Suppressor question for my Grendel

[James260]

I am building my first 6.5 Grendel and want to put a suppressor on it. It will be built around an Alexander 16" barrel, w/ the mid-length gas system.

My question is, will the suppressor have any affect on cycling and if so, what do I need to do to correct it?

Also any suggestions on suppressors would be nice as well.

Thanks

James

[Josh]

Yes, the added back pressure from the suppressor will speed up cycling of the action. It'll also cause it to get dirtier faster. You're gun will probably still cycle just fine, you may notice more gas coming from the charging handle area. Heavier buffers, adjustable gas blocks, gas blocking or redirecting charging handles, etc. are all options to help. I prefer to adjust the gas system, I'd rather treat the cause of the issue rather than cover up the symptoms.

SLR and MicroMOA both make good adjustable gas blocks. I like the MOA as it's faster to adjust once set up. Set up can take a lot longer though.

Black River Tactical makes a valve that can be installed in your gas block. It's a good choice for restricting the gas flow if you'll be shooting suppressed all the time. It isn't readily reversible though, so not a good choice if you'll be shooting unsupressed as well.

As for suppressors, see what your local dealer has in stock for .30 caliber cans and go with the one that strikes your fancy.

[Bigs28]

Thunderbeast arms corp suppressors
Silencerco (omega)
Amtac suppressors


Adjustable gas block

[Klem]

Cycling
Suppressors increase the barrel pressure and hold it for longer. This will aid cycling in your 16"/mid length. Maybe even be to the point you have to tame it. A variable gas block will help here although in your setup its probably not critical. It does help wear on the gun to have no more port pressure than you need for reliable cycling. Heavier buffers also help but it's better to regulate this excess energy earlier.

Cleaning
A lot more spit and soot comes back around the case as it unlocks. Your receiver is going to get dirtier and if you are a left-hander it will spit in your face via the ejection port (I wear glasses when using suppressors although if you don't have them squinting and knowing its coming helps). If you re-load your cases will be dirtier so leave them longer in the tumbler or get an ultrasonic cleaner. Your suppressor will get dirty and caked too so need cleaning from time to time also - Regardless of whether they are permanently sealed or come apart. Watch for corrosion as suppressors attract moisture as they cool.

POI Shift
Your POI is likely to shift from when shooting non-suppressed. I have never known it not to having shot many suppressors over the years. Some shooters claim their POI does not change although I suspect for some it's more a boast about choosing 'quality' than truthfulness. A phenomenon called, 'Freebore boost' will increase your velocity up to 10fps with a suppressor attached and if this doesn't change your POI then there's something wrong with the laws of physics. You end up preferring to shoot with it on or off to save the hassle of re-zeroing all the time. If you shoot with and without a suppressor devices like the Kestrel permit you to have offset POI's for the same gun which makes dialling for long range easier.

Hearing Loss
If you are shooting volume like when load testing I recommend you still wear ear protection. Let's face it, after all the cost and effort you will be tempted to leave your ear-protection off but multiple impulses at a lower level will still damage your hearing. Workplace OSHA regulations limit noise to around 80db which is the sound of a kitchen blender or vacuum cleaner for all-day constant noise. While your suppressor will limit each impulse by around 30db the residual noise will still be above 100db. Too many shots over a period of time above 100db and you get permanent hearing loss, the same as if you fired it once without protection.

Baffle Strike
If it's a screw-on type without a locking mechanism be mindful to keep it screwed-up tight. Centrefire suppressors collect a lot of heat, especially semi-autos where you end up shooting volume fire that exceeds 1rd/min. The suppressor expands when heated. This will crack the bind at the thread from when you put it on cool. If you keep shooting they have a tendency walk down the thread when loose and it only takes a small amount of run-out caused by gravity to give you a baffle strike. An over-barrel suppressor with a tight fitting grommet or O ring helps but the risk is still there. There is only about 0.5mm clearance between the bullet and the baffles so be sure to check it regularly (e.g. suppressors for 6.5mm calibre tend to have 7.5mm baffle holes). Be careful touching the suppressor after volume fire, they get hot.

I don't see this in the 6.5 bullet range but some bullets will damage your suppressor. Lehigh for example, introduced a 30cal 'CQB' bullet with petals designed to fragment at low velocity on impact with flesh. At high rpm (1:7 twist barrels) the petals were coming apart exiting the but barrel within the suppressor. They now have a qualifier on their website about velocity and barrel twist. The point being, make sure your handloads are stable coming out of that barrel. - If they yaw too much then you risk baffle strike.

[montana]

Cycling
Suppressors increase the barrel pressure and hold it for longer. This will aid cycling in your 16"/mid length. Maybe even be to the point you have to tame it. A variable gas block will help here although in your setup its probably not critical. It does help wear on the gun to have no more port pressure than you need for reliable cycling. Heavier buffers also help but it's better to regulate this excess energy earlier.

Cleaning
A lot more spit and soot comes back around the case as it unlocks. Your receiver is going to get dirtier and if you are a left-hander it will spit in your face via the ejection port (I wear glasses when using suppressors although if you don't have them squinting and knowing its coming helps). If you re-load your cases will be dirtier so leave them longer in the tumbler or get an ultrasonic cleaner. Your suppressor will get dirty and caked too so need cleaning from time to time also - Regardless of whether they are permanently sealed or come apart. Watch for corrosion as suppressors attract moisture as they cool.

POI Shift
Your POI is likely to shift from when shooting non-suppressed. I have never known it not to having shot many suppressors over the years. Some shooters claim their POI does not change although I suspect for some it's more a boast about choosing 'quality' than truthfulness. A phenomenon called, 'Freebore boost' will increase your velocity up to 10fps with a suppressor attached and if this doesn't change your POI then there's something wrong with the laws of physics. You end up preferring to shoot with it on or off to save the hassle of re-zeroing all the time. If you shoot with and without a suppressor devices like the Kestrel permit you to have offset POI's for the same gun which makes dialling for long range easier.

Hearing Loss
If you are shooting volume like when load testing I recommend you still wear ear protection. Let's face it, after all the cost and effort you will be tempted to leave your ear-protection off but multiple impulses at a lower level will still damage your hearing. Workplace OSHA regulations limit noise to around 80db which is the sound of a kitchen blender or vacuum cleaner for all-day constant noise. While your suppressor will limit each impulse by around 30db the residual noise will still be above 100db. Too many shots over a period of time above 100db and you get permanent hearing loss, the same as if you fired it once without protection.

Baffle Strike
If it's a screw-on type without a locking mechanism be mindful to keep it screwed-up tight. Centrefire suppressors collect a lot of heat, especially semi-autos where you end up shooting volume fire that exceeds 1rd/min. The suppressor expands when heated. This will crack the bind at the thread from when you put it on cool. If you keep shooting they have a tendency walk down the thread when loose and it only takes a small amount of run-out caused by gravity to give you a baffle strike. An over-barrel suppressor with a tight fitting grommet or O ring helps but the risk is still there. There is only about 0.5mm clearance between the bullet and the baffles so be sure to check it regularly (e.g. suppressors for 6.5mm calibre tend to have 7.5mm baffle holes). Be careful touching the suppressor after volume fire, they get hot.

I don't see this in the 6.5 bullet range but some bullets will damage your suppressor. Lehigh for example, introduced a 30cal 'CQB' bullet with petals designed to fragment at low velocity on impact with flesh. At high rpm (1:7 twist barrels) the petals were coming apart exiting the but barrel within the suppressor. They now have a qualifier on their website about velocity and barrel twist. The point being, make sure your handloads are stable coming out of that barrel. - If they yaw too much then you risk baffle strike.

Great review Klem, thankyou!

[James260]

Thank you for all the great info!!

Is there a preference for a screw-on suppressor or an over-barrel one? In my suppressor virginity, I thought they all screwed on.
But then that's why I asked... Cause I don't know

Thanks again,

James

[explorecaves]

Thank you for all the great info!!

Is there a preference for a screw-on suppressor or an over-barrel one? In my suppressor virginity, I thought they all screwed on.
But then that's why I asked... Cause I don't know

Thanks again,

James

All screw on to the barrel somehow. Some just use a proprietary muzzle device (brake or flash hider) as the interface. The over barrel may or may not have a required muzzle device. Either way, if there is a muzzle device you must make sure you use shims if it needs to be timed to a specific orientation. Use of a crush washer will induce a cant to the suppressor which typically leads to a baffle strike or even complete destruction of the can...

[Klem]

Thank you for all the great info!!

Is there a preference for a screw-on suppressor or an over-barrel one? In my suppressor virginity, I thought they all screwed on.
But then that's why I asked... Cause I don't know

Thanks again,

James

Depends on a couple of things.

Over-barrel (or 'Reflex') permits more volume for the first 'blast' chamber. This then permits a shorter suppressor forward of the muzzle to achieve the same sound reduction as a traditional muzzle-forward device. The volume of the first chamber depends on how long it comes back from the muzzle, the OD of the suppressor and the ID of void that sits over the barrel. By void I mean the ID of the sealed blast chamber that is designed to fit the majority of barrels thicknesses of all likely customers. For example, an AR barrel might be 18.25mm in thickness but the ID of the over-barrel suppressor void is probably more like 22mm - This means there is some potential volume that is unused in that situation. That is a concern if buying an off-the-shelf over-barrel design. Of course this point is moot if you have a bespoke over-barrel made to fit your barrels OD.

Over barrel designs require a length of free barrel back from the muzzle. No bayonet lugs, gas blocks etc. You might also consider whether you want the suppressor to go inside a handguard or forward of it. Centrefire suppressors can be up to 1.75" OD and there are few handguards that are that wide ID. For example, Seekins make a BAR handguard that is 1.8" ID and it feels like you are holding a watermelon with your off-hand. But, having the suppressor go inside the handguard does allow for a decent sight radius if you use BUIS. And more forward rail to grab, use clip-on's and bipods. The narrower the OD of an over-barrel suppressor the more choice you have in handguards however the longer the suppressor will need to be to contain the same volume. Typical lengths back from the muzzle for over-barrels are 4-6". Over-barrels also reduce the moment of weight you have to cope with. Less weight forward means a more manageable gun. They also make for a shorter over-all rifle length which helps when manoeuvring the gun around in vehicles, scrub and buildings.

Less muzzle forward lessens the chance suppressor will be damaged if it takes a decent knock. Some designs have a grommet or O ring to support the suppressor on the barrel as well as the muzzle however their principal bind is the same as muzzle-forward which is at the shoulder of the muzzle thread.

The downside of over-barrels is that muzzle pressure wants to go forward in the direction it's been travelling. Expecting the gas to change directions 180degrees without resistance and inefficiency is wishful thinking. There is also a growing acceptance that the less efficient design of over-barrel is more pronounced when using subsonic ammunition. So, if intending to use the suppressor mostly subsonic (e.g. Blackout) the latest advice I have heard is to prefer a muzzle-forward. Subsonic ammunition tends to have less expanding gas to contain/slow/cool so a large initial blast baffle is not needed. Subsonic AR ammunition might typically burn 5 grains of powder in a 9mm upper or 12 grains in the 300 Blackout compared to our normal supersonic loads approaching 30 grains.

Less muzzle forward means the suppressor is more tolerant of muzzle thread run-out. If an AR manufacturer expects most customers to never fit a suppressor they can be tempted to take short-cuts in precision when threading the muzzle. The difference between squaring the muzzle thread to the outside of the barrel as opposed to the inside will affect accuracy when a suppressor is fitted. Unlikely a poorly threaded muzzle will cause a baffle strike but it does mean the suppressor is on at a slight angle, and that means escaping gas will be channelled unevenly around the bullet as it leaves the suppressor. This will cause the bullet to yaw and take longer to settle. All other things being equal your group sizes will be larger from a suppressor fitted to a muzzle with poor run-out. Sourcing a barrel from a quality manufacturer mitigates this risk. Commissioning a gunsmith to thread the muzzle knowing you will be using it for a suppressor is another solution (for example, buying an upper with a longer barrel than you want, or a longer drop-in barrel and taking it to a trusted gunsmith to cut it shorter, thread and crown at the length you want with the thread rate of the suppressor you have). The class of thread from bulk AR barrel manufacturers might also not be precise enough for the suppressor. Thunderbeast for example, advertise their threads as Class 3 which implies more precision than typical threads which are Class 2. You might end up with a cheap and cheerful barrel threaded at the muzzle to a tolerance of Class 1. It won't matter that your suppressor is threaded to Class 3 as the tolerance of the combined system will be compromised by its weakest link.

Lastly, muzzle-forward suppressors are simpler designs implying they are easier to make - This should make them cheaper, all other things being equal.

Addendum
There is a third type of suppressor you might want to explore and that is an Integral. This is where the barrel is machined to be also the suppressor. It will contain bleed holes and internal voids. I have seen these in other calibres but never in an AR. Someone else might know more here and chime in.

[montana]

This maybe a new breakthrough development in suppressor development. http://www.thefirearmblog.com/blog/2...design-brevis/

[Klem]

This maybe a new breakthrough development in suppressor development. http://www.thefirearmblog.com/blog/2...design-brevis/

That's an interesting find for sure.

I see they've gone short and fat using all the available diameter of the generous AR 2.5" bore-sight height. Level with the top of the rail at 2" diameter is no coincidence. That's fatter than the 1.5" and 1.75" industry standards. The writer doesn't give much away like internals and sound reduction so we can only go by his impressions; not as quiet as some but quieter than others... Hmmm.

I like the manufacturing technique of one solid chunk. More expensive than most guns it goes on so customers need to appreciate the 20 or so decibel drop (and they'll still be wearing ear protection).

[montana]

That's an interesting find for sure.

I see they've gone short and fat using all the available diameter of the generous AR 2.5" bore-sight height. Level with the top of the rail at 2" diameter is no coincidence. That's fatter than the 1.5" and 1.75" industry standards. The writer doesn't give much away like internals and sound reduction so we can only go by his impressions; not as quiet as some but quieter than others... Hmmm.

I like the manufacturing technique of one solid chunk. More expensive than most guns it goes on so customers need to appreciate the 20 or so decibel drop (and they'll still be wearing ear protection).

The game changer is the weight, or lack of.

[Klem]

The game changer is the weight, or lack of.

At 210 grams it is light. Its one-piece titanium construction is also a big plus, because it will last longer than others. My experience is that suppressors get absolutely punished in centrefire semi-auto's. Light weight's don't last as long as heavier 'tanks'. Like a muffler on a one-stroke engine (which is really what it is) it gets hammered. If you have to pay $200 tax and go through all the paperwork and wait then you'll want it to last as long as possible. In New Zealand where there is no paperwork; light-weight, cheap, almost disposable suppressors are popular. When they wear out, buy another one next time you're in town.

Comparing suppressors with the local DPT design I sent you yesterday...


The potential volume in the titanium TFB is 4,790mm2 and weighs 210grams. It costs $1,500. The equivalent $1380 alloy version should be about the same weight and volume.


The equivalent size New Zealand DPT (unscrew 2 baffles so you are left with 3 baffles including the stainless steel blast baffle) is 5,000 mm2 and weighs 185grams. It costs equivalent $300 USD including local retail tax and postage.


I am certain the sound reduction between the two would be similar. Different regulatory regimes I know and also different market forces at play so it's not a fair comparison. But I will make the point that for $1,500 plus $200 tax you really want that thing to perform, and last. And, when you are paying out of your own pocket you have to think about what price partial sound reduction is worth.

[explorecaves]

The game changer is the weight, or lack of.

That is the advantage of Additive Manufacturing.... Watch the market the next 5 years and you will see it really take off.

[montana]

At 210 grams it is light. Its one-piece titanium construction is also a big plus, because it will last longer than others. My experience is that suppressors get absolutely punished in centrefire semi-auto's. Light weight's don't last as long as heavier 'tanks'. Like a muffler on a one-stroke engine (which is really what it is) it gets hammered. If you have to pay $200 tax and go through all the paperwork and wait then you'll want it to last as long as possible. In New Zealand where there is no paperwork; light-weight, cheap, almost disposable suppressors are popular. When they wear out, buy another one next time you're in town.

Comparing suppressors with the local DPT design I sent you yesterday...


The potential volume in the titanium TFB is 4,790mm2 and weighs 210grams. It costs $1,500. The equivalent $1380 alloy version should be about the same weight and volume.


The equivalent size New Zealand DPT (unscrew 2 baffles so you are left with 3 baffles including the stainless steel blast baffle) is 5,000 mm2 and weighs 185grams. It costs equivalent $300 USD including local retail tax and postage.


I am certain the sound reduction between the two would be similar. Different regulatory regimes I know and also different market forces at play so it's not a fair comparison. But I will make the point that for $1,500 plus $200 tax you really want that thing to perform, and last. And, when you are paying out of your own pocket you have to think about what price ipartial sound reduction is worth.

Excellent observation Klem. The end result would be the actual sound reduction, weight, durability and price. The DPT and common sense suppressor laws gives you much better options, "I'm so jealous" lol. Hopefully with greater market growth as explorecaves predicts the price will lower. Having the option of an effective suppressor for my Grendel with minuscule weight is just the ticket for low volume shooting such as hunting and carrying as a pack gun.

[TOU]

Great review Klem, thankyou!

Absolutely...agreed! Thank you.