175gr SMKs and N140

[jlorenzo]

Have a decent amount of both of these, have Starline match 308 small primer, Lapua large primer and Lake City match.

This load will be for a 308 gasser. With Varget and Nosler 175gr custom comps, 41.8 was the limit before I started seeing ejector swipes. I may turn down the gas a bit more and be able to go higher.

I seem to notice you can load a little bit more N140 vs. Varget with the same bullet. I was going to start at 41.5, load single rounds in .2gr increments up to 42.5 and chrono those to see where I'm at.

I've found this gun like the 169 SMK with around 44.5gr of N150, gets me 2675 with a 20". Came down from 44.7 because that seemed a bit hot.

 

[DocBII]

jlorenzo,

N-140 and the 175 Sierras or 178 Hornadys work fine in my AR-10s, Taper crimped and I work up to whatever gives the best velocity with either bullet. Case fill and precision are great.

HTH,
DocBII

 

[jlorenzo]

jlorenzo,

N-140 and the 175 Sierras or 178 Hornadys work fine in my AR-10s, Taper crimped and I work up to whatever gives the best velocity with either bullet. Case fill and precision are great.

HTH,
DocBII

What loads are you using and what are the specs on your gas gun? Just looking g for data points to compare against.

I spent last night loading up some 175s and N140. I started at 41.5 and went all the way up to 42.6. 5 rounds of each charge in .2gr increments. Wanted to shoot today but it's 7F outside and I need to make food for the week.

 

[mgunderson]

Tapered crimp comment was a good one. Keep checking to see if the bullet is moving when the bolt slams home. Gotta watch that neck tension or the seating depth will not be consistent.

 

[jlorenzo]

I found 43.2gr of N140 to be the limit for my gun with the 175 smk. 43gr looked fine and then blanked a primer with 43.2.
Starline 308 match small primer, Federal Gold Medal AR primer. Loaded to mag length. N150 with 169gr SMK has got be 2650ish so it may be better suited to the 175 as well.

 

[kevinbritvec]

Lake City brass requires a full 2.0 grain reduction in powder charges because of reduced internal capacity. I'm running 41.5 grains of VihtaVuori N150 in Lake City under 168 grain SMK's in my gas gun. I have never chronographed this load, but accuracy is good and brass looks great. Ejection is close to 3:00 o'clock.

N150 and N140 are very close to one another for charge weights and velocities. Maximum loads are usually around .5 grain difference across multiple calibers and bullet weights.

IMO, 2650 fps is too fast from a 20" barreled gas gun with 168/169 grain bullets. I would drop the charge at least 1.0 full grain, maybe more. 2550 fps to 2600 maximum. My best shooting loads in my 22" M1-A Super Match rifle are only going 2500 fps. It tied for first place at the state championships in 1989 @ 500 yards only going that fast.

 

[Belly Benchrester]

42.9 of N150 worked really well in an M40A5 clone with 175s. Around 2620 FPS. Hammered. Only have experience with 200s and N140

 

[DocBII]

jlorenzo,

Sorry about the delay in response. The load is 41.5 with CCI 34 and nominal cartridge specs. The rifle is a 20" Davidson Defense upper on a Palmetto State lower. Load has not been tested for velocity, 1/2 to 3/4 MOA accuracy with two different shooters over 10 round strings.

Recently obtained a canneluring tool, I'll be testing a couple of bullets with a full crimp, eventually. It might allow a slower powder to get closer to complete combustion in the short barrel.

HTH,
DocBII

 

[jlorenzo]

jlorenzo,

Sorry about the delay in response. The load is 41.5 with CCI 34 and nominal cartridge specs. The rifle is a 20" Davidson Defense upper on a Palmetto State lower. Load has not been tested for velocity, 1/2 to 3/4 MOA accuracy with two different shooters over 10 round strings.

Recently obtained a canneluring tool, I'll be testing a couple of bullets with a full crimp, eventually. It might allow a slower powder to get closer to complete combustion in the short barrel.

HTH,
DocBII

Here is what I found d with 41.6