6MM DTI vs 6x45

L

Lacounty72

New member
Looking to put together another AR and have tried to extensively research these two calibers in comparison and I'm curious of anyone's opinion that has either/both. Basically what I'd like to do is potentially run a 55 grains Nosler BT in the 3500 speed range (if possible) with a 20" barrel..preferably NOT 22". It seems pretty much doable with the 6DTI but didn't know if any of you had a 6x45 with that length of barrel and what kind of top speeds combined with accuracy you've experienced with the 55's. I'd rather run the 6x45 due to brass availability and cost but am considering the 6mmDTI from Dtech because of the probability of fitting those desired requirements of a 20" light contoured barrel that will get me either 3500 or pretty close to it. If you have specifics on 1:10 vs 1:12 twist that'd help as well.

Thanks,
Lacounty72
 
55s and 8208 will get you close to 3500 and h322 will get you over 3500 in the 6dti if memory serves me. Your not gonna get there with the 6x45. Accurate 2200 is fast but not as accurate as other powders in mine. My longest 6x45 is 18" and only 3000 with h4895 and 55s but I think double up said his 20" was just short of 3400 with 55 ballistic tips.
 
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multiple guys running 6x45 at close to 3700 with 55 tips out of 24" bolt guns on accurate shooter so you should at least make it close if you are on the upper end of pressure. To ensure you are going to get 3500 with the shorter barrel go 6dti but then you get to buy and lose brass vs pick up free range brass. Also need a different bcg
 
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I did get 3,400 in my AR a few times with IMR4198 using either 55 Nosler Ballistic tips or 55 Nosler Varmageddons, but 3,300 is more reasonable I'd say. Mine is a 20" barrel but with 8 twist, so you might punch it on up there closer to 3,500 with a 10 or even better a 12 twist.
 
if you are shooting light bullets a 12 twist 6x45 is gonna get you dang good performance. If you are going to do some version besides off the 223 case (more expensive and harder to find brass at times) then i would go 6mmAR a necked down 6.5 grendel so you get the best case capacity and most speed. Easy to get and cheap brass. That or find someone who will build a slow 12 twist in 6ARC.

So I would vote
6x45
6mmAR
6ARC
then lastly 6DTI
 
Don't overlook the 6X6.8. It is a hammer with the light bullets. You can hit your goal with a 55 without any sweat at all. I use Redding bushing dies so I can control neck tension. Probably have over 100 loads on the books with various bullets for this versatile round.

Greg
 
Yeah I'd most likely go with 1:12. I've talked to Matt few times a Dtech and they built an upper for me years ago and it's way more of a shooter than I certainly am. Good outfit with great customer service. I really like the brass option on 6x45 but mentally I'm gunnin for 3500 fps and it'll prolly most likely be just that...a mental hurdle.
 
Originally Posted By: Hayabusa1321Greg what speeds have you seen from the 6x45 builds with 55 grain bullets compared to 6x6.8

My 6X45 is a 24" tube. I found across the board most powders were maxing out at 3400 but got 3500 with AA2200 and the winner was TAC at 3604. It is polygon so I figure 25 FPS loss/inch on shorter set ups..

My 6X6.8's were shot with 58's and no 55's. I would add about 50 FPS if I went to the 55. Out of an 18" tube I found H322 hit 3546 in one barrel and 3460 in the other. I shot some 748 in a 20" and got 3550. Mid-3450's were pretty normal across the board. I did not push the 6X6.8's hard to any extent with brass life being extremely good. I have a couple of lots of brass that have 10+ firings on them.

By and large I usually concentrated on the 70 weight bullets in both chamberings as I love the TNT and what it does on warm targets. As an aside I have shot the 87 Hornady at 500 yards in both in F-Class and was very pleased with the results. I eventually ended up with a 243 LBC bolt and AR 24" for that work shooting 95 SMK's thanks to the shorter case handling them better as the 87's were about max for the other two.

Greg
 
Guess I'm cheap in my thinking of free range pick up brass and availability. Thats why i thought a 20" or 22" 6x45 pushed hard with 55 grainers would get you close to your speed requirements. Easy to find dies and no bolt carrier group change.
 
Ounce for ounce I don't think there is a better 6MM on the market when you look at performance and price. I own six of them..lol

Greg
 
I would go 6x45 simply for the brass availability.

I just built two 6x6.8s this summer, one 18" and another in 22". They are polygonal barrels from Ritch's Precision Guns and are actually made by Tactical Ordinance. I did tons of research and wanted the extra speed of the 6.8 case but I never found it, mostly because my chambers are out of spec for the 58s and 55s, which it was supposed to be designed to shoot the 58s!! I can only load to like 2.18 COAL with 58s and thats a compressed load that ruins seater stems using their load data of 31.5gr of 8208. Most of these fast velocity numbers are using old original SSA brass that is no longer made and mostly unobtainable. S&B brass is supposedly excellent and has the largest case capacity of the 6.8 brass currently produced but its been unobtainable as well, been trying over a year to get some. I ended up with Starline, its really good thick brass but the case capacity is smaller than the SSA or S&B. If a person could get S&B brass regularly it might be different on velocity numbers.

With Ritch and Gregs load data using 31.5gr of 8208XBR my 22" barrel runs 3473 with 58vmax and 3471 with 55NBTs.

The 18" runs 3373 with the 58vmax and 3346 with the 55NBTs.

The 55 Noslers was actually slower in both barrels, my speed was measured using a Magneto Soeed V3 that is spot on with all my PRS rifles so in conclusion the speed I was trying to get never happened.

Maybe with a chamber that was in spec where you could actually load 58s and 55s to mag length and if a person could actually buy brass that isn't made anymore or something with a higher case capacity you could reach those speeds.

With the limited brass issue and limited powders for the 6.8 currently I'd go 6x45 and never look back.
 
Thanks Greg for detailed responses...I'm curious what polygonal barrels you're running?...fair warning I'm a low totem pole novice in the reloading/wildcat game and this new 6mm AR15 will be my first venture into the world of wildcats so don't feel like you can simplify any of your answers to much to me ha.
 
Thanks Kino I'm hoping to call Ritch's and pick his brain here next week on the spec's I'd like to see if they're possible. I've got a crap ton of 223 brass and that of course is the main reason I'd like to go the route of 6x45. It doesn't appear I'd be sacrificing much looking at it vs. the 6DTI or even the 6mmAR.
 
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