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Durkin Tactical Franklin Armory
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Posted: 8/10/2017 7:04:22 AM EDT
Good afternoon gents,

I am currently torn btw purchasing either the DD Mk18 or DD 300S.  Both have a 10.3 barrel.  Currently, I have a Colt 6920 with a few mods, and a 16 inch barrel, that I do not intend on shortening.  I am sold on DD for my first SBR, and have already acquired my trust.  After extensive research, I am at a stalemate, and was hoping you guys could provide me with some info and advice that I am not aware of.  Therefore, which weapon system is better for home defense and competition purposes?   I haven't decided which route I want to go with the SBR yet.  Also do you guys think I am better served using my 6920 for 3 gun comps, while utilizing an SBR for home defense purposes?  Or vise versa?  I have an aimpoint pro & magnifier, and LMT stock on it.
It is impossible to hurt my feelings, so please be brutally honest.  

Thank you
Link Posted: 8/10/2017 7:20:18 AM EDT
[#1]
Tough call, both are good. If you live in an apartment or something I'd go 5.56mm as it fragments more and penetrates less. But yeah 300BLK is made for short barrels and works great for home defense or hunting also, the rounds tend to stay together more and penetrate more. So if you're worried about shooting through walls I'd go 5.56mm, otherwise 300BLK is pretty sweet. Of course 5.56mm is cheaper and easier to find ammo for. But 300BLK tends to be a little quieter suppressed, especially if you use subsonic ammo. But I've been going back to supersonic 300BLK ammo as it does a better job. Get some Barnes black tipped 110 grain 300BLK ammo. But then again the Black Hills 5.56mm TMK 77 grain stuff is pretty wicked as well. I don't think you can go wrong either way really. 
Link Posted: 8/10/2017 7:43:44 AM EDT
[#2]
I have the 300S. Blackout is probably better for interior defensive use, especially with a suppressor, due to the versatility of the 300blk loads. Mine has a 3-lug on it for my Optimus, rated for both subs and supers.

You already have a good 223 in a barrel length that is well suited to the round. Get the 300blk in a barrel length (10.3") well suited to that round.

The best gun for competition is the gun you already have, so the 6920 will be fine for deciding whether you enjoy it enough to buy hardware more suited to competition.
Link Posted: 8/10/2017 8:58:05 AM EDT
[#3]
Don't BS yourself OP; the question is which to get "first".

My opinion is get the DD 5.56 in 10.3
Then buy a 300bo in an 8.5" later.

(FYI - a second short barrel upper will lead to another SBR'd lower)
Link Posted: 8/10/2017 3:59:02 PM EDT
[#4]
No trying to hijack, but I've been giving some thought to my first SBR and am kinda wondering about which one of these roads to travel also. If shooting super's with a suppressor, how would say an 8.5" 300 BLK compare to an 11.5" 5.56 sound level wise?
Link Posted: 8/10/2017 5:20:15 PM EDT
[#5]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Don't BS yourself OP; the question is which to get "first".

My opinion is get the DD 5.56 in 10.3
Then buy a 300bo in an 8.5" later.

(FYI - a second short barrel upper will lead to another SBR'd lower)
View Quote
+1 on everything
Link Posted: 8/10/2017 7:15:50 PM EDT
[#6]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I have the 300S. Blackout is probably better for interior defensive use, especially with a suppressor, due to the versatility of the 300blk loads. Mine has a 3-lug on it for my Optimus, rated for both subs and supers.

You already have a good 223 in a barrel length that is well suited to the round. Get the 300blk in a barrel length (10.3") well suited to that round.


The best gun for competition is the gun you already have, so the 6920 will be fine for deciding whether you enjoy it enough to buy hardware more suited to competition.
View Quote
Agree....
 I hardly even shoot the 5.56 anymore...
Link Posted: 8/10/2017 7:18:14 PM EDT
[#7]
7" 300blk
10.3" 556
12" 6.5 grendel
16" 308
Link Posted: 8/11/2017 2:06:45 AM EDT
[#8]
Gents,

Thank you for the feedback.  I think I'm going to pursue the .300 BO.  My follow up question is: where would I obtain a 8.5, or 9 inch barrel from?  What companies are the best in that category?  Also, which companies sell complete SBR's with that specific barrel length?


Thanks again
Link Posted: 8/11/2017 7:30:45 AM EDT
[#9]
Noveske has an 8.5. I built mine but used their barrel, bcg, receiver, nsr rail, etc.
Link Posted: 8/11/2017 8:27:25 AM EDT
[#10]
Consider White River Armory for a 300 barrel. My first build, I decided to go economical on the barrel as opposed to one of the top shelf mfg's and I couldn't be more pleased. I reload and I'm all about shooting suppressed, where this platform really shines.

Size really matters when it comes to gas port size in a short barrel. My 8" heavy barrel profile came with an .093 gas port. You get bolt hold open on supersonic rounds but not always with subsonic unless it's suppressed.

Before I started my build, I lived at 300blktalk.com. Great place to learn all things 300 BO.

Good luck. The journey to acquire more knowledge is half the joy!
Link Posted: 8/11/2017 5:08:17 PM EDT
[#11]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Don't BS yourself OP; the question is which to get "first".

My opinion is get the DD 5.56 in 10.3
Then buy a 300bo in an 8.5" later.

(FYI - a second short barrel upper will lead to another SBR'd lower)
View Quote
Now that sounds familiar...  Picked up a DDMK18 pistol in 5.56 with a .308 can last year .  I picked up a BCM 9" 300 bo upper for it once the stamps came in back in Jan...
Link Posted: 8/11/2017 6:11:03 PM EDT
[#12]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Consider White River Armory for a 300 barrel. My first build, I decided to go economical on the barrel as opposed to one of the top shelf mfg's and I couldn't be more pleased. I reload and I'm all about shooting suppressed, where this platform really shines.

Size really matters when it comes to gas port size in a short barrel. My 8" heavy barrel profile came with an .093 gas port. You get bolt hold open on supersonic rounds but not always with subsonic unless it's suppressed.

Before I started my build, I lived at 300blktalk.com. Great place to learn all things 300 BO.

Good luck. The journey to acquire more knowledge is half the joy!
View Quote
Ok Marine, this is why I told you to come here. Above poster just gave you valuable info about very short barreled sbr's.{see red} What we were talking about the other day.

With the right load a 300BLK would be fine for home SD and the suppressor will reduce muzzle flash and sound enough that you wont be blind and deaf if you have to light up a perp in your house.

Your 6920 set up is fine for 3 gun.

say hello to ahkbar for me
Link Posted: 8/12/2017 7:22:33 AM EDT
[#13]
First of all, I can't thank you enough for blowing my cover as a secret Marine agent.  I guess you were never taught the significance of OPSEC.
Second, I'm loving the creativity of your username.  It def relates to your lame personality.  Third, I like to explore all potential options, and cross each one off the list as I go through them.  Its called being "open minded".  Furthermore, I'm curious to see how other people view different setups.  It gives me more information on the matter, which allows me to make an "educated decision".
Link Posted: 8/12/2017 11:08:27 AM EDT
[#14]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
First of all, I can't thank you enough for blowing my cover as a secret Marine agent.  I guess you were never taught the significance of OPSEC.
Second, I'm loving the creativity of your username.  It def relates to your lame personality.  Third, I like to explore all potential options, and cross each one off the list as I go through them.  Its called being "open minded".  Furthermore, I'm curious to see how other people view different setups.  It gives me more information on the matter, which allows me to make an "educated decision".
View Quote
Link Posted: 8/22/2017 1:11:14 PM EDT
[#15]
I'll pitch in my thoughts and opinion...

First thought is that I don't like SBRs shorter than about 9.5." A 16" carbine is, imo, a pretty handy set up. A 10.5" or so SBR with a 6" or so, light weight suppressor ends up a bit shorter than the 16" carbine with an A2 and maintains excellent balance. Just about perfect. So, I think a barrel length in the 9.5" - 11.5" range makes for an excellent start for an SBR.

I own an 10.5" and an 11.5" 5.56 and on occasion own a 9.5" - 10.5" 300BLK. I miss the 300BLK SBR or upper when I don't own one but I can live without... Not so regarding a 5.56 SBR, which I shoot a heck of a lot more for a lot of reasons, including ammo price.

A 300BLK paired with supersonic ammo doesn't do much for me, especially considering I own and prefer an 11.5" 6.8 SBR. However, as quiet as it is, a 300BLK shooting subsonic ammo always brings a smile to my face.

With the right ammo selection and a suppressor, I don't think there is much to choose between a supersonic 5.56 and supersonic 300BLK SBR for effective home defense.

So, as noted by other members, plan on acquiring both uppers eventually, but start with a 5.56. [But, if you reload, go with the 300 first.]

JPK
Link Posted: 8/22/2017 7:25:06 PM EDT
[#16]
Are you planning on a can sometime down the road?
Link Posted: 8/24/2017 2:11:34 PM EDT
[#17]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
No trying to hijack, but I've been giving some thought to my first SBR and am kinda wondering about which one of these roads to travel also. If shooting super's with a suppressor, how would say an 8.5" 300 BLK compare to an 11.5" 5.56 sound level wise?
View Quote
Sound level seems to be higher with anything 5.56 to me supersonic.
Also, there just seems to be more gas in my face with 5.56 suppressed.
I don't have specific numbers but that's just my experience.
I dumped my 9.25" and 11" 5.56 uppers and have no regrets.
Link Posted: 8/31/2017 10:51:36 AM EDT
[#18]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Are you planning on a can sometime down the road?
View Quote
This. I have cans for my 7.5 5.56 and my 8.5 300blk. Subs out of the 300blk are stupid quiet for me. Fun to shoot but I don't have enough free time to reload anymore. Going to sell all my 300blk stuff later this year and build another 5.56.
Link Posted: 8/31/2017 12:16:43 PM EDT
[#19]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Gents,
Thank you for the feedback.  I think I'm going to pursue the .300 BO.  My follow up question is: where would I obtain a 8.5, or 9 inch barrel from?  What companies are the best in that category?  Also, which companies sell complete SBR's with that specific barrel length?
Thanks again
View Quote
When I decided to go subsonic .300 SBR with can, I wanted my first to be a complete build meant for my purposes. I decided on a Spikes Compressor 8.5" w/LRS2 can. Now that I've built a couple of AR's, I can really appreciate all of the subtle nuance they built into that rifle. It's a frikkin work of art, and it shoots like a dream. 100% outta the box awesome.

Attachment Attached File
Link Posted: 9/2/2017 1:05:27 PM EDT
[#20]
Discussion ForumsJump to Quoted PostQuote History
Quoted:

This. I have cans for my 7.5 5.56 and my 8.5 300blk. Subs out of the 300blk are stupid quiet for me. Fun to shoot but I don't have enough free time to reload anymore. Going to sell all my 300blk stuff later this year and build another 5.56.
View Quote
If I had bought the .300 just for fun, I'd have regretted it.    5.56 is just half the cost to shoot for fun.
Link Posted: 9/3/2017 2:42:18 AM EDT
[#21]
300 BLK Barrel
8.5 inch in that 300 BLK factory ammo is set-up for 9-inchs, but a 9-inch barrel is hard to find, and if found expensive
1x7 twist in case you want to shoot heavies. Yes, some folks say 1x8 is OK but why worry, just get 1x7.
Nitride for corrosion and wear issues. IMHO nitride is the only type of barrel to buy at this point in time.
Link Posted: 9/4/2017 4:01:04 AM EDT
[#22]
Ballistic Advantage makes nice barrels as well as full uppers
Link Posted: 9/5/2017 2:21:32 PM EDT
[#23]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
300 BLK Barrel
8.5 inch in that 300 BLK factory ammo is set-up for 9-inchs, but a 9-inch barrel is hard to find, and if found expensive
1x7 twist in case you want to shoot heavies. Yes, some folks say 1x8 is OK but why worry, just get 1x7.
Nitride for corrosion and wear issues. IMHO nitride is the only type of barrel to buy at this point in time.
View Quote
Fwiw, my 10.5" 300BLK was 1:8" and was fine with everything I shot with it, which included 220gr bullets, but not heavier. I shot it suppressed about 100% of the time and between the lack of oblong holes in paper targets and the lack of end cap strikes with that set up, I wouldn't hesitate to go 1:8" again. Wouldn't hesitate to go 1:7" either.
Link Posted: 9/6/2017 12:14:15 AM EDT
[#24]
Discussion ForumsJump to Quoted PostQuote History
Quoted:


When I decided to go subsonic .300 SBR with can, I wanted my first to be a complete build meant for my purposes. I decided on a Spikes Compressor 8.5" w/LRS2 can. Now that I've built a couple of AR's, I can really appreciate all of the subtle nuance they built into that rifle. It's a frikkin work of art, and it shoots like a dream. 100% outta the box awesome.

https://www.AR15.Com/media/mediaFiles/461570/st-295084.JPG
View Quote
Wow that screams buy me and love me 
Link Posted: 9/28/2017 2:49:51 AM EDT
[#25]
Gentlemen,

Thanks again for all your knowledge and input.  I wound up going with the DD MK18 5.56 SBR, which has a 10.3 in barrel.  Gonna have to wait some time for the tax stamp to come back now.  However, I have also been heavily contemplating adding a can to it.  I have done extensive research on the matter, and understand there are pros and cons to it.  My biggest priority is to have the shortest length possible without sacrificing quality.  I know we do not live in a perfect world, and I am not going to be able to obtain a can with all the desired attributes.  With that being said, what do you gentlemen recommend?  I am looking to stay below $800, with a length no more than 6.5 inches.  Also what suppressors have been known to perform well with the MK18?  Thank you in advance.
Link Posted: 9/28/2017 2:23:45 PM EDT
[#26]
I would look at the Dead Air Sandman K.  They can be had for under $600 right now, built solid and great mounting system, no minimum barrel length. Also from everything I have heard their CS is good, although I haven't had to find out for myself yet.  

It is a .30 cal can, so if you are looking for a dedicated 5.56 there are other good options out there.  But you will be able to use this on your 300blk when you get it too.

It is not the quietest out there, but I don't think any can will make the 556 sbr hearing safe.  But it should take it down to a manageable level.
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