223 Hornady 75gr ELD-M and Shooter's World Precision

[Raydee]

I am working up a load for a 300 yard benchrest match and found two nodes where the vertical is close the same. The first one is between 24.0gr and 24.2gr and the second one is between 24.8gr and 25gr. My barrel is a 26" Wylde with a 1-8 twist. When I plug the info into Gordon's it shows max overpressure at 24gr. I worked up loads from 23gr up to 25gr and never saw any signs of over pressure. Right now I am seating the 75gr ELD-M's at the lands and plan to adjust from there but I am not sure if the 24.8-25gr node is too hot and if I should go with the lower 24.0-24.2gr node. Average velocity is around 2800 in the lower node and 2900 in the higher node. What do you guys think?

 

[jelenko]

I get 44,7000 psi in GRT using a Wylde chamber, 24 gr of SW Precision and COAL of 2.45 [I guessed at the COAL that would touch the lands in a Wylde chamber].

 

[Raydee]

I don't see where I can select Wylde chamber in the program. Maybe that would help. My OAL is 2.39".

 

[jelenko]

Try using the the 5.56x45 version of 223 - it produces similar pressures.
With COAL of 2.39 the max pressure goes to 49,000+.

GRT shows 25 grains of SW Precision produces 56K+.

What case volume are you using? Have you changed the Initial Pressure?

Did you fire a few rounds across a chrono and enter the velocities into GRT?

 

[Raydee]

Try using the the 5.56x45 version of 223 - it produces similar pressures.
With COAL of 2.39 the max pressure goes to 49,000+.

GRT shows 25 grains of SW Precision produces 56K+.

What case volume are you using? Have you changed the Initial Pressure?

Did you fire a few rounds across a chrono and enter the velocities into GRT?

I did switch to the 5.56mm version and it no longer shows over pressure until I am up over 25gr. I am using the stock case volume and have not changed the internal pressure. I have chronographed all the loads but for the most part it looks like the velocity data on Gordon’s matches what I had at the range. For example my 25gr velocity was right around 2900 and that is what it shows on Gordon’s. I also checked Shooters World load data and I think the max they recommend is 25.3gr so I am still under but I still may drop the charge to the lower node so once I start seating the bullets deeper in the case I don’t get any real pressure spikes.

I decided to skip the match today and work on some loads first.