Trying to Understand Minimum Barrel Requirements

When I was shopping around for suppressors, one thing I noticed was minimum barrel length requirements. As an example, the Silencerco Harvester. I saw the videos measuring the suppressed noise level, and it is impressive, better than the Rugged radiant. But then I see that the minimum barrel length for 5.56 is 16"! Well that is a non-starter for me, so the Silencerco Harvester is a hard pass except for maybe on a 308 bolt gun. Perhaps that's why it's called "Harvester"; it's for hunting (?).

Why the 16" minimum barrel requirement? I have read that unburned powder has a sand blasting effect. Is this a matter of how well the can is able to deal with a harsher setup?

good question. I don't know why...maybe bigger than a small size backpack so that you can't go into town with it while concealing?

Ask Godot.

He'll be by soon.

eruby said:

Ask Godot.

He'll be by soon.

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Does Godot have a forum I can subscribe to?

Shorter barrels have higher pressures at the muzzle. The suppressor has to be built to handle that. It can be lighter if they tell you not to use it on a short barrel. So yeah, a Harvester is for hunting where a guy would prefer a lighter rifle combo.

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calicojack said:

Does Godot have a forum I can subscribe to?

Click to expand...

I've been trying to set up a forum, but he hasn't yet granted the permission I need.

So I'm waiting for Godot.

As mentioned short barrels have much higher muzzle pressures.

calicojack said:

When I was shopping around for suppressors, one thing I noticed was minimum barrel length requirements. As an example, the Silencerco Harvester. I saw the videos measuring the suppressed noise level, and it is impressive, better than the Rugged radiant. But then I see that the minimum barrel length for 5.56 is 16"! Well that is a non-starter for me, so the Silencerco Harvester is a hard pass except for maybe on a 308 bolt gun. Perhaps that's why it's called "Harvester"; it's for hunting (?).

Why the 16" minimum barrel requirement? I have read that unburned powder has a sand blasting effect. Is this a matter of how well the can is able to deal with a harsher setup?

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How old was this video? I recently called SiCo to ask about a certain barrel length and caliber and they told me they no longer have minimum barrel length requirements for their cans.

223 is hard to suppress. If this caliper is one of the primary use cases I would suggest a dedicated purpose built suppressor for it. Source: I have shot 223 out of my silencerco hybrid with the 22 endcap and was not impressed.

engineerbrian said:

How old was this video? I recently called SiCo to ask about a certain barrel length and caliber and they told me they no longer have minimum barrel length requirements for their cans.

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Not in the video; it's in the specs provided by Silencer Shop:
https://www.silencershop.com/silencers/7-62mm-rifle/silencerco-harvester.html

Heat, pressure, erosion, etc. Many have different barrel length requirements for different calibers, maybe 10.5" in 5.56 and 16" in 308. Even without a minimum length requirement, short barrels erode baffles faster. Not a big deal on a modular can, or one with a good warranty and customer service, more a rapid wear thing than a can blowing apart thing.

My soapbox about metering numbers, sorry for the slight detail OP:

The thing everyone needs to understand is that 99% of all silencer metering videos are complete crap. They have no bearing on reality and produce no statistically significant results. That includes most you tubers, manufacturers, and silencer shop. Also most of the numbers published by manufacturers are either fabricated or best case scenarios. This has to do with the metering equipment they use. PEW Science’s proprietary setup, BK Pulse, and 2209s are about all that’s available that MIGHT offer high enough sampling rates to get good information.

Thunder Beast, Griffin Armament, Suppressed Nation, and a few others are publishing decent videos with good metering practices now.

engineerbrian said:

How old was this video? I recently called SiCo to ask about a certain barrel length and caliber and they told me they no longer have minimum barrel length requirements for their cans.

Click to expand...

They still publish minimums. I’d get a second opinion and assume the first person had no clue.

Uncorking pressure on a 4” .308 is about 8x higher than one at 16” IIRC, between the pressure behind the bullet and then I burned powder that is going to expand in to an burn in the suppressor...

I highly, highly doubt there are no minimums.

Possible he meant with subsonic ammo there is no minimum, and that might well be true. A subsonic 300BO out of a 4” barrel has lower pressure than a .308 20” barrel supersonic.

Minimum barrel lengths are about both pressure and heat. Blast baffle design has to be able to accommodate the heat of the muzzle blast without erosion (or within the anticipated life).

A shorter barrel has both higher pressure and hotter gases, especially if short enough the powder hasn’t fully burned yet.

The Silencerco Harvester is an aluminum and stainless steel silencer designed for hunting. Which means it is light weight, relatively inexpensive, and not intended for any kind of sustained firing schedule. Aluminum is very tough material, but it just isn’t going to hold up to regular semi auto or full auto use in a centerfire rifle caliber. It also just isn’t going to be as durable or non-melty as the materials commonly used for hard use suppressors: 17-4, inconel, stellite, and now even titanium (Thunder Beast Dominus in particular).

The “No minimum barrel lengths” thing was popularized by Dead Air and Rugged, and a lot of companies chose to follow suit and adjust their marketing literature. That whole “NO BARREL LIMITS HARDCORE!” thing plus a good warranty was like catnip for people buying silencers. Does that mean that a suppressor with no barrel length restrictions is going to hold up indefinitely and not wear out earlier when being subjected to heavy firing schedules, high pressures from shorter barrels, etc? No, not in the least. Take something extreme like a 2” .300 win mag barrel vs a typical 26” barrel. One of those is a bomb, and the other is a firearm component. But companies did the math and realized the increased profits from people buying more of their products product due to perceived indestructibility along with a strong warranty more than offset the costs of repairing cans from people who do unreasonable things with their suppressors.

Silencerco and Griffin armament are two examples of companies that have eased up on barrel restrictions in the past couple years in response to no limits/unlimited warranty advertising from other companies. Griffin has openly admitted that this was driven by the market, and abuse is still going to destroy a can. It just means not many people do that to their NFA items, and that they’ll repair or replace it under most conditions.

All that said if everyone started running their Rugged or Dead Air cans on short barreled .300 WSM belt fed machine guns, I suspect they would pretty quickly update their marketing to include barrel length or firing schedule restrictions for certain cartridges.

TLDR: yes the harvester is a hunting can. If it’s not going on a rifle with a relatively normal to long barrel length that you fire with a similar schedule to a bolt action rifle you pull out of the safe for hunting season, then it is probably not a good fit for your purposes.

SiCo definitely still has minimums for their cans. That said, the Sakers and Chimera don't really have any, and the 9mm cans are good to go with 300 subs at any length (IIRC).

When it comes to 300 subs, I'm WAY more worried about stabilization than I am about baffle erosion. I use pretty heavy subs (240gr), and if anything goes wrong with stabilization, they could definitely cause some pretty spectacular damage.