N140 fps 20" 75-77gr

[95GTSpeedDemon]

I loaded some 75 and 77gr pills in new starline brass, 24.1 n140 in a 20" wylde chamber.
Consulting sierra, berger, & VV data (all i have) and compared to quick load and gordon's, im a little stumped.

VV says 25.5 max, which with how cruncy 24.1 was, how will it fit?
This data is much higher than the other two max's.

2nd, both softwares says it would be 80k psi.
They also said i should get 2700-2750 with 24.1, but yet i only got 2590. Sierra said 2600 with that load and barrel length.

Thoughts?

 

[kyotekiller25]

You need a droptube.

Software and manuals are only approximates. Doesn't replace actual data from YOUR rifle and components.

 

[dhagerty40]

you also need to take account on when your powder was made. In 2019, VV N140 was changed and is faster burning than the older powder.

I found that out in my 6.5x47L where I started piercing primers with the new lot. I had to drop the load 1.5grs to stop it from doing this.

The only way I could tell the difference is the bottle on the newer powder will say it has a decoppering agent while the older lots do not say this.

I know for a fact that VV, Berger and Sierra manuals are based on the older powder. Quickload updated the burn rate in the 2021.

 

[95GTSpeedDemon]

You need a droptube.

Software and manuals are only approximates. Doesn't replace actual data from YOUR rifle and components.

I get that. If it said 65k i wouldnt have second guessed it. Past that stuff gets hairy kinda quick. I know its an estimate, but how far off from reality is it. 80k is much higher than a sane person would expect a book max load to be at. Im sure the book value is safe, but how did VV get such a safe max value compared to other books ontop of im pretty sure most get pressure signs before 25gr.
If they are using a special chamber, they should probably denote that.

 

[95GTSpeedDemon]

you also need to take account on when your powder was made. In 2019, VV N140 was changed and is faster burning than the older powder.

I found that out in my 6.5x47L where I started piercing primers with the new lot. I had to drop the load 1.5grs to stop it from doing this.

The only way I could tell the difference is the bottle on the newer powder will say it has a decoppering agent while the older lots do not say this.

I know for a fact that VV, Berger and Sierra manuals are based on the older powder. Quickload updated the burn rate in the 2021.

Well, i guess that would have possibly changed my decision to buy two jugs, or instead of the 20" barrel i bought, i might have opted for a 24".
I guess ill get to find out where the limit is the like everyone else. I was hoping to not have to push the pressure very hard.

I was contemplating seating long and milling out the mag/lower/barrel extension to clear. Im not sure if i can really gain fps that way, software says loading long reduces pressure/fps and i just end up having to use more powder to offset that effect and end up with pretty much the same fps. Any real world data on that?

 

[mike mccormick]

There is a big difference in case capacity from new to once fired. As to the charge weight, 24.1 is what I have used for xtc, and seems like a good year round load.

 

[95GTSpeedDemon]

There is a big difference in case capacity from new to once fired. As to the charge weight, 24.1 is what I have used for xtc, and seems like a good year round load.

I tried measuring, it seems 30 unfired and 31 fired. Just a small droplet makes a pretty big difference in weight is what I found so there could be some error in my test

 

[kyotekiller25]

I get that. If it said 65k i wouldnt have second guessed it. Past that stuff gets hairy kinda quick. I know its an estimate, but how far off from reality is it. 80k is much higher than a sane person would expect a book max load to be at. Im sure the book value is safe, but how did VV get such a safe max value compared to other books ontop of im pretty sure most get pressure signs before 25gr.
If they are using a special chamber, they should probably denote that.

VV data is also for a 25" tube. You have a short 20", so that's also where some of the velocity difference shows up.

I use N540 with the 75g eldms at 24.7g for 2975fps from a 28" tube with a COAL of 2.5". I think VV max calls for around 25.8g at 2960fps. I ran it up to 25.6g at 3090fps before I pierced a primer. I'm also using Lapua brass which doesn't have as much capacity. So essentially, I'm getting there max velocity with 1 full grain less powder with my 28" barrel and Lapua brass. It's all subjective based on your rifle and components.

 

[95GTSpeedDemon]

VV data is also for a 25" tube. You have a short 20", so that's also where some of the velocity difference shows up.

I use N540 with the 75g eldms at 24.7g for 2975fps from a 28" tube with a COAL of 2.5". I think VV max calls for around 25.8g at 2960fps. I ran it up to 25.6g at 3090fps before I pierced a primer. I'm also using Lapua brass which doesn't have as much capacity. So essentially, I'm getting there max velocity with 1 full grain less powder with my 28" barrel and Lapua brass. It's all subjective based on your rifle and components.

Seeing what others say they get for fps, jonnys reloading bench got 2644 with an 18" at 24.1, i guess i just have a slow barrel.
Im going to make a drop tube and push the limits on the new barrel. If i can get 2700-2750 and not be too hot I'll be happy and keep it there.

 

[Walt Krafft]

24.0 N140 77 Sierra Match King seated to 2.250 OAL. From a 20" service rifle it shoots small in every rifle I have tested. The speed is what it is, accuracy is what counts.

 

[95GTSpeedDemon]

To a degree fps does matter for me. I need it to have over 1800fps @ 400yds. I basically need 2700fps at the muzzle.

 

[95GTSpeedDemon]

Wow, a drop tube really kept a 25.5gr n140 charge from going into the neck. Pretty cool

 

[chkunz]

24.0 N140 77 Sierra Match King seated to 2.250 OAL. From a 20" service rifle it shoots small in every rifle I have tested. The speed is what it is, accuracy is what counts.

This is my experience also.

 

[95GTSpeedDemon]

2.25 huh. Book has it at 2.26 like most. Some aac tmk ammo i bought was like 2.23x, seated very deep.

 

[kyotekiller25]

Wow, a drop tube really kept a 25.5gr n140 charge from going into the neck. Pretty cool

Yup, the 223 is the only cartridge I need a drop tube for. I was crunching powder anything much over 24g. With a drop tube I could go up to 25.5 or so before I started crunching. Helped out a lot with getting consistent seating depths also.

 

[bpm990d]

you also need to take account on when your powder was made. In 2019, VV N140 was changed and is faster burning than the older powder.

The only way I could tell the difference is the bottle on the newer powder will say it has a decoppering agent while the older lots do not say this.

Thank you very much, I did not know this. That might explain a few things.

 

[95GTSpeedDemon]

Yup, the 223 is the only cartridge I need a drop tube for. I was crunching powder anything much over 24g. With a drop tube I could go up to 25.5 or so before I started crunching. Helped out a lot with getting consistent seating depths also.

I was starting to think it was the frankford seating die causing the variations lol

 

[LVLAaron]

Use caution here. Starline brass is good stuff, but the 223/556 brass has MUCH less case capacity than other brands.

 

[95GTSpeedDemon]

Use caution here. Starline brass is good stuff, but the 223/556 brass has MUCH less case capacity than other brands.

Thats what i read, but fired starline is somewhere in the 30.7gr range and fired AAC cases were 30.5x, still less than what LC is said to hold though.

 

[Walt Krafft]

Just because you can fit 25.5 in the case, is no reason to do it. You will be WAY over the maximum pressure. At the minimum your cases will be one and done. Worst case you will have catastrophic failure. Hope you don't hurt yourself.