I am swapping out some old 308 and 223 ARs with semi custom-builds I ordered to take advantage of the modern cartridge choices and the improved accuracy the best rifle builders are achieving. I’m excited that some of the most accurate gas guns are now getting close to the long range accuracy performance of the best bolt guns with the same chambering and barrel length.
I needed to make some decisions about platform, chambering and barrel length for three different use cases. The tradeoffs today are more complex and nuanced than they used to be 25 years ago when I bought my ARs. This is due to the performance overlap and differences that now exists between the various cartridges for each platform, and even between platforms. One example: an AR15 in 6mm ARC shooting the same 108 gr high BC bullet as an AR10 in 6mm Creedmoor or GT, where the same performance can be achieved with a short barrel AR10 vs a long barrel AR15. Another: better terminal performance, wind drift and ammo availability of 6.5 CM vs lower recoil and better bullet drop of 6 GT.
To help make decisions I created the attached detailed long range ballistics performance comparison chart with some observations. I am sharing this in case it helps someone who needs to make similar decisions, or simply finds it interesting. The pros around here know all about this, but I hope this way of documenting some of the pertinent tradeoff information might be helpful to average shooters like me.
I narrowed down the options to the following in the comparison:
* AR15s in 6 ARC and 223 with barrel lengths from 16" to 26" (for completeness, not because I would build a 25" AR15)
* AR10s in 6.5 CM, 6 GT and 6 CM with barrel lengths from 16" to 26"
The chart is probably best read with a PDF viewer because when printed out the document is dense and fonts are pretty small. A printer with good resolution and a magnifying glass, or good eyesight, will also work. I didn't want to make it complicated with a multipage format, hence the single page density.
I needed to make some decisions about platform, chambering and barrel length for three different use cases. The tradeoffs today are more complex and nuanced than they used to be 25 years ago when I bought my ARs. This is due to the performance overlap and differences that now exists between the various cartridges for each platform, and even between platforms. One example: an AR15 in 6mm ARC shooting the same 108 gr high BC bullet as an AR10 in 6mm Creedmoor or GT, where the same performance can be achieved with a short barrel AR10 vs a long barrel AR15. Another: better terminal performance, wind drift and ammo availability of 6.5 CM vs lower recoil and better bullet drop of 6 GT.
To help make decisions I created the attached detailed long range ballistics performance comparison chart with some observations. I am sharing this in case it helps someone who needs to make similar decisions, or simply finds it interesting. The pros around here know all about this, but I hope this way of documenting some of the pertinent tradeoff information might be helpful to average shooters like me.
I narrowed down the options to the following in the comparison:
* AR15s in 6 ARC and 223 with barrel lengths from 16" to 26" (for completeness, not because I would build a 25" AR15)
* AR10s in 6.5 CM, 6 GT and 6 CM with barrel lengths from 16" to 26"
The chart is probably best read with a PDF viewer because when printed out the document is dense and fonts are pretty small. A printer with good resolution and a magnifying glass, or good eyesight, will also work. I didn't want to make it complicated with a multipage format, hence the single page density.
