N135 6br question

[Wellington]

Wasn't sure whether to put this in reloading or here. New build using N135. 70 gr Sierra Match HPBT. .010 off the lands. VV website lists max at 33.9 as max. At 32.6 I was getting slight marks on case and at 32.8 I had a hard bolt lift so I quit at one shot. Velocity at 32.8 was just over 3400. So what gives?

 

[JEFFPPC]

It's showing you the limit of what your rifle can handle with that load. It is what it is. Sounds ok to me if it's the most accurate load. It is about accuracy not velocity. If that load shoots .6 but 110 fps less shoots. 2's, then I would be shooting at the lower velociy.

 

[Wellington]

Most accurate is 32gr. Just wondering why I am so far off of published data is all.

 

[PatMiles]

It's not a cookie cutter world so published data is somewhat meaningless as you have discovered. Listen to what the target is telling you.

 

[Mulligan]

Wasn't sure whether to put this in reloading or here. New build using N135. 70 gr Sierra Match HPBT. .010 off the lands. VV website lists max at 33.9 as max. At 32.6 I was getting slight marks on case and at 32.8 I had a hard bolt lift so I quit at one shot. Velocity at 32.8 was just over 3400. So what gives?

Differences in brass alone can account for that difference.
Differences between Lapua, Alpha, and Peterson can be significant in a BR or variant.
CW

 

[taylorw]

Most accurate is 32gr. Just wondering why I am so far off of published data is all.

Bore dimensions are sometimes overlooked also..

The good thing about stopping at “bolt lift” is it will allow you to find the top node and pressure curve for your rifle and still stay safe, for each combo that’s tried.

The weakest link of the rifle will show up first and give you the indication of heavy lift (bore volume, chamber finish, brass yield point, powder/primer lot variances, bullet type, weather, etc)...

I would go with what others above have said and listen to your rifle and the target.

 

[WyleWD]

Most accurate is 32gr. Just wondering why I am so far off of published data is all.

FWIW, I tried N135 in a 12 tw and 68gr bullets and couldn't get much above 32 either. I just assumed that it was a .236 bore or something. Accuracy was decent. WD

 

[AckleymanII]

Turn over a few rocks.

Web dimension on new brass

Web dimension on a 2x fired piece of brass

Some chambers are too tight for Lapua brass dimensions, or reamer wear has cut a smaller chamber that what is right for Lapua brass. I learned this the hard way.

Mulligan's post is right on the money.

 

[Bill Norris]

Differences in brass alone can account for that difference.
Differences between Lapua, Alpha, and Peterson can be significant in a BR or variant.
CW

Absolutely, brass can often times determine your powder charge. For instance my Peterson 6BR brass weighs 10 grains MORE than my Lapua 6BR brass. That within itself caused me to reduce my charges 1.5 grains of powder to begin my load development in my 6BRX.

 

[Lefty Trigger]

^^^^ This, I just switched to Peterson brass and I'm having to reduce loads as well. I think the trade off will be a huge life span of super duty Peterson brass.

 

[SSeal]

32.2gr of n135 makes right at 3480fps in my 14 twist straight 6br with 68 gr bullets and Lapua brass. So your results aren't too far off from mine.