9mm Question about OAL and Pressures.

[coach482]

I have some 9mm Berrys 125gn FMJ they have a conical nose. The OAL says 1.05 - 1.12
In order to feed and chamber these I have to size the length 1.08 Then they will chamber and eject just fine, any longer and they hit the rifling and will no go full battery. I tried in 4 different pistols, XDm, Sig P229, Sig938, Sig P6. I have only cycled I have not fired any of the bullets yet.

They are in specs but this is my first time reloading 9s so being extra careful. When crimped they leave a little visible ring in the case where the bottom of the bullet stops. I took one apart to check and I also took apart a factory load, I am not pressing them in any father than the factory load because these bullets are shorter.

My concern is with the visible ring I charged the case with powder and it is just below the ring with 4.5 grains of powder. When does the pressures start to go up? When I touch the powder with the bullet or does it take a lot of compacting before this takes place?
Sorry the description is long I do much better when I can point and grunt.

 

[insulinboy]

Are you sure you're reading your calipers right? I only ask becuase I load with berrys (though I've not seen a FP bullet like that one when loading) and I always load to 1.160" OAL I use 1.170" for my 1911 9mm's but the double stack guns (XDm, and PT111) magazines will jam anything longer than 1.160. I've never had any issue with a bullet touching the rifling

Regardless the load manuals normally leave you a little bit of leway so that they don't get sued if you screw one up and set it 1/100th deeper than they said to and blow your gun up.

even running the max load (which I've found is almost never the most accurate load) you're within spec so you will be fine, just police your brass and check for signs of over pressure.

 

[coach482]

I am reading the calipers correctly, the factory load in the pic for comparison is 1.15 and I have some factory HPs that are 1.085. I also have and EGW 9mm gauge and it just touches bottom when I drop the shell in. My only concern is what makes the pressure rise do I need an air gap between powder and bullet or is touching ok? I know I have to stay off the rifling.

 

[coach482]

The difference in projectile length is .066

 

[noylj]

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

>Regardless the load manuals normally leave you a little bit of leway so that they don't get sued if you screw one up and set it 1/100th deeper than they said to and blow your gun up.

No, this is covered by starting at the starting load and working up. COL in a manual is nothing more than the COL they used for testing.

In case you haven't read this before:

Per Ramshot:

"SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH “COL”

It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must be seen as a guideline only.

The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.

This parameter is determined by various dimensions such as

1) magazine length (space),

2) freebore-lead dimensions of the barrel,

3) ogive or profile of the projectile and

4) position of cannelure or crimp groove.

• Always begin loading at the minimum "Start Load".

• Increase in 2% increments towards the Maximum Load.

• Watch for signs of excessive pressure.

• Never exceed the Maximum Load."


Your COL (OAL) is determined by your barrel (chamber and throat dimensions) and your gun (feed ramp) and your magazine (COL that fits magazine and when the magazine lips release the round for feeding) and the PARTICULAR bullet you are using. What worked in a pressure barrel or the lab's gun or in my gun has very little to do with what will work best in your gun.

Take the barrel out of the gun. Create two inert dummy rounds (no powder or primer) at max COL and remove enough case mouth flare for rounds to chamber (you can achieve this by using a sized case—expand-and-flare it, and remove the flare just until the case "plunks" in the barrel).

Drop the inert rounds in and decrease the COL until they chamber completely. This will be your "max" effective COL. I prefer to have the case head flush with the barrel hood. After this, place the inert rounds in the magazine and be sure they fit the magazine and feed and chamber.

You can also do this for any chambering problems you have. Remove the barrel and drop rounds in until you find one that won't chamber. Take that round and "paint" the bullet and case black with Magic Marker or other marker. Drop round in barrel (or gage) and rotate it back-and-forth.

Remove and inspect the round:

1) scratches on bullet--COL is too long

2) scratches on edge of the case mouth--insufficient crimp

3) scratches just below the case mouth--too much crimp, you're crushing the case

4) scratches on case at base of bullet--bullet seated crooked due to insufficient case expansion (not case mouth flare) or improper seating stem fit

5) scratches on case just above extractor groove--case bulge not removed during sizing. May need a bulge buster.

 

[coach482]

I read all that Ramshot has written before the post. All shells run through bulge buster. My question Is about when the bullet contacts the powder in the shell, I know that compressing it raises the pressure. When does this start to happen?

 

[noylj]

Compressing does NOT raise the pressure.
Where did you hear that?
If you look in a manual with compressed loads, you will NOT find a sudden increase in pressure/velocity as the load works up to being compressed.
Compressed loads have been safely used for over 90 years (not counting black powder that is always compressed), and yet we still have people who are afraid of compressed loads.
The question is, is the short COL as long as you can seat the bullet and get easy feeding and chambering—and you STILL have to work up the load from the start and not just go from one bullet to another without working up the load again.
The whole idea that using the same seating depth gives the same pressure only works if both bullets are the same length such that the chamber volume when the bullet hits the lede is the same—and I have my doubts that it is true even before that. Unless you can measure pressures, don't assume anything.

 

[coach482]

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

 

[1006]

The guys above are giving you the straight scoop.

I will add that the deeper you seat the bullet the higher your pressure will be. The faster the powder, the more this is true.

The safegaurd against case rupture is in the process of working up the load.

You will have to seat those fat bullets deeper.

Compressing the charge is not a big deal, but you might as well switch to a powder that fits the case and bullet, because it is hard to keep the bullet COL from growing between the seating step and the crimping step, as the powder will try to push the bullet upwards between these steps. I like several different powders as does everyone here. You might try TiteGroup, Bullseye, W231, or AA #2 for your purposes--plinking, or target shooting at standard factory velosities.

All of the above in this post applies to straight walled, semi-auto, taper crimped bullets.

So, reduce you charge, seat them deeper, and see how it works.

Also, unfired rounds do not have to eject easily, only fired cases. So, only concern yourself with bullet feeding.

Good luck--keep the safety first mentality.

 

[Flashover16]

The difference in projectile length is .066

This sounds odd to me!
IF they are the same caliber and the same design (not a hollow point VS a flat/ conical point) and made of the same material then there should NOT be much difference in the length of the projectile.
I mean if its the same diameter and the same weight, then where does the added length come from?
are these the same weight projectile?