Very few reviews on the D&H ten round 6.5 Grendel magazines. To my knowledge Palmetto State Armory is the primary vendor for these mags. Buffman Range does videos where he chronographs a lot of ammo. Buffman has been testing some 6.5 Grendel ammo using a 12" and 18" PSA 6.5 Grendel AR-15's. Buffman has been using a D&H mag with good results.
If your having feed issues you can try loading a few 6.5 Grendel cartridges in a 5.56 magazine to compare function. A 5.56/223 mag will work with a few 6.5 Grendel cartridges but get to many rounds in the mag and they don't stack properly and will start to bulge the 5.56/223 mag.
It is not uncommon to encounter feed issues with a 6.5 Grendel if an AR-15 is over or under gassed.
https://dh-tactical.com/mag-65-Grendel.html
If your having feed issues you can try loading a few 6.5 Grendel cartridges in a 5.56 magazine to compare function. A 5.56/223 mag will work with a few 6.5 Grendel cartridges but get to many rounds in the mag and they don't stack properly and will start to bulge the 5.56/223 mag.
It is not uncommon to encounter feed issues with a 6.5 Grendel if an AR-15 is over or under gassed.
https://dh-tactical.com/mag-65-Grendel.html