VV N120 220gr subsonic help

[jgieske]

I decided to try out VV N120 after reading it was the beez kneez for subsonic loads here on 300blktalk. Problem is, I'm not sure where to start.

I'm using the SMK 220gr BTHP seated to 2.089" OAL, converted hornady brass, and CCI #41 primers. These rounds are for a suppressed, 9 inch barrel, pistol gas AR15 platform rifle.

I did a search here and read that 9.7 grains is a good start; however, this is a compressed load as I could hear the powder crunching as the projectile reached its seating depth of 2.089 OAL.

Is 9.7 too much? Is a little compression OK with this powder/bullet combo? The goal is 1000 fps unsupressed.

Any help would be much appreciated!

[dellet]

What data are you using?

[jgieske]

What data are you using?

Hornady's book based on their 225gr BTHP starting at 9.7 grains.

[dellet]

What data are you using?

Hornady's book based on their 225gr BTHP starting at 9.7 grains.

Is that the length given for the 225? Sounds very short

[jgieske]

What data are you using?

Hornady's book based on their 225gr BTHP starting at 9.7 grains.

Is that the length given for the 225? Sounds very short

No, but I guess I could set it out a bit further. What's the longest I can go without binding in the mag?

[dellet]

Hornady's book based on their 225gr BTHP starting at 9.7 grains.

Is that the length given for the 225? Sounds very short

No, but I guess I could set it out a bit further. What's the longest I can go without binding in the mag?

Depends on the magazine. I load that bullet to 2.255" in a Lancer without problems. That puts it around.015" off the lands.

If you put the .250" diameter of the bullet on the rib in any mag, it should feed fine.

N120 works fine compressed, but I think that will be a bit much.

I would start it at about 10 grains with the bullet just barely pushed into the powder. Probably around 2.200".

I use a fired case so the bullet slips in and out, drop the charge in, set the bullet on and measure.COL is .010" shorter.


JBM lists most popular bullet lengths, compare the SMK to the Hornady. If you use Hornady length data for a start, the Sierra will be shorter by the same length difference as the bullet.

http://www.jbmballistics.com/ballistics ... ml#Hornady

[mauidiver]

I finally reloaded my first bullets ever with N120. I followed my Hornady book and shot a few unsuppressed to make sure they were running correctly. I used 208 grain Hornady ELD Match with a
2.250 COL. I ran 3 different loads to run numbers. Only a few registered on my Pro chrono as the sun was a killer.


11.5 - 1207, 1204
11.0- 1182
10.3– 1031

[jgieske]

Thank you both for the responses. I contacted vihtavuori and this was their response:

Thank you for contacting us at Capstone PG. Unfortunately the use of N120 will not be a good match for this type of an application. This is due to the fact that this would have to load to fill ratio of 114% due to the slow burn rate of the powder for the application and would simply be an issue of having to use more powder than would be able to fit inside the case and still be able to properly seat the bullet even with very heavy compression of the powder charge. Please do not hesitate to get back with any of us with the Capstone Tech. Team if we can be of further assistance.

Could have sworn N120 was highly recommended around here for subs.

Wondering what you all think about this.

[rebel]

That can be their little secret. It works fine, as said before, forget the load length you are using. Pop it out to 2.255 and check function and accuracy. Seat deeper if you need to find your rifles sweet spot in .001 increments.

[dellet]

Thank you both for the responses. I contacted vihtavuori and this was their response:

Thank you for contacting us at Capstone PG. Unfortunately the use of N120 will not be a good match for this type of an application. This is due to the fact that this would have to load to fill ratio of 114% due to the slow burn rate of the powder for the application and would simply be an issue of having to use more powder than would be able to fit inside the case and still be able to properly seat the bullet even with very heavy compression of the powder charge. Please do not hesitate to get back with any of us with the Capstone Tech. Team if we can be of further assistance.

Could have sworn N120 was highly recommended around here for subs.

Wondering what you all think about this.

I think it's Bullshit and who ever wrote that email should lose their job.

Bullet 13,0 g / 200 gr FMJBT, Lapua C.O.L. 57,0 mm / 2.244 inch
Powder Starting load Maximum load
Type Weight Velocity Weight Velocity
[g] [grs] [m/s] [fps] [g] [grs] [m/s] [fps]
N110 0,54 8.3 319 1047 0,79 12.2 436 1430
N120 0,66 10.2 316 1037 1,02 15.7 459 1506

Tables don't copy well but that's a 200 grain bullet with a starting load of 10.2 grains at 2.244" and a max load of 15.7 grains. That oddly enough comes in just over 110% load density. I have found my best accuracy around 103-5%. Those loads are good for about 2.5" at 200 yards.

https://www.vihtavuori.com/reloading-da ... rtridge=19

viewtopic.php?f=141&t=97746






I have no problem using the powder for subs or supers. I think you might have asked the question poorly. That much compression, as I said before,can be a problem. But that powder for subs is very good.

It's also possible whoever answered the email had their head in their ass and can't read Vihtavuori's own data. Using a bullet they designed for subsonic use with Lapua.

If those pictures don't load let me know. I will redo them.

[Edit to add link to old Sierra data for 300 Whisper:
Starting load 11.5 @ 2.260 for 1000fps in a 10" barrel

http://up.sur-la-toile.com/iFsk