What if...for slimjim by request, or anyone else, feel free.

slimjim

fnuser wrote:

Did you recognise what kind of magazine he was using?

It looks like a MagPul though it may not be their latest version.

slimjim

fnuser, how is the project going? I think I may call Mike at Dedicated technologies and talk with him about his 6mm DTI Wildcat based of the 6.8 case. He said via eamil that he would sell me just a barrel. I'd like to talk with him and see what initial load data he has and discuss the merits of this wildcat in 6.5mm. Let me know what you think.

Mike Milli
Dedicated Technology
(218) 444-7419

www.dtechsuperstore.co...mation.htm

slimjim

I've been eyeing one of these for my upper.

www.alexanderarms.com/...=2&item=80

I think the side charge handle is an interesting option.

fnuser

what about that other upper you showed me that the side handle was independent of the carrier?

slimjim

There is merit to their design. I just don't feel like its as beefy as the one from Alexander. Maybe I should look into it more and also find out the price.

slimjim

found some more products of interest.

www.ar15performance.co...ng_6mmbrs_

I like this!

"The 6mm BRX shooting 105 Bergers or 107 SMKs will produce the best exterior ballistics from the AR15 platform. These uppers could be used for highpower or sniper type competitions, hunting or Varmint shooting. The 6BRX is pushing 105gr Bergers to 3000fps from a 22" barrel, making it the flattest shooting cartridge to fit a normal AR15. "

slimjim

ok, fnuser. Guess you have been on holiday (did I say that correctly, Vince?). I'm getting more serious about the performance potential of the 6mmBR case. I am pondering going to

6mmBRX (which moves the shoulder 0.1 inches forward by fireforming),
6.5mm BR (which you only have to neck-size up), or
6.5mm BRX (both of above)

The case is very efficient and you can pretty much get close to the performance of a .260 or or 6.5mm-.284.

what say thou?

slimjim

this site shows the differences between cases.

www.6mmbr.com/cartridg...grams.html

fnuser

I saw that too, am leaning toward the 6.7 but the .308 bolt face you showed me at ar15performance has peaked my interest because i always wanted a 6mmbr or family member trying to figure out which mag they are using i may need to read that again

slimjim

They are using PRI 6.8 mags
www.midwayusa.com/Sear...-4_8-16-32

Check out this forum
www.ar15techforums.com...y.php?f=40

slimjim

I've been leaning toward a 6.5mm because I want to be able to shoot at longer range. As part of my analysis, I look at several variables. IMO, if a cartridge can't achieve at least 3000 fps with lighter bullets for that caliber, its not an efficient case-bullet match for my application. Initially, I was excited about the 6.5 Grendel. However, after analysis I didn't move forward and kept investigating options. Below is the analysis I did. Yes it had better long-range performance than the .223 and 6.8 SPC but when you looked at the trajectories, they weren't very flat at all.

slimjim

You can see that the 6.8mm bullets are light for the .277 caliber and don't have very good BC for longer range application. They do good, however, for short barrel, short-to-medium range AR applicaitons. The 6.5 Grendel has better bullets BC-wise but the muzzle velocities are too low resulting in arcing trajectories.

fnuser

It looks like the 6.8 110 g. is a nice performer what we don't see in this chart are the resulting velocities at various ranges and this is where the b.c. really pays off as in the formula for energy the velocity is a bigger factor then bullet weight but I still like the 6.8 over the 6.5 for the ability to use standard mags with a slight mod not possible w the 6.5 also the resulting trajectories will be within a vitals area of each other at normal hunting ranges below 300 yrds. so that is a wash. I'm not saying the 6.8 is the end all do all cartridge, heaven forbid, We need to save excuses for the next project. I am still thinking the 6mmbr for that but I bet the mags are a major pain in the back pocket for those. I have a long barreled .280 ackley w a 1-8 twist barrel that I have chronied the velocity at 2900 fps w 180 bergers go crank that through a ballistics chart if you like looking at numbers its an awesome cartridge. and a pretty package also if you like o.d. green manners stocks.

slimjim · Last edited by slimjim on Mon Aug 16, 2010 5:08 pm; edited 1 time in total

fnuser wrote:

It looks like the 6.8 110 g. is a nice performer ...

Now that the 6.8 SPC is gaining in popularity, they bullet manufacturers are coming out with more light-weight .277 bullets. The 110 Barnes TSX takes up too much powder capacity with a resultant drop in velocity. Barnes now has an 85gr all-copper bullet. After reloading and shooting the .270 for a couple of years, I have a hard time appreciating the 6.8 SPC unless you compare it to short-barreled 5.56s. 6.8/.227 bullets just don't have high enough BCs to go the distance very well as the graph shows.

slimjim

fnuser wrote:

what we don't see in this chart are the resulting velocities at various ranges ...

I only show the velocity at 1000 yards just because that is my long-range shooting objective for this next rifle. I think I should see if I can introduce trajectory drop an wind drift into the chart.