Cartridge OAL varies

max503

max503

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I have noticed that the OAL on the 9mm's I've been loading varies. It can vary by as much as .005" Is that too much? Today, I'm using Berry's 124 grain Target HP's and mixed brass. I've noticed the same phenomenon when loading my cast, powder-coated bullets.

I'm wondering if maybe my ancient RCBS single-stage press hasn't developed some play over the decades? Any way to check for that?

I've check to make sure the primers are seated properly and not protruding.

.005 isn't a lot. Some bullets take more effort to seat, probably due to case wall variations. I'm wondering if maybe the extra effort doesn't distort the bullet.
 
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Unless you are at maximum safe pressure, 0.005" difference between shortest and longest OAL is likely fine. Plated, cast lead, and swaged lead bullets can suffer deformation during seating, that will cause variations in OAL. A primer that is not seated perfectly flush with or slightly below the level of the base of the case will show up as a variation in OAL.
 
Unless your seater fits on the tip of the bullet--and most do not, wadcutters primarily--you're seating by ogive length, not COL. If you were to measure the cartridge base to ogive length, you'd probably find the length much more consistent. Bullet length varies more than many think. As long as they feed and chamber properly, it's a non-issue.
 
As noted, base to ogive dimensions are probably consistent. The die's seating plug contacts the case down from the bullet tip and toward the case mouth. You can buy tools from Sinclair / Brownells that fit on calipers to measure the ogive to base length. Rifle shooters looking to get the tightest groups may use these tools. In my opinion, there's no value for 9mm reloading.

Depending on you shellholder, there's probably a groove and a hole that clears high primers. So a slightly high primer shouldn't affect bullet seating depth. A high primer could fool you when measuring overall length, though.

Your point about distorting the bullet tip might have merit. Berry's bullets are nearly as soft as lead; the plating isn't very thick. Do you see any deformation where the seating punch contacts the bullet?

Lastly, 0.005" variation is too tiny to worry about with pistol rounds.
 
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I agree that mixed brass might cause problems.

Just the other day my 115gr coated lead RN shot well in my 5" 9mm pistol,

but when I tried this load at the 1.12" OAL, I was getting several feeding problems
in my 3.5" pistol.

The chamber was a little tighter and was not letting the load "Go home".

The OAL dia. of this coated bullet also had a .0015" difference, that needed to be
seated to a maximum of 1.11" to pass the plunk test.

It is wise to KNOW how shallow or DEEP you can go with any bullet
weight or style, before going with minimum or maximum powder loads.

Tight groups. to you.
 
I have noticed on a lot of plated bullets (9mm 124 HP), the ogive varies a bit. I had trouble with some plated bullets varying .007"-.009" when premium bullets could be held to .002" on the same press, dies, etc.. I closely examined some bullets visually with my magnifying visor and strong light and could see a slight different ogive shape (different lot? different machine?). On occasion I have had my cast suffer from a similar defect in nose shape and/or ogive (operator error). With my handload, mixed brass made no difference in OAL...
 
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max503 said:
I'm using Berry's 124 grain Target HP's and mixed brass.
Click to expand...

Most hollow-points (that don't have a polymer plug) are really flat nosed & as such using a flat seating plug will give you the most consistent results verses using a rounded seating plug.

Straight-walled pistol brass of varying length have no affect on COAL".

Brass of varying case wall thickness & stiffness can affecting seating depth due to changes in seating resistance.

.
 
That is a very smell measurement- .005 is impossible to see without a micrometer. For me anyway. Is that affecting any of your shooting operation?
 
Just a FWIW; some may call it OCD, but I like to keep my tolerances down as much as possible. For me .005" is too much variation for OAL and I'll rarely go beyond .003". I know the main difference is in my head, but I can hold .003" with little trouble. Like many, if I like my handloads, feel good about them, they shoot better. Similar to "sometimes a guy just wants to know", it is important to some, but not really necessary to others. I keep my handload tolerances as tight/ low as possible and I feel better...:rolleyes:
 
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mikld said:
Just a FWIW; some may call it OCD, but I like to keep my tolerances down as much as possible. For me .005" is too much variation for OAL and I'll rarely go beyond .003". I know the main difference is in my head, but I can hold .003" with little trouble. Like many, if I like my handloads, feel good about them, they shoot better. Similar to "sometimes a guy just wants to know", it is important to some, but not really necessary to others. I keep my handload tolerances as tight/ low as possible and I feel better...:rolleyes:
Click to expand...

If this is important to you, try loading cast bullets that are all from the same batch that have been run through the same bullet sizing die, and brass from the same batch that's been fired approximately the same number of times. Incredibly small variance in OAL if any at all, but I don't know if it means much...
 
Seating and crimping in separate steps helped me get more consistent OAL. You could also modify a seating stem to be flat. Either grind it flat or fill it with epoxy.
 
Paul in Nevada said:
Seating and crimping in separate steps helped me get more consistent OAL. You could also modify a seating stem to be flat. Either grind it flat or fill it with epoxy.
Click to expand...

Good point as I forgot to mention the seating step as a part of OAL uniformity. I also prefer seating and crimping in separate steps. I generally crimp only handgun ammo, and lightly at that regardless of the cartridge and regardless of the type crimp used.

I've informally tested the separate step process vs. seating and crimping in one step. I know the "conventional wisdom" of the two-step process, but my results have been inconclusive.
 
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rockquarry said:
If this is important to you, try loading cast bullets that are all from the same batch that have been run through the same bullet sizing die, and brass from the same batch that's been fired approximately the same number of times. Incredibly small variance in OAL if any at all, but I don't know if it means much...
Click to expand...

I do. For my 44 Magnums cast, I cast all at once, size and lube all at once and occasionally use all the same headstamp brass. My 38.357 Mag, my 30 cal. and my 45 cal. cast are the same. My Garand handloads are often the same, including counting number of trips through the process. I'm not the greatest shot, but I have waay more time for reloading than shooting so I occasionally use methods some may see as "not necessary or a waste of time", but my handloads, my guns, my time...
 
The op probably has his question answered and if it is important to have each round exactly the same length you can accomplish that with one of the micrometer type seating die. Set the die a few thousands long and seat the bullet and measure and set the needed movement with micrometer head in the die and do the final seating. This way every round should be exactly the same length.
 
For the 9 x 19mm, OACL is an extremely important consideration. No other autopistol /cartridge combination has been tinkered with and effected as much as this 120 year-old auto cartridge. One reason OACLs are on the short side in handload data. No fancy gadgets or gimmick tools required to sort this out. Basically it's the same method I use for determining OACL for a particular bullet in a rifle's chamber, but a bit easier. You WILL need a .355” jacketed bullet though. With a FIRED WIN case you can just barely start a new bullet into it. With the barrel removed from your pistol, gently enter this "dummy" into the chamber and lightly push on the case-rim until it stops in the chamber. This requires a bit of finesse, so use a slight twist as you remove the "dummy" from the chamber. Measure it's OACL and repeat the procedure 4 more times to ensure you're getting the same exact result. This measurement is MAX-Length and where the bullet comes into contact with the Leade/throat/rifling. At that OACL or any longer, cartridge pressure will rise dramatically. So, depending on what your press set-up is capable of in OACL uniformity, you'll need to load shorter than the length you find with the “dummy” test. Shortening by .010” works fine. Always remember to “plunk and spin” and be sure that the bullet isn't the first thing making contact, because it may be the plunk you here. Cartridges should spin easily in the chamber.
 
Wouldn't it make more sense to just use the manufacturer's COL and then make sure the finished rounds pass the plunk test? Measuring off the rifling is great for match grade rifles, pointless for 9mm.
 
I always sort brass by manufacturer, yes even pistol brass. I toss all the foreign brass in the scrap bucket. S&B, gfl, aguila, etc. I don’t even fool with it any more.

ALWAYS, seat and crimp in separate steps! Always…. Buy a micrometer seating die if you wish. CLEAN the seating/ crimp dies occasionally as they will both become gunked up, even with jacketed bullets, and that is often overlooked.

Usually when I load 9mm it’s in lots of 10,000 rounds at a time ( my wife shoots a lot!). 45 acp and gap 5,000 rounds in a lot.

Because if these steps over the years, I might have one out of 1,000 that won’t drop in/drop out of a Wilson case gauge. BUT, that round will still chamber, fire and extract!

Regards, Rick Gibbs
 
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