Thread: Low velocity and pressure Howa 223

Originally Posted by earplay

I recently picked up a Howa 223, put a few loads together and finally got out to test earlier today. I picked the 73gr ELD-M as it seems to shoot well for many people, and 2208 as it’s what I had on hand.
I consulted ADI data and setup a profile in GRT which suggested I’d be hitting max pressure around 2750 fps at 24gr of powder in a 20 inch barrel. I loaded a couple of charges for reference, at 23, 23.5 and 24 gr at a COAL of 58.5mm However, on testing, all velocities were about 150fps short of where they should be, with 24gr barely pushing 2600 fps. They shot well enough for my purposes, but the low velocity is puzzling.
If there is a linear relationship between pressure and velocity, does this mean I can keep increasing my charge weight toward my expected velocity? Are some barrels just slow? (I’ve used this same batch of powder in another load that was ok, so don’t think it’s that).

Have you measured/calculated what the bullet jump is? A reasonable jump can decrease pressure/velocity. Also like @Tentman says, because of the small case volume (I assume), it can be quite sensitive to changes in case volume, so measure what you have. I've been playing around with 6mm-223 loads, and the last few have been within around 10 fps of the GRT model I've set up.

Also what is GRT saying your burn ratio is? 2208 might be a bit slow, and lower burn % may result in inaccurate modelling. I try and pick a powder/projectile combo that results in 95-100% burn, my theory (and its only that) being a more complete burn gives less room for variances in velocity, all other things being equal. Might be complete BS on my part, who knows!