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 AR-10 SBR
vtmactech  [Team Member]
6/27/2011 9:32:48 AM
Ok, I have a bunch of parts left over and would like to build an SBR. Only thing I would have to buy is a rail, either LaRue or Troy TRX. I have a 20" T SS barrel that I would like to cut down to approx 12.5", profiled as light as possible. What gas system do I use? Someone mentioned that Noveske uses a proprietary length on theirs, is this true? If so, what length is it? Will a carbine length gas system function properly? What size gas port should I have drilled? Or should I bite the bullet and buy a new Noveske barrel? Thanks.
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madcratebuilder  [Member]
6/27/2011 9:43:07 AM
Noveske has the 12.5" Leonidas, I'm sure they would share info.

http://noveskerifleworks.com/cgi-bin/imcart/display2.cgi?item_id=125-762&cat=174&page=1&search=&since=&status=

Slash  [Dealer]
6/28/2011 2:42:01 AM
Before you attempt to build a .308 SBR, it would be best to ensure that you have plenty of:
SaturationTech  [Team Member]
6/28/2011 8:37:44 AM
As per the Noveske website on their 12.5" barrel : it is a proprietary length gas system.
http://noveskerifleworks.com/cgi-bin/imcart/display.cgi?item_id=b-125-762&cat=160&page=1&search=&since=&status=

vtmactech  [Team Member]
6/28/2011 10:25:43 AM
Thanks all (except Slash, destroyer of hope ). It's funny Clint, I have an email draft ready to send to you about this. I'm also waiting to see if/what Armalite does for their usual July 4th sale.

Noveske offeres the Leonidas length gas tube here. I've been calling them but haven't gotten an answer. My thought was to use the Leonidas tube and an adjustable gas block. I'm really just after an ultra light AR-10. An A2 carbine is my fall back plan if I decide the SBR is too daunting a project.
panzer  [Team Member]
6/28/2011 4:41:42 PM
Might I recomment the SWS rail then? I have 2 rifle length ones in use, one on a NM AR10 that gets ALOT of sling pressure, and another on a Carbine with a 16 in barrel and both are rifle length. Its the same ones used by Noveske, only the Noveske ones have QD cups built in. Light weight and very strong. Look on the show us your AR0's post around page 54 or so for some good close ups of the rail. I really like it, and its an easy install.
TREADMARKS  [Team Member]
6/28/2011 4:53:24 PM
Originally Posted By vtmactech:
Thanks all (except Slash, destroyer of hope ). It's funny Clint, I have an email draft ready to send to you about this. I'm also waiting to see if/what Armalite does for their usual July 4th sale.

Noveske offeres the Leonidas length gas tube here. I've been calling them but haven't gotten an answer. My thought was to use the Leonidas tube and an adjustable gas block. I'm really just after an ultra light AR-10. An A2 carbine is my fall back plan if I decide the SBR is too daunting a project.


I bought a Leonidas gas tube from Noveske today. I have a low profile JP adjustable gas block and JP modular free float handguard (carbine version) VTAC to experiment with.

In the pictures at Noveske website the Leonidas gas tube looks alot like the short carbine version. If that is the case then it might work with my extra DPMS AP4 barrel that I re-profiled to be a lightweight.

I am looking to build an AR10 SBR as well and have been searching for the right bbl for the right price for quite some time. For me 12" sounds about right for the barrel, now I need to decide on which upper to use (A2 or A3-I have both).

Any other AR10 SBR ideas? I would love to hear/see them.
panzer  [Team Member]
6/28/2011 6:03:29 PM
I have an 11 in SBR FAL, and knowing what I know now and having had it for awhile, i would rather have a 13-14 in Barrel. The option at the time was 11 or 13 in.

Expect about 2300 fps from a 11 in or so Barrel with LC 762 surplus. The leonidas barrel at its length makes perfect sense. If I were to ever cut down my AR10 Carbine it would be to 14 from 16 in, but reality is the 2 inches don't make enough difference to justify the costs or work. There isn't much pf a real difference between a 16 and a 14, but once you start getting shorter around the 12 in mark, the differeces are big and noticeable. The "rule of thumb" for velocity loss per inch isn't quite right either.

The same LC surplus from 21 in FAL same day was 2800 FPS. So a 500 FPS loss over 10 inches, while the 16 in AR10 ( different day and conditions) was running 2700 Fps. Through a 20 In AR10 ( Krieger barrel) was running 2800. So 200 fps over 4 inches, and the Krieger routinely gives higher velocities than any other similar length 308 I have. And it can be pushed HARD. Its match load runs the 190's at 2650 FPS, not even a whimper or pressure sign either . Another huge advantage of the AR10 system. It will eat a bolt gun load that would kill an FAL, M14 or G3 type. The 5R at 24 in gives 2850 with the same LC round.

You can see the velocity loss is more exponitial than linear as you get shorter and shorter.Although it would seem to average out at 50 fps per inch, because in the case of the FAL it is for that one lot of ammo same system etc., its not that cut and dried exactly. Remember it was only 50 fps faster with 4 more inches of barrel in a bolt gun, and 100 fps slower with 5 less inches in an AR10. And the same speed with 1 inch less barrel in an AR10 as well as compared to the FAL. It really is less to around 16 or so then its a steady increase in loss down to 11. And it depends on the load and burn rate of the powders.

M118 Lr with the slower burning powder in the 21 in FAL was just at 2600, ( and Hard on the rifle without tuning the gas for it BTW and even then hard on it) and Barely at 2000 from the 11 inch FAL. And 2800 in a 5R with the 24 in barrel. Also 2700 in the Krieger AR10, and 2500 in the Carbine AR10. I have found on the 308 SBR's with the short short barrels that a 125 or the 135 Sierra HPBT with a fast powder to be accurate and maintain speed and a good gas volume/ preassure curve to keep them running. The good news is if you run a brake on it, they seem to work better in the SBR's. The 11 in FAL creates a HUGE fireball naked, but the PWS gets to work with alot more gas and is very effective. I will replace the Vortex on the AR10 with a PWS when I get home.

Different rifles and systems I know, but a fair comparison as far as length affects. Just something to consider when going with the SBR route. Granted even with the 11 in barrel the FAL is the same exact length as an AK47, and can throw a 147 at the same speed as the 123 in the AK, more accurately as well. But end of the day the 14 + inch guns get alot more velocity and the 16 in AR10 isn't That big of a rifle, and can take some stout reloads if you work your way into them for your rifle. Just some thoughts from my experiences with some 308 SBR's. Hope this helps.
SaturationTech  [Team Member]
6/28/2011 7:55:56 PM
Originally Posted By TREADMARKS:
Originally Posted By vtmactech:
Thanks all (except Slash, destroyer of hope ). It's funny Clint, I have an email draft ready to send to you about this. I'm also waiting to see if/what Armalite does for their usual July 4th sale.

Noveske offeres the Leonidas length gas tube here. I've been calling them but haven't gotten an answer. My thought was to use the Leonidas tube and an adjustable gas block. I'm really just after an ultra light AR-10. An A2 carbine is my fall back plan if I decide the SBR is too daunting a project.


I bought a Leonidas gas tube from Noveske today. I have a low profile JP adjustable gas block and JP modular free float handguard (carbine version) VTAC to experiment with.

In the pictures at Noveske website the Leonidas gas tube looks alot like the short carbine version. If that is the case then it might work with my extra DPMS AP4 barrel that I re-profiled to be a lightweight.

I am looking to build an AR10 SBR as well and have been searching for the right bbl for the right price for quite some time. For me 12" sounds about right for the barrel, now I need to decide on which upper to use (A2 or A3-I have both).

Any other AR10 SBR ideas? I would love to hear/see them.


Here ya go


jchock  [Member]
6/28/2011 9:14:53 PM
Originally Posted By TREADMARKS:

Any other AR10 SBR ideas? I would love to hear/see them.


How about a 12.5" Leonidas Switchblocked 7.62 SBR? Here's a closer shot of the switchblock and muzzle:


The Leonidas 12.5" gas length is proprietary and shorter than a midlength, but longer than a carbine. Barrel has been bilocked for use with GemTech TPR-S (thus the usefulness of the switchblock). Handguard is modified from a RainierArms RA10-X11 rail set (by Sampson). The QD mounts are rotation limited as well.

MV of South African is ~2480fps, Prvi 150gr is ~2440fps.
vtmactech  [Team Member]
6/29/2011 8:04:43 AM
Originally Posted By jchock:
Originally Posted By TREADMARKS:

Any other AR10 SBR ideas? I would love to hear/see them.


How about a 12.5" Leonidas Switchblocked 7.62 SBR? Here's a closer shot of the switchblock and muzzle:
http://i8.photobucket.com/albums/a42/jchock/IMG_5874_sm.jpg

The Leonidas 12.5" gas length is proprietary and shorter than a midlength, but longer than a carbine. Barrel has been bilocked for use with GemTech TPR-S (thus the usefulness of the switchblock). Handguard is modified from a RainierArms RA10-X11 rail set (by Sampson). The QD mounts are rotation limited as well.

MV of South African is ~2480fps, Prvi 150gr is ~2440fps.


Is that a specific 7.62 switchblock? What gas port hole size in the barrel?
jchock  [Member]
6/29/2011 3:08:56 PM
I used a 5.56 switchblock as there isn't a 7.62 switchblock beyond the "beta testing" being done at Noveske. I don't recall the "factory" gas port size on the 12.5" barrel.
panzer  [Team Member]
6/29/2011 9:22:23 PM
There is a 16 in SASS barrel for sale right now in the EE, could be cut down, or left alone. And 7.62SASS website has some on sale as well now, a thinner profile.
vtmactech  [Team Member]
7/1/2011 3:38:06 AM
Called Noveske today, they wouldn't disclose either the exact length of the Leonidas gas system nor the diameter of the gas port used for that length system/upper.
TREADMARKS  [Team Member]
7/1/2011 12:19:06 PM
Now that is sweet!


Originally Posted By jchock:
Originally Posted By TREADMARKS:

Any other AR10 SBR ideas? I would love to hear/see them.


How about a 12.5" Leonidas Switchblocked 7.62 SBR? Here's a closer shot of the switchblock and muzzle:
http://i8.photobucket.com/albums/a42/jchock/IMG_5874_sm.jpg

The Leonidas 12.5" gas length is proprietary and shorter than a midlength, but longer than a carbine. Barrel has been bilocked for use with GemTech TPR-S (thus the usefulness of the switchblock). Handguard is modified from a RainierArms RA10-X11 rail set (by Sampson). The QD mounts are rotation limited as well.

MV of South African is ~2480fps, Prvi 150gr is ~2440fps.


jchock  [Member]
7/1/2011 2:03:45 PM
Yes, it's been a great shooting rifle so far.


Of course, now I have the problem of not enough .308/7.62 to shoot and keep myself entertained. :)

Also, the 12.5" is very loud. The suppressor assistance is very significant in noise reduction. Noveske makes the barrel much heavier than a "light weight" solution as well, but given that it provides a lot more steel for if one shoots at a more rapid rate, that's not a bad thing given that it's not a chrome lined barrel.
SShinkle  [Member]
9/1/2011 12:21:13 PM
Who's rail is that on the above rifle?


My PL...

jchock  [Member]
9/2/2011 1:03:52 AM
Originally Posted By SShinkle:
Who's rail is that on the above rifle?


I assume you mean mine (the switchblocked one). The handguard is modified from a RainierArms RA10-X11 rail set (by Sampson). By modified, I mean I used a hacksaw, Dremel, and airbrushed KG GunKote to create the cutout in the same style as the Noveske 10.5" Light Shorty Switchblock upper in 5.56mm.
crocodile427  [Member]
9/2/2011 9:43:54 AM
Originally Posted By jchock:
Originally Posted By SShinkle:
Who's rail is that on the above rifle?


I assume you mean mine (the switchblocked one). The handguard is modified from a RainierArms RA10-X11 rail set (by Sampson). By modified, I mean I used a hacksaw, Dremel, and airbrushed KG GunKote to create the cutout in the same style as the Noveske 10.5" Light Shorty Switchblock upper in 5.56mm.


Did you need to mod the gas port or anything to make the switchblock work? I know Armalite uses M-15 gas blocks, but I dont know about the port size. I have been wanting to snatch one these up but Noveske says they are not for 7.62. I dont see why it would not work since Armalite uses standard AR-15 blocks on their AR-10s.
jchock  [Member]
9/2/2011 10:16:53 AM
Originally Posted By crocodile427:

Did you need to mod the gas port or anything to make the switchblock work? I know Armalite uses M-15 gas blocks, but I dont know about the port size. I have been wanting to snatch one these up but Noveske says they are not for 7.62. I dont see why it would not work since Armalite uses standard AR-15 blocks on their AR-10s.


I did have to mod the gas port on the barrel slightly. (You have to do this at your own risk as this change is not supported by Noveske, so if you foul it up, you're responsible for your replacement barrel. Also, I'll warn you I take no responsibility for your actions either... ) This mod was because when I was done, the switchblock worked _perfectly_ in "S" mode with the suppressor, but the barrel short stroked when in "open" if there wasn't a suppressor attached. Todd (at Novekse) did imply that they would have preferred my barrel be installed on a lower using a factory AR10 stock tube and buffer rather than with an AR15 buffer tube and Slash heavy buffer and that most likely that was the cause of the short stroking when "open." There was also some concern by Todd that the straight line formed by the gas tube between the AR10 upper and 5.56 switchblock would cause an "off angle" problem resulting in a mis-aligned/canted gas tube that would contribute to less than 100% function.

Anyway, you cannot mod the gas port on the switchblock (well, you could, but it will probably ruin your drill bits) as the switchblock is very hard after it's heat treatment/case hardening and finishing. It also involved modifying and creating a gas tube with the new ports as the 5.56mm gas tube that came with the switchblock was not the same length as the Leonidas. Plus, the gas ports on the gas tube require a new gas tube roll pin hole to be drilled.
crocodile427  [Member]
9/2/2011 10:34:29 AM
That sounds like too much work for me. Atleast at this point in time in regards to my tools and abilities. I think Ill just wait for the 7.62 switch block. I think the one on the Armalite SASS is a Noveske, but I may be incorrect in that assumption. they only sell that block when you by the SASS handguard kit. Comes with special tube as well. Thanks for the info.

I do have a 20" barrel, would that make any difference? I assume you are using it on a 12.5" barrel, so maybe pressures might be adequate on the 20" setup? Thanks again
PraesulPresul1  [Member]
9/7/2011 4:15:26 PM
Originally Posted By crocodile427:
That sounds like too much work for me. Atleast at this point in time in regards to my tools and abilities. I think Ill just wait for the 7.62 switch block. I think the one on the Armalite SASS is a Noveske, but I may be incorrect in that assumption. they only sell that block when you by the SASS handguard kit. Comes with special tube as well. Thanks for the info.

I do have a 20" barrel, would that make any difference? I assume you are using it on a 12.5" barrel, so maybe pressures might be adequate on the 20" setup? Thanks again


Noveske has been in the testing stage of 7.62 Switchblock for months now and the last time I asked Todd I didn't get an answer which implied they were on the cusp of finishing. If you go this route, I wouldn't think at this point any time this year.....

Armalite SASS block is Armalite's design and proprietary also. The 16" barrel requires a special gas valve and gas tube neither of which Armalite or 762SASS sell anymore. SASS gas tube is flared at the end and shorter than a regular 16" so it would take some considerable skill to replicate. You can buy the SASS kit minus the handguard from 762SASS but it only works 100% on the 20" barrel according to them.
Croft32  [Member]
9/7/2011 4:53:52 PM


Noveske has been in the testing stage of 7.62 Switchblock for months now and the last time I asked Todd I didn't get an answer which implied they were on the cusp of finishing. If you go this route, I wouldn't think at this point any time this year.....

Armalite SASS block is Armalite's design and proprietary also. The 16" barrel requires a special gas valve and gas tube neither of which Armalite or 762SASS sell anymore. SASS gas tube is flared at the end and shorter than a regular 16" so it would take some considerable skill to replicate. You can buy the SASS kit minus the handguard from 762SASS but it only works 100% on the 20" barrel according to them.


There has been talk of a 7.62 switchblock since the inception of the 5.56 one. I got excited when I saw that IRA had one on their .308 autoloader, but it was still in the testing stages then. I feel like every time that there's input about one, it is in the testing stages

Must be giving them more trouble than they thought.
cityboy172  [Team Member]
11/8/2011 8:11:25 PM
This is relative to my interests....
PraesulPresul1  [Member]
11/16/2011 10:54:22 AM
Originally Posted By PraesulPresul1:
Originally Posted By crocodile427:
That sounds like too much work for me. Atleast at this point in time in regards to my tools and abilities. I think Ill just wait for the 7.62 switch block. I think the one on the Armalite SASS is a Noveske, but I may be incorrect in that assumption. they only sell that block when you by the SASS handguard kit. Comes with special tube as well. Thanks for the info.

I do have a 20" barrel, would that make any difference? I assume you are using it on a 12.5" barrel, so maybe pressures might be adequate on the 20" setup? Thanks again


If you go this route, I wouldn't think at this point any time this year.....


Obviously proved me wrong here as Noveske and Rainer Arms have them in 16" and 18". Really want to see a 12.5"
StonerAR10  [Member]
11/18/2011 2:33:59 AM
I just read a great article in one of the AR mags that did a test on AR15 SBRs and concluded that in an AR15 any barrel less than 14" reduced the effectiveness of the round dramatically. Thye look cool but lose power and effect quickly past a certain length. Same for 308 but more so.
cityboy172  [Team Member]
11/18/2011 7:30:58 PM
Originally Posted By StonerAR10:
I just read a great article in one of the AR mags that did a test on AR15 SBRs and concluded that in an AR15 any barrel less than 14" reduced the effectiveness of the round dramatically. They look cool but lose power and effect quickly past a certain length. Same for 308 but more so.


Borrowed the stats from elsewhere.

150 gr HPBT Win 748 loaded to a chamber pressure of 56.4K PSI WARM load 45 gr NOT a starting load. I chose 748 as the powder as it is most like NATO powder.

26" = 2918 FPS MP= 6.6K PSI –– 99.6 % powder burnt - 2836 ft/lbs
24" = 2873 FPS MP= 7.4K PSI –––––––––––––––––––––––––––– 2750 ft/lbs
22" = 2823 FPS MP= 8.2K PSI –––––––––––––––––––––––––––– 2655 ft/lbs
20" = 2766 FPS MP= 9.2K PSI –– 98.7 % powder burnt - 2548 ft/lbs
18" = 2700 FPS MP= 10.5K PSI –––––––––––––––––––––––––––– 2428 ft/lbs
16" = 2623 FPS MP= 12.0K PSI - 97% powder burnt –––– 2291 ft/lbs
14" = 2531 FPS MP= 14.0K PSI –––––––––––––––––––––––––– 2133 ft/lbs
12" = 2417 FPS MP= 16.7K PSI - 94% powder burnt –– 1946 ft/lbs
10" = 2273 FPS MP= 20.5K PSI –––––––––––––––––––––––––– 1721 ft/lbs
8.0"= 2080 FPS MP= 26.0K PSI - 87% powder burnt. - 1441 ft/lbs
6.0"= 1800 FPS MP= 34.1K PSI -79.4% powder burnt -1080 ft lbs


madcratebuilder  [Member]
11/19/2011 12:45:01 PM
Originally Posted By StonerAR10:
I just read a great article in one of the AR mags that did a test on AR15 SBRs and concluded that in an AR15 any barrel less than 14" reduced the effectiveness of the round dramatically. Thye look cool but lose power and effect quickly past a certain length. Same for 308 but more so.



I have to disagree with that article. Now this is a 5.56 but I'm down less than 250 fps from a 16" carbine.



Accuracy isn't bad either.





Of course this doesn't answer how short you can go with a 7.62. A 12.5 barrel would be interesting to try out.


ARKAR  [Team Member]
11/20/2011 12:09:22 AM
I've heard the same thing. The shorter barrels reduce velocity and shorten the distance at which
the 5.56 round fragments. This is what really affects it's performance. The 7.62x51 round doesn't
depend on fragmentation for performance and I'd think it's performance would be less affected by
the loss of velocity from a shorter barrel.

As for the 12.5 inch barrel, Noveske has been making the "Leonidas" AR10-based rifle for a while
now: Noveske Leonidas!


ARKAR
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