Jump to content
308AR.com Community
  • Visit Aero Precision
  • Visit Brownells
  • Visit EuroOptic
  • Visit Site
  • Visit Beachin Tactical
  • Visit Rainier Arms
  • Visit Ballistic Advantage
  • Visit Palmetto State Armory
  • Visit Cabelas
  • Visit Sportsmans Guide

New AR Project, looking for caliber suggestions.


Recommended Posts

So I decided to build an 80% receiver this time, and I'm thinking about trying out a different caliber. I have been a 5.56 and 7.62 shooter for a long time and have both of those on the AR platform now. I finished an LR308 on a Tactical Machining lower/DPMS upper with a Fulton Armory barrel last year, and I love it. I know that I can get barrels in a variety of calibers, but I don't know anything about most of the new stuff like 6.8SPC and 300 Whisper / Blackout, so I'm looking for any ideas. These days I'm just a range shooter, and the local range is limited to 600 yards, which is fine for the 308 but a bit much for my 223. Maybe something in between, but which?

Link to comment
Share on other sites

You might want to do a search of .260 Rem or 6.5X47 for long range, and 6.8 SPC, 300BLK or even 7.62X40 Wilson for mid range. Each of the three mid range cartridges all have advantages and drawbacks compared to the others. You have to decide if factory ammo is a must, are you trying to build it as inexpensivly as possible, do you want the most commonality with the .223 guns, etc. All three of the mid cals will use the same AR 15 type lower so if your planning to make your own you could get started and wouldn't need to commit to the cal until you were ready to buy your bolt and barrel.

Link to comment
Share on other sites

My vote is the 6.8 spc....ive got two of em,they are awesome!  its a pricey load,but coming down below a buck a throw these days. after shootin one of these I always have a smile on my face ! This is galfriends 6.8...it now has a 6x18x40 scope instead of the red dot....she's good out to 300 shootin this lil guy <thumbsup> Wash


Link to comment
Share on other sites

Heres my opinion, the 6.8spc is a great mid caliber round. It hits harder than the 223/556 and is more availible than some of the newer hot caliber rounds. Factory ammo is going for $17 to $22 /box of 20, reloading is the way to go after you get enough brass. All of the parts are standard AR15 mil spec parts except the barrel,bolt & mag.

I have four 6.8 guns , a 16" and 3- 24". They are dead on accurate. Range is 300 yards for hunting and accurate to 600 yards.

If you choose this you will not be unhappy !  <thumbsup>

Link to comment
Share on other sites


sounds like the popular opinion is that the 6.8 is the best choice, I don't own one so you should give more weight to the posts by those that do, but, just to pass along what I've been told/have read on it, it is supposed to be a ballistically  good round, hard hitting as stated above, the complaints that I've heard, are that the mags are proprietary (unlike the BLK), and some have reported reliability issues with them.  there have also been posts about bolt longevity problems due to the AR 15 type bolts being relieved to accept the larger base of the 6.8 cartridge. They are also going to be more expensive to shoot than some others. I don't know what the max effective range of the 6.8 is, but from my 18" barreled 300BLK AR, I have found that my 125 gr hand loads show a substantial drop at 200 yds. I haven't tested 110 gr loads yet, but I'm thinking that your going to need an optic with a BDC reticle set up for 300BLK if you hope to use it at long range. I think of the BLK as a 300m cartridge. I haven't experimented with the Wilson, but if you decide to I'd like to hear your results. I think that it may  help in trying to decide on a caliber, if you narrow down your parameters. What specifically will you use it for, how many rds are you likely to put through it a year, would the possible shorter bolt life be something that might deter you from the rd?  And now I have a new cartrige to research, 30HRT. Good luck with your project and please keep us informed.

Link to comment
Share on other sites

Thanks for all the tips, and the reasoning that goes along with. I should have mentioned that I reload, so that eases some issues. Budget isn't a big thing. I'm not trying to build on the super cheap, and I have time, but I don't want to spend 3 grand on it either <laughs>. Also, since I'm thinking mid-range, optics are the way to go. The only restriction really is the limit of an Ar15 lower. I'll take a close look at the 6.8 and the others as well, and let you all know when I have more of a plan. Course now that people are talking about an LR260, I'm thinking of another 80% project!! Maybe a 260 carbine with mid or rifle length gas. Yikes, looks like this is gonna cost 3grand anyway.

Link to comment
Share on other sites

:o oh baby! A 16"-18" LR260 would be hot.
Yeah, I'm thinking strongly about that as an add on upper to my 308. I'm also thinking about what parts to take off my other rifles for upgrades to them that I can transfer to the new rifle. Get a CTR for my 308, put the A1 on the new project.

I see no one mentioned 6.5 Grendel. Any love for that round? Seems to be more accurate than some of the others. MikedaddyH says 6.8 SPC "dead on accurate."  Other people finding it so? If so what barrel is best? I've read that accuracy isn't 6.8SPC's strong point.

Link to comment
Share on other sites

MikedaddyH says 6.8 SPC "dead on accurate."  Other people finding it so? If so what barrel is best? I've read that accuracy isn't 6.8SPC's strong point.

I have a Quentin upper 16" its great at 200 yards. The 24" barrels were made McGowen blanks and chambered by my Gunsmith, He is the best barrel guy in AZ, 90% of his work is done on bolt action rifles for high end manufactures.

On the 6.8spc round most use 110gr bullets. The 115gr and 120gr bullets are more accurate.

Link to comment
Share on other sites

  • 2 months later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...