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

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  #1  
Old 03-12-2019, 10:35 PM
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Default Handguard length and muzzle device woes

Just finished building my second AR, first .308!

I am wondering how far my muzzle should be away from my handguard. I don't want my handguard to be destroyed.

16" barrel with 15.75" handguard. Without the muzzle, it's flush with the barrel threads.




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  #2  
Old 03-13-2019, 12:10 AM
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12" or 13" length would look much better.
The front of that handguard is going to get super dirty from the muzzle brake discharge.
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Old 03-13-2019, 12:11 AM
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Based on the port shape on that brake I seriously doubt you will have a problem. The very end might get a little sooty.

Seriously though, wear double hearing protection (like foam plugs under your muffs) shooting that thing, and don’t let anyone stand next to you. 16” barrel with that brake is going to be LOUD.


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Old 03-13-2019, 5:13 AM
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Not sure but it looks like the 4th port is partially blocked.

Either a shorter handguard or a 18 inch barrel would work better.

The 4th port will direct the gases into the handguard.
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  #5  
Old 03-13-2019, 9:06 AM
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The amount of leg you're showing concerns me.
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Old 03-13-2019, 12:33 PM
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Originally Posted by Spyder View Post
The amount of leg you're showing concerns me.
this
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Old 03-13-2019, 12:36 PM
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I like those PRI handguard tubes.
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Old 03-14-2019, 7:21 AM
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Not what you want to hear, but I'd consider a longer barrel. 16" for what's seems to be forming into a precision LR .308 rifle.

Either that or I would find a shorter hand guard. That is a nice one though. Not one I'd swap out w/o shedding a few tears. What you have, IMO is a collection of neat parts that just aren't very well matched to each other.

One other possible solution: ditch the brake and use a linear comp.
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Old 03-14-2019, 7:57 AM
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Quote:
Originally Posted by Ki6vsm View Post
Not what you want to hear, but I'd consider a longer barrel. 16" for what's seems to be forming into a precision LR .308 rifle.

Either that or I would find a shorter hand guard. That is a nice one though. Not one I'd swap out w/o shedding a few tears. What you have, IMO is a collection of neat parts that just aren't very well matched to each other.

One other possible solution: ditch the brake and use a linear comp.
This^

That AR seems very confused as to what it wants to be.
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  #10  
Old 03-14-2019, 8:09 AM
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At this point your best option is to get a shorter hand guard, the gasses from that muzzle break will be directed sideways and diagonally back, and that could be dangerous.
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Old 03-14-2019, 8:12 AM
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+1 on shorter handguard...
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Old 03-14-2019, 8:29 AM
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The first port on the brake concerns me. Blockage not good.

As far as aesthetics go I'd loose the side rail segments otherwise good assembly.

Get back to us if there are any glitches when it attempts to cycle.
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Old 03-14-2019, 4:02 PM
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What's that collar around the barrel, BTW? The thing with the teeth that cover the first port.
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  #14  
Old 03-14-2019, 4:11 PM
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Quote:
Originally Posted by Ki6vsm View Post
What's that collar around the barrel, BTW? The thing with the teeth that cover the first port.
Jam Nut, the set-up sure looks nice:

https://www.vg6precision.com/vg6-lambda-prs65
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  #15  
Old 03-14-2019, 10:35 PM
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Default Handguard length and muzzle device woes

the first port blockage by jam nut is intentional to design of self tightening jam nut (see the angled cuts on the nut). Its a nice setup (assuming you are going to have a jam nut that is). Actually I dont think the handguard will be an issue, but an 18" barrel would have been viable. go shoot it out and replace later.
Edit: clarified “nice”

Last edited by lordmorgul; 03-17-2019 at 10:28 AM..
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  #16  
Old 03-15-2019, 6:32 AM
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Quote:
Originally Posted by tony270 View Post
Jam Nut, the set-up sure looks nice:

https://www.vg6precision.com/vg6-lambda-prs65
Ah. Thanks. I'd searched for pics of that brake. Nothing I saw had that jam nut. I should have looked at the mfr's site.
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  #17  
Old 03-15-2019, 7:50 AM
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Quote:
Originally Posted by lordmorgul View Post
the first port blockage by jam nut is intentional to design of self tightening jam nut (see the angled cuts on the nut). Its a nice setup. Actually I dont think the handguard will be an issue, but an 18" barrel would have been viable. go shoot it out and replace later.
Go to this link, scroll down and look at the different muzzle brake blast:

https://precisionrifleblog.com/2015/...und-signature/
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  #18  
Old 03-15-2019, 8:19 AM
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That's very cool to see.
Thanks

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/
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  #19  
Old 03-15-2019, 9:52 AM
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Quote:
Originally Posted by lordmorgul View Post
the first port blockage by jam nut is intentional to design of self tightening jam nut (see the angled cuts on the nut).
I don't see angled cuts... looks very wrong.
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  #20  
Old 03-15-2019, 10:04 AM
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I finally found that brake... weird design. The other VG6 762 (3-port) brakes I have seen come with crush washers. Blocking the port is so weird, but I can't argue if it actually "self-tightens with every shot". I prefer crush washer to non-self tightening jam nuts, hahah.

https://www.opticsplanet.com/aero-pr...BoCna4QAvD_BwE
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  #21  
Old 03-15-2019, 10:10 AM
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Quote:
Originally Posted by tony270 View Post
Jam Nut, the set-up sure looks nice:

https://www.vg6precision.com/vg6-lambda-prs65
The description posted there is comical.
Muzzle brakes don't have a crown that can effect accuracy as they do not contact the bullet.
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  #22  
Old 03-15-2019, 3:37 PM
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Quote:
Originally Posted by ar15barrels View Post
The description posted there is comical.
Muzzle brakes don't have a crown that can effect accuracy as they do not contact the bullet.
I saw that but didn't want to say anything.
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  #23  
Old 03-15-2019, 4:21 PM
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Quote:
Originally Posted by ar15barrels View Post
The description posted there is comical.
Muzzle brakes don't have a crown that can effect accuracy as they do not contact the bullet.
I don't know that, it looks like those prongs on the jam nut is the crown they are refering to, not the one that we are familiar with. If it is, maybe they needed that crown on the jam nut to direct the gasses, or whatever, to compensate for the directional gasses that stabilize the recoil, maybe those directional gasses have an affect on accuracy, that jam nut with the 11° looking prongs.
Just a thought.
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  #24  
Old 03-15-2019, 4:22 PM
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Quote:
Originally Posted by Ki6vsm View Post
I saw that but didn't want to say anything.
That is a very nice looking design, looks very attractive.
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Old 03-15-2019, 4:50 PM
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I also love how the nut inhibits the "uninhibited flow of gas".

Quote:
The LAMBDA PRS65 is the next evolution in precision rifle shooting muzzle brakes.
It features a two-piece design consisting of the LAMBDA Muzzle Brake and the Jam Nut, which combine for an amazingly simple tool-less installation of the device.
The LAMDA PRS Muzzle Brake features an 11º target crown for accuracy and a bold four chamber design that works in conjunction with the jam nut to self-tighten during every shot.
The LAMBDA PRS65's chamber design virtually eliminates recoil allowing the shooter to stay on the scope and identify their impacts downrange.
The first chamber allows an uninhibited flow of gas to the left and right of the shooter, while the three remaining chambers direct the gas backward acting as a buffer to help reduce the side concussion resulting in a more pleasant shooting experience.
The LAMBDA PRS65 is a feature-packed two-piece muzzle brake designed from the ground up to deliver absolute accuracy and groundbreaking recoil reduction for the discerning precision shooter.
This product was designed using state of the art engineering techniques, utilizing CFD (Computational Fluid Dynamics) and CAE (Computer Aided Engineering).
This product is 100% CNC machined for optimal performance.
Quote:
Originally Posted by tony270 View Post
That is a very nice looking design, looks very attractive.
I guess that's all that matters to some people.

Last edited by ar15barrels; 03-15-2019 at 4:55 PM..
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  #26  
Old 03-15-2019, 4:58 PM
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Quote:
Originally Posted by ar15barrels View Post
That's obvious.

I also love how the nut inhibits the "uninhibited flow of gas".





I guess that's all that matters to some people.
It is obvious that you have no ability to figure what they are refering to. I completely understand it. I guess it's like reading a map or interpreting a mechanical malfunction, some can do it, and some can't. I'm not here to share my knowledge or ability with rude guys like you anyway.
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Old 03-16-2019, 10:07 AM
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Quote:
Originally Posted by tony270 View Post
That is a very nice looking design, looks very attractive.
Huh? This is a response to my comment about not wanting to go into the oddness of the 11° crown claim?

FYI, their reference to a target crown can't mean anything else but how a target crown is, shown in this pic (borrowed from Old Glory Gunsmith Shoppe). Which is why the claim of accuracy assistance seems spurious. What good would this do on a brake, which doesn't touch the bullet?:

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Old 03-16-2019, 10:42 AM
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Quote:
Originally Posted by Ki6vsm View Post
Huh? This is a response to my comment about not wanting to go into the oddness of the 11° crown claim?

FYI, their reference to a target crown can't mean anything else but how a target crown is, shown in this pic (borrowed from Old Glory Gunsmith Shoppe). Which is why the claim of accuracy assistance seems spurious. What good would this do on a brake, which doesn't touch the bullet?:

This should tell you that I know that, and that's not the crown on the muzzle brake.
You must have missed what I posted in post #23:

Post #23
Quote:
I don't know that, it looks like those prongs on the jam nut is the crown they are refering to, not the one that we are familiar with. If it is, maybe they needed that crown on the jam nut to direct the gasses, or whatever, to compensate for the directional gasses that stabilize the recoil, maybe those directional gasses have an affect on accuracy, that jam nut with the 11° looking prongs.
Just a thought.
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Old 03-16-2019, 11:35 AM
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^^^ I may have missed the meaning of your earlier post. So what you are saying, I should say purely assuming sounds like, is that VG-6/Aero appropriated a standard term and gave it a completely different definition, just for this brake? Why would they do that? That makes no sense at all. May as well say the brake has a "tight head-space for better combustion".

That and the description very clearly says it's the brake with the target crown! But you think you might see some 11° angle on the nut?... so you assume that's what they mean? I believe you're hearing hoof beats and thinking unicorns.
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Old 03-16-2019, 12:03 PM
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Quote:
Originally Posted by Ki6vsm View Post
^^^ I may have missed the meaning of your earlier post. So what you are saying, I should say purely assuming sounds like, is that VG-6/Aero appropriated a standard term and gave it a completely different definition, just for this brake? Why would they do that? That makes no sense at all. May as well say the brake has a "tight head-space for better combustion".

That and the description very clearly says it's the brake with the target crown! But you think you might see some 11° angle on the nut?... so you assume that's what they mean? I believe you're hearing hoof beats and thinking unicorns.
Those little splines on the locking nut that are impeding the flow of gas in the first port most definitely improve the accuracy of the bullet.
Because they don't touch the bullet either...
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Old 03-16-2019, 12:23 PM
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Default Handguard length and muzzle device woes

The jam nut is definitely not the crown. VG6 knows the difference. Note that no other VG6 muzzle devices have a “target Crown” but this one, and the Jam Nut is clearly identified as such in the description. It is stated that the jam nut self tightens, whether or not it actually does would depend on test data, do any of you have it?

Randall is correct that VG6 infers the crown is on the terminal face of the muzzle device.

That said, I certainly would not make a claim that an angled front face of a muzzle device cannot affect accuracy because it cannot touch the bullet until I’d performed a study of that effect myself. Have any of you? Have you modeled it with CFD and a competent CFD engineer and simulation software? If not have you performed an exhaustive study of manufactured variations and tested it with statistically relevant results from a valid design of experiments? If not, you’re not a credible source of certainty that it has no effect; you can have an opinion but not an authoritative one.

Similarly, to say that the first chamber which is shaped differently than the remaining chambers and has partial blockage (a grille pressure drop effect actually in CFD ) could not possibly have the desired effect of having only lateral flow out of the chamber while the other chambers in fact have a backward deflected flow is a rather arrogant position to take without having tested or modeled either.


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Last edited by lordmorgul; 03-16-2019 at 12:30 PM..
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Old 03-16-2019, 12:28 PM
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Quote:
Originally Posted by Ki6vsm View Post
Huh? This is a response to my comment about not wanting to go into the oddness of the 11° crown claim?

FYI, their reference to a target crown can't mean anything else but how a target crown is, shown in this pic (borrowed from Old Glory Gunsmith Shoppe). Which is why the claim of accuracy assistance seems spurious. What good would this do on a brake, which doesn't touch the bullet?:



Note that no “crown face” ever touches the bullet on a barrel either, the edge of the crown does and the 11deg face does not. It does have a direct impact on pressure drop of expanding gasses surrounding the bullet as it has exited the barrel but is potentially deflected by gas flows that do touch the crown.

Gasses flow around a muzzle brake too. Does it matter if it has a shaped crown? Not sure, but this is not the first device to have shaped features on that face either.


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Old 03-16-2019, 12:53 PM
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The jam nut is shapped like a crown, and the manufacture refers to a crown, so commonsense will tell you that's the crown they are refering too.

Those 11° prongs on the jam nut could direct gases that effect the bullet as it leaves the break. Do you know differently, again, no you don't.

It is about comprehension, anyway, I take it that the manufacture conducted test before writing such a statement. Just because some person that can't even figure out a sentence, makes them an expert on what effects installing this product over the existing rifle berral muzzle crown, I think not.

Ask the OP'er.
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Old 03-16-2019, 2:11 PM
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Quote:
Originally Posted by tony270 View Post
The jam nut is shapped like a crown, and the manufacture refers to a crown, so commonsense will tell you that's the crown they are refering too.

Those 11° prongs on the jam nut could direct gases that effect the bullet as it leaves the break. Do you know differently, again, no you don't.

It is about comprehension, anyway, I take it that the manufacture conducted test before writing such a statement. Just because some person that can't even figure out a sentence, makes them an expert on what effects installing this product over the existing rifle berral muzzle crown, I think not.

Ask the OP'er.
"...shaped like a crown".... okay, now I know you're just messing with everyone. Good one. Had us going. You deserve a crown for being the king troll. Either that or you're very drunk.
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Old 03-16-2019, 2:17 PM
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Quote:
Originally Posted by Ki6vsm View Post
"...shaped like a crown".... okay, now I know you're just messing with everyone. Good one. Had us going. You deserve a crown for being the king troll. Either that or you're very drunk.

Quote:
Originally Posted by lordmorgul View Post
Note that no “crown face” ever touches the bullet on a barrel either, the edge of the crown does and the 11deg face does not. It does have a direct impact on pressure drop of expanding gasses surrounding the bullet as it has exited the barrel but is potentially deflected by gas flows that do touch the crown.

Gasses flow around a muzzle brake too. Does it matter if it has a shaped crown? Not sure, but this is not the first device to have shaped features on that face either.


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When I study what they wrote, they are writing that the muzzle brake itself has the 11° target crown, they don't show the front. Why do I need to explain this to you?

I deleted that post and combined it with this one:

Here's your 11° crown. In the future, I won't share with you how to problem solve, lol.

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Old 03-16-2019, 3:06 PM
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I'll bite again. First off, who's "they" and who's "you", specifically. your post is a little confusing.

But mainly, what the front looked like was never in question. It was obvious from the MFR's description. We don't need to see a picture.

The only issue raised was, as I put it, the spurious nature of the claim that the front shape does anything beneficial. Lord countered with the fact that we have no proof that it doesn't. And so there we are. Except for one guy who's all over the road, first saying the nut must be a "crown" and now claiming... ah never mind.
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Old 03-16-2019, 5:43 PM
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Quote:
Originally Posted by lordmorgul View Post
The jam nut is definitely not the crown. VG6 knows the difference. Note that no other VG6 muzzle devices have a “target Crown” but this one, and the Jam Nut is clearly identified as such in the description. It is stated that the jam nut self tightens, whether or not it actually does would depend on test data, do any of you have it?

Randall is correct that VG6 infers the crown is on the terminal face of the muzzle device.

That said, I certainly would not make a claim that an angled front face of a muzzle device cannot affect accuracy because it cannot touch the bullet until I’d performed a study of that effect myself. Have any of you? Have you modeled it with CFD and a competent CFD engineer and simulation software? If not have you performed an exhaustive study of manufactured variations and tested it with statistically relevant results from a valid design of experiments? If not, you’re not a credible source of certainty that it has no effect; you can have an opinion but not an authoritative one.
If the brake is doing it's job of expanding and stripping most of the gas away from the bullet, the front face of the brake will have NO effect because there would be little pressure/flow left to deflect off of the base of the bullet against that face.

We can clearly observe this happening in high speed video of bullets traveling through muzzle devices.
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Old 03-16-2019, 7:40 PM
lordmorgul lordmorgul is offline
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Default Handguard length and muzzle device woes

Quote:
Originally Posted by ar15barrels View Post
If the brake is doing it's job of expanding and stripping most of the gas away from the bullet, the front face of the brake will have NO effect because there would be little pressure/flow left to deflect off of the base of the bullet against that face.



We can clearly observe this happening in high speed video of bullets traveling through muzzle devices.


Yes, mostly agreed, except there remains a “likely small” but not necessarily entirely negligible force of compression from the bullet ogive traveling through a gap into not exactly open space bounded on one side by that muzzle face. Experience may tell you to ignore it, but I contend that you’re putting a lot of faith in that “likely small” to claim the effect of non-linear equations are so obvious as to be ridiculous.


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Old 03-16-2019, 7:46 PM
lordmorgul lordmorgul is offline
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Default Handguard length and muzzle device woes

While I’m being a pain in the butt devils advocate, I honestly think they just cut that face at 11 deg because why not, it has to be cut at some angle. They most likely just picked 11 because it makes a difference on barrels so “maybe” it does here too and it’s hardly any effort to make it so.

So the marketing may be crap, but I can’t be sure.


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  #40  
Old 03-17-2019, 12:24 AM
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Quote:
Originally Posted by lordmorgul View Post
While I’m being a pain in the butt devils advocate, I honestly think they just cut that face at 11 deg because why not, it has to be cut at some angle.
Way back in the day, a guy ( I believe it was Ferris Pindell) did a bunch of testing and determined that an 11 degree crown gave him the best accuracy with his specific barrel shooting his handmade flatbase bullets in the 6ppc that he co-designed with Lou Palmisano.
Ever since that was published somewhere, everyone thinks that 11 degrees is the best angle.
Of course it does not matter as none of us are using the specific barrel and the specific bullets in ferris pindell's specific 6ppc.

But that's how the 11 degree crown angle came to be a thing.
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