9mm bullet seating depth

[gasr55]

I have a question about the minimum depth that you can seat a bullet. I read somewhere that a bullet should be seated no less than the diameter of the bullet yet i am trying to reload 9mm lugers and the bullet,shellcasing combination that i am using only allows for .112 bullet seat depth. All components are winchester and are what is recommended for use, the bullet seat depth of a winchester factory load is only .050 more than what i am getting coming in at .162.
  Need opinions please your help will be greatly appreciated.

[John Traveler]

gasr,

The "rule of thumb" for bullet seating depth of one bullet diameter applies to rifle caliber bullets and cartridges.

Many cartridges, particularly pistol cartridges, do not have enough case length to allow one full bullet diameter seating depth.  The lighter weight 9mm bullets make it impossible to get that one diameter seating depth.  You have to rely on a secure neck-to-bullet fit to get a secure assembly.

As long as your loaded cartridge does not exceed maximum OAL and the bullet is securely held in the case against feeding impacts, recoil, and handling, you don't need to worry.

Military ammunition uses an asphaltum sealant to provide water proofing, increase bullet pull, and make the bullet-to-case assembly more secure.  You may want to try that to get a tighter fit.

HTH
John

[Iowegan]

Bullet seating depth is VERY CRITICAL in 9mm cartridges. The cartridge typically runs chamber pressures in the 35-37,000 psi range. A bullet seated just .020 too deep can raise the chamber pressure to 50,000 psi or more. You want to shoot the gun not wear it so be very careful.

If you haven't already done so, buy a good reloading manual or better yet, two. Speer, Hornady, Sierra and others list the cartridge overall length (COL) with each bullet for each cartridge.  If you seat the bullets to their recommended depth, you will find it optimum for chamber pressure, accuracy, and function.  Also, you will need a dial caliper to measure the OAL.

[Black Jaque Janaviac]

Something doesn't seem right here.

0.020" is not much difference.  I would imagine that this difference could easily be crossed just by using different bullet designs - weight kept the same.  I'll have to measure my 125 grain truncated cone and my 125 grain round-nose.  Both bullets are the same weight - thus you'd use the same recipe and same OAL.  However, if the bullet lengths vary, the seating depth will vary.

Why do we use OAL anyway?  Wouldn't using the "real" seating depth be more useable?  If case length is known and the recipe gives us seating depth - we could all figure out the OAL for ourselves after measuring the length of the bullet we are about to use.

[Iowegan]

Black Jaque, I've seen several references on dangerous seating depth for 9mm's. I found one in the old Speer #11 Manual that states: "Loads that produced 28,000 cup went to 62,000 cup when bullets were seated .030 deeper". The new Speer #13 manual has a caution about seating deeper but doesn't list actual pressures.

[unspellable]

For some reason SAAMI and the US manufacturer's decided that Georg Luger's design wasn't good enough and shortened the OAL.  Today's SAAMI maximum OAL is the original DWM minimum length.  This is the principal reason the Luger has a poor reputation for reliablity.  The Luger magazine works like a 22 LR magazine, the cartridge nose rides up on the front of the magazine.  If the OAL is too short the pistol jams.  Presumably other currently manufactured pistols are set up for the shorter length.  It's a mystery why the cartridge was shortened as all it would seem to do is raise pressures and cause Lugers to jam.

[Black Jaque Janaviac]

Iowegan,

I'm not doubting that you can find reliable references on this seating depth issue - I'm just confused why they don't take into account bullet lenght if 0.020" can be dangerous.

If the publishers develop a load using a 125 grain round nose with is 0.750" long and set the OAL accordingly, then a reloader uses a 125 grain truncated cone or even a hollow point which is 0.770" long and loads to the recipe's OAL they have just crossed the line.

With .38 spl, because of the case capacity, such small variations in bullet lenght don't seem to matter - or are at least made up for by using the "starting charges".  

However, the manual publishers don't seem to give us the impression that there is much forgiveness in the 9mm - yet they still give the OAL without letting us know the actual seating depth.

[Iowegan]

Balak Jaque, The Speer manual and others addresses this. They give COL's that compensate for seating depth and warn not to substitute other bullets for the ones listed. This is not unique to 9mm's, it also applies to 38 Super, 40 S&W, and 10mm. They all run chamber pressures in the 30-35,000+ PSI range.  Deeper seating results in very high chamber pressures.

You have probably noticed the reported KaBooms, especially with the 40 S&W, and primarily with the Glocks. This phenomenon is caused by repeated loading and unloading a duty gun with the same cartridge. After a few loads & unloads, the bullet gets pushed deeper in the case and when the round is finally fired, the pressure skyrockets resulting in a KaBoom. Glock feed ramps (older frames) tend to bump the bullets and that's why you hear of so many incidents. Many times the round had not been previously chambered. Glock has since reworked their feed ramps so they won't do this.

I've been retired from gunsmithing for 5 years but back when the 9mm was the most popular LE gun, I used to get S&W's in the shop quite often with blown barrels. Mostly S&W mod 39/59's and some 2nd generation S&W models. Their barrels were weak to start with, compounded by the "deep bullet syndrome".  That was before "forums" so the word didn't get around as much. I also had several 10mm Delta Elites with fractured slides. The Colt barrels held up well but the intense pressure made the slides crack.

You're right about the 38 Specials. The larger (mostly empty ) case is loaded to 18-22,000 psi chamber pressure. Seating a bullet deeper will increase the pressure but not to dangerous levels. The 45 Colt, 45 ACP, and 44 Special are other very forgiving low pressure rounds.

Unspellable, The origional Luger ammo was loaded with a pointed 125 grain bullet that did indeed make it longer and made it feed better. That bullet design was notorious for over penetration and was later replaced with a lighter & shorter round nose design. Most newer 9mm magazines won't accomodate the older and longer ammo. Also, the 9mm is the most popular chambering in the world. As such, there are literally hundreds of ammo makers that produce this round. SAAMI has good compliance here in the US but much of the foreign made 9mm ammo does not comply with SAAMI specs for length and chamber pressure. You won't see me shooting anything but US made ammo in any of my 9mm guns.

[unspellable]

Iowegan,

I'll have to sit down and calculate how various bullet shapes end up for weight.  I and another guy have a long term project going to make the Luger work the way it was supposed to.  You might be onto something with the bullet shape, I'll see how it works out.  Still seems a bit arrogant for the manufacturers to decide to load them all shorter than the original minmum OAL.  DWM loaded quite a variety of bullet shapes, all intended for the Luger.

How do I decide whether or not the feed ramp in my 10 mm Glock is the way it should be for not shoving bullets back?  Never had any feeding problems except for one factory load that was oversized and would not chamber even when hand loaded.  (Got one like that for my 32 Special too!)

PS.  What part of Iowa do you hang out in?

[Iowegan]

Unspellable, There are some tricks to get a Luger to feed reliably. You hit on one, the COL. They do like longer cartridges. Check your bolt face. They have to be very smooth, no protrusion from the firing pin hole, no rough spots or horizontal scratches. Next are the magazine lips. They tend to get spread with use and may have to be reshaped. With spread lips, the round doesn't pop up at the right time and the bullet nose will strike high and jam. Too tight (lips) make the nose point down and again will jam. These are very precision guns but if one little thing gets off, they won't feed properly. Also, the recoil springs and extractors weaken with age and create feeding problems.

The 9mm Luger or Parabelum, or just plain 9mm was introduced 100 years ago. The case dimensions have remained the same however the bullet designs have gone through changes. The Geneva Convention mandated the change from sharp nose to round nose. SAAMI has made it's standards for civilian ammo, then of course there's the military and foreign made stuff. To add to the confusion, there's ammo made for sub-machine guns. All different of course.

Glock is a strange company to say the least. They never admit there is a problem with any of their guns. No recalls, no press. For at least 2 years, they have been replacing the original frames with the newer design (customer returns from LE). Someone else on the forum might know the dates. If your Glock was made over two years ago, it probably has the old frame. I wouldn't get too worried about it. Just don't shoot cartridges that had been previously chambered unless you measure them compared to a fresh one.  If you reload, make sure you get a tight taper crimp and seat the bullets to the recommended depth.  KaBooms have happened with guns that seemed to feed perfect so it's not a matter of jamming, it's what the bullet does on the way to the chamber.

P.S. I live in Sac City,  NW part of IA.

[unspellable]

GLB,

We have been conducting a very in depth research project into what it takes to make a Luger work and the history there of.  (Meaning the history of cartridge changes, functioning, etc., not Luger variations for the collector.)

First and foremost with any self loading pistol is a good magazine.  Drop any magazine on its head once too often and you have a problem.

All the mechanical engineers keep telling me that springs do not weaken with age.  Once they do weaken, failure is eminent.  One of the things we have learned is that when we open up a shooter grade Luger we are liable to find anything and everything in the way of a non-original recoil spring.  Over the years people have been tinkering with the recoil spring without any real understanding of what hey were doing.  We have an in depth analysis going to determine the correct spring vs cartridge impulse for various levels of loading.

The original first military issue 9 mm Parabellum round had a truncated cone shaped bullet.  This is the one that was regarded as questionable and brought about the change to a round nose bullet.  On the commercial side, circa 1904 DWM offered four different bullets for the 9 mm Parabellum, including both a “pointy” round nose and a “round” round nose.  All of which they seem to have been able to load while maintaining the correct OAL.  So it’s still something of a mystery why the industry shortened the OAL.  At first I thought your idea of the “round” nose shortening the OAL might have something to it, but DWM had such a bullet by 1904.

Another mystery is why the industry under loads the 7.65 mm Parabellum.  The SAAMI maximum average CUP is too low.  Both the 7.65 mm and the 9 mm should run the same pressure.

Another mystery is why the barrel groove diameter is oversized in both calibers.  Not conducive to accuracy.  We have a project going to make a bullet as near to groove size as the chamber neck diameter will allow.  Another guy is thinking about making some barrels sized to fit the existing ammo.

This has been going on for some months.  It all started when I got tired of all the hearsay and decided to find out what was REALLY going on.

I get over in your area every once in a while to visit the relatives.

[Sieger]

For some reason SAAMI and the US manufacturer's decided that Georg Luger's design wasn't good enough and shortened the OAL.  Today's SAAMI maximum OAL is the original DWM minimum length.  This is the principal reason the Luger has a poor reputation for reliablity.  The Luger magazine works like a 22 LR magazine, the cartridge nose rides up on the front of the magazine.  If the OAL is too short the pistol jams.  Presumably other currently manufactured pistols are set up for the shorter length.  It's a mystery why the cartridge was shortened as all it would seem to do is raise pressures and cause Lugers to jam.

Greetings Noel!!!

Sieger

[gasr55]

Thank you to all that replied to my post the information was very helpful.