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Centerfire Rifles - Semiautomatic or Gas Operated Centerfire rifles, carbines and other gas operated rifles.

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  #41  
Old 03-17-2019, 9:02 AM
Ki6vsm Ki6vsm is offline
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^^ Thanks. I googled it yesterday. Founds lots of pics and lots of conjecture on other forums about the 11-degree thing. I read everything from "it makes cleaning easier" to "it came from Army tests", and that's where I said forget it---no one knows. But this 6ppc version sounds most probable.

BTW, all this conjecture about VG-6 being diligent and doing "testing" before going to market? Pfft. They do make nice stuff, that's for sure, but this is the company that used to claim that their 5.56 Omega brake's ripply front shape "helped to reduce muzzle flash". Then myself, and no doubt a bunch of other people, wrote to them explaining that their wording was poison to potential California buyers. So they quietly removed that wording from the packaging. If they'd tested it and found that the front end had any reduction on flash, I don't think they would have been so compliant.

So much of this is about marketing. Take that jam nut. No one has said it yet, but does it solve any kind of real problem? Are muzzle brakes really coming loose on properly torqued installations? I guess this would be a question for Randall, since he's seen more barrels than most people. And is "amazingly simple tool-less installation" all that important? For how much more than a regular brake this thing costs, a guy could buy a lot of Craftsman 3/4" open end wrenches and crush washers.
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  #42  
Old 03-17-2019, 9:35 AM
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ar15barrels ar15barrels is offline
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Quote:
Originally Posted by Ki6vsm View Post
So much of this is about marketing. Take that jam nut. No one has said it yet, but does it solve any kind of real problem? Are muzzle brakes really coming loose on properly torqued installations? I guess this would be a question for Randall, since he's seen more barrels than most people. And is "amazingly simple tool-less installation" all that important? For how much more than a regular brake this thing costs, a guy could buy a lot of Craftsman 3/4" open end wrenches and crush washers.
Jam nuts are all about cosmetics.
They allow you to put a muzzle brake on a bolt gun barrel with no visible shims/spacers.
Shims and spacers are generally not desireable on bolt guns because bolt guns have traditionally had muzzle brakes fitted by gunsmiths.
A machinist/gunsmith can cut the barrel shoulder so that the muzzle brake aligns with no shims necessary.

The nut on the brake makes it so people can install the brake themselves without machining.

The downside that people don't see and (of course) the manufacturers won't tell you is that the lock nut method does not hold a brake anywhere near as straight as a machine fitted brake because you now have two sets of threads that are part of the alignment.

I'll just let this video I made do my talking:



The 2nd and 3rd brakes use a nut to lock the brake into alignment.
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Last edited by ar15barrels; 03-17-2019 at 9:37 AM..
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  #43  
Old 03-17-2019, 10:18 AM
lordmorgul lordmorgul is online now
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Default Handguard length and muzzle device woes

Thanks Randall that history is useful. And it would certainly only be an ďoptimumĒ solution for the same ogive, at the same velocity, at the same atmosphere, at the same caliber, etc.

For my TC Compass I bought the POF 3G muzzle brake which comes with a jam nut.

Found a few issues trying to mount it:
- Jam nut is sized to cover end of barrel that doesnít have a shoulder at all next to the threads, itís meant for AR10 applications so that makes sense but was a problem installing on the Compass which has a shoulder on the barrel right before the threads that did not fit inside the jam nut
- Jam nut would also have used up more thread length than a shim or crush washer so runout may be even worse with less length to help align
- POF made the threaded depth of this brake crazy long (nearly twice the available thread length of the Compass) but the thread is cut rather generously and the brake literally wobbled at the thread engagement that the jam nut would have provided, forget runout measurement it wobbled... checked thread diameter on the rifle as itís good.

I used a crush washer instead and itís fairly solid on there but donít have a setup to measure runout and I doubt itís good. Havenít shot it yet. I donít think jam nuts are all that great from that experience.

https://pof-usa.com/product/3g-muzzle-brake/

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Last edited by lordmorgul; 03-17-2019 at 10:20 AM..
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  #44  
Old 03-17-2019, 10:50 AM
lordmorgul lordmorgul is online now
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Default Handguard length and muzzle device woes

Quote:
Originally Posted by tony270 View Post
Go to this link, scroll down and look at the different muzzle brake blast:

https://precisionrifleblog.com/2015/...und-signature/

While I donít think any of these really show us what the jam nut ďgrille pressure dropĒ behavior of the VG6ís first port flow direction might be... itís interesting to look at, and the APA Fat Brake May be the closest without looking inside the chamber shapes.

For OP: that flow graphic if you imagine it overlayed on your rifle would tell you the several comments about getting sooty is likely, but also not likely to apply extremely high velocity flows to damage your handguard, the flow even on that one where there is no jam nut slowing backward flows it traverses at least an inch outward and the presence of the handguard there is going to further deflect the flows due to boundary layers, Iíd feel ok risking it with my money for the chance that causes cracking in the structure over time (but as Iíve called out others above, this is a semi-educated unprofessional guess without supporting data! After all Iím an RF Engineer / Analyst who has some opportunity to be dangerous with CFD software every once in awhile and the CFD guys remind me I donít know what Iím doing)

- they missed an opportunity to call out Seekins here for the odd asymmetry in the forward port gasses, itís just odd, same issue with Tubb Precision

- related to crown shapes, there are a good number of variations shown in just these pics for instance the JP with a deliberately recessed 90deg cut crown which would require a separate machine cut so not zero cost, was it purely style? Weight? Marketing too?

- the Shrewd clearly has a non-90 deg cut crown, is it 11? Itís not square. More marketing?



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  #45  
Old 03-17-2019, 11:29 AM
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I'm just a retired heavy and light mechanic OP. I have acquire over 37 years of Government sponsored safety training, spanning 9 different job titles, working for the Army, Navy, and USMC, and 3 years active Army, Infantry, 11-B-10 Rifleman. And much, much, much, more. I drove the turnip truck, but started in the back.

I suggest that you go out and shoot a few rounds at night, and observe what comes out of the berral. I can tell you, a flame ball behind the bullet, as big a soft ball or bigger, with a tail, or in the case of my AK, a flame ball the size of a soccer ball.

So call the manufacture and ask them this, "what is minimum clearance distance from the muzzle brake and handguard"? Then please let us know for safety.

That's the prudent thing to do, as well as the safest.
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  #46  
Old 03-17-2019, 11:53 AM
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11 degree crowns are the stainless exhaust tips of the firearms industry.
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  #47  
Old 03-17-2019, 1:19 PM
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This image is from this link, the VG6, just for example:

https://gunmagwarehouse.com/blog/vg6precision/

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  #48  
Old 03-17-2019, 2:00 PM
Ki6vsm Ki6vsm is offline
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^^^ Cool. Yep. That's the brake I mentioned above, though I got the name wrong. I think I called it the Omega? It's the Gamma. I'm not that great with the Greek alphabet I guess. It's those radial flutes on the front that VG-6 originally said helped to reduce flash. They stopped saying that ultimately. Not sure what anyone else might have said to them, but I called attention to the fact that they already make a nice "flash suppressor" version of the Gamma with their Epsilon. It's basically the Gamma with three big prongs on the front. So it made sense to advertise one as a FS-brake and one that's purely a brake-comp. And the slits on the top direct the flash squarely INTO the shooter's field of vision a little, avoiding one definition of FS as it's spelled out in CA.

Very nice brake though. I have one on an 18" stainless Green Mtn barrel. Oddly, I also have an Epsilon on a GM 20" stainless barrel and that thing is ear-splittingly loud compared to the Gamma. Don't ask me to explain why since they are so similar. Next time, I'll run my CAGE dealie on the Epsilon I guess and see how well it cuts down on the concussion.

BTW, that's a cool looking hand guard on the AR in the article. But to install the CAGE he would have had to pull off the hand guard to attach it to the brake. It secures with two Allen set screws at 12 oclock. It's possible though that he just slipped it over the brake for photo purposes.


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Last edited by Ki6vsm; 03-17-2019 at 2:09 PM..
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  #49  
Old 03-17-2019, 7:47 PM
lordmorgul lordmorgul is online now
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Default Handguard length and muzzle device woes

Ki6vsm, I have a 556 Epsilon and two 556 Gamma brakes (one EX) and have a similar observation that the epsilon is louder. I donít own a cage device yet but plan to buy one, do you like it on the gamma?

Everyone should evaluate safety of their setup and comfort level with it. But Iíll tell you this light is still working fine after a few hundred rounds mounted here with a poly Magpul Mlok rail section holding it at a pretty significant cantilever length... ok itís 556, but the blast is not blowing it up. It hasnít loosened up. If the light fails or the mount cracks Iíll try to remember to stop back in. Yes this lens gets very dirty but you know what itís also very easy to wipe clean (and easier when lightly greased beforehand).




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  #50  
Old 03-18-2019, 7:01 AM
Ki6vsm Ki6vsm is offline
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Quote:
Originally Posted by lordmorgul View Post
Ki6vsm, I have a 556 Epsilon and two 556 Gamma brakes (one EX) and have a similar observation that the epsilon is louder. I donít own a cage device yet but plan to buy one, do you like it on the gamma?
At the risk of sounding a little lame, I haven't actually used it yet on either barrel. Where I go shooting is out in the desert and so I have no neighbor to worry about bothering. If I go out there with friends we're typically 15-20 ft apart. And I tend to fiddle with sights and load workups and targets and so forth, so I always run short of time to experiment with small stuff. Darnit. Some day though.
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  #51  
Old 03-18-2019, 7:03 AM
Ki6vsm Ki6vsm is offline
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BTW, where's the OP?

I think we scared off another one.
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  #52  
Old 03-18-2019, 11:47 AM
lordmorgul lordmorgul is online now
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Nothing lame about prioritizing your range time. Hopefully OP is lurking that went a little off track.


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  #53  
Old 03-18-2019, 11:59 AM
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Quote:
Originally Posted by tony270 View Post
That'd be funny if it was designed wrong and they used Marketing BS to cover it up... lock ring looks great when it sits flush like that pic. I actually wonder about lock rings on items like the DPMS-JM comp... do not prefer them.

"Just tell them it is MILSPEC and self-tightening".

Never wonder about crush washers backing off.
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