Precision AR .223 load development

[Nature Boy]

Sub title: trying to make an AR do things it wasn’t meant to do.

Warning: there will be a lot of pics and data

I started a thread in the rifle section about my project to build an AR to shoot in NRA AR Tactical matches here:

https://www.thehighroad.org/index.php?threads/rifle-build-for-nra-ar-tactical-class.889744/



Instead of adding a very crunchy load development post to it I figured it would be more appropriate to start a thread here.

I’m working on heavy-for-caliber .223 loads using Lake City brass (LC13 & LC14), Varget, CCI BR4s and 4 different bullets; SMK 77, Berger 80.5 Full Bore, Berger 85.5 LRHT and Berger 90 VLD.



I’m using a Dillon 650 as a single stage press with a Redding Comp micrometer seating die



I use the press to throw a short charge then trickle up to my final weight using an FX 120i and Autotrickler



I use a 4 step process to arrive at the optimal load

1. a modified OCW for change weight
2. Seating depth test
3. primer test (I’m going to fore go this step)
4 verification at 500 yards

Next post will be step 1

 

[Nature Boy]

Yesterday I shot loads for each bullet going from 24.0 to 24.6 in 0.2gn increments. I can narrow my a targeted charge weights because I already have experience loading for my son’s F/TR rifle using 90 VLDs and have a pretty good idea where the node might be. Because of this I narrowed it down even further for the 85.5 and 90 Bergers.

Here are the results:



In this process you look for the centroid of each 3 shot group and compare the change in vertical distance between adjacent groups.

I decided to start with the 80.5 Full Bores as it was pretty flat across all 4 charges indicating a wide accuracy node.



I settled on 24.3 and proceeded to seating depth testing.

It’s important to note here that I don’t care about group size. I’ll tighten that up by adjusting seating depth

 

[Nature Boy]

Having measured the distance to the lands with each bullet type I start with a 0.010 past touching (into the lands) and back out from there in 0.005 increments. The 80.5 Bergers touching the lands was measured at 1.974 base to ogive. I stopped at -0.015 as the ogive was close to being completely into the neck of the case.

Here’s the results:



As noted, anything between -0.005 and -0.010 should be the most accurate.

I’ll load 20 at -0.007 and shoot them at 500 to verify that, hopefully this weekend

 

[Hooda Thunkit]

Thanks for the explanation of the targets; what you are looking for and why.

I've reloaded for decades, but am just now looking to get into the longer distances and something more than hunting precision.

 

[CoalCrackerAl]

Nice work. I love varget with 223 loads.

 

[N555]

Oh man I don't load anything like that.
I'm more into expanding bullets and 64gr or less.

 

[Varminterror]

Sub title: trying to make an AR do things it wasn’t meant to do.

Warning: there will be a lot of pics and data

1. a modified OCW for change weight
2. Seating depth test
3. primer test (I’m going to fore go this step)
4 verification at 500 yards

In this process you look for the centroid of each 3 shot group and compare the change in vertical distance between adjacent groups.

 

[Bartojc]

I just try to follow along and learn a thing or two. . Most of this is past what I will ever try to do but you’re never to old to learn.

Jeff

 

[Walkalong]

You had me at hello

Well of course he had us, duh, but it takes a little more to entice some folks......

 

[BushMaster-15]

I just try to follow along and learn a thing or two. . Most of this is past what I will ever try to do but you’re never to old to learn.

Jeff

You can grasp what he's doing ; Nature Boy ; Is working up heavy for caliber .224" loads ,so as to determine accuracy based on bullet selection ,Powder and their respective charge weights and setting bullets at different depths ,so as to change distances from the lands in his Rifles chamber . Once he determines the correct combo for His Rifle , I'll assume he is going to compete in the NRA Tactical Matches

It's commonly referred to as Finding the Groove or sweet load development among other cliches .

 

[Bartojc]

You can grasp what he's doing ; Nature Boy ; Is working up heavy for caliber .224" loads ,so as to determine accuracy based on bullet selection

Absolutely. I also have an interest in the heavy .224 loads. Some day I want to buy/build s bolt to shoot heavies in .224 just because.
Jeff

 

[Nature Boy]

Absolutely. I also have an interest in the heavy .224 loads. Some day I want to buy/build s bolt to shoot heavies in .224 just because.
Jeff

When you do, make sure the barrel has the chamber cut to accommodate these really long bullets. The ISSF reamer is generally what is used.

I kind of gimped myself on this project. My LGS had a Proof carbon barrel with a Wylde chamber in stock and the owner made me a deal on it. As a result the tuning window for seating depth is much more narrow. I can fix that with a throating reamer, which I may do at some point in the future.

 

[Nature Boy]

setting bullets at different depths ,so as to change distances from the lands in his Rifles chamber

My thoughts on why this is important has changed over time.

It’s not so much how close you are to the lands than it is how much bullet is into the case. The distance to the lands is just a reference point on how far out you can go. Once I find the optimal seating depth I’m leaving it there and not “chasing the lands” as the throat erodes. I’m not seeing any drop off in accuracy over time, even in rifles that have had a few thousand rounds down the barrel where the throat has moved up to 0.060”

That’s my current theory on it, others will disagree

 

[Nature Boy]

Here an aid I use for setting up the press for seating depth. Many of you may know this but I thought I would share it for folks that don’t.

I cut slits in a case neck, as you see below, which allows me to move the bullet with my fingers. This greatly simplifies the set up process.



I have one of these made for every cartridge I load for.

 

[JFrank]

Nice work’
A lot of guys miss the information on post #2

Can you please expand on why location is more important than group size ?

 

[Varminterror]

My thoughts on why this is important has changed over time.

It’s not so much how close you are to the lands than it is how much bullet is into the case. The distance to the lands is just a reference point on how far out you can go. Once I find the optimal seating depth I’m leaving it there and not “chasing the lands” as the throat erodes.

 

[Nature Boy]

Nice work’
A lot of guys miss the information on post #2

Can you please expand on why location is more important than group size ?

I’ll say it in my own way and others can chime in.

Think of precision (or accuracy) as eliminating variation in the horizontal (X) and vertical (y) axis. I realize I’m using linear terms to define an admittedly non-linear pursuit, but bear with me.

The charge weight is the big knob to turn for controlling the y axis.

The optimal charge weight is the one that has the least amount of change vertically compared to adjacent charges. The wider rage of charges that vary the least, the wider the “accuracy node”.

As conditions change so do the burn characteristics of the powder, some more than others. Finding the middle of that accuracy node gives some assurance that a stable load developed on a 50 degree day won’t become unstable when it’s 95.

Think of the seating depth as a more granular adjustment, followed by primer selection as a very fine tuning knob.

Controlling the horizontal (x axis) is mostly the shooter. It’s how consistently we drive the rifle and how well we can read the wind.

 

[Varminterror]

Newberry’s OCW really works the same way as the Audette Ladder, just fired at individual points of aim rather than a single POI. We look at vertical clustering of groups in Ladders, while OCW looks at the very same vertical consistency from one group to another.