Seating depth

[American_Fusilier]

I know seating a bullet too deep will cause pressure issues, but how soon does that occur?

For instance: I was loading 9mm the other day, and according to my data c.o.a.l. Is supposed to be 1.150. But a few of them went s little deep like 1.149 or 1.148. I'm guessing it's all safe to shoot those. Is it?

How deep would I have to go before running into trouble?

 

[Blue68f100]

Your plenty safe. Factory ammo varies 0.010-0.015". The pressure spike is more related to the powder being used and when your at max load. Ultra fast powers like TG get real moody when compressed. Some powders not so.

 

[stillquietvoice]

I know seating a bullet too deep will cause pressure issues, but how soon does that occur?

For instance: I was loading 9mm the other day, and according to my data c.o.a.l. Is supposed to be 1.150. But a few of them went s little deep like 1.149 or 1.148. I'm guessing it's all safe to shoot those. Is it?

How deep would I have to go before running into trouble?

You should be safe to shoot 1.148 provided that the bullet isn't jammed into the lands of your pistol. Oal will vary with bullet type, shape, ojive. I load my Smith 9mm at 1.12 with my current 124 lrn bullets. Any longer they won't fitting my chamber.

Most oal's listed in reloading data ate suggestions based on what worked in their test gun, pressure tester. Oal has a range that saami approves of Iirc 1.090 to 1.169".

Pressure rises faster in smaller cases and will be dependent on the load you are using.

 

[fxvr5]

see the plots on page 3;

http://www.castpics.net/LoadData/Freebies/RM/Ramshot/Ramshot_3.pdf

 

[Charlie98]

How deep would I have to go before running into trouble?

As Blue mentioned... there are several factors to consider, besides seat depth. A max charge of TiteGroup in a heavy or stepped case... yes, you might very well get into trouble. A moderate charge of Unique in a commercial case... not so much. The cartridge is something to consider, too... 9mm has a max SAAMI pressure of 35K PSI, something like the .45ACP... only 21K PSI. The smaller case of the 9mm can make small changes into big differences, pressure-wise.

 

[NMexJim]

I know seating a bullet too deep will cause pressure issues, but how soon does that occur?

For instance: I was loading 9mm the other day, and according to my data c.o.a.l. Is supposed to be 1.150. But a few of them went s little deep like 1.149 or 1.148. I'm guessing it's all safe to shoot those. Is it?

How deep would I have to go before running into trouble?

Just some information for you from Hodgdon:

"Normally a pistol or rifle shell case is considered full, or 100% loading density, when the powder charge sits at the base of the bullet when the bullet is fully seated. It is possible with some powders and cartridges to increase the powder charge slightly above this point, such that when the bullet is seated it actually compresses the powder charge slightly. This condition is known as a compressed load. Hodgdon notes in its reloading data if the subject charge is a compressed load. A full case, or lightly compressed charge is an ideal condition for creating loads with the most uniform velocities and pressures, and oftentimes, producing top accuracy."

If you don't have notations warning of a compressed load at max velocity, then you're good to go.

 

[Jonesy814]

When I started reloading, small variations in OAL like that would drive me crazy. I found that sorting & loading my brass by head stamp almost eliminated that variance

 

[Otto]

So all of your cartridges vary no more than 2 thousandths?

 

[forrest r]

You're doing better than most if you're only getting +/- 2/1000th's" variance in oal's while reloading 9mm's.







Figured I'd post the 38spl wc's also. They used to be the bad boys on the block along with bullseye powder. This combo blew up many a revolver.
The wonder 9 came on the seen and titegroup claimed it's fare share of tupperware.

The real issue facing 9mm reloaders today is the firearms mfg's are saving $$$ by omitting 1 simple step in the bbl making process. Namely no more throating of the bbl. This causes reloaders to make ammo with extremely short oal's with certain bullet designs.

 

[AJC1]

You're doing better than most if you're only getting +/- 2/1000th's" variance in oal's while reloading 9mm's.

View attachment 973411

View attachment 973412

View attachment 973413

Figured I'd post the 38spl wc's also. They used to be the bad boys on the block along with bullseye powder. This combo blew up many a revolver.
The wonder 9 came on the seen and titegroup claimed it's fare share of tupperware.

The real issue facing 9mm reloaders today is the firearms mfg's are saving $$$ by omitting 1 simple step in the bbl making process. Namely no more throating of the bbl. This causes reloaders to make ammo with extremely short oal's with certain bullet designs.

Those graphs are sweet, what book is that?

 

[fxvr5]

View attachment 973412

What's the source for this graph? Is this measured or predicted speeds/pressure? Thanks.

 

[WeekendReloader]

My press and seating die seating tolerance is about +/- 0.005 depending on bullet nose shape. I figure this is not a big deal and looking at the charts seems just fine. My loads are typically mid-range, so I am not worried.

I did run some test ladder loads with the same powder charges and cast bullet a few years ago for curiosity. One set with a longer OAL and another set with a shorter OAL. I could tell a difference between the two sets. Low charges on the long OAL did not cycle my gun. Low charges on the short OAL cycled the gun just fine, similar to the long OAL with 0.3 grains more powder. I'd have to look at my notes, but I think there was 0.050" difference between the OAL.

 

[Walkalong]

A .005 variance in 9MM OAL is fairly normal, some bullet/seater stem combos do better, some a little more.

 

[AJC1]

I seem to get the best consistency with flat nose bullets. Might be because I'm pushing and measuring on the same surface while round or other profiles are measured and seated from different locations.

 

[rfwobbly]

For instance: I was loading 9mm the other day, and according to my data COAL is supposed to be 1.150". But a few of them went a little deep like 1.149 or 1.148". I'm guessing it's all safe to shoot those.

As Mr Stillquietvoice told you in the second post... as long as the bullet is not jammed into the rifling. That's the VERY FIRST thing to check.

>> Every bullet is different and every barrel from every maker is uniquely different. That means the combination of how a unique bullet interfaces with a unique barrel creates a one-off situation for the reloader. YOU must determine what is safe for your bullet in your gun. There is no one, single, defined, safe OAL for any 9mm ammo.

>> Furthermore, the OAL listed with your load recipe is simply a report of what the laboratory used. It is most definitely NOT a recommendation of what you should be using with your ammo. It is simply a starting point from the standpoint of chamber pressure safety. SAAMI allows a wide range of OALs to be used in auto pistol ammo. You have to determine what is safe in your pistol. In this sense, revolver ammo is different from auto pistol ammo.

Here's the risk for YOU the shooter. It is possible for a longer OAL than the chamber can handle to allow the gun to fire out of battery (OOB). If that occurs the head of the case will blow out, covering the shooter with super hot gasses and red hot brass fragments. If the shooter is using a polymer pistol, then there is also a very high likelihood that the gun will be destroyed in the process. There is that much force involved.





Hope this helps.

 

[Blue68f100]

What's the source for this graph? Is this measured or predicted speeds/pressure? Thanks.

I believe it came form the Lyman Book.

 

[fxvr5]

I believe it came form the Lyman Book.

Which Lyman book? What page?

Is this measured or predicted speeds/pressure?

(p.s. this is not a guessing game)

 

[American_Fusilier]

So all of your cartridges vary no more than 2 thousandths?

No, all the ones that are too deep. I measure the length on every cartridge that I load (I'm still somewhat new to reloading). Most of my loads are deliberately a little longer than the 1.150. I liked to keep them in the 1.155 area give or take a couple thousandths. My guns seem to run everything just fine.

 

[American_Fusilier]

I've always been scared to load the bullet to oal for some reason

 

[murf]

the trouble is when your bullet travels up the feed ramp, hits the top of the barrel chamber and gets seated an additional 30 thousandths (about where your pressures go up substantially). your seating die really can't get you into "deep seating" trouble especially when you check the oal every tenth or twentieth round, or until you are satisfied that the seating die is working correctly all the time.

i don't worry about the seating die. i check a new load in the gun and make sure the loading process isn't deep seating my bullet for me.

luck,

murf