OAL and bullet time.

[gonoles_1980]

Note: time should be type (sorry typo and can figure out how to fix title line)

Could be a dumb thought, but here goes. Shouldn't we also discuss bullet type when we discuss OAL? I would think that a flat point seated the same distance inside the case would have a lower OAL than a round nose. So maybe when reporting OAL we should also report the bullet type?

Or am I completely confused on this one.

 

[RKRCPA]

You are absolutely correct. Each bullet profile will have it's own appropriate OAL. That is different than the maximum COAL for a particular chambering.

 

[LiveLife]

I totally agree. I usually post bullet brand, type and nose profile when posting OAL/COL.

 

[rfwobbly]

I also agree. This really shows up in auto pistol. What we should really be discussing is seating depth, or how much of the bullet is inside the cartridge case, which defines the volume under the bullet. Unfortunately that is not directly measurable, and so we end up with discussions of OAL.

 

[ReloaderFred]

For semi-auto handguns, a lot of times the OAL is determined by the magazine and leade of the chamber. I've got some pistols that will accept an OAL that the magazines won't accept, even though a longer OAL produces better accuracy than the loads that will feed through the magazine without binding, or won't go in the magazine at all.

On the other hand, I've also got handguns with short leades, so the bullets have to be seated deeper in the case just so they'll chamber, but the magazines would accept rounds much longer. The important part of OAL, after the feeding issues are addressed, is the volume of the case after the bullet is seated. This has a direct impact on the pressure a given charge of powder is going to produce in that cartridge.

So, in answer to the OP's question, yes, the type of bullet is definitely important when discussing OAL in any caliber. Different bullets have different ogives, which will contact the rifling at different lengths. That's why there's no "one OAL fits all" when loading ammunition, which often confuses new reloaders. Each combination of components should be tailored to the firearm. Or, like in commercial ammunition, to the most finicky firearm in your inventory in that caliber.

Hope this helps.

Fred

 

[Sunray]

The ogive has nothing to do with OAL. SAAMI MAX OAL is measured from the pointy part to the flat part. Ogives apply to the off-the-lands distance in rifles when you have a load and want to tweak it for the chamber dimensions of your rifle.
Like Ron says, mag length is usually the biggest thing to consider in mag fed firearms(all of 'em.). However, the MAX OAL for say a .38 SWC is the same as an RN of the same weight. Is for a 9mm Truncated Cone 9mm too.
Using the Max OAL with the bullet given in your manual will save you a lot of mucking around. The whole off-the-lands thing isn't necessary at all. Totally trial and error thing anyway. Every rifle chamber is slightly different and will have a slightly different off-the-lands distance.

 

[ReloaderFred]

Sunray,

You're referring to rifles, and I'm referring to semi-auto handguns, when discussing the ogive of the bullet and it's relationship to OAL. Many handgun chambers will engage the ogive of some bullets when the suggested OAL length is loaded. Bullets with long bearing surfaces and short ogives are a good example. I believe everyone understands that the OAL is measured from the "pointy part to the flat part" when referring to the nose of the bullet and base of the case, and the distance in between. Revolvers are a whole other consideration, since they can tolerate much more variation.

You also refer to "different off-the-lands distance" as being variable, and that's what I said. When bullets are seated deeper to get them off the lands, or out of the leade, then that affects the OAL. SAAMI maximum OAL is just that, the maximum standard manufacturers use when producing ammunition. There is no rule that says a handloader can't exceed that length. Only the individual firearm, and the components used, will dictate what that maximum can be when tailoring your own ammunition.

Hope this helps.

Fred

PS: You always come off as a grouch. Are you really that grouchy???

 

[Reloadron]

Two bullets both 230 grain 0.451" diameter and the bullet on the left is in fact longer. The bullet on the left is a Speer Gold Dot and the bullet on the right is a Hornady XTP. The suggested Speer trim length for a .45 ACP case is 0.888". Speer list a COL of 1.200" while Hornady list a COL of 1.210" with a case trim of 0.893".

While the differences are small and likely each bullet could be loaded with the others load data it doesn't hurt to use the bullet makers load data whenever possible.

Edit: Changed the trim to length to 0.893 verse 1.893.

Ron

 

[Bart B.]

If we're gonna do this, we also need to measure from the case headspace point to the bullet tip because the case head is rarely, if ever against the bolt/breech face when the round fires. A few to several thousandths case head clearance is normal.

If its the actual bullet jump to the rifling, then the bullet ogive diameter where it first contacts the rifling is what needs to be measured to from the case headspace point. That diameter's 3 to 5 thousandths smaller than the barrel's groove diameter and about the same on the bullet.

 

[Hillbilly Jim]

Whats a case trim of 1.893 mean?

 

[Reloadron]

Whats a case trim of 1.893 mean?

It means reloading manuals have a suggested case "trim to" length and the suggested trim to for the bullets I used as an example have the suggested COL with the trim to lengths I mentioned. I also need to correct my post as Hornady in my example should read Trim To: 0.893 verse 1.893 as I typed. My bad.

Also, we want to consider what Bart mentioned.

Also, we should distinguish handgun and rifle. Rifle we tend to get concerned with "Bullet Jump" as the bullet travels to the lands, there is the distance traveled. Most handgun, which I used as an example, there is not much concern as to the bullet jump.

Ron

 

[Bart B.]

Rifle we tend to get concerned with "Bullet Jump" as the bullet travels to the lands, there is the distance traveled.

I agree; lots on concern among rifle shooters. Very few can discern the 1/4 MOA degradation in best accuracy 1/15th to 1/10th increase in bullet jump to rifling as the barrel wears out shooting ammo with a fixed OAL for magazine use. A 308 Win's throat advances .001" for every 30 to 40 rounds fired. 30 caliber magnums' throats advance that much every 10 to 13 rounds

 

[Reloadron]

I agree; lots on concern among rifle shooters. Very few can discern the 1/4 MOA degradation in best accuracy 1/15th to 1/10th increase in bullet jump to rifling as the barrel wears out shooting ammo with a fixed OAL for magazine use. A 308 Win's throat advances .001" for every 30 to 40 rounds fired. 30 caliber magnums' throats advance that much every 10 to 13 rounds

Years ago I "chased the lands" and the reason it becomes a "chase" is because with each bang the damn lands move further down the road. There are things which have a very pronounced or strong impact on accuracy and things which have a lesser impact and things which have such a minor effect you will only see it or appreciate it in a few rifles. When I load I no longer really "chase the lands" since the only one I need to make happy with my groups is me and when they suck, I write it off to age and walk off the range happy. As to COL? Make them like the book says and worry about chasing the lands when you have a rifle where it really matters.

Ron