COL deviation from ideal...

[Furncliff]

You are loading 9mm on a progessive, the ideal COL for the powder and bullet combination is 1.125.....

What are you willing to accept either side of the ideal?



And.....

Are dies like the Redding competition seating dies for pistol calibers really the cats meow?

 

[Walkalong]

A .005 spread is pretty average. A very good fit of the bullet to the seater stem and no sizing going on at the same time can do better.

I would be happy with 1.120 to 1.125, or 1.125 +/- .2 or .3, or 1.125 to 1.230 OAL.

What are you getting?

 

[Furncliff]

I'm getting 1.129 on the long end and 1.120 on the short end. However those seem to be just a few, most seem to be + or- - .002, which makes me feel pretty good about the Hornady seater I'm using.

Bullets are Hornady 115 JHP I bought on a sale from Midway some time back.

I decap, size, prime and bell in a separate run on the LNL AP. And I use a separate Redding crimp die.

 

[gamestalker]

I think that sounds pretty typical, and I do load those same bullets. Several thou variation is fine.

But I tend to get a little bit nervous when things get near the .010" variation, but I also load full tilt +P with jacketed bullets.

GS

 

[FROGO207]

Overall length could vary significantly if the bullets are not the exact same shape/profile. Say they are from different machines on an assembly line. The ogive might be a slightly different shape and that is where you are pushing the bullet in from on your die, so the total length could end up being different in that respect. If you are not at the MAX load when seating them then a so so variation would not be a large concern to me. Good enough for blasting ammo. Just one of the several reasons I do not load full tilt loads if the accuracy is still there. In general the more you spend on a projectile the more closely matched as well as accurate they all are it seems as I continue to gain experience.

 

[Bart B.]

I think the objective measuring cartridge length is to find out if each bullet will jump the same distance to the rifling. So, consider the following issues......

First, the point on the bullet that first touches the rifling is at some diameter between the barrel's bore diameter and that of the bullet. 9mm barrels have bores at about .346" and grooves at about .355"; some diameter in that range on the bullet is where it first touches the rifling.

Second, that diameter's distance from the case head will vary a small amount as all bullets made in the same set of dies will not have the exact same shape.

Third, as 9mm cases headspace on the case mouth, unless all cases are exactly the same length, whatever spread they have in case length will transfer to how far the bullet jumps to the rifling.

Therefore, one should not expect the distance from the bullet's tip back to its case head to have any relationship to how much the bullet moves before it touches the rifling.

You can blacken a bullet at its large diameter with a Sharpie then seat that bullet into the rifling. Where the ink's rubbed off is the diameter at which it touches the rifling.

So, with a .003" spread in case length, a .003" spread in bullet tip to case head, and a .003" spread in the bullet contact diameter to its tip, a batch of loaded rounds can easily have several thousandths spread in their bullet's jump to the rifling even if they all have exactly the same length from bullet tip to case head.

 

[345 DeSoto]

I followed the tip someone Posted on this site, about using epoxy to reshape the bullet seater on my Hornady slideing sleeve seater die. It worked wonders for seating the bullet straighter, more iniform seating depth, no deformation of the ogive...

 

[Walkalong]

For rifle the best seater stem will touch the ogive and not the tip, and will closely resemble the slope of the bullet. Measuring base to tip is worthless except when making sure they fit the mag.

For pistol calibers, such as the 9MM in question, I doubt many of us go through the trouble to figure ogive to base of the case, I know I sure don't. I come up with an OAL that feeds and is accurate, and call it good.

I use a couple of Redding Competition seaters for pistol and I like being able to dial to my setting and go, vs twiddling with getting the seater plug set every time I switch bullets. That is the advantage of them for me. It does a good job of seating the bullet straight if you start it straight. No sliding sleeve set up will seat a bullet super straight if it is started poorly. It will straighten it some, but can't substitute for starting the bullet straight to begin with.

Any seater that is straight, fits the bullet/case well and has a centered seater stem that fits the bullet well will do a good job.

For rifle the "dead length" seater by Lee with the floating seater stem does a great job. I wonder why they haven't done it for pistol. Maybe they figure the o-ring on the seater stem flexes enough. Dunno.

Anyway, a .005 spread in OAL for 9MM is pretty common. I just checked a favorite load of mine with an X-Treme 124 Gr HP and I listed the OAL at 1.060. I didn't even bother to list the spread or +/-, and I do for most loads. Shoots great though.

 

[LiveLife]

If your OAL/COL variation is due to bullet nose variation or tilting of bullet during seating, proper (flat vs round) or custom seating stem will help.

If your OAL/COL variation is due to shell plate tilt/deflection, using separately resized brass will help as effort needed to flare case mouth, seat bullet and crimp case will cause less shell plate tilt/deflection.

As others posted, variation of a few thousands is OK for me but I would look into why I have more significant OAL variation.

For me, I am more interested in neck tension and whether chambered rounds will experience bullet setback and will measure OAL before and after I chamber dummy rounds (no powder/no primer) from the magazine. If I measure OAL reduction of more than a few thousandths, I will investigate why.

 

[Bart B.]

With bottleneck cases headspacing on their shoulder and all COL's exactly the same, if there's a .004" spread in case headspace, there'll be a .004" spread in bullet position in the chamber.

It's the case shoulder that's in the same place for every round in the chamber. With such ammo, head clearance to the bolt face will also have the same .004" spread.

 

[LiveLife]

You are loading 9mm on a progessive, the ideal COL for the powder and bullet combination is 1.125.....

What are you willing to accept either side of the ideal?

Repost from another thread discussion - http://www.thehighroad.org/showthread.php?p=9916498#post9916498

I notice that reloaders list exact OALs like 1.089 or 1.135 etc. etc. But my lengths will vary a little. Current setting varies from 1.129 to 1.134 with most around 1.131 to 1.133.

That's the target we aim for. Depending on the press type/bullet brand/brass condition etc., reloaders may experience +/- several thousdandths to even hundredths in OAL/COL variation.

A variance of .005" maximum is normal for a single stage press. Up to .010" for a progressive.

+1. Depending on the brand/manufacturing process and type of bullets/nose profile along with how rough the shipping company employees treat the bullet boxes (that could cause the bullets to be out of round), you will have variations in OAL/COL, especially for progressive press with shell plate tilt/deflection.

 

[Archie]

For semi-automatic handguns, the COL is determined by:

Is it short enough to fit and function through the magazine and action?

Is it long enough not to bounce back and forth in the magazine in recoil?

Then if it shoots and groups 'satisfactorily' (whatever that may be), I don't care how long they measure.

For revolvers, the loaded round should be as long as possible to provide maximum powder capacity and short enough to allow the cylinder to rotate. With bullet seated and crimped in such fashion to not allow bullets to 'pull'.