Cartridge OAL varies

[max503]

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.

 

[stansdds]

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.

 

[H Richard]

Measure a bunch of factory loads and you will probably find as much or more variance.

 

[SMSgt]

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.

 

[Krogen]

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.

 

[rockquarry]

Using mixed brass can add to the variance.

 

[Nevada Ed]

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.

 

[mikld]

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...

 

[ArchAngelCD]

Measure a bunch of factory loads and you will probably find as much or more variance.

Ain't that the truth!

I wouldn't worry about 5/1000 of an inch. Seriously, .005" is really nothing to worry about.

 

[BLUEDOT37]

I'm using Berry's 124 grain Target HP's and mixed brass.

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.

.

 

[Maddog 521]

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?

 

[mikld]

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...

 

[rockquarry]

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...

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...

 

[Paul in Nevada]

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.

 

[rockquarry]

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.

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.

 

[mikld]

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...

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...

 

[jjrr]

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.

 

[TexasViking]

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.

 

[Paul in Nevada]

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.

 

[Rlg#17]

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

 

[Nevada Ed]

In my test with this Berry plated HP design, I found that a short OAL was accurate in my 3.5 & 5" pistols.
However, I did have to use a long OAL, in order to get enough of the Alliant flake powders into the case
to get higher fps that was needed to improve some targets vs the low target speeds.
Alliant flakes work great for light target loads but for 1200fps, the small grained powders are best.

My top fps load came with BE-86 with CFE-p a close second.

Here is a picture of my OAL's that I used in my test.
For some odd reason, the 1.10" oal did not do well in my pistols.

 

[Nevada Ed]

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.

That would work perfectly if every pistol barrel was drilled to the same exact chamber spec
but we all know that this is never going to happen even though there are SAMMI spec's out there for them to follow.

Not only is there the go, no go problem but also a tight or over size dia. chamber, that could be in a pistol or revolver.

I will stop here, now that you got my motor running.

 

[TexasViking]

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 suppose so if you want your loads unnecessarily short which means greater "jump" from the cartridge case into the Leade/Throat/Rifling. Just as with handloading for rifle, minimizing "jump" typically improves accuracy, and using a longer OACL without exceeding the Max, will reduce pressure. I work with Imperial and metric units and have found that with slower burning powders for the 9 x 19mm like Silhouette, True Blue and AA No 7, with a .010"/.25mm OACL length increase you can equalize pressure and velocity by adding .1 gr. per
a length increase of .010"/.25mm. Same in reverse when shortening, decrease by the same amount. As powder burn rate gets faster, or if you're using a fast burner, you should not change the powder charge. Predominatly, my loads and tests are geared toward defense, but wanting match grade accuracy as part of that. Likewise, I am partial to JHPs for autoloaders, particularly the 9 x 19mm to have longer, more slender and rounded ogives vs truncated cone shapes that typically require the shortest OACLs. If you're loading Plated bullets you'll need to use your press and seat in steps of small increments if you want to match OACL to the pistol's chamber. I rarely load anything other than JHPs or hardcast/polycoated SWCs, but every jacketed bullet I used gets tested for its OACL specific to the chamber, or chambers since all of mine are relatively close in length.
If your load will be used in multiple pistols, load for the one with the shortest chamber. Unless it is an unusual model, your handloads will be longer than what is typically used in handload data. Think about who SAAMI is? They're both data providers and ammunition manufacturers. Their ammo and their data must consider the shortest possible chamber the loads will be fired from, and essentially, one-size-fits-all. If that seems excessively labor intensive, that's up to the handloader. But if you load for rifles, you're likely doing the same thing anyway. And buying cartridge gauges is a waste of time and $ for me. The best cartridge gauge you can use is the chamber in your pistols barrel.
Also, the plunk test alone is not enough. In some cases with truncated cone type JHPs like SIERRAs and the XTP the shoulder hitting the leade will also "plunk". You need to make sure that after the "plunk" the round will easily spin in the chamber.
This is also worth mentioning: through the gen 3s (haven't tested a gen4) Glock used chambers that allow OACL to be longer than what will fit in your magazine. Same for SIG, IME. So the "Marksman" barrel of the genV was basically a shortening of the chamber to get better accuracy from the shorter OACLs typical of commercial ammo.

 

[TexasViking]

That would work perfectly if every pistol barrel was drilled to the same exact chamber spec
but we all know that this is never going to happen even though there are SAMMI spec's out there for them to follow.

Not only is there the go, no go problem but also a tight or over size dia. chamber, that could be in a pistol or revolver.

I will stop here, now that you got my motor running.

Good point Nevada Ed! Catridge gauges are little more than a Go, No Go gauge. And they can give a pass to a cartrdge that may not properly fit the chamber of your pistol's barrel and the best cartridge gauge you can use.

 

[BLUEDOT37]

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.

Finding the max COAL" for a particular bullet & in a specific barrel is easily accomplished as TexasViking described but it's only valid with that combination.

In another pistol it may not be.

The plunk test let's you verify that a finished round will also work in another.

To get there, presumably, you started with a too long COAL" & slowly seated it deeper until it passed the plunk test in the test pistol. (PS: don't forget to remove any case bell-mouth/flare with a lite taper crimp before you "plunk & spin" or you may get a misleading result.)

The plunk test is a confirmation test of a previously determined result that used a combinations of factors in a given setting.

If it passes in another setting then good. If it doesn't then it needs to be changed.

I like to seat my bullets out as much as possible too without exceeding the SAAMI max COAL" & still feed reliably.

Not all bullet manufacturers provide load data for there bullets.

I started buying RMR's 9mm bullets & found out that their MPR bullet's profile caused issues where I never had them, even in my 3rd Gens which typically have plenty of freebore/leade.

And when my son bought a 9x19 Kris Vector SDP KV-90 (which I reload for) I found it's no freebore barrel created even more problems as most of what worked fine in the 3rd Gens did not in the KV-90.

.

KV-90 barrel: no freebore
.


.
.

Freebore, yes (between the chamber shoulder & start of the rifling)
.


.

 

[TexasViking]

Finding the max COAL" for a particular bullet & in a specific barrel is easily accomplished as TexasViking described but it's only valid with that combination.

In another pistol it may not be.

The plunk test let's you verify that a finished round will also work in another..

The method I described is for JHPs in 9mm. And as I mentioned, if you are loading for multiple 9mm pistols, but still desire to get a longer load than the data provides, and don't want to make multiple length loads, you would need to use an OACL that works for the pistol with the shortest chamber, and easily found using this method.

You can not rely on the plunk test alone. In some case as mentioned, you can get a plunk from a truncated cone type JHP bullet from the bullet's shoulder making first contact.

I should have pointed out that your case-rims should always be flush or slightly below the barrels hood. So there have been examples where a handload with a TC JHP has plunked, the rim being flush or slightly below the hood, but does no spin freely. So the proper term is "Plunk and Spin."

For over-diameter bullets like plated and cast you'll need to use your press and seat the bullet in steps until you are close to getting the case-rim flush with the barrel hood, then take smaller seating steps like .005" or less.

I don't shoot much plated, and for 9mm and .45 ACP I use SWCs. 125 gr. 9mm RN-SWCs from SNS casting in particular. And regardless of a handloading manual stating a best length for SWCs, one statement that's pretty reliable is that the bullet's shoulder should be about 1/32" above the case-mouth, or less. But when it comes to reliable feeding, you'll need to do some experimenting to find the "best" length for .45 ACP. In the case of the 9mm 125 gr. RN-SWC, the nose of the bullet above the shoulder is under-diameter which allows them to be loaded longer. 1.142"/29mm in the case of my loads.

 

[Nevada Ed]

I have one 9mm pistol that has so much freebore, that I can shoot loads that are too long to fit in it's magazine !!

I also have a 9mm pistol that will not let the slide go "Home" if a certain shaped RN bullet, does not have a short enough OAL.

One reason, that I tinker with "Dummy loads" to get the min/max OAL for a new bullet
before I grab a primer and start the loading process.

 

[TexasViking]

I have one 9mm pistol that has so much freebore, that I can shoot loads that are too long to fit in it's magazine !!

I also have a 9mm pistol that will not let the slide go "Home" if a certain shaped RN bullet, does not have a short enough OAL.

One reason, that I tinker with "Dummy loads" to get the min/max OAL for a new bullet
before I grab a primer and start the loading process.

N. Ed, seen that happen with several pistols. My P-226 and a Taurus 92 I had for a while. Just sold a Canik TP9sa that did the same. Not sure about the Gen IV Glocks because I've only loaded for Gens I - III which can take loads longer than what will fit in the mags.
Most American makes, have shorter chambers and ammo is tied into that because they're all members of SAAMI, with most bullet makers now manufacturing ammo, and providing data. Just not to me! HK and CZ use chambers that are similarly short and are pretty compatible with the American brands with the exception of Ruger, unless they've gone shorter with the American model, which I doubt, but someone correct me if that's incorrect. My last Rugers were SR models.

 

[BLUEDOT37]

You can not rely on the plunk test alone.
In some case as mentioned, you can get a plunk from a truncated cone type JHP bullet from the bullet's shoulder making first contact.

"Plunk" is the sound the brass case makes when it contacts the chamber's shoulder when you drop a round in the chamber.

When the bullet, of what ever design or construction, contacts the rifling first you don't get the proper "plunk" sound.

Experienced handloaders can usually tell the difference but if not, yes, there's more that can be done.

In addition to the spin step, which isn't foolproof either, if you press FIRMLY on the nose down inserted cartridge in the chamber, & then tip the barrel up, it should freely fall out. If it sticks inside the chamber the COAL" is too long.

Sometimes it takes all three.

.

 

[BillBro]

Granted I am going to use rifle rounds as my example but these are very hot true 5.56 NATO rounds produced by probably the most respected and well known manufacturers in the business, and theyre known for being some of the most accurate rounds available, the mk262 mod2 round as produced by Black Hills Ammunition. Its a 77gr SMK doing an avg of 2760fps out of my mk12. Ive bought 2 500rd bricks of it and have shot more than that. Ive measured alot of it to help with my attempts to clone it. It, the BHA all vary as much as .008" and the BHA especially shoots better than anything Ive ever shot or loaded.
My handloads are always more uniform in both OAL and powder charge and still dont shoot quite as well as the BHA. I certainly cant attain the velocity of the BHA, of course theyre using a different grade of powder.
No, this is neither a 9mm round nor is it even a pistol caliber but as far as COAL mattering that much, Im sure it does somehow but maybe not the slight variations youre having.