool head is floating, and that's on purpose. It is square, with the seating position diagonally opposed to the resize/deprime station. At the bottom of the stroke there is pressure on all die stations. I can imagine that if the resistance of depriming/resizing varies from case to case (because of brand, grit, primer pocket size and tension) then there could be a slight tipping of the tool head affecting the seating depth across the tool head. Of course it is also possible at the bottom of every stroke the tool head is fully flush against the upper lip of its channel an no tipping can possibly happen, but when you have a floating tool head I suspect some variation can and will happen based on its movement.

[Old School 611]

Plese understand I'm not being condesending and respect you as one of my few peers. We probably have a conflict in terms.

 

 

What else would you call it? Cartridges can headspaceon a belt, on the shoulder, on the rim, on the case mouth - in this instance it is headspacing on the extractor - or maybe to be more precise, the extractor groove. If the extractor is holding the cartridge against the breech, it's headspacing on the extractor. If it didn't, the firing pin would drive the case into the chamber until the case mouth contacted ridge in the chamber that on which it is supposed to headspace. If the distance was great enough, the primer may not ignite. The head space of the chamber of a rimless case is measured from the cartridge head to the shoulder of the chamber. So if the extractor is holding the case head against the bolt face the mouth of the case must be bearly or just short of contact with the chamber shoulder. Agreed?

 

How would a variance in bullet shape affect OAL. The OAL is determined by the distance from the shellholder to the seating stem. A longer or shorter bullet would just seat deeper or shallower - OAL would be the same. I've found variance in the shape of the nose(ogive)of bullets to vary the seating depth. Also if the seating ram/cup misaligns on the bullet slightly the depth could vary. Even prmium benchrest bullets vary slightly in shape enough to change OAL slightly. That's why the make ogive comparitors for benchrest shooters.If a case has thicker walls it will offer more resistance to the bullet being seated. Yes, the expander button of the die is the same diameter regardless of wall thickness of the case, but as that expander button exits the case, there would be a degree of "springback" (metal has a certain amount of elasticity, or we wouldn't be able reload a case multiple times). The "springback" will result in a smaller inside case diameter and thus more resistance to bullet seating. That greater resistance may result in greater flex of the turret (wouldn't happen on a single stage press or one with a fixed tool head) thus increasing the distance from the shellholder to bullet seating stem. IIRC, we are only talking .007". I can't think of anything else that would account for the increase in OAL.

 

Adios,

 

Pizza Bob

 

 

Are we on the same page?

[Sigman 41]

How are you measuring your OAL? If its with a caliper maybe YOU'RE the reason for variance (tipped ctg, pushing the jaws too hard)?

 

Maybe your primer is not seated flush or below?

 

Dreck has a point. I've noticed some difference in wadcutters if the top isn't mirror flat and has some imperfections. You may not always hit the tip of the bullet with the caliper. Inconsistent pressure holding the caliper can cause some differences.

 

I've also noticed what Frank mentioned above about the "shape" of the bullet head itself and how it seats in the ram cup - also good point.

[Old School 611]

Dreck has a point. I've noticed some difference in wadcutters if the top isn't mirror flat and has some imperfections. You may not always hit the tip of the bullet with the caliper. Inconsistent pressure holding the caliper can cause some differences.

 

 

Rick, you also get lead or lube build up in the seating die which I'm sure you've noticed.

[Sigman 41]

Rick, you also get lead or lube build up in the seating die which I'm sure you've noticed.

 

Yes - I always give them a swab with a q-tip to make sure they're clean.

[Pizza Bob 1,488]

Old School wrote:

<<The head space of the chamber of a rimless case is measured from the cartridge head to the shoulder of the chamber. So if the extractor is holding the case head against the bolt face the mouth of the case must be bearly or just short of contact with the chamber shoulder. Agreed?>>

 

Agreed. So what you have is excessive headspace.

 

Wikipedia definition of headspace:

In firearms, headspace is the distance measured from the part of the chamber that stops forward motion of the cartridge (the datum reference) to the face of the bolt.

 

 

By literal definition headspace of a rimless cartridge is measured from the breech face to the shoulder of the chamber. However, since the shot cases exhibit no signs of excessive headspace, it must be headspacing on something else - to wit, the extractor. It is the extractor, not the chamber shoulder, that stops the forward motion of the cartridge in the chamber. Thus, it is said that rimless, semi-auto cartridges, in effect, headspace on the extractor.

 

As to the second point that variance in the shapes of the noses of bullets being loaded may cause the OAL variance, I can see where that would be possible, but I would think that the disparity in shape would have to be too extreme to have an effect on cartridge OAL. Here is an illustration that shows what I'm talking about...

 

 

The bullet nose shape would have to vary enough that it would contact the bullet seating stem differently.

 

BTW - There is currently a thread over on PAFOA forums (under Ammunition & Reloading) that is discussing the same thing and it has reached many of the same conclusions we have.

 

Adios,

 

Pizza Bob<-----always clearheaded