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300BO barrel- Is 5.5 too short? Login/Join 
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I'm intrigued by the Sig MCX Rattler. Pretty much the same dimensions as the MPX, but 300BO. I like the idea of being able to use AR mags and using my Omega suppressor.

Do 5.5" work decently with 300BO? Can the loads be tailored to optimize that barrel length?
 
Posts: 8074 | Location: The Red part of Minnesota | Registered: October 06, 2002Reply With QuoteReport This Post
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Before I bought a 300BLK barrel for my SBR project I talked to Dr. Phil Dater @ the SAR Show in PHX. Since he is one of the suppressor industries most respected member/founders (Gemtech) and I have talked to him in person many times over the years, I took his advice. He said that 8" was the shortest 300BLK bbl. length that could be effectively suppressed.

I bought a CMMG 8" barrel for use with my Omega 300. HTH


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Posts: 2836 | Location: AZ | Registered: July 18, 2011Reply With QuoteReport This Post
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I have a Rattler but I didn’t buy it to suppress. I bought it to be short and throw supers and it excels in that role. That being said, I’ve seen plenty of them suppressed. I think Tim from the Military Arms Channel suppresses his.

I had some concerns about the 5.5” barrel but it works well and is very accurate. Apparently Sig had to speed up the twist to get it to work right but work right it does.
 
Posts: 7933 | Location: Hiram, GA. | Registered: October 24, 2007Reply With QuoteReport This Post
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Any idea what the velocities are from 5.5" as compared with longer barrels?

And that's a pretty hefty foregrip pictured above. What make/model?




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Posts: 40313 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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quote:
Originally posted by sigfreund:
Any idea what the velocities are from 5.5" as compared with longer barrels?

I have a copy of one guy's "ballistics by the inch" for Barnes factory 110 grain blackout loads. It seems to be one of the better comparisons done, for barrels of 4" to 24" long, in 1" increments. Sadly it no longer seems to be on the webz, probably due to image hosting issues. I'm doing some interpolation for a 5.5" barrel.

Values are barrel length in inches -- MV in fps -- energy in foot pounds

5.5" -- 1790 fps -- 784 ft #
8" -- 2051 -- 1027
11" -- 2221 -- 1206
16" -- 2397 -- 1403

IIRC, rifle barrel lengths are measured from the breach to the end of the barrel. So that means the 300blk bullet probably contacts only 3.5"-ish of barrel before popping out into the air. That's not a lot of distance for the pressure to accelerate the bullet. And that's why the MV and energy figures are so low for uber-short barrel lengths.

When I looked at a 300blk SBR, I consulted heavily with the LGS guys -- who had a pretty fair working knowledge on the cartridge. IIRC my ATF papers are listed with a minimum barrel length of 8", which is what they stated was the absolute minimum for a gun -- not just a noise maker. I decided on an 11" barrel, after analyzing bullet flight ballistics, bullet energy levels, and suppressor issues.
 
Posts: 6172 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
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Thats why im looking at the Honey Badger by Q - seems like a happy balance between short OAL, and good barrel length for ballistic performance and ability to suppress.



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Posts: 7337 | Location: Alpine, Ut | Registered: February 17, 2010Reply With QuoteReport This Post
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