Need some advice on low velocity rounds

[airmonkey13]

REM 300WM 5r Factory 24" barrel-thicker varmint style approx. 50 rounds thru
WW Brass
Fed 215 Primers
Nosler 180 E-Tips
H1000 81Grns
5 rounds 3008 fps average ES 14 SD 5.8
6 rounds 3001 fps average ES 34 SD 13
2nd case fired and annealed. Shots were at least 3 minutes apart to reduce barrel heat.

Used a Sinclair comparator so the numbers may be a 1/2" higher than expected on measurements. Here are measurements for your thoughts. Freebore is long and I plan on working up 210 Berger loads a little later. But I need these for CA -darn Condors.

Nosler Book Max is 3.340" for standard and 3.300" for E-tips 81 grains is book Max (103%) at 3123 fps
Book Max As loaded Lands
CBO 3.636" 3.777" 3.879"
COAL 3.340 3.482" 3.581"

So I am .101" off the lands and .142" over standard COAL. I am curious if anyone has an idea on velocity increases by distance when you get closer to book max COAL pushing the bullet in. I am not sure if I should start more towards COAL and work out? Or start compressing the bullet and find velocity increases. Trying to get an accurate load. These are currently 1MOA accurate but I have been working for nodes mostly. 81 grains seem to be a node for me. Had one flat primer, no swipes at 81. and then started seeing some pressure signs at 81.5-more flatter primers with one crater, no swipes or hard bolt.

So I would appreciate any advice especially if you have a formula for pressure increases.

 

[Milo 2.5]

But I need these for CA Condors.

I hunt California condors with a 32" 12 gauge, full choke, 00 Buck, lead of coarse, don't reinvent the wheel.

 

[redneckbmxer24]

Are you asking why your rounds are slower than the data, or why your second string went slightly slower?

If the latter and everything stayed the same between your strings then I'd guess you're either using a shoot through chrono which are not consistent string to string due to lighting, or you had a round or two go way low reducing your average which also explains the increased ES on that string. I'd be trying to figure out why that happened.

If you're asking about the difference in data, you can't trust it or expect it to match up. It's there as a guide line only, there's way too many factors. You've got a factory barrel which are notorious for being on the slow side and at 50 rounds is nowhere near broken in and sped up, and Nosler likely used a universal receiver and a mid to higher end tube to get the data. Then you have to consider any differences in their chamber and jump, their brass volume (which I'm sure they used for testing) vs your Winchester, the lot of powder and primers they used vs your, and so forth.

It's also not unusual for a manufacturer (especially that one) to inflate their performance data.

I recommend only using the factory data as a guide. Determine where the bullet likes to be seated for YOUR barrel, and where YOUR lot of powder and primers starts showing signs of pressure in YOUR barrel, and what charge shoots the best.

 

[airmonkey13]

Redneckbmxer-I realize my rounds are slower in velocity, because I have essentially created a larger case space for the powder to expand in. I was wondering since I am so far off the lands right now, should I compress the bullet in the case and if there is a formula that expresses- Case volume vs. psi.

If I bring it .050" in will that give me a 100fps increase?

Yes. I had a low 2982fps round on the first shot that expanded my ES

 

[redneckbmxer24]

The only time I've seen a significant increase in pressure and velocity from seating depth is when you start getting into the lands.

If it shoots great where it's at, why worry about it? 100fps really isn't going to make much difference in ballistics either way. If you're not satisfied with the ballistic performance of the load the rifle likes and want more energy down range, or better trajectory and drift then you're better off moving on to a longer heaver bullet.

Remember that your barrel will continue to speed up for the few hundred rounds and then settle. I've seen as much as a 150fps increase on some factory tubes once they settle although 50-100fps seems to be about the norm. The Tubbs Final Finish system helps accelerate this process and works very well.

I stopped chasing velocity a long time ago. I pick the best bullet and then let the rifle tell me what velocity it likes.