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sbr with 7" barrel

pyplynr

Full Member
Full Member
Minuteman
Apr 4, 2010
982
344
42
Oklahoma
I'm building a sbr with 7" barrel. Does the twist matter in this short of a barrel? I've been looking at the Noveske Diplomat barrel with a 1/7 twist. I'll be shooting regular 55 grain bullets
 
Re: sbr with 7" barrel

It will be mainly for plinking fun. Might take it along on a coyote hunt or two for the short shots. To be honest I'm really not expecting super accuracy.
 
Re: sbr with 7" barrel

I would like a 7" AR for a PDW in a truck just incase I were to run into trouble you could manipulate it in a truck.
 
Re: sbr with 7" barrel

I have one, and it's a fun barrel to shoot. I built it to test and use in a training environment for vehicle-borne training operations. I'm going to be doing some ballistic testing later this spring to determine what loads will actually effectively work out of the weapon (for terminal performance, not external ballistics).
1:7 twist is necessary. I train with standard M193/XM193 and it works just fine. The accuracy is fairly good, but long range suffers.
The rifle is extremely fun to shoot, but it is really really damn loud. The muzzle blast and concussion is pretty pronounced. The muzzle flash looks like a large fireball. Because there is so much unspent powder coming out of the barrel, you need a muzzle brake/suppressor that will direct the discharge forward. This is why Noveske designed the KX3 flaming pig can brake. The KX3 directs the blast forward and away from the shooter and those that are next to you. The only other brake I found that looks like a viable option is the Troy Claymore flash suppressor/brake. If you don't get a can-style brake/suppressor, the concussion from the barrel is much higher.
Because of the pistol-length gas system and short barrel, I made several upgrades to the gas system to slow down the bolt. I installed a Sprinco upgraded 5-coil extractor spring and a Sprinco extra-power chrome silicon recoil spring. I'm also running a Noveske H2 buffer, which is what Noveske recommends for that barrel. With those modifications, the rifle has had no mechanical malfunctions so far. I am still seeing some damage to the case rims from extraction, which tells me that the bolt is still pulling out a little too fast. It's not bad, but just enough that I'm going to try an H3 buffer to see if it makes any difference.

Here is my 7.5" Noveske Diplomat/KX3 build:

img_3522.jpg

img_3461.jpg

img_3465.jpg

img_3474.jpg
 
Re: sbr with 7" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: USACS</div><div class="ubbcode-body">I have one, and it's a fun barrel to shoot. I built it to test and use in a training environment for vehicle-borne training operations. I'm going to be doing some ballistic testing later this spring to determine what loads will actually effectively work out of the weapon (for terminal performance, not external ballistics).
1:7 twist is necessary. I train with standard M193/XM193 and it works just fine. The accuracy is fairly good, but long range suffers.
The rifle is extremely fun to shoot, but it is really really damn loud. The muzzle blast and concussion is pretty pronounced. The muzzle flash looks like a large fireball. Because there is so much unspent powder coming out of the barrel, you need a muzzle brake/suppressor that will direct the discharge forward. This is why Noveske designed the KX3 flaming pig can brake. The KX3 directs the blast forward and away from the shooter and those that are next to you. The only other brake I found that looks like a viable option is the Troy Claymore flash suppressor/brake. If you don't get a can-style brake/suppressor, the concussion from the barrel is much higher.
Because of the pistol-length gas system and short barrel, I made several upgrades to the gas system to slow down the bolt. I installed a Sprinco upgraded 5-coil extractor spring and a Sprinco extra-power chrome silicon recoil spring. I'm also running a Noveske H2 buffer, which is what Noveske recommends for that barrel. With those modifications, the rifle has had no mechanical malfunctions so far. I am still seeing some damage to the case rims from extraction, which tells me that the bolt is still pulling out a little too fast. It's not bad, but just enough that I'm going to try an H3 buffer to see if it makes any difference.

Here is my 7.5" Noveske Diplomat/KX3 build:

img_3522.jpg

img_3461.jpg

img_3465.jpg

img_3474.jpg
</div></div>

Nice rig! Thanks for the info on the recoil springs and buffer. I'm just waiting on my form 1 to finish my build. Good info.
 
Re: sbr with 7" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: USACS</div><div class="ubbcode-body">I have one, and it's a fun barrel to shoot. I built it to test and use in a training environment for vehicle-borne training operations. I'm going to be doing some ballistic testing later this spring to determine what loads will actually effectively work out of the weapon (for terminal performance, not external ballistics).
1:7 twist is necessary. I train with standard M193/XM193 and it works just fine. The accuracy is fairly good, but long range suffers.
The rifle is extremely fun to shoot, but it is really really damn loud. The muzzle blast and concussion is pretty pronounced. The muzzle flash looks like a large fireball. Because there is so much unspent powder coming out of the barrel, you need a muzzle brake/suppressor that will direct the discharge forward. This is why Noveske designed the KX3 flaming pig can brake. The KX3 directs the blast forward and away from the shooter and those that are next to you. The only other brake I found that looks like a viable option is the Troy Claymore flash suppressor/brake. If you don't get a can-style brake/suppressor, the concussion from the barrel is much higher.
Because of the pistol-length gas system and short barrel, I made several upgrades to the gas system to slow down the bolt. I installed a Sprinco upgraded 5-coil extractor spring and a Sprinco extra-power chrome silicon recoil spring. I'm also running a Noveske H2 buffer, which is what Noveske recommends for that barrel. With those modifications, the rifle has had no mechanical malfunctions so far. I am still seeing some damage to the case rims from extraction, which tells me that the bolt is still pulling out a little too fast. It's not bad, but just enough that I'm going to try an H3 buffer to see if it makes any difference.

</div></div>

Thanks for the info. And super nice SBR. It's pretty much the same setup I'm looking at except I'll be using a midlength Spikes/Seekins Precision handguard. I got a Noveske KX3 for it. Where did you get the Sprinco springs if you don't mind me asking? I've also got a Spikes ST-T2 buffer laying around. I'm curious about using the Noveske Switchblock.
 
Re: sbr with 7" barrel

Just found this. I'm thinking I may go with this barrel http://www.rainierar...product_id=1026 It starts as a Shilen blank and it's 1/8 twist. A little faster twist and $100 cheaper than the Noveske. Anyone ever use a barrel from Rainier Arms?
 
Re: sbr with 7" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pyplynr</div><div class="ubbcode-body">Just found this. I'm thinking I may go with this barrel http://www.rainierar...product_id=1026 It starts as a Shilen blank and it's 1/8 twist. A little faster twist and $100 cheaper than the Noveske. Anyone ever use a barrel from Rainier Arms?</div></div>
Sprinco springs: http://sprinco.com/tactical.html

As for the Rainier barrel, Rainier barrels are good barrels, but in this instance the Noveske is the preferred barrel. The Rainier is a 1:8 twist, which is SLOWER, not faster. Also, the barrel does come with a proprietary gas tube, but there's no indication of a gas block. I don't know if it comes with one, or if you have buy one separate. If you have to get a separate one, how does it attach? The ideal low profile gas block should have set screws or should be pinned. There's no indication of which system it uses, but I would assume it's dimpled for set screws. Rainier does sell a proprietary lo-pro match gas block, which costs another $48. I don't know if they include it with the barrel or not.

I personally prefer the Noveske, because the barrel is the faster 1:7 twist, which is the preferred twist for an SBR. The Noveske also uses a pinned AND set screw proprietary gas block which is super strong and secure.

The switchblock is only necessary if you are going to put a suppressor on the weapon. There are very few suppressors that will work well with a barrel that short though.
 
Re: sbr with 7" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: USACS</div><div class="ubbcode-body">
Sprinco springs: http://sprinco.com/tactical.html

As for the Rainier barrel, Rainier barrels are good barrels, but in this instance the Noveske is the preferred barrel. <span style="color: #FF0000">The Rainier is a 1:8 twist, which is SLOWER, not faster</span>. Also, the barrel does come with a proprietary gas tube, but there's no indication of a gas block. I don't know if it comes with one, or if you have buy one separate. If you have to get a separate one, how does it attach? The ideal low profile gas block should have set screws or should be pinned. There's no indication of which system it uses, but I would assume it's dimpled for set screws. Rainier does sell a proprietary lo-pro match gas block, which costs another $48. I don't know if they include it with the barrel or not.

I personally prefer the Noveske, because the barrel is the faster 1:7 twist, which is the preferred twist for an SBR. The Noveske also uses a pinned AND set screw proprietary gas block which is super strong and secure.

The switchblock is only necessary if you are going to put a suppressor on the weapon. There are very few suppressors that will work well with a barrel that short though. </div></div>

Sorry, I just cut and paste from another forum I had the same topic in. In that forum I was also thinking about a Rock River Arms barrel that is 1/9 twist.
 
Re: sbr with 7" barrel

Noveske doesn't sell their 7.5" with a Switchblock.

41
 
Re: sbr with 7" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: USACS</div><div class="ubbcode-body">
Here is my 7.5" Noveske Diplomat/KX3 build:

img_3522.jpg

</div></div>

Jee'z that is a beautiful weapon!! A few months back I saw a your link to your page on this build, and I have to admit to you, that I have copied some of your build I love it so much! Exactly the look and setup I was imagining and then there it was on your page!!

I will be using a UBR stock, and a seekins lower though and a different caliber! When my form 1 comes back I will have to post it up!

Thanks for sharing your build with us, and I hope you don't mind that I copied you haha!
 
Re: sbr with 7" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pyplynr</div><div class="ubbcode-body">It will be mainly for plinking fun. Might take it along on a coyote hunt or two for the short shots. To be honest I'm really not expecting super accuracy. </div></div>


I would not be so concerned with accuracy as I would bullet effectiveness on target, if you are pursuing game.

7.5" bbl gives up A LOT compared to even a 16" 5.56 bbl. I averaged 2790fps with 62gr M855 (70deg, almost sea level alt., 65% hum) from an 11.5" bbl, but have not chrono'ed from a 7.5". I would stake a claim at 2500fps or so from the 7.5 with 55gr though.

Not a pellet gun; but definitely not a power house.
 
Re: sbr with 7" barrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BigDKC</div><div class="ubbcode-body">

Jee'z that is a beautiful weapon!! A few months back I saw a your link to your page on this build, and I have to admit to you, that I have copied some of your build I love it so much! Exactly the look and setup I was imagining and then there it was on your page!!

I will be using a UBR stock, and a seekins lower though and a different caliber! When my form 1 comes back I will have to post it up!

Thanks for sharing your build with us, and I hope you don't mind that I copied you haha!</div></div>
I have a 11.5" Daniel Defense/LaRue build pending BATFE approval right now, and once that's done I'm going to be doing a 10.5" Noveske .300AAC Mk18 build (probably next year).
Go ahead and copy the photos.
Here are a couple more that are more current:

IMG_4045.jpg

IMG_4066.jpg






<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TallShot</div><div class="ubbcode-body">

I would not be so concerned with accuracy as I would bullet effectiveness on target, if you are pursuing game.

7.5" bbl gives up A LOT compared to even a 16" 5.56 bbl. I averaged 2790fps with 62gr M855 (70deg, almost sea level alt., 65% hum) from an 11.5" bbl, but have not chrono'ed from a 7.5". I would stake a claim at 2500fps or so from the 7.5 with 55gr though.

Not a pellet gun; but definitely not a power house.</div></div>
The big concern with barrels that short is the velocity. I haven't gotten around to getting chrono reading on the gun, but you might be pretty close with the velocity. Hornady has informed me that for SBRs, they highly recommend 55gr or lighter loads. Those loads will fly faster so they'll have better terminal ballistics. I am going to be doing a gelatin test some time this spring with Hornady TAP Urban 40gr and TAP Urban 55gr, Federal Tactical Bonded SP 55gr, and possibly Hornady TAP BTHP 75gr. I foresee decent results with the lighter TAP loads, but everything else is a "MAYBE". Since the gun is designed as a PSD PDW system, TAP Urban loads would appear to be ideal for operational use in that role. Still, I'm curious how the Federal 55gr barrier loads will perform.
 
Re: sbr with 7" barrel

Regarding ammo, in government testing from an 8" barrel (LWRC PSD) the best performers tested at 100 yards were 55 gr. Federal Tactical Bonded (penetration 16.8", expansion 0.43" and retained wt. 55 gr.) and 64 gr. Speer Gold Dot (pen. 16.2", exp. 0.45", ret. wt. 61 gr.). There are probably others that would do as well but the testing was limited to seven types of ammo. The full report is available to LE agencies.