What causes bullet accuracy issues when designing baffles.

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What causes bullet accuracy issues when designing baffles.

Post by Grounded » Tue Aug 20, 2013 8:38 pm

I am working on some new baffle designs but i'm curious about what in particular causes instability in the round? I've seen some cases where I will get a bullet strike on some of the first few baffles and have it barely nick the end cap and thats with a 300 bore on 5.56. Any thoughts?
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Re: What causes bullet accuracy issues when designing baffle

Post by doubloon » Tue Aug 20, 2013 8:59 pm

I would think stability should be established before passing the crown of the muzzle.
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Re: What causes bullet accuracy issues when designing baffle

Post by Grounded » Tue Aug 20, 2013 9:29 pm

doubloon wrote:I would think stability should be established before passing the crown of the muzzle.
I would have expected the same but with the bore size I have the axial alignment could be significantly off and still give a clear path through the end cap. Can this be a result of having vent holes in the baffles?
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Re: What causes bullet accuracy issues when designing baffle

Post by Historian » Wed Aug 21, 2013 10:02 am

A parameter that is not often mentioned is
the number of twists in the barrel.

I became most aware of this when I got my Ray Brandes'
Bully Barrel for my S&W 41 with its 1:8 twist as opposed
to the factory barrel of around 1:16. It noticeably stabilizes
a round, especially in extremum the Aguila 60 grain.*
Now that would put a crimp in your can.

*"Aguila SSS Sniper Subsonic Ammunition
22 Long Rifle 60 Grain Lead Round Nose"

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Re: What causes bullet accuracy issues when designing baffle

Post by Fulmen » Wed Aug 21, 2013 12:11 pm

Long, marginally stabilized bullets can supposedly have a bit of wobble as they leave the muzzle, and asymmetrical designs can also affect the bullets as they pass through the can. I would avoid asymmetry in the blast chamber, and perhaps add a brake/diffuser-design to "strip" the high pressure muzzle blast from the bullet as soon as possible.

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Re: What causes bullet accuracy issues when designing baffle

Post by twodollarbill » Wed Aug 21, 2013 1:45 pm

Baffle strikes "baffle" people...period.
If we maintain alignment and allow for clearances we should be safe
and free from a baffle strike, but that has shown not to be true for some here.
If the bullet fired is not designed for that barrel twist you could be in trouble too.
The AR market is full of light to heavy loads and multiple barrel twists (and lengths).
If you are shooting reloads or factory ammo (foreign) that is improperly crimped
you could lose a "loose" jacket as it exits the muzzle and enters the can.
My MAC10 bullet hose leaves more scrap copper inside my suppressor than I would like.
But then again.....I'm shooting reloads.
Just a thought. :roll:

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Re: What causes bullet accuracy issues when designing baffle

Post by doubloon » Wed Aug 21, 2013 2:18 pm

Jacket separation is an awful thing.

I had a 9mm that suffered from the occasional jacket separation and it would leave shrapnel in half the chambers of my suppressor. The only way to fix it was get rid of the rifle. Unsuppressed it sometimes looked like somebody was shooting wingnuts out of a slingshot at my target.

Going back to my original statement, shoot your rifle/ammo on paper at 25, 50, 100 and 150 yards. Just one or two shots at each range, make sure the holes aren't touching. This isn't an accuracy test, it's a stability test. See if any of the holes are oblong at any range. IMHbneO if any holes are not perfectly round than you have rifle/ammo stability issues and it doesn't much matter at that point what your suppressor is doing.

If everything is perfectly round and you're feeling froggy throw some rounds at the same range suppressed. Should answer once and for all if it's the suppressor or not.
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Re: What causes bullet accuracy issues when designing baffle

Post by Capt. Link. » Wed Aug 21, 2013 2:55 pm

Grounded wrote:I am working on some new baffle designs but i'm curious about what in particular causes instability in the round? I've seen some cases where I will get a bullet strike on some of the first few baffles and have it barely nick the end cap and thats with a 300 bore on 5.56. Any thoughts?
Destabilization of bullets inside a can not caused by mechanical alinement or insufficient rifling twist is from energy that is focused by the baffle and causes yaw of the stable projectile, spacing can change this with possible loss of suppression.A near miss of a baffle can cause effect "as a hit,I call the phenomena "bounce". The theory of gas jets causing the yaw of bullets is yet another thought.In all cases a larger bore hole is required to alleviate the problem.Baffles that are know to cause a high percentage of yaw are not all asymmetric or use any gas jets and can be quiet.Destruction of bullets inside the suppressor is yet another subject.
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Re: What causes bullet accuracy issues when designing baffle

Post by doubloon » Wed Aug 21, 2013 3:33 pm

Capt. Link. wrote:... from energy that is focused by the baffle and causes yaw of the stable projectile, ...
Do you think it is fair to say the projectile is not sufficiently stabilized for suppression?

I know it's a fine hair to split but the crux of my question is do you believe this "bounce" can destabilize any projectile, just projectiles on the fringe of stability or can it randomly destabilize any projectile regardless of the integrity of the stabilization?

I know stabilization can be represented by a formula, that I don't want to drag out, which produces a number representing the calculated stabilization within a "range" where below a certain number is marginally stable and below another number is unstable.

Just wondering if it might be possible to calculate a reliable stability number for suppressed projectiles vs. unsuppressed.
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Re: What causes bullet accuracy issues when designing baffle

Post by Grounded » Wed Aug 21, 2013 3:39 pm

doubloon wrote:
Capt. Link. wrote:... from energy that is focused by the baffle and causes yaw of the stable projectile, ...
Do you think it is fair to say the projectile is not sufficiently stabilized for suppression?

I know it's a fine hair to split but the crux of my question is do you believe this "bounce" can destabilize any projectile, just projectiles on the fringe of stability or can it randomly destabilize any projectile regardless of the integrity of the stabilization?

I know stabilization can be represented by a formula, that I don't want to drag out, which produces a number representing the calculated stabilization within a "range" where below a certain number is marginally stable and below another number is unstable.

Just wondering if it might be possible to calculate a reliable stability number for suppressed projectiles vs. unsuppressed.
Just to include some additional info to my OP this occurred with M855 (65gr) on a 14.5" 1:7 twist.
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Re: What causes bullet accuracy issues when designing baffle

Post by Fulmen » Wed Aug 21, 2013 4:01 pm

doubloon wrote:Just wondering if it might be possible to calculate a reliable stability number for suppressed projectiles vs. unsuppressed.
It's a good thought, but I fear you'll have to gather a whoooole lot of empirical data to make any usable predictions. There are simply too many variables to consider, caliber, barrel length, bullet, twist, silencer design just to mention a few. Some simple rules of thumb might be possible by studying good and failed designs, so by all means continue your line of thought.

One of the causes could be high pressure flow around a bullet while it passes a baffle. If the bullet isn't perfectly centered it will cause uneven flow around the bullet, and some designs might amplify this further. And "proper" stability will not make the bullet absolutely immune to deflection, in fact a properly stabilized bullet will keep the nose "into the wind" during flight. I'll admit that this happens over longer times and distances and with less deflection than what would typically cause a baffle strike, but then again the pressures and flow velocities inside a can are way above what a bullet experiences during bullet flight.

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Re: What causes bullet accuracy issues when designing baffle

Post by doubloon » Wed Aug 21, 2013 4:15 pm

Fulmen wrote:... I fear you'll have to gather a whoooole lot of empirical data ...
Si, I don't have the resources to attempt it and even if I did I fear the work would have very few practical applications that could not be solved quicker than trial and error.

It's just the mention of this "bounce" that sent my brain on a side trip. I know rotating baffles has an effect on POI, as evidenced by the ratcheting LID/LCD/Nielsen on available suppressors. It just never occurred to me this "bounce" might be strong enough to destabilize a projectile.
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Re: What causes bullet accuracy issues when designing baffle

Post by doubloon » Wed Aug 21, 2013 4:32 pm

Grounded wrote:...
Just to include some additional info to my OP this occurred with M855 (65gr) on a 14.5" 1:7 twist.
Should be stable at nearly any velocity.

Based on interweb calculators, "marginal" stability (from spin) doesn't come into play until you have something .223 in diameter and nearly an inch long leaving a 1:7 twist barrel at less than 600 fps. If you have a 65gr bullet that's an inch long then it would probably have to be hollow like a chocolate easter bunny.

If it is "bounce" that's jacking the yaw then stability calculations would appear to be useless unless someone can quantify the force of the bounce and include it in the math. Read that as never going to happen.

I still think a paper stability test is worth the time. If there is some significant imperfection in the crown or lands/grooves near the muzzle it will show on paper. Outside of that I guess you could look for some horrific feed problem mangling the bullet or case neck on chambering or your chamber could be out of spec ... visions of catastrophic failures dance around chambers out of spec.

In short, except for pinning it on the mystic "bounce" the well of problems that could contribute to instability is deep but remember my musings are far, far and away from expert ... one might even say barely informed.
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Re: What causes bullet accuracy issues when designing baffle

Post by Capt. Link. » Wed Aug 21, 2013 4:40 pm

It's just the mention of this "bounce" that sent my brain on a side trip. I know rotating baffles has an effect on POI, as evidenced by the ratcheting LID/LCD/Nielsen on available suppressors. It just never occurred to me this "bounce" might be strong enough to destabilize a projectile.
I think it's a ground effect of a close pass of a aerodynamic shape in rotationCL
One of the causes could be high pressure flow around a bullet while it passes a baffle. If the bullet isn't perfectly centered it will cause uneven flow around the bullet, and some designs might amplify this further. And "proper" stability will not make the bullet absolutely immune to deflection, in fact a properly stabilized bullet will keep the nose "into the wind" during flight. I'll admit that this happens over longer times and distances and with less deflection than what would typically cause a baffle strike, but then again the pressures and flow velocities inside a can are way above what a bullet experiences during bullet flight.
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