Insight on switching to a 6.5” barrel

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brupe
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Insight on switching to a 6.5” barrel

Post by brupe » Sun Dec 16, 2018 4:39 am

Howdy all,
New to the forum, new to shooting 300, first post.

I’m wanting to put a VSeven 6.5” match grade barrel on my 300 pistol, would run it with subs through a SilencerCo Octane (still waiting on the tax stamp).

The main reason I want a 6.5” barrel is to have the suppressor tucked in the handguard; I like the aesthetics, and appreciate the added length of the handguard.

Any advise, tips, reasons to/not to run a 6.5” barrel?

Thanks In Advance.

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one80
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Re: Insight on switching to a 6.5” barrel

Post by one80 » Sun Dec 30, 2018 11:22 pm

I have been looking at the VSeven and also the Veritas and SLR both of those barrels are 5". I have been reading that with the micro barrels, the back pressure can cause damage to your gun and/or can. Make sure your can is rated for that barrel length in 300 blk.
I am looking at getting an OSS can because they vent the gasses better than most other cans.

I like the aesthetics also with a can tucked.

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Dolomite_Supafly
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Re: Insight on switching to a 6.5” barrel

Post by Dolomite_Supafly » Wed Jan 02, 2019 12:30 am

A short barrel will not physically damage the firearm itself if the gun is properly gassed. Short barrels shooting supersonic loads can damage silencers but I seriously doubt subsonic loads will. Subsonic loads are about like most pistol calibers. Matter of fact the 300 Blackout case capacity is almost identical to a 357 Magnum. If I remember correctly 45 ACP has more capacity than the 300 BO. The longer bullets used for subsonic loads mean less case capacity. That means less powder and less powder means less muzzle blast and pressure that might damage a silencer.

I would not buy a silencer because of a fear of backpressure. Backpressure means the silencer is working by holding onto the hot gassed until they cool and slow. You won't find any OSS users here because there are better, and quieter, options on the market and especially for subsonic loads.

Any damage that could be caused by a firearm being over gassed is easily mitigated using an adjustable has block. You can easily find the bolt speed to spec. I ran my AR with barely enough gas to cycle but even so it was still loud.

And finally, with shorter barrels an AR will be louder. Shorter barrels require more powder to get to the same velocity as a longer barrel. More powder means more noise, both out of the silencer as well as coming out of the chamber during extraction as well as our of the ports in the bolt. This leads to more gas in your face as well.

If you want quieter then use the longest barrel you can tolerate. The longer the barrel the more reliable and quieter it will be.

I will never shoot another AT in 300NO because no matter what they are loud. In a single shot, with loads using fast powders, the 300BO is magical in how quiet it is. In my 16" Encore housing heavy bullets and fast powders you can hear the hammer fall. I smile every pull of the trigger.

We have a member with an 300BO AR that has a 3.75" barrel. It hasn't damaged his gun at all but it is also properly gassed.
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dellet
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Re: Insight on switching to a 6.5” barrel

Post by dellet » Wed Jan 02, 2019 7:43 am

Dolomite_Supafly wrote:A short barrel will not physically damage the firearm itself if the gun is properly gassed. Short barrels shooting supersonic loads can damage silencers but I seriously doubt subsonic loads will. Subsonic loads are about like most pistol calibers. Matter of fact the 300 Blackout case capacity is almost identical to a 357 Magnum. If I remember correctly 45 ACP has more capacity than the 300 BO. The longer bullets used for subsonic loads mean less case capacity. That means less powder and less powder means less muzzle blast and pressure that might damage a silencer.
.
This is one of those statements that is both true/false and deserves more discussion, I know we’ve talked about it a lot. I think powder choice will prove to be very important in the long run if people really start shouting ultra short barrels.

With a normal subsonic load and powder in a 6 1/2” barrel, you basically have the same pressure as a 308 with a 20” barrel shooting supers.

What people forget to think about is is powder blasting material. In a 308 you will have 5% of 50 grains or 2.5 grains of un-burned powder at 10,000 psi. exiting the muzzle. In the Blackout using something like 1680 you have 30% of 12 grains or 4+ grains of powder at the same pressure and a lot more heat.

That leaves commercial ammo of the table if you do a lot of shooting. Hand loads with faster powders will move it into the pistol class burn rates that will lower muzzle pressure and blasting material.

For what it’s worth, most supers in a 6 1/2” barrel have the same muzzle pressure as a 10” 308. Pushing 20,000 psi.
300 Blackout, not just for sub-sonics.

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Dolomite_Supafly
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Re: Insight on switching to a 6.5” barrel

Post by Dolomite_Supafly » Wed Jan 02, 2019 11:47 am

Supersonic loads out of a 6.5" barrel will be REALLY hard on a silencer regardless of powder choice. Some powders will be less damaging than others but either way a supersonic load coming out of a 6.5" barrel will be very hard on any silencer. Lil'Gun is a great powder for both supersonic and subsonic loads but it burns hotter than most other powders and would be a poor choice for these ultra short barrels.

I am sure my 3.5" barreled gun has a serious amount of muzzle pressure with subsonic loads but with the proper powder choice I am sure I can mitigate most of it. I wish I could find a super fast powder that is bulky enough to use. I have tried Trail Boss but I have to compress it. Some other powders leave too much space in the case causing problems with powder position within the case. I might need to look at using dacron as a filler with the ultra fast powders I think I need. Right now I am in love with Blue Dot, it is quieter than the powders I typically use and it will cycle ARs with shorter barrels but they go supersonic with longer barrels. When I have enough Blue Dot to cycle an AR it is too much powder to keep the bullets subsonic with longer barrels.

I tore down my last 300 Blackout AR a few months back. I am just not happy with how loud it is to the shooter.
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Re: Insight on switching to a 6.5” barrel

Post by bangbangping » Wed Jan 02, 2019 12:20 pm

Dolomite, have you looked at Tin Star (N32C)? It's fast and about 2/3 as bulky as Trail Boss.

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dellet
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Re: Insight on switching to a 6.5” barrel

Post by dellet » Wed Jan 02, 2019 12:29 pm

bangbangping wrote:Dolomite, have you looked at Tin Star (N32C)? It's fast and about 2/3 as bulky as Trail Boss.
I love TinStar and heavy bullets in a hand fed action.

More or less works the same as Trail Boss, the main difference is that you can get enough under a heavy bullet to blow an AR up, before it cycles. :shock:

I know I used it with a 240 SMK, I think with a 230 Berger which is probably the longest bullet out there.

This is a powder you can pop a primer and need a piece of pipe lift your bolt on a bolt action. I generally treat it more like loading supers, starting low.
300 Blackout, not just for sub-sonics.

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Re: Insight on switching to a 6.5” barrel

Post by Dolomite_Supafly » Sun Jan 06, 2019 12:09 am

I loaded up some 225g Hornady and my 265g usin VV N320 today. I was pleasantly surprised with it but Blue Dot was quieter. I have some “surplus” pistol powder I also tried. I started piercing primers before I broke the speed of sound. I think Blue Dot will be my go to powder for the 3.5”.
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Re: Insight on switching to a 6.5” barrel

Post by warthog97 » Sat Mar 02, 2019 9:53 pm

You will find one OSS user on this site. I'm running an OSS Helix QD and like it so far. One thing about the OSS QD mount is that you absolutely can run it under the hand guard without any issue because the Helix doesn't have any latches like some cans have (not sure about the one you are looking at). However, not sure that would be recommended practice with any removable can. All of my mounts (one for 300 BLK, 308 Win, and 556) all are brake style mounts, wouldn't want to run the risk of firing unsuppressed with my hand anywhere near the break. That's just me though.

Best of luck with whatever can decide to run with. That's what's great about this forum, we can all buy different stuff and compare notes!

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Re: Insight on switching to a 6.5” barrel

Post by STINKEY » Sun Jun 23, 2019 12:58 am

I have a 7.5" AR Pistol. Cycles just fine sub-sonic but will not cycle properly without the can..... the back pressure is what is needed.
Have used everything from 225 ELD to 175 Match. Got MOA at 100 yds with 180 match grade bullets but couldn't consolidate a point of aim for both 100 and 50 yds. This is with a 3 MOA red dot set way far down the rail. Going to need more work. Spent a lot of time and money in working up the Load/Bullet weight combination. NOT even going into shooting sub in a 16" platform ...........
Just hope someone has a bit more insight to help me out on this one...................

Enjoy,

John
If they say it can't be done.... I have or at least thought about it....... 8)

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