Need a little help.

[npro04]

Ok so here’s what I have at the moment. I have a 270wsm that I’ve been running the Winchester 130NBT through with good success. The factory rounds are listed at 3275fps and I’m getting 3220 through my chrono. I’ve finally hit the point of reloading for it as I’ve finally dwindled my factory ammo down. The load I’m having issue with is out of the nosler book.
65.5gr RL19 ( Nosler listed max load )
CCI 250 primer
130gr NBT
OACL 2.850” ( Nosler listed test length )
They have it listed as achieving 3302fps. I’m getting 3020fps through my chrono ( avg 5 shot group). Their test barrel is 24” 1-10 twist. My tikka is a 24.3” barrel with 1-10 twist. My question is how am I coming up 280fps slower? I’d understand 50-100fps but 280 seems like a lot. I weighed and trickled each powder load +\- 0.1gr. And measured OACL of each finished round to a range of 2.848-2.851”. Any suggestions?

 

[Rifles And More]

Could be a lot of factors. Same brass, primer, etc? Could be just the barrel.

Have you seen any pressure signs? If not, you could continue up - but why run at the ragged edge. If you accuracy is good, run with it.

 

[Cahunter805]

Many factors contribute to velocity and published data. I’d recommend switching powders if your after more speed. H1000, IMR 7828, IMR7977, Magpro.

 

[npro04]

The nosler data was using nosler brass and I’m using the once fire Winchester nickel brass from the factory loads I shot. Nosler was also using WLRM primers and I’m using CCI LRM primers. With the ones I loaded the cartridge to cartridge consistency velocity wise is outstanding and the accuracy groups are better than the factory rounds. I’m just coming up 280fps avg slower than the nosler book and it just seemed like a lot to me. I figured if they listed it at that charge weight with similar length and twist barrel at 3302 I’d be around 3250ish+

 

[npro04]

No pressure signs at all. Easy bolt lift and nice round primers

 

[Rifles And More]

The nosler data was using nosler brass and I’m using the once fire Winchester nickel brass from the factory loads I shot. Nosler was also using WLRM primers and I’m using CCI LRM primers. With the ones I loaded the cartridge to cartridge consistency velocity wise is outstanding and the accuracy groups are better than the factory rounds. I’m just coming up 280fps avg slower than the nosler book and it just seemed like a lot to me. I figured if they listed it at that charge weight with similar length and twist barrel at 3302 I’d be around 3250ish+

It could be brass volume and primer 'hotness'. Just enough different to show in velocity. Sounds like a great load - nothing really wrong.

 

[Operator]

No pressure signs at all. Easy bolt lift and nice round primers

As Rifles and More posted you could go up in charge, you are not getting signs of over pressure. Go up 1/2gr and shoot 3 rnds. through the chrony and check your primers for pressure if none and your bolt- case isn't sticky you can try the next 1/2gr up. I do this when working up a load, if the case gets sticky I back off 1/2gr. One more thing I like to set my bullet in a hunting rifle 25-40 thousandths off the lands in my rifle gives more volume in the case with the bullet not seated all the way in.

 

[ptmn]

In our sniper rifles, which are all the same, we have some that have "faster" barrels than others even with the same lot of ammo. On the other hand, we never experienced anything near a 280 fps difference.

As others mentioned, primers and case volume have an effect. Lyman states different brand primers can account for 2000 cup difference. As for case volume, even if it is the same brand case, there are lot to lot variances. Switch to a different brand case and there can be more variance. While 308 Winchester is a different caliber than what you have, a lot of long range 308 Winchester shooters prefer Winchester brand cases because of their usually larger internal case capacity.

Powder lots also have some variance, even if it's the same powder, one lot may have up to +/- 5% variance from another lot. That's why it's a good idea to either buy an 8lb powder container or several 1lb powder containers from the same lot. That way if you develop a sweet load, it's more easily repeated with the same powder lot. On that note, if you have worked up to a max load, be cautious of using the exact same load if you run out of the lot of RL19 and switch to a different lot of RL19. It's safer to reduce and work back up.

 

[npro04]

I have more testing planned. I have three more loaded up at 65.5gr. And then three at 66.0, 66.5, 67.0, and 67.5gr. The working up part doesn’t bother me I was just a little taken back by the velocity discrepancy. To be honest I never accounted for the fact that my once fired and bumped brass is bigger than a never fired piece of brass thus creating more volume less pressure etc. I appreciate the help guys. I just hadn’t been that far off of book values before 50-100 absolutely but 280 just seemed out of sorts for me.