9mm Question about OAL and Pressures.

[Flashover16]

It is the shape of the ogive that determines a working COL.
COL in the normal range has very little effect on pressure/velocity.

.

There you go!
I use to use Raniers projectiles, then I got a few Berry projectiles when the times got tough a few years back.
the berry had a different shape and so I had problems with them until I shortened the OAL, there by giving more room to the nose.
I would mention that weapons with near perfect chamber dimensions will bottom out on the rifling, ask any CZ owner that reloads.
they are known for having short precise chamber throats.
I say back off 10 % on the load, shorten the OAL until it works in your gun, test fire and work them back up to the pressure/ performance gets where you want it and is safe.

 

[Flashover16]

It is my understanding that with faster powders if they are compressed the pressures rise, maybe I misread.

actually most any compressed powder will raise pressure simply because you have more of it in the case than if its not compressed!
anything that reduces case capacity will increase pressure, including the length of the projectile as it then may need to be set farther into the case.
this is why longer all copper projectiles/ frangible projectiles have lower loading rates generally.
of course there is a breaking point at how much powder that you can put in the case and how short that you can make a cartridge.

 

[Gun Nut]

Cartridge over all length is more for not seating a bullet to deep. to a certain point the deeper you seat a bullet the higher the pressures will be. Just like people who unload their pistols and chamber the same round every time this can cause an over pressure. As the bullet hits the feed ramp time after time it is pushing the bullet deeper into the case. You see the opposite on revolvers and light bullets especially the light frame J frames. With +P and magnum loads and light bullets the recoil is working like a kinetic bullet puller. I had a Ruger LCR 357 and the lightest bullets I could shoot in it was the 145gr. If I used 125gr after the 3rd shot the bullets would move forward enough to stop the cylinder from rotating. And I put the heaviest crimp on them I could. The shape of the bullet is also going to determine your C.O.A.L. Setting a bullet to deep is dangerous in a rifle setting it to long is dangerous, if it is setting on the rifling. Thats why you have a throat in a rifle chamber. The only difference in a .223 and 5.56 chamber is the 5.56 has a longer throat. That is why it is not advisable to shoot 5.56 out of a .223 chamber along with a couple of other things that can effect the pressures. Hope this helps.

 

[RamRoddoc]

It appears none has fired a round that has been loaded, ejected, loaded several times to cause significant bullet setback compressing the charge.

Modern firearms are designed to tolerate much more pressure than maximum standards such as factory "proof loads".

Compression is a critical variable. Too little, a round that has it's primer ignited outside the gun will pop and not even break skin. However, surround that round with a chamber and bit of barrel to compress the explosion and the bullet picks up speed exponentially.

Seal that outlet of hot gasses and a grenade is created. There are several things one can do to speed up a chemical reaction. Adding heat is one common method; rounds left out in the hot sun or in car will typically produce higher pressures and velocity. The other is compress the reaction. This is basic science.

Some smokeless powder is fine to compress, in fact it should be annotated as such in the manual. Some is not. Will it blow up a modern firearm? Likely not but ruptured/deformed primers, case blow outs or just a distinct difference in sound report and recoil are expected in a powder that does not like to be compressed.

Very interesting are the guns that have blown up from "TOO LITTLE" of a powder charge, but that's another subject.

So what the heck do I do when it appears I might compress the charge on a powder that isn't suppose to be a compressed charge? I toss the charge in the case, tap it a tad to settle it some and take the calipers and measure to the top of the case. Subtract that from the bullet add the case length +/- factor added and that's the really the "minimum" OAL. The maximum OAL is as noted; contact with rifling and or function issues.

So, next time one round noticeably pops off louder and has more recoil, instead of thinking it was an error with a "bit more powder" consider the bullet just got shoved back in the case and compressed the charge as another possible variable and check the crimping pressure used.

I check my crimp by cycling a few of the reloaded rounds through a tighter (match) chambered pistol and measure to see if they are shrinking and adjust by tiny amounts until it stops then a tick more for the +/- factor.

Revolvers have the opposite problem with too little crimp, the bullets will grow and could/can lock up the cylinder. It's worse with small/light weight heavy recoiling magnums. I load up a small batch and fire 5 of them (six shooter) and measure that last round to observe if it has grown (in my most light/small gun in that caliber). If so more crimp is order. Too much crimp and it distorts the bullet and adversely affects accuracy.


9mm is a robust high pressure cartridge and most pistols have a substantial amount of steel surrounding it so it's safer than loading say .40 S&W also a high pressure round.

 

[Gun Nut]

It appears none has fired a round that has been loaded, ejected, loaded several times to cause significant bullet setback compressing the charge.

Modern firearms are designed to tolerate much more pressure than maximum standards such as factory "proof loads".

Compression is a critical variable. Too little, a round that has it's primer ignited outside the gun will pop and not even break skin. However, surround that round with a chamber and bit of barrel to compress the explosion and the bullet picks up speed exponentially.

Seal that outlet of hot gasses and a grenade is created. There are several things one can do to speed up a chemical reaction. Adding heat is one common method; rounds left out in the hot sun or in car will typically produce higher pressures and velocity. The other is compress the reaction. This is basic science.

Some smokeless powder is fine to compress, in fact it should be annotated as such in the manual. Some is not. Will it blow up a modern firearm? Likely not but ruptured/deformed primers, case blow outs or just a distinct difference in sound report and recoil are expected in a powder that does not like to be compressed.

Very interesting are the guns that have blown up from "TOO LITTLE" of a powder charge, but that's another subject.

So what the heck do I do when it appears I might compress the charge on a powder that isn't suppose to be a compressed charge? I toss the charge in the case, tap it a tad to settle it some and take the calipers and measure to the top of the case. Subtract that from the bullet add the case length +/- factor added and that's the really the "minimum" OAL. The maximum OAL is as noted; contact with rifling and or function issues.

So, next time one round noticeably pops off louder and has more recoil, instead of thinking it was an error with a "bit more powder" consider the bullet just got shoved back in the case and compressed the charge as another possible variable and check the crimping pressure used.

I check my crimp by cycling a few of the reloaded rounds through a tighter (match) chambered pistol and measure to see if they are shrinking and adjust by tiny amounts until it stops then a tick more for the +/- factor.

Revolvers have the opposite problem with too little crimp, the bullets will grow and could/can lock up the cylinder. It's worse with small/light weight heavy recoiling magnums. I load up a small batch and fire 5 of them (six shooter) and measure that last round to observe if it has grown (in my most light/small gun in that caliber). If so more crimp is order. Too much crimp and it distorts the bullet and adversely affects accuracy.


9mm is a robust high pressure cartridge and most pistols have a substantial amount of steel surrounding it so it's safer than loading say .40 S&W also a high pressure round.


View attachment 707706

PSI for the 9mm is 35,500 +p is 38,500. I have seen rds that have been chambered so many times the mouth of the case is showing. Gun left in a hot car all day you just added more pressure. The chances of blowing up a gun is very slight but the first round I send at a BG I would rather have in specs. I was just letting the guy know a longer seated pistol bullet as long as it will work in the mag and a good crimp is not going to hurt anything.

 

[noylj]

Added weight comes from length of bearing surface, shape of ogive, width of meplat--it's all geometry.
Look at Lee's 1R and 2R bullet molds and you'll see the effect of ogive. Look at a short "button-nose" SWC and an H&G #68 clone SWC.
All these issues are taken care of by one simply act: start at the starting load and work up.

 

[Gun Nut]

Doesn't matter how long the bearing surface is the weight of a bullet is just that the weight. Looks at a FWC to a HP. They can be pushed to the same velocities and a FWC has a lot more bearing surface. Even simpler is to have a good manual look at the PSI for the given bullet. What's the mean pressure for a 9mm, 10mm, 44 mag, 454 Casul, don't cheat and google them. Give me the Max PSI for each cartridge and again don't google.

 

[hikingthehills]

Wish I could help you with the Berry's 125's, with 115's I have been loading to 1.125 OAL with 4.4 grains of Universal. It's has been working like a champ in my Glock G19.

 

[coach482]

Old thread. I have figured it out and all ready shot close to 1000 of these with out the first hick up. Thanks to all who replied.

 

[hikingthehills]

Old thread. I have figured it out and all ready shot close to 1000 of these with out the first hick up. Thanks to all who replied.

What recipe are you using?