newbie question c.o.l.

[Malice]

Hey guys. I am a little confused about something. The data I am using (from hodgon) states a "c.o.l." for each load. Does this mean this is the MAXIMUM overall length if the completed cartridge, the minimum, or what it needs to be EXACTLY? How much leeway do I have? Let's say I am doing a minimum load, the c.o.l. says 1.455 and I come out at 1.42, or 1.47 is this acceptable?

 

[Malice]

This is the response I got from their customer support:

"Actually, the length we show is neither minimum nor maximum.* It is the length we used.* Most of the time it is the recommended length established by the bullet
maker.*"

This is sort of an answer to my question, but doesn't exactly set my mind at ease...

 

[243winxb]

COL

the c.o.l. says 1.455 and I come out at 1.42, or 1.47 is this acceptable?

Yes, if your loading 38 special. For bottle neck rifles, any COL is fine with a starting load. It must fit the magazine. Must chamber, not to long. Not so short that the bullet falls into the case on seating.

 

[Otto]

Depends on the company publishing the data.

As an example, Vihtavuori's manual says:

"Caution: When loading handgun cartridges it is vital to
maintain the minimum cartridge overall length (C.O.L.) listed
in the tables. Shorter overall lengths may double chamber
pressures."


When in doubt, consult the company which you apparently did.

 

[MEHavey]

The published COL (="OAL" = "COAL" depending on the writers) is the tested overall length.
It is also the "normal" length that would fit most all commercial/military chambers
and not unintentionally engage into the rifling.

Normal bullet shape variation can result in ± 0.002" in OAL (unless you custom seat each bullet)
and will be totally unnoticeable. I would also offer that going as much as ± 0.010" won't make
a hill-of-beans difference for the normal reloader either, but I would be as consistent as possible
from loading session to loading session.

In auto pistols (as opposed to revolvers), the acid test is whether the action will close securely
each & every time as the gun cycles. If not (i.e., the bullet is too long, hits the start of rifling,
and prevents the slide from closing), then gradually seat more deeply until it does. This is normally
a "fine-tune" adjustment, not anything radical.

 

[kingmt]

I was going to tell you the same thing CS did. Now if you want to know max-min I can help you with that also or you can just load what the book says for now while you learn some other things.

 

[Malice]

Kingmt,

I guess I am not too concerned about min and max... I'm just trying to make sure having an col of 1.42 when the data says 1.45 isn't gonna blow my gun up.

 

[kingmt]

I would like to know the rest of the data before I made a statement but that is a big difference but shouldn't be enough to blow up your gun. If you was on the break of blowing it anyhow it might push it over the edge.

What kind of bullets are you using?

 

[sage5907]

Malice, you haven't said what cartridge you're reloading. An easy way to solve your problem is to buy a RCBS Precision Micrometer Bullet Seating Die. They can be had for $58 on eBay. You also need a Sinclair chamber length guage and they cost about $8. With the micrometer you can find the exact distance from the back of the cartridge case to the lands in the barrel. A lot of reloaders interested in accuracy set their bullet seating depth in the case to be .020 off the lands. The micrometer also lets you set the length of your sizing die so the resized case length is set to 0 as per the SAAMI chamber length. (Small Arms and Ammunition Manufacturers Institute) That way you don't work the brass very much each time you reload. The Sinclair guage lets you find the exact length of the cartridge chamber so you can determine how much trim room there is in front of the SAAMI maximum cartridge length. Ask more questions and you'll get the answers. BW

 

[Malice]

Sorry for the lack of details.

I am loading .38 special in a lee classic loader (the kind where you hammer the bullets in).

Here is my process:

Take the new Winchester brass I bought, neck size it.
Flare the case mouths.
Prime the cases with a separate Lee Had Primer tool.
Measure the powder in my RCBS 10-10 scale.
Charge the cases with the powder.
Seat the bullets.
Crimp the case mouths.

I loaded 25 rounds with Hornady XTP 125 gr JHP bullets over 4.2 grains of Titegroup.

I also loaded 25 rounds of Speer Plinker lead 158 gr SWC bullets over 3 grains of Trail Boss.

These are both minimum or near minimum loadings.

Both of these rounds have data specifying a COL of 1.455"

When I measure them with my Frankford Arsenal dial calipers, I get readings between 1.420" and 1.442" or so. I have noticed that the measurements are different depending on the placement of the calipers on the cartridge, how hard I turn the wheel tightening the calipers down on the round, etc.

All of these finished rounds look identical to one another, and each one looks visiualy extremely similar or identical to the factory loaded ammo in similar loadings I have.

The case mouth on the bullets seems to be in the right place; on the crimp channel with a teeny tiny bit of the crimp channel still visible.

Could these differences in length simply be due to different brass sizes, slight bullet inconsistencies, and user error in measuring the rounds? Since the bullet seating mechanism is locked down, I do not see how else the COL of one round could be any different from the one loaded immediately before or after it.

Also, a google search and browse through archived THR and TFL forum posts showed a consensus of "as long as the COL is not extremely off, seat the bullets properly in respect to the case mouth on the crimp channel; this is the correct seating depth for any given bullet."

 

[1SOW]

JMHO:

Malice, First COL/OAL and safety:
If the load data gives a COL of 1.455 it also gives a "pressure" rating with THAT col and load.
If you load to a LONGER col, 'your' cartridge pressure will "decrease" or be less than what's in the data. That is not a safety problem.

Now if you load "SHORTER" than the coal in the data, 'your' cartridge pressure is going to INCREASE to something more than the data gives.

Here is where you should be concerned. How much is it going to increase? Titegroup is a very hot powder and has a small load range compared to slower powders. Loading "shorter" with this powder can have a much bigger increase in pressure than slower powders.

+/- .005 or even .006"" can be caused by press variation plus reloader handle pull variation. When you get into .035" shorter, that's a lot.

RE "JHP" caliper measurement: My hollowpoints can vary (a little) by where the caliper jaws are located. The cut portions of the hollowpoint sometimes aren't all exactly equal. Use the 'flat' wide portion of the caliper jaws, and center them over the hollowed out portion of the bullet nose, then turn the cartridge a little and measure again. The measurement should be close to the same if you're centered on the nose. Don't force the caliper jaws together, just make contact with cartridge.

Try this and see if you get closer measurements.

 

[kingmt]

The fattest part of your caliper jaws isn't the most precise but they are probably close enough. The harder you push the more they dig in & that isn't the part you want to measure. Just tight enough to measure & be able to repeat the same pressure each time. I would agree a bulkier powder would make a less of a difference but I still don't see you blowing up your gun with that load.

 

[Funshooter45]

You did it just right Malice. When loading for a revolver, you seat the bullet so that the case mouth almost covers the crimp cannelure, with just a teeny tiny amount of the cannelure still visible. Whatever that happens to be is your seating depth and you don't worry about it. The .38 spl is a pretty low pressure round to begin with so the increase or decrease of pressure is not really a concern in a modern revolver.

It gets trickier with auto loaders and rifles.

 

[sage5907]

Malice, new cases can be different lengths and cases grow in length every time they are fired. The only way to get all of your cases the same length is to trim them each time you reload. A 38 Special case maximum length is 1.155 and the Speer manual shows a trim length of 1.150. If you trim every case to 1.150 and then are consistent in crimping each into the bullet cannulure grove then each bullet's overall length will be the same. BW

 

[ranger335v]

"Actually, the length we show is neither minimum nor maximum.* It is the length we used.*

It's the first time I've seen that from a book maker but it's true. When I started reloading few manuals included any OAL measurement at all and some still don't because it causes more confusion than it helps. I THINK the book makers started listing the OAL they used to develop the data because lawyers wanted a layer of protection between them and dummies who want to sue when they hurt themselves; book makers can go to court and say the guy didn't follow directions. And be right.

Find an OAL that works for you and develop your charge at that length. I know you want something more authoritative and detailed than that but that's all there is to it; no one can tell you what OAL your rig and load needs any more than they can tell you what a given powder charge will do.

None of it comes from what bullet makers say, none of them have a clue what your specific firearm needs.