Precision? https://www.cavitybackbullets.com/product-p/cb-pri-mod-5.56.htm
I bought two,, never had any issues whatso ever.
These are new PRI 10 round .223/5.56 SPC magazines that have been modified to load longer than standard magazine length.
They have been professionally modified to allow loading up to 10 cartridges to an over all length of 2.36 inches in a standard AR15 lower magazine well. This will allow the reloader to load his projectiles longer than standard magazine length. Allowing for adjusting the projectile closer to the lands for accuracy or increased performance. Bench-rest shooters single load to take advantage of the benefits. Now you can get the same in an AR15 without the hassle of single loading.
We chose PRI to use as they are the most reliable and strongest magazines made. Due to this they are also costly to acquire.
They will work with any calibers based on the .223/5.56 parent case. .223, 5.56, 300 Blackout or any other cartridges based on the .223/5.56 case.