OCW analysis with 223 Remington and 80 grainers

[glock24]

I could use some second opinions on a pair of OCWs I just completed with my new 223 Remington rifle. I think I might be trying to get too greedy with my velocities, but please confirm.

Both tests were shot from an 18" Bartlein with a 1 in 7.5" twist. The chamber is throated for 80 grainers, so my COAL is around 2.5" for both loads. I saw zero pressure signs with all of these loads.

Conditions included 50F temps and some 10 mph cross-wind gusts. I'm going to blame the wind for just a bit of my horizontal.

First up is an old stand-by; 80g Sierra Match Kings and Hodgdon Varget. It seems the smart money is on 24.1 grains, but I really, really like 2800 fps velocity I'm getting at 25.3 grains (not compressed).

Question1; Do I dare keep exploring at the top end, or just be happy with 24.1 grains?

Question2; Why did my group size seem to open up at the higher velocities? Is this something I should be concerned about?

Next up is an 80.5g Berger HPBT with the new IMR 8208 XBR. This load seems to have a very stable OCW. I see very little POI movement. Since I didn't see pressure signs, should I keep exploring the top end, or should I just pick from this test? 23.8g looks good to me. Thoughts? Any reason to like or dislike this test as compared to my test above?

 

[TravisB]

Re: OCW analysis with 223 Remington and 80 grainers

Did you do a ladder test?

 

[Seawalker]

Re: OCW analysis with 223 Remington and 80 grainers

24.1 Varget (nice wide node)
23.8 8208 (looks promising, adjust bullet seating), but it looks like your target doesn't match the data--24.4?

 

[glock24]

Re: OCW analysis with 223 Remington and 80 grainers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TravisB</div><div class="ubbcode-body">Did you do a ladder test? </div></div>

Nope. No ladder tests for me. I like OCW round-robins followed by long-range accuracy confirmations.

 

[glock24]

Re: OCW analysis with 223 Remington and 80 grainers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Seawalker</div><div class="ubbcode-body">24.1 Varget (nice wide node)
23.8 8208 (looks promising, adjust bullet seating), but it looks like your target doesn't match the data--24.4?
</div></div>

Thanks. I was thinking the same thing. Part of me wants to be happy with the nice wide Varget node, but another part of me wants to be greedy, and try to optimize the 8208 XBR which offers me around 100fps more velocity.

I'll play with seating depth and see what happens. I might as well also try the 80g SMK with the 8208 XBR powder.

 

[Niles Coyote]

Re: OCW analysis with 223 Remington and 80 grainers

If your not compressed at (varget) 25.3 and not seeing pressure signs I would continue to explore the top end. I like your numbers at 24.1 and groups, if that continues.

You could also play with the seating depth at the top end to see if you can tune that high velocity load in.

Dont be offended, as there is no mean spirt here... You may what to check your data in the tables, I assume your shooting 8208, not 8028, you state COAL is ~2.5 but table says 2.960 and your power weight table doesnt match the pic 100%.

 

[Niles Coyote]

Re: OCW analysis with 223 Remington and 80 grainers

opps someone beat me to it

 

[Niles Coyote]

Re: OCW analysis with 223 Remington and 80 grainers

I had a conversation with a bench rest shooter the other day. He was telling me any powder charge can be accurate. Its all about bullet seating depth and tuning it to the pressure by seating deeper or shallower.

I have not yet tested his advice but I can see some logic behind it. He was shooting a custom chamber 30 benchrest. So not your run of the mill "wana be, know it all"

 

[glock24]

Re: OCW analysis with 223 Remington and 80 grainers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Niles Coyote</div><div class="ubbcode-body">If your not compressed at (varget) 25.3 and not seeing pressure signs I would continue to explore the top end. I like your numbers at 24.1 and groups, if that continues.

You could also play with the seating depth at the top end to see if you can tune that high velocity load in.

Dont be offended, as there is no mean spirt here... You may what to check your data in the tables, I assume your shooting 8208, not 8028, you state COAL is ~2.5 but table says 2.960 and your power weight table doesnt match the pic 100%. </div></div>

LOL! No offense. Thanks for pointing out my dyslexia. I will update my 8208 data to reflect reality.

As for the COAL, understand I use a comparator, so my numbers are higher than normal. In reality, 2.5" is what the loaded cartridge measures.

 

[glock24]

Re: OCW analysis with 223 Remington and 80 grainers

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Niles Coyote</div><div class="ubbcode-body">I had a conversation with a bench rest shooter the other day. He was telling me any powder charge can be accurate. Its all about bullet seating depth and tuning it to the pressure by seating deeper or shallower.

I have not yet tested his advice but I can see some logic behind it. He was shooting a custom chamber 30 benchrest. So not your run of the mill "wana be, know it all" </div></div>

I've seen bullet seating depth change my group size significantly. In fact, seating depth is usually my next step after determining OCW. I think I want to avoid trying to tune just any charge weight however. I'd rather tune the most resilant charge weight, which is what the OCW tests helps determine.

I'll keep playing. Lots of options still . . .

 

[kyreloader]

Re: OCW analysis with 223 Remington and 80 grainers

With the 8208, I like the looks of 23 or 23.1g. That seems to be a pretty stable area, although only for 2 groupings(22.9 and 23.2g). I would explore the higher node if I were you and not seeing any pressure signs. I would like to see a 24.4g and a 24.7g to see if POI settles down.

With Varget, I would shoot a 5 shot group with 1 of each of the first 5 powder charges. If all hit in the same group, I would pick the middle charge and go with that load. That is a huge node that I would be very happy working in. Pick the middle work with seating depth and go shoot your barrel out.

 

[MitchAlsup]

Re: OCW analysis with 223 Remington and 80 grainers

I see a node for the 80 SMK with Varget going from 23.2 through 24.4. This would be a true 'throw and go' load without even bothering to measure charge weight. However some 300 yard targets would confirm just how wide the node is.

The berger/8208 node is quite narrow.

 

[pjparker]

Re: OCW analysis with 223 Remington and 80 grainers

Glock

I, too, found 8208 to give higher velocities than obtainable with Varget.

Shooting F Class, so my platform is somewhat different than yours, but the load is virtually the same.

Derived from a ladder test, (just my preference, don't be hatin')
I settled on the following:

Lake city 09 brass sorted and prepped
JLK 80 gr VLD
24.7 gr IMR 8208 XBR
Wolf standart small rifle primer
COAL 2.500
M.V. 2900 fps (30" Krieger 8 twist)

I don't shoot groups too often, so I don't have pics to show, but this load will shoot scores in the 590's (out of 600) on the F class 0.5 moa target at 300,500 and 600 when I get the wind doped correctly.

Published data for 8208 seems to be quite conservative, but watch all of the standard pressure signs just to be sure. I have had my bolt bushed for a tight fit with the firing pin, which helps to handle loads on the upper end, which, in my rifle, it is.

Paul

 

[glock24]

Re: OCW analysis with 223 Remington and 80 grainers

I decided to try the 80.5g Berger HPBT with Varget in hopes of seeing the same, wide OCW node, but with the advantages of the higher B.C. Berger.

What I found (below) was a bullet that acts a bit different. There does seem to be a node between 23.5 and 24.1 grains, but there also seems to exist a node between 25.0 and 25.6 grains.

Would it be wise of me to explore this higher node, or am I just being greedy again? As you can see from my velocity notes, I did see pressure at 25.6 grains (ejector marks)


<span style="text-decoration: underline"><span style="font-weight: bold">Details:</span></span>

mid 40s
no wind
light rain
0.015" off the lands
Lapua brass
CCI BR-4 primer

 

[MitchAlsup]

Re: OCW analysis with 223 Remington and 80 grainers

I see a definate node between 25.0 and 25.6, and maybe it is close to 25.3. So, I would survey the region between 25.1 (as 25.0 is still scattering rounds) and 25.5 (staying under the pressure limits seen at 25.6--but watching pressure signs intently above 25.3). For this survey, I would switch to 5-shot groups and be ready to demill at signs of pressure.

You can plot the centyroid of the groups and notice the centroid is rising through 24.7 and then is descending by 25.6; with a flat area between 25.0 to almost 25.6.

I notice this was done at 40dF, so in this case perhaps a bit of additional caution is in order if the ammo is to be used in the summer time (i.e. hot weather).