C.Oa.L.

[Jwjarrett]

I shoot mostly 40 S&W and I have read a lot about bullet setback leading to overpressure and kaboom. So, here is my reloading question. What is acceptable variations in published cartridge overall length (COL)? For example, my load data calls for a COL of 1.125. If I have one measuring 1.120, 1.115 etc. At what point am I approaching trouble?

We've already established that I'm anal and I'd love to hit 1.125 every time, but I know that's not going to happen. I just want to make sure I establish safe habits.

 

[robertrwalsh]

That's easy. IT DEPENDS. A "normal" .40 cartridge is loaded fairly close to the edge of the envelope anyway so any significant set-back could get "interesting." I am guessing (and it is a GUESS) that 1.120 is not a big deal unless you are at a top load anyway, and 1.115 is probably moving into risky territory.

 

[TMan51]

I shoot mostly 40 S&W
For example, my load data calls for a COL of 1.125. If I have one measuring 1.120, 1.115 etc. At what point am I approaching trouble?

Keep in mind that when you are loading for most of the rounds in a semi auto handgun, you have no way of knowing what the pressures are with ANY changes to a load recipe. A flattened primer in that scenario would indicate you are way over the top.

With a die set to seat a bullet to 0.125", (or any other depth), variations in OAL will be in 0.000x range for variation with any commercially available bullet, (not a big deal). If you load to a reduced OAL with greater differences, you need to back the load down to prevent excess pressures from biting you where it hurts.

Without a lot of detail with respect to components, it's impossible to say how much is too much.

Be safe, don't shorten the OAL below spec, unless you cut the load back at least 10%, maybe more, depending.

 

[AlHunt]

I doubt that you'll see +/- .005 if your dies are properly setup and locked down. The 40 is a taper crimp and as long as you make sure you get it right, setback shouldn't be an issue.

Setback is really more an issue with a round that's chambered repeatedly, like the top round in a carry weapon that's loaded and unloaded every day.

The test for your crimp is to try pushing the bullet in with your thumb or against the bench. Play with a dummy round would be my suggestion.

Get the correct COL for the exact bullet your using, stay away from max loads until you master the taper crimp and you should be fine.

 

[LostintheOzone]

I don't think a hundredth of an inch really matters. At least it doesn't for me.

There are a number of signs that may indicate unsafe pressure. Neither of my loading manuals suggest that a small variance in COL affects pressure to any great degree.

I'm no pressure expert so I'm just going with what my Hornady and Speer manual says.

 

[rockquarry]

You will always have slight OAL variation and slight variation doesn't matter as long as you're not seating below recommended OAL. If you're seating deeper than what is recommended (and there is no good reason to do this), reduce the powder charge.

If you use mixed brass, the OAL variation will almost always be greater than when using uniform (same) brass. As for crimping, whether taper crimping or roll crimping, crimp just enough to hold the bullet in place both under recoil and as cartridges feed through a magazine and are chambered.

You won't get bullet setback if you do this right, but it takes some experimentation with your gun as there is no set rule on the degree of crimp. Most handloaders crimp too much and this can and often does affect accuracy adversely.

This is probably all covered in various paper handloading manuals, so you might check there if you haven't already done so. I'd avoid YouTube. Good luck-

 

[Jwjarrett]

I loaded 200 today. I measured each on with a quality (and calibrated) Mititoyo digital caliper accurate to 0.0001. I was certainly getting more variation in the COL than I would expect. Some of it was inconsistent technique on my part, but some I can't explain. I am using Lee dies. They are tightly locked in. I'll take a closer look tomorrow, clean and readjust. Something isn't quite right.

I set to nuts on 1.125. Most were +/- .003. Every once in a while (8 out of 100) I would get one below 1.120. I set them aside and used my homemade inertia tool to move the bullet out. If it were 1.120 to 1.127, I left it alone. I tested in my EDC. looks like I could get by with up to 1.130 but I'm not doing that.

My load is a 165 Berry's copper plated with 7.1grains of CFE Pistol. The load range on Hodgedon's site calls for 6.9 to 7.5. Pressures, according to Hodgedon, should be 28k @ 6.9 and about 33.9k @ 7.5. I think I am fine, but I want to be absolutely sure. These 200 rounds are the first I have ever reloaded. I'll do some range shooting this weekend.

 

[Rogeronimo]

If you're not trimming your brass, I wouldn't put a lot of worry into this. If you are, carry on.

 

[rockquarry]

Have you measured the overall length of the bullets (not cartridge OAL) ? You'll likely find they vary considerably which will account for some of the variance in cartridge OAL you are seeing.

 

[rwsmith]

It's better to have them....

... a few thousandths too long than too short, as long as they chamber right. I had some off brand round ball stuff that was ABSOLUTELY unforgiving of anything 1/1000" over.

 

[BLUEDOT37]

I am using Lee dies.
I set to nuts on 1.125. Most were +/- .003. Every once in a while (8 out of 100) I would get one below 1.120.
My load is a 165 Berry's copper plated with 7.1grains of CFE Pistol.

What style Berry's bullets is that? Flat nose, round nose, hollow point with a flat tip?

Lee's seating die is for round nose bullets but the majority of bullets I load are JHPs which actually have a flat tip.

Using a flat seating plug, on flat tipped bullets, will give you a lot more consistent COAL" than when you use a round seating plug.

Believe me, like you an inconsistent COAL" drives me crazy, especially with max loads seated to max. COAL.

You can order a flat seating plug from Lee, if that's what you require, no need to send a sample bullet for these.

Use this link:
Custom Bullet Seating Plug - Lee Precision

.

 

[Jwjarrett]

I think we have a winner!

What style Berry's bullets is that? Flat nose, round nose, hollow point with a flat tip?

Lee's seating die is for round nose bullets but the majority of bullets I load are JHPs which actually have a flat tip.

Using a flat seating plug, on flat tipped bullets, will give you a lot more consistent COAL" than when you use a round seating plug.

Believe me, like you an inconsistent COAL" drives me crazy, especially with max loads seated to max. COAL.


You can order a flat seating plug from Lee, if that's what you require, no need to send a sample bullet for these.

Use this link:
Custom Bullet Seating Plug - Lee Precision

.

I do believe you have the answer! Yes, these are flat and didn't give that a second thought. I checked the length on a dozen or so bullets and they were too consistent to lead to much variance in OAL.

I've been using precision instruments for 40 years. I have grown picky, but this is more than me being picky. It is what should be a dialed in set of dies producing inconsistent results. the round seating tool vs. flat surface makes a whole lot of sense. Thanks!

 

[Jwjarrett]

Making dummy loads first is prudent.
Case tension holds the bullet in place.
If you are using a three die set, seat first then reset your die to remove the flair and how much to taper crimp is a topic unto itself.
If you are seating and crimping in one step... don't.

Once you have things under control with dummies then seat a bunch and reset the die and crimp.

Which model Mitutoyo gives you a .0001" readout?
thx
RT

Mitutoyo Digimatic. They are great, except mine do not have an auto shutoff.

I did about half a dozen dummy rounds. I need to do more. I got tired of removing the bullet.

 

[Jwjarrett]

If you're not trimming your brass, I wouldn't put a lot of worry into this. If you are, carry on.

I bought this brass primed. My trim tool uses the primer hole to align. I have measured a few dozen. I can't remember the length off hand, but they were consistent to my satisfaction.

 

[Rule3]

Brass TRIM length has nothing to due with COL UNLESS you are setting to a specific point in a crimp groove or cannelure.


COL is not the sane as SET Back,

 

[AlHunt]

OP, are you using lubricated lead bullets? Is there maybe lube in your seating die? Is your measuring method consistent? Maybe lock your caliper to length on one round and see how the others compare.

Once that die is set, it should seat to the same depth every time. Unless there's a buildup of old lube inside the die.

Variance in the bullet length can lead to differences in case volume but it I doubt there's enough to be of concern to most reloaders.

As mentioned above, consistent case lengths are critical to a consistent crimp but that has nothing to do with COL.

 

[mikerjf]

And, as it sounds like you are doing, you can always arrange your variance so it's all *above* the minimum... i.e. 1.125 to 1.135, rather than 1.120 to 1.130.

Good call on the flat-nose plug, gonna get one of those.

Homemade inertia tool... I'm picturing a 12 ga shell firing a chamber gauge holding the bullet into a block wall... bullet out!

 

[SMSgt]

At times I almost wish they'd stop listing COL in load data as it causes more confusion that solves.

I set my COLs at the longest length possible that will fit the magazine, fit the chamber, and feed reliably. It is usually longer than published COL and sometimes significantly longer. It all works fine and concerns about seating too deeply are nonexistent.

 

[Rule3]

At times I almost wish they'd stop listing COL in load data as it causes more confusion that solves.

I set my COLs at the longest length possible that will fit the magazine, fit the chamber, and feed reliably. It is usually longer than published COL and sometimes significantly longer. It all works fine and concerns about seating too deeply are nonexistent.

True, it is just the COL they happen to have tested it at.

SAAMI lists the MAX COL for the bullet they show but there are hundreds of other bullets.


On Hornady bullets I found if you did not trim the brass (handgun) to exactly what they did, the bullet will not match up to a Cannelure (if it has one) So all Hornady bullets I have loaded are a little bit different than the "manual"


What the OP needs to me concerned with is MINIMUM OAL especially with a dreaded 40 SW

 

[Nevada Ed]

At times I almost wish they'd stop listing COL in load data as it causes more confusion that solves.

I set my COLs at the longest length possible that will fit the magazine, fit the chamber, and feed reliably. It is usually longer than published COL and sometimes significantly longer. It all works fine and concerns about seating too deeply are nonexistent.

This is my standard setup for target rifle and pistol loads.
I will shorten the OAL in pistol loads if I want higher FPS, if needed but see no need for "Minimum OAL" for a bullet in 99% of my loadings........
since I usually get poor accuracy and sometimes LESS fps !!

Carry on.