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7.5" vs 10" suppressed ar?

Discussion in 'Handguns: Autoloaders' started by horsey300, Mar 26, 2020.

  1. horsey300

    horsey300 Member

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    In advance thanks for the constructive input, we're talking ar pistols, likely in .223 of some flavor. I like shorter for maneuvering capabilities, but like ballistic performance of longer barrels..... That being said, do the -2.5" make up for enough maneuvering with suppressors attached to justify the bullet performance? Under 50 yds, likely under 30 yds, looking at controlled chaos, ttsx, gmx and other sturdier but expanding bullets for this one.
     
  2. TonyAngel

    TonyAngel Member

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    I was just asking myself this same question over the last couple of weeks. I've settled on 10.5. A buddy of mine that served in the military and was, until recently, on our local SWAT team told me that 7.5 just doesn't get a .223/5.56 to the velocity that it needs to reach to be effective at any range practical for such a pistol. I don't know if he went out and shot a bunch of hams or what, but I trust the guy enough to take him at his word. He tells me that a properly built 10.5 will do whatever you need it to do out to just past 100 yards and it will run its a$$ off. So, I decided 10.5, if I go 5.56. Now I'm on the fence with maybe still going shorter, but considering something in 9mm or perhaps 300BO.

    There are youtube videos and such on the subject.
     
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  3. herrwalther

    herrwalther Member

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    Referring BBTI, difference between 8" and 10" barrel for most 223 loads is about 200FPS. 10" obviously being faster. If compact is the name of the game you will see more length savings depending on what suppressor you settle on, rather than the barrel length of the rifle. A Surefire Socom is 4" long. The 556-SD from AA is about 7" long. The Surefire is also twice the price. This is one project where it might work best to think of the suppressor first and the rest of the rifle around that.

    http://ballisticsbytheinch.com/223rifle.html

    https://www.pewpewtactical.com/best-ar15-suppressors/
     
    Last edited: Mar 27, 2020 at 2:38 AM
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  4. entropy

    entropy Member

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    A 10.5" with a carbine length gas system will run much better than a 7" with a pistol length system, this I have learned firsthand. A 10.5" barreled AR pistol with a 15" handguard and a can that fits inside* (which is most of them, from what I've seen), is still no longer than a 16 barreled AR.

    * just sticking out the end
     
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  5. horsey300

    horsey300 Member

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    Valkyrie would get the speed but I feel a waste of potential for my purposes lol!
     
  6. Telekinesis

    Telekinesis Member

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    Make sure you know the rating of your suppressor too. IIRC not many cans are rated for sustained fire from a 7.5” .223. If you’re planning on defensive use, I’d probably recommend getting a can rated for FA at whatever barrel length you decide on.

    My SBR (.300 Blk) has a 10.5” barrel and that’s probably as short as I’d want to go unless I was planning on shooting only suppressed and had a handguard that went over the can. A 10.5” barrel is a very handy size, and even with an 8” suppressor, your still about the same length as if you had a 16” barrel with an A2 flash hider. Anyway, if/when I get another upper in .223 for the SBR, it’ll probably be an 11.5” because it opens up a lot of suppressor options.
     
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  7. TonyAngel

    TonyAngel Member

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    Man, the Valk round looks REAL interesting. I'm almost afraid to take a closer look.
     
  8. 12Bravo20

    12Bravo20 Member

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    I have a couple of pistols in 223/5.56 and 10.5" is the shortest I will go. I have been looking hard at a shorter upper in 300 since it performs way better out of short barrels.
     
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  9. wally

    wally Member

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    Careful! Before you consider a 7.5" suppressed 5.56 verify with your suppressor maker that it is rated for the much higher "uncorking" pressure from the 7.5" barrel. Many specify (if you can find the specs) a minimum of 11" or 10" barrel.

    Damaging an expensive and long wait to replace item like a can, would be a bummer.
     
  10. GarrettJ

    GarrettJ Member

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    I had a 7.5” upper for an SBR several years ago and never cared for it. Handling felt weird, lots of noise and blast, even with a can. Extraction was violent. When it started ripping rims off the cases I finally just sold it off. This was maybe 15 years ago.
    Be aware, a can under the hand guard looks pretty slick and works well with a pistol-caliber gun. But a rifle can gets HOT really quickly, and it will transfer that heat to the hand guard.

    Something to keep in mind.
     
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  11. Gordon
    • Contributing Member

    Gordon Contributing Member

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    My Noveske 7.5" Diplomat upper never ran 100% with out the Flaming Pig it came with attached. It was , in fact , designed to run with it OR a suitable suppressor attached ,
    Both my son and I have 8" .300 Blackouts that run fine with pistol length gas and no muzzle attachments.
    I would NOT go shorter than 10" on 5.56 for many reasons in a serious combat gun.
     
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  12. climbnjump

    climbnjump Member

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    And it's not just pressure to be concerned about. With a 10.5" barrel in .223/5.56, you are burning only about 60-70% of the powder charge in the barrel so that's a lot of burning powder that is hitting the baffles in your suppressor. The problem is even worse, of course, with a 7.5" barrel.

    A few rounds here and there is probably no big deal, but a steady diet of it probably isn't a real good idea. However, if you are a hand loader, then you can use powders and design loads that will minimize this problem.

    The 300 BLK uses pistol powders and is designed for shorter barrels in the first place, so you can get about a 90-95% powder burn in a 10.5" barrel which might be easier on your suppressor.
     
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  13. mavracer

    mavracer Member

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    I wouldn't go shorter than 10.5" for 5.56 and prefer 11.5" with Carbine gas as it is easier to get to run without overgassing.
    300 blackout is superior 10.5" and shorter anyway I built a 8" and a 10.5" blackout and sold my 11.5" 5.56. Shortest 5.56 I have now is 14.5" with pinned gemtech flash hider.
     
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  14. Goosey

    Goosey Member

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    7.5" 223 is a toy IMO. There's no need for that and if you do want such stubbiness there's better options.
     
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  15. barnetmill

    barnetmill Member

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    I would like to read more. I have pistol length AR's in 300 blackout and 7.62x39. The 7.62x39 in a 7.5 inch barrel really has a muzzle blast for sure. The .223/5,56 is not a good choice in a super short barrel. For the AK upper I can use bullets intended for the .327 fed mag and for the .300 blackout I can used bullets meant for the M1 carbine. I have just gotten these uppers for cheap money, but only have one other/pistol receiver and need to get more if I decide to keep more than one of the uppers. I need to get a handstop to prevent my hand from getting level with the flash on these super short barreled guns.
    ONGUN.jpg
     
  16. mjsdwash

    mjsdwash Member

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    I loose 300FPS going from 16" to 10.5". 450 going from 20" down to 10.5. Sure its a lot, but a 55gr at 2600 or higher is nothing to laugh about.This is with starting loads of H335. I have no doubt I could knock this past 2700 pushing harder. Yes, this is chrono verified. You will loose about 200 FPS going from 16" to 10.5" in a 30 cal. I would not go below 10.5, for reliability reasons though. You can shorten up the stock to save length.
     
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  17. barnetmill

    barnetmill Member

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    I certainly want to read more. 2700 fps from a 10.5 inch barrel is very impressive and this is especially true when backed up by a good chronograph.
    I found a link on this http://www.sadefensejournal.com/wp/barrel-length-studies-in-5-56mm-nato-weapons/ and it does appear that 10 inch is the critical length for 63 grain M855 cartridge. So higher velocities would be expected for a 55 grain bullets.
    upload_2020-3-28_7-27-8.png
     
  18. Armored farmer

    Armored farmer Member

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    I'm not an AR expert, just a fan.
    My 10.5" runs my .22lr conversion kit very well. It is my understanding that the shorter lengths wont work as well.
    20180819_164717.jpg
     
  19. mjsdwash

    mjsdwash Member

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    I have never hit 2700, but my light loads of H335 with 55gr RMR bullets run 2590-2650 when I chronoed them. While the F1 isn't the best chrono out there, I have compared it in line with others, and its within a few 10's FPS. Lyman 49th lists a very high amount of H335 for .223 in their data, and that has gotten me 3150+ from a 16" barrel, where as the staring loads get me around 2900. I bet I could squeeze another 50-60 FPS with that extra 10% charge, considering I get another 250 from a 16". The max load, while it does not show clear signs of excess pressure, it does tear up cases. I have head seperation at 5 loadings, so I don't use that load much. But its nice to know its there.


    EDIT TO ADD Lymans starting loads are around Hodgdon Max loads. Lyman Max loads are alarming.
     
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  20. mavracer

    mavracer Member

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    One thing to keep in mind will be effective range @2600 muzzle velocity will be down around 2000 @200 yards well below the Army's threshold for m855 or m193. I'd be looking at other bullets for any SD or most hunting even with a 10.5" and the 7.5" is worse.
    My 8.5" blackout only lost ~125 fps from my 16" which is why the 16" got replaced by a 10.5".
    There are plenty of bullets for the blackout that are very effective at blackout pistol velocities. I use Speer 125 TNTs in mine now they're violent at 308 velocities but at Blackout velocities they just mushroom nicely.
     
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  21. mjsdwash

    mjsdwash Member

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    this is correct naturally. I didn't include it because most don't use sub 14" beyond home defense/can blasting range, but it is definitely relevant for those going far out. I would guess im doing 2100 or less at 100 yards. Interesting tip on the TNS's. I just started loading them in 300 AAC, and am getting 2160 at max charges. 16" barrel.
     
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  22. mavracer

    mavracer Member

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    Most I see don't shoot 16" guns past 50 yards lol.
    I suspect you're above 2100 at 100 I just lowered my 62gr m855 load to 2600 on streloc and it was just over 2100 at 200. I doubt there's a 55s with a BC bad enough to drop that low at 100.
     
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  23. mjsdwash

    mjsdwash Member

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    good to know. I can only look at ballistic drop table, and make a guess. I shoot the 10.5 at a 3'x2' steel plate at 100, and cans/bottles at 40. Its just a toy really. I got it on the $300 AR bandwagon. Grand total out the door was 330$, using a PSA kit on special, a Anderson lower on special, Surefeed aluminum mag, and discontinued flipsight bought locally on clearance. It IS a fun toy.
     
  24. mavracer

    mavracer Member

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    There's a free version of Streloc you can download to your phone it has the ability to change velocity and bullets.
    If you're into external ballistics it's a lot of fun to play with.
     
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  25. Lennyjoe

    Lennyjoe Member

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    I built a SBR in .300 Blackout with a 10” barrel and AAC Cyclone suppressor. The suppressor is 8” long so it makes the rifle a bit long for PP in the house. If you want close quarters suppressed why not consider the .300 Blackout over a .223. With subs and a suppressor you will be Uber quiet.

    Here’s mine below. I’m either gonna go with a shorter barrel or I’m gonna build a 4” barreled, suppressed 10MM AR Pistol for in the house.

    8C7CC6E7-56E5-4723-ADC1-CB79A8FB7205.jpeg
     
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