The DTI Line AR
Back in the summer of 2009, one of my customers from Iowa asked me about a 6 mm cartridge that would be somewhere between the 6 x 45 and the .243 WSSM. He already had a .223 Remington upper, as well as a .243 WSSM upper, but just wanted something a little less expensive to shoot than the WSSM, and something with more horsepower than the .223.
The 6mm DTI was my first in the DTI line. The idea behind the 6mm DTI was to offer something between the 6 x 45 and the .243 WSSM. It was everything I had hoped for and more! I have taken several nice white-tail deer with it, and countless varmint. The 6mm DTI, like all of the others in the DTI line, is simply a 6.8 Remington SPC case necked-down to 6mm and the shoulder blown forward to 30 degrees. One pass through the FL sizing die, and you are ready to load. The shoulder will blow forward to the sharper angle in the first firing, but virgin brass is plenty accurate for hunting. I have achieved consistent 1/2" groups with virgin brass.
I have been building 6mm DTI uppers in two twist-rates so far: The 1:10 and the 1:12. I have been using the 1:10 twist for my big-game upper, and built a 1:12 twist upper for long-range varmint hunting. I used the 85 grain Nosler partition for white-tail, and have been using the 70 grain Sierra Blitz-King for long-range varmint. The 85 grain partitions are leaving the bore at about 3000 FPS, and the 70 grain Sierra's at a little over 3200 FPS.
The 25 DTI was, much to my surprise, the "king of the hill" when it comes to the DTI line. Where the .25 caliber bullet line-up may be limited, the .25 DTI makes up for it in performance. With the same basic case-capacity of the 6mm DTI and the added bore-capacity of the .257" bore, the 25 DTI does VERY well with an 18" barrel. That makes this hot little round nothing short of magic for predator and big-game hunters alike. Lack of time, coupled with very poor hunting conditions, have limited my actual hands-on experience with the .25 DTI. Fortunately, I have had plenty of customers with more time and better hunting conditions than me. The .25 DTI is responsible for numerous large white-tail and countless coyote and cats being taken in it's relatively short career. Bullet length is a huge factor with any magazine-fed weapon.
Bullet selection gets to be quite a factor in what kind of velocity you will be able to achieve. With my 18" .25 DTI, I was able to safely drive a 90 grain bullet at 3000 FPS. That bullet was produced by Sierra for Federal to use in their "Federal Premium" ammunition line. It was a flat-base hollow-point. If you take a slightly lighter bullet with polymer tip and a boat-tail, you probably will not equal the velocity that I achieved with that heavier flat-base hollow-point because of the added length. Working with the 100 grain bullets I have found the same trend. The shorter, flat-based bullets often exceeded the longer polymer-tipped bullets by a significant amount.
