Thread: Low velocity and pressure Howa 223

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).

Yes there is a direct relationship between pressure and velocity. Ive shot 73s in 3 20" Howas and they are all quite happy at 2800. But Ive not used 2208 with 73s With 80s a very common load is 24.5 of 2208. Have you fully "calibrated" GRT with your actual case capacity and overall length etc? If you have then you can further "tune" GRT to your rifle using the OBT button. Im too slow a typist to give instructions here but its very straightforward.

Originally Posted by Tentman

Yes there is a direct relationship between pressure and velocity. Ive shot 73s in 3 20" Howas and they are all quite happy at 2800. But Ive not used 2208 with 73s With 80s a very common load is 24.5 of 2208. Have you fully "calibrated" GRT with your actual case capacity and overall length etc? If you have then you can further "tune" GRT to your rifle using the OBT button. Im too slow a typist to give instructions here but its very straightforward.

No, you are wrong.

It is possible to have high pressure loads that do not reach the same velocity as lower pressure rounds due to incorrect powder choice.

Originally Posted by caberslash

No, you are wrong.

It is possible to have high pressure loads that do not reach the same velocity as lower pressure rounds due to incorrect powder choice.

Steady on. Tentman wasn't suggesting that one velocity means the same amount of pressure with every powder.

We know that they all have different burn rates and generate different pressure curves. There is a direct relationship between velocity and pressure. The relationship is just different depending on what the powder is.

Originally Posted by caberslash

No, you are wrong.

It is possible to have high pressure loads that do not reach the same velocity as lower pressure rounds due to incorrect powder choice.

Ouch. Too much salt in your porridge this morning?

223 is very sensitive to specific brass for pressure and speed.

I'd also steer towards something faster than 2208 for 73s, e.g. 2206H.

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!

I tend to back off & accept GRT to 90% fill / 100% burn rate . To me Burn rate is important.
Yet I have mates that don't follow that rule but are getting amazing results & 2206H with 85 % burn rates, it seems to be a foregiving powder. Wish we could buy it!

Originally Posted by flock

I tend to back off & accept GRT to 90% fill / 100% burn rate . To me Burn rate is important.
Yet I have mates that don't follow that rule but are getting amazing results & 2206H with 85 % burn rates, it seems to be a foregiving powder. Wish we could buy it!

I'm not convinced 2206h is correct in GRT, I've switched to using the values for H4895, and I seem to be getting results closer to real world...

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).

Greetings @earplay,
The problem is the Hodgdons/ ADI data. I have experienced exactly the same problem with BM8208 even in a 26" barrel. Recently, as posted elsewhere, Hodgdons upgraded it's .223 data to PSI pressures and the same time reduced max pressures from 52,000 CUP (about 60.000 PSI) to 55,000 PSI. Additionally their new pressure barrels seem to produce significantly more velocity. ADI still lists the CUP data for now at least and that is what I use. Unfortunately there is no CUP data for the 73 grain and no CUP data for any projectile with BM8208. It is possible that the Hornady manual has better data for the 73 grain ELD-M and AR2208.
To answer your initial question, in my opinion at least, there is a linear relationship between pressure and velocity with the same powder and components. Heavier cases, with their reduced capacity will also push pressure up. Case weights run from around 90 grains to well over 100 grains and the heavier ones will produce more pressure and velocity.
Regards GPM.

Appreciate the input.
Re. GRT – I am reasonably familiar with this and have used the OBT function to match up with data – just not sure why it is so far out. I’ve used the same powder in a 7mm08 load that was much closer to begin with (in GRT).
Re. case volume – have not been able to properly measure this. Internet sources suggest 30.4 gr H2O for PMC brass. My scale only goes to 100gr so not sure how I can measure case full of water, short of just tipping water into the pan which I assume won’t be very accurate.
Re. jam length – I measured this to be around 3.4mm with this projectile and OAL. I have entered this into GRT, which brings pressure down but doesn’t shift velocity radically.
I appreciate 2208 isn’t the ideal powder but keen to make do for now. Based on current data, GRT suggests I should be loading about 25gr for 2750 fps, although this will be heavily compressed at mag length. I’m guessing this is where I should be aiming.
All this to say, I managed to get out for walk in the Ruahines yesterday and shot a couple deer at a measly 2550fps! (Albeit not far shots).

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You'll probably need to load it at 24.5gr, IE 100% case fill with the 73's seated to "Standard length". This does 2640 out of my 18" barrel and 2720 out of a friend's 20".

2206H works much better if you are chasing velocity, if you can find it anywhere in a useful quantity. The same load as above but with 06H yields almost an extra 100fps in my 18" barrel.

The speed you are currently getting still kills things just fine with 73's. Imo it isn't a bullet you want to push to hard, to close, they are very splashy.

So I had a play on the CNC and made up a prototype mag housing that would allow for longer OAL. Turns out it works better than expected so will probably just become the working model until I can source a better material. Should allow for 61mm pretty comfortably, and 25gr powder without too much crush.

So to update, got back to the range with some 25gr 2208 loads at 61mm OAL. Only got two rounds across the chrono at 2750 and 2755, so pretty inline with GRT estimates after adjustment. Some primers looked a little flat so thinking I'll back off a pinch and call it done.