zchaparral
Member
- Joined
- Mar 3, 2014
- Messages
- 24
This is a bit of information I promised readers and responders a couple of months ago that I would submit. Sorry it took so long I hope some of you get a chance to read it. I hope it is helpful to someone.
I am new to reloading as many here on THR are. When I started last January I started with an RCBS starter kit (a 15 year old in-law gift) which came with a Speer Manual 13th Edition and twenty years of used brass. After reading the manual I purchased an RCBS powder meter and case trimmer. I could go on and on and on from here about my trials and errors but I must cut to the chase.
After loading several hundred starting loads of several calibers I ran into a problem. A certain 9mm bullet I had purchased online did NOT match a starting load C.O.L. I was working with. It would not manually cycle through my pistol. After a long pause and some thought I made a dummy round (no primer or powder) and seated the bullet until it passed the plunk test and matched some factory ammo I had. It was .025 less than the recommended C.O.L. That is when I first came across THR in my search for any answers. I was stumped!
After many prompt helpful and different replies, thank you guys, I ordered another reloading manual, a Hornady 9th Edition. What I found in it was that the closer a bullet is to the land the greater the pressure. In my opinion (my new theory at the time) and in other words, if the bullet is into the rifling a couple of thousands it takes more powder burn i.e. more chamber pressure to get the bullet into motion. The further away from the rifling the bullet is i.e. a shorter C.O.L. the less chamber pressure because the bullet has uninterrupted space to build momentum.
So I decided the only way I was ever going to be 100% sure, ok, maybe just comfortable with an answer was to test my theory. I purchased a chronograph. Unfortunately I am a city boy and would have to wait until the end of April, my annual spring break trip to the great Michigan North, in order to blast off hundreds of my homemade rounds for the first time. This required lugging my reload equipment.
F@#$ing data already! Got it. Here it is. I am not a scientist, engineer, scholar or even an educated man. This is just simply one knuckle heads data. Take it for what you will.
Pistol: CZ 9mm Luger P07 Duty
Bullet: Nosler JHP 124 Gr. P/N 1041
Powder: 4756 5.2 Grains
These are four round groups. Everything is averaged. The first round or longest is the perfect fitting plunk test round and the first C.O.L. that would manually cycle through the pistol.
OAL 1.075 velocity=1008ft./sec.
OAL 1.065 velocity=976ft./sec.
OAL 1.063 velocity=992ft./sec.
OAL 1.056 velocity=1002ft./sec.
OAL 1.050 velocity=1010ft./sec.
OAL 1.042 velocity=1009ft./sec.
OAL 1.038 velocity=1036ft./sec.
OAL 1.025 velocity=1041ft./sec.
All the spent brass had no deformation, separation, or splits. I did notice more barrel rise with greater velocities.
I assumed when starting this experiment that higher pressure would necessarily relate to higher velocity. I’m not convinced of that any longer for different reasons. What I do draw from this is exactly what I needed. Although it should never be necessary to make such a dramatic O.A.L. adjustment when setting up a load; I feel 100% comfortable with making the proper length cartridge first to any firearm for any minimum powder load, regardless of recommended cartridge length. I don’t think I’ll explode (and I did think I might explode). What do you think? I appreciate all input and experience.
p.s. sorry about format
I am new to reloading as many here on THR are. When I started last January I started with an RCBS starter kit (a 15 year old in-law gift) which came with a Speer Manual 13th Edition and twenty years of used brass. After reading the manual I purchased an RCBS powder meter and case trimmer. I could go on and on and on from here about my trials and errors but I must cut to the chase.
After loading several hundred starting loads of several calibers I ran into a problem. A certain 9mm bullet I had purchased online did NOT match a starting load C.O.L. I was working with. It would not manually cycle through my pistol. After a long pause and some thought I made a dummy round (no primer or powder) and seated the bullet until it passed the plunk test and matched some factory ammo I had. It was .025 less than the recommended C.O.L. That is when I first came across THR in my search for any answers. I was stumped!
After many prompt helpful and different replies, thank you guys, I ordered another reloading manual, a Hornady 9th Edition. What I found in it was that the closer a bullet is to the land the greater the pressure. In my opinion (my new theory at the time) and in other words, if the bullet is into the rifling a couple of thousands it takes more powder burn i.e. more chamber pressure to get the bullet into motion. The further away from the rifling the bullet is i.e. a shorter C.O.L. the less chamber pressure because the bullet has uninterrupted space to build momentum.
So I decided the only way I was ever going to be 100% sure, ok, maybe just comfortable with an answer was to test my theory. I purchased a chronograph. Unfortunately I am a city boy and would have to wait until the end of April, my annual spring break trip to the great Michigan North, in order to blast off hundreds of my homemade rounds for the first time. This required lugging my reload equipment.
F@#$ing data already! Got it. Here it is. I am not a scientist, engineer, scholar or even an educated man. This is just simply one knuckle heads data. Take it for what you will.
Pistol: CZ 9mm Luger P07 Duty
Bullet: Nosler JHP 124 Gr. P/N 1041
Powder: 4756 5.2 Grains
These are four round groups. Everything is averaged. The first round or longest is the perfect fitting plunk test round and the first C.O.L. that would manually cycle through the pistol.
OAL 1.075 velocity=1008ft./sec.
OAL 1.065 velocity=976ft./sec.
OAL 1.063 velocity=992ft./sec.
OAL 1.056 velocity=1002ft./sec.
OAL 1.050 velocity=1010ft./sec.
OAL 1.042 velocity=1009ft./sec.
OAL 1.038 velocity=1036ft./sec.
OAL 1.025 velocity=1041ft./sec.
All the spent brass had no deformation, separation, or splits. I did notice more barrel rise with greater velocities.
I assumed when starting this experiment that higher pressure would necessarily relate to higher velocity. I’m not convinced of that any longer for different reasons. What I do draw from this is exactly what I needed. Although it should never be necessary to make such a dramatic O.A.L. adjustment when setting up a load; I feel 100% comfortable with making the proper length cartridge first to any firearm for any minimum powder load, regardless of recommended cartridge length. I don’t think I’ll explode (and I did think I might explode). What do you think? I appreciate all input and experience.
p.s. sorry about format