How deep?

[alphabrace]

First time attaching picture so I hope it came with this message.
I have hard cast bullets that have a straight body, then a step, a short straight before the olgive begins. Question on this 9mm bullet is this: Do I seat bullet so that end of brass is on the larger straight diameter or do I set bullet so that the brass is up to or over the straight portion of the bullet? I undersand that its critical not to seat to deep on 9mm but according to my measurements I can go past the straight portion of the bullet well within a safe zone I have before I compress any powder. I do not have any info from bullet manufacture. Bullet length is .610. Straight body is .357 dia x .245 long. Dia after step is .336". Lenth of bullet shown in picture is 1.110" with brass at step in bullet. Thanks.

[Bruce51]

I like to seat them with the case even with the shoulder. There is no need to go further unless they were to exceed the OAL that works in your guns magazine.

In my guns that style of bullet was never very accurate, but they were good for practice.

Bruce

[jepp2]

Your bullets look like S&S cast bullets.

What OAL did your load source list? You can get into trouble with the 9mm without being compressed.

I tend to load long (near the SAAMI max of 1.169"). Since many loads were developed with shorter length, I have to adjust the powder charge to get the same pressure.

I load the 125 gr. S&S LRN to 1.169" and don't have any problems with the bullets being against the lands on any 9mm's I load for.

[alphabrace]

Originally Posted by jepp2

Your bullets look like S&S cast bullets.

What OAL did your load source list? You can get into trouble with the 9mm without being compressed.

I tend to load long (near the SAAMI max of 1.169"). Since many loads were developed with shorter length, I have to adjust the powder charge to get the same pressure.

I load the 125 gr. S&S LRN to 1.169" and don't have any problems with the bullets being against the lands on any 9mm's I load for.

Yes these are sns bullets. At 1.169 I'll be just ahead of the wax ring or lubricating ring (not sure what it is called). Does the bullet seat in the gun on the shoulder of the bullet or case when there is no shoulder?

[OKFC05]

Does the bullet seat in the gun on the shoulder of the bullet or case when there is no shoulder?

Unless you have a fat bullet or seat it too far out, the bullet does not seat on the gun in the chamber before firing. A 9mm is speced for headspace off the mouth of the case, which is why it uses a taper crimp of modest amount.

[jepp2]

Here is the dummy I use to set up my seating die. Shows you how the SNS bullet looks seated to 1.169".

[alphabrace]

Thanks for all the great responses so far. I had a chance today to shoot 12 rounds loaded with 3.5 grains W231 and 12 rounds with 3.9 grains. My OAL was about 1.110" for all. Interesting enough the 3.5 grains felt more stouter than the 3.9 grains. The brass from the 3.9 fell only a few feet to the right out of my m&p 9mm while the 3.5 brass ejected a little farthur. I was thinking that perhaps the 3.9grain load does not have enough room left to burn properly in the casing. Any thoughts?

[jepp2]

Originally Posted by alphabrace

I was thinking that perhaps the 3.9grain load does not have enough room left to burn properly in the casing. Any thoughts?

Data from the Hodgdon website:
125 GR. LCN Winchester 231 .356" 1.125" 3.9 1009 25,700 CUP 4.4 1086 31,200 CUP

The 3.9 gr load should be higher in pressure than the 3.5 grain load. There is plenty of oxygen in the load to support combustion. Depending on barrel length (4" on M&P?) you might not get all the powder burned before the bullet exits. But it should still be the stouter of the 2 loads.

Your loads are below the Hodgdon site loads, but your OAL is considerably shorter. The Hodgdon data uses a conical nose bullet, which is much shorter than the SNS bullets. I have LCN 122 gr that measure .555" long, versus the .607" of my SNS bullets. And the Hodgdon data calls for 1.125 with the shorter bullet.

Seating depth is what determines pressure. A shorter bullet with the same OAL of a longer bullet will have less seating depth. Thus lower pressure.

[alphabrace]

Originally Posted by jepp2

Data from the Hodgdon website:
125 GR. LCN Winchester 231 .356" 1.125" 3.9 1009 25,700 CUP 4.4 1086 31,200 CUP

The 3.9 gr load should be higher in pressure than the 3.5 grain load. There is plenty of oxygen in the load to support combustion. Depending on barrel length (4" on M&P?) you might not get all the powder burned before the bullet exits. But it should still be the stouter of the 2 loads.

Your loads are below the Hodgdon site loads, but your OAL is considerably shorter. The Hodgdon data uses a conical nose bullet, which is much shorter than the SNS bullets. I have LCN 122 gr that measure .555" long, versus the .607" of my SNS bullets. And the Hodgdon data calls for 1.125 with the shorter bullet.

Seating depth is what determines pressure. A shorter bullet with the same OAL of a longer bullet will have less seating depth. Thus lower pressure.

I am going to load up some at the 1.169 length at 3.5 and 3.9 grains. Don't remember if I mentioned it, but the factory loads I shot right after felt much more stout. They were winchester white box.

[jepp2]

Winchester White Box is loaded to the SAAMI max length of 1.169". With the longer length, I expect you will have issues with sufficient pressure to cycle your slide. The pressure drops off quickly.

If you like I can calculate the theoretical pressure from QuickLoad, for your previous loads.

[jepp2]

These calculations are based on the standard assumptions and using SNS 125 LRN bullets. Remember, they are just theoretical calculations, your actual case may be different.

The loads you tried:
3.5 Gr. W231 1.110" OAL 21.8K press, 924 fps, 99% propellant burn
3.9 Gr. W231 1.110" OAL 27.2K press, 1005 fps, 99.95% propellant burn

If you try what you suggested:
3.5 Gr. W231 1.169" OAL 17K pressure, 875 fps, 97.8% propellant burn
3.9 Gr. W231 1.169" OAL 21.2K pressure, 952 fps, 99.5% propellant burn

If I was developing this load, these are my starting and max loads, but I would chronograph them and check for signs of pressure along the way:
4.2 Gr. W231 1.169" OAL 24.8K pressure, 1007 fps, 99.9% propellant burn
4.5 Gr. W231 1.169" OAL 28.9K pressure, 1060 fps, 100% propellant burn

I find that if I keep my pressure in the 25-30K range, I get reliable slide action with my 9mm's with stock recoil springs. YMMV. But you can see how much the pressure drops when you increase the OAL for the 9mm.

The calculated values for the 4.2-4.5 grains are very close to the Hodgdon site data if you take into consideration the difference in bullet length.