QUESTION ON CARTRIDGE OAL VARIANCE

[oldguyguns]

Just started reloading pistol ammo. Am using a Lee 4 stage turret press but--since new to reloading am doing a single stage at a time and hand weighing and loading each charge. Am measuring the various dimensions frequently and notice a 1 to 2 thousands variance coming out of the bullet seating die---prior to going to the factory crimp die. I.E. if set at .980 in might get a .979 or .982 etc. Questions, is this normal to get a small variation? Is it ok to be a few thousands over the recommended COAL? thanks for input!!!! Note for the published load I was using the COL was listed as .980.

 

[rvb]

Just started reloading pistol ammo. Am using a Lee 4 stage turret press but--since new to reloading am doing a single stage at a time and hand weighing and loading each charge. Am measuring the various dimensions frequently and notice a 1 to 2 thousands variance coming out of the bullet seating die---prior to going to the factory crimp die. I.E. if set at .980 in might get a .979 or .982 etc. Questions, is this normal to get a small variation? Is it ok to be a few thousands over the recommended COAL? thanks for input!!!! Note for the published load I was using the COL was listed as .980.

a lot has to do with the consistency of the bullet itself. IMO +/- 2 to 3 thou is fine (and probably 1/5th what you see in factory loads).

-rvb

 

[flashpuppy]

Speaking in broad generalities, OAL has more to do with magazine fit and proper feeding than anything else. Loading mixed head stamp pistol rounds in what is not the worlds most sturdy press (not knocking it, just stating a fact) with probably not a match grade type bullet, yes I would expect a couple grand variance.

 

[T4rdV4rk]

Like the others stated, don't worry about it. If you are right around the recommended COAL (cartridge overall length) you will be fine.

 

[XtremeVel]

That variance is normal... You will be fine, assuming your data and listed OAL is correct and you verify it fully chambers...

The variance is caused due to either the inconsistency on the bullet profile where your seater plug/stem contacts the bullet or the surface you are measuring over...

Contrary to that you might guess, I usually find more variance when loading FP's than I do round nose... I like shooting a Hornady 124gr FP in .355 dia and I see MUCH more variance then what you are seeing... My eyes aren't great, but I can just tell looking at the inconsistent flats and tell which ones will measure .010/.015 shorter...

 

[BGDave]

Be sure to check for slightly high primers too. Most people measure over them. A strong light and a flat surface will work.

Keep in mind a human hair (depending on color is about .003).

 

[oldguyguns]

Thanks for advice folks. Much appreciated. Am using round nose Hornady bullets and have been checking the primer seating and using a case length gauge. Feel safer now. Don't know what I would do with access to you knowledgeable people!!!!!!!!!!!!!!!!!!

 

[U.S. Patriot]

It's where the die contacts the bullet (ogive). No bullet is perfect. So there will be variance. I normally see + .005" variance. Which is not an issue at all.

 

[Broom_jm]

Now, if you see .010" variance...stop and figure out what's going on.

 

[tenring]

Some of the best money I ever spent was to buy an OAL Hornady tool [formally Stoney Point] when I got 5000 M1 173 bullets. They were all over the 10 ring, but after miking the ogives and placing them in separate boxes, the groups shrank dramatically. Use that tool to set all my loads for different rifles for how much off the lands they should be.

 

[flashpuppy]

Some of the best money I ever spent was to buy an OAL Hornady tool [formally Stoney Point] when I got 5000 M1 173 bullets. They were all over the 10 ring, but after miking the ogives and placing them in separate boxes, the groups shrank dramatically. Use that tool to set all my loads for different rifles for how much off the lands they should be.

Have you ever played with meplat uniforming?

 

[tenring]

Never tried that , seems a lot of the pro's have tried it and weren't too pleased with the BC being changed to the detriment. Too far above my limited expertise though.

 

[Leo]

Like tenring commented, bullet weight and consistancy in the ogive to the lands measurement is a more active participant in accuracy than OAL. I had also bought thousands of 173 gr rifle bullets where measuring and sorting made drastic differences in accuracy for rifles shot at the 300 and 600 yard targets. Unless you are a VERY accomplished pistolero with a VERY special pistol, you will not see the difference on the target if the ogive bumps around even as much as .025". As long as the OAL will feed in your mag/pistols, you are good to go. High levels of OAL (like .100") may give you some pressure spikes you will want to stay away from.

 

[rvb]

There's more to oal than just relationship of the bullet to the lands. I once had a .45 load w/ clays I was working up for uspsa, very light at around 170pf. Std Dev over the chrono was something like 100fps. I shortened the oal and was able to get the std dev down to ~10fps.

-rvb

 

[Electronrider]

Something else to think about since your new to reloading. Load up a batch and check you COAL and jot down the numbers. Now go buy a box of ammo off the shelf and measure those COAL's. You will be shocked! LOL. 2-3 thousanths is fine.

 

[Leo]

There's more to oal than just relationship of the bullet to the lands. I once had a .45 load w/ clays I was working up for uspsa, very light at around 170pf. Std Dev over the chrono was something like 100fps. I shortened the oal and was able to get the std dev down to ~10fps.

-rvb

That is interesting. I would have never guess a powder as fast as Clays would need the additional pressure to burn right. I never ran into that except on powders that are too slow for target use. Something else to watch.

 

[oldguyguns]

Being a new reloader , I had an additional question on COAL/COL. For the 380acp all the manuals give .984 as the max COL. When I look at specific loads (say 100gr FMJ RN) some manuals state the COL as min COL and others just don't say what it is. Example: Hornady Manual for a Hornady FMJ RN 100gr bullet they list the COL as .980 and don't say if it's min or max or target. Take the Lee Reloading manual for a "100gr Jacketed Bullet" they list the min COL as .980. So---my question is-----is the target between .980 and .984---or if not--what is it? thanks

 

[45fan]

You will find that COAL will vary from one bullet design to the next. Max COAL is typically going to be the same number no matter who published the number. It is set as a standard not to exceed. There will probably always be exceptions to the "do not exceed" length, but sticking with typical for caliber bullets in published manuals you will probably not run into this.

When I start out working up a load for an auto pistol caliber (we will use 380 for an example) I will start out with the manufacturers Max COAL to begin with, and make sure it will function through the magazine and chamber into the gun. I then will put a magazines worth (or 5-6, depending on mag capacity) to ensure that that cartridge length will function through the pistol in question without issue. Some bullets in some of my pistols prefer to be slightly shorter than the max OAL for proper and smooth function.

Revolver bullets tend to have a crimp groove, and as such leave a bit less wiggle room to adjust COAL, but the function of the revolver is normally less dependant on the overall length to function properly (assuming the loaded round does not protrude from the front of the cylinder).

Best of luck to you, and never be afraid to ask questions. Better to wait a few and be sure than to jump in uninformed and get yourself or someone else injured.

 

[oldguyguns]

Measured some 380's from a box of American Eagles and they have a slightly higher variation than I get on my Lee Turret press. Makes me feel good.