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- Thread starter volunteerbee
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Your rifle might like RL17 with another bullet, or the 150 BT with another powder, or RL17 with the 150 BT at another charge, or different primers, etc. A 2" group seems kind of big in any case. What rifle are you shooting? Have you clean it or tinkered with it since getting the good groups with the Barnes?

Mark

This may be off the wall to you, but I calculated the OBT node loads for you. If you want to take a chance, load 3 of each and see what kind of group accuracy you get. This is for RL-17 with 150gr Nosler ballistic tip.

67.8gr node 3, expected 3319fps

66.1gr harmonic between nodes 3 and 4, expected 3241fps

64.3gr node 4, expected 3161fps

If you try it, let us know whether the OBT loads are good.

If you can find some try Vihitavouri N550 at 66grains sparked by a Fed215GM for the 150's and thank me later! START LOW AND WORK UP this powder has some ZING to it. My rifle shoot 150grn TTSX anywhere from .500-.6!

This may be off the wall to you, but I calculated the OBT node loads for you. If you want to take a chance, load 3 of each and see what kind of group accuracy you get. This is for RL-17 with 150gr Nosler ballistic tip.

67.8gr node 3, expected 3319fps

66.1gr harmonic between nodes 3 and 4, expected 3241fps

64.3gr node 4, expected 3161fps

If you try it, let us know whether the OBT loads are good.

Freelunch, how are you calculating OBT when I didnt see where he told us the length of his barrel.

I'm running a 155 Scenar out of a 28" barrel using cci br2's and 67.6 grns of 4831. Very accurate

Scout1 concerning OBT method,

For those who do not know, OBT is optimal barrel time and is a theory that the accuracy nodes for any caliber, bullet and powder is dependent on specific barrel time nodes (pressure waves). People use Quickload to determine the exact powder load to equal the pre-calculated OBT node times.

The tables for OBT Scout1, are in 1/2" barrel length increments, and the time adjustment for each increment merely adjusts it so all barrel lengths will give the same OBT node. So in this case I just chose a barrel length of 24". I could have used 26 or 20" and it would have resulted in the same OBT node results.

I had an ulterior motive in calculating the OBT nodes for volunteerbee. This was a double-blind statistical test of OBT where volunteerbee probably didn't know about OBT and I didn't know the accuracy nodes beforehand for 300WSM.

Yeah, I was "using" volunteerbee as a test subject for my own purposes in proving or disproving the OBT method. But, but, if the OBT method calculates good accuracy nodes then volunteerbee gets them for use rather than using the max load for RL-17 from the Alliant website as he did (69.3gr), which wasn't on an accuracy node.

For those who do not know, OBT is optimal barrel time and is a theory that the accuracy nodes for any caliber, bullet and powder is dependent on specific barrel time nodes (pressure waves). People use Quickload to determine the exact powder load to equal the pre-calculated OBT node times.

The tables for OBT Scout1, are in 1/2" barrel length increments, and the time adjustment for each increment merely adjusts it so all barrel lengths will give the same OBT node. So in this case I just chose a barrel length of 24". I could have used 26 or 20" and it would have resulted in the same OBT node results.

I had an ulterior motive in calculating the OBT nodes for volunteerbee. This was a double-blind statistical test of OBT where volunteerbee probably didn't know about OBT and I didn't know the accuracy nodes beforehand for 300WSM.

Yeah, I was "using" volunteerbee as a test subject for my own purposes in proving or disproving the OBT method. But, but, if the OBT method calculates good accuracy nodes then volunteerbee gets them for use rather than using the max load for RL-17 from the Alliant website as he did (69.3gr), which wasn't on an accuracy node.

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Sorry for highjacking the thread,

Jon Hetzler

Scout1,

When the loads I mentioned are under the max load, they are safe in any rifle. In this case, volunteerbee used 69.3 gr max load already and didn't see overpressure signs. The loads I calculated are lower than he already used--they are guaranteed safe. I agree that when you have the exact H2O capacity of the brass used and COAL used, then OBT gives a more precise calculation.

When the loads I mentioned are under the max load, they are safe in any rifle. In this case, volunteerbee used 69.3 gr max load already and didn't see overpressure signs. The loads I calculated are lower than he already used--they are guaranteed safe. I agree that when you have the exact H2O capacity of the brass used and COAL used, then OBT gives a more precise calculation.

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