Suppressors Necessary Baffle Clearance

[akmtnrunner]

What is the mechanism that demands how much clearance a bullet has through the baffles? Is it the risk of actual physical contact as there is always some less than perfect bore alignment? Or, is there some interference from energy waves that reflects off a baffle back upon the bullet if there is too little space?

I understand that no manufacturer would advise exceeding a suppressor's nominal caliber size, but I am seeking to understand why, when it appears there is ample physical clearance.

 

[Huckmeat]

Most ratings I've seen have to do with the pressure and heat from the particular caliber - ie rated for .308 but not 300 winmag, or whatever.

As for baffle clearance, no idea.

 

[akmtnrunner]

Most ratings I've seen have to do with the pressure and heat from the particular caliber - ie rated for .308 but not 300 winmag, or whatever.

As for baffle clearance, no idea.

Rating is probably the wrong description so I’ve edited the original.

 

[TxWelder35]

My .30 cal can is like .375 iirc and my 223 can is somewhere around .300

 

[Mordamer]

Avoiding physical contact is the only decider of minimum bore size. There is very little difference in sound attenuation between a dangerously tight bore and a very generous bore so why risk going small? Most manufacturers are sizing their bore somewhere between .040" and .080" over design caliber diameter.

 

[akmtnrunner]

There is very little difference in sound attenuation between a dangerously tight bore and a very generous bore so why risk going small?

Because I would like to use my 10 oz 30 cal suppressor on my 338 win mag. Practically all 338 cans are designed for a 338 Lapua amount of gas, but my 338 wm burns less powder than the 30 cal magnums that my 30 cal can is designed for.

 

[Mordamer]

Because I would like to use my 10 oz 30 cal suppressor on my 338 win mag. Practically all 338 cans are designed for a 338 Lapua amount of gas, but my 338 wm burns less powder than the 30 cal magnums that my 30 cal can is designed for.

First shot should create enough clearance.

 

[akmtnrunner]

There is already enough physical clearance, but I am still wondering if the above second mechanism would spoil the accuracy?

 

[SDet]

You could try contacting the manufacturer. That said, from clearance standpoint, you don't have to get a strike for accuracy to go bad. If you're reducing that clearance, the chances of your accuracy going goes up a lot.

 

[Supersubes]

There is already enough physical clearance, but I am still wondering if the above second mechanism would spoil the accuracy?

By “enough”, what does that mean? .338 bullet through a .340 hole etc?

 

[The38Super]

In the context of Form 1 cans, the initial clearance recommendations I heard were in the .060" range. My builds have always been in the .035-.050" range, with no negative impact (that I could detect) on accuracy. And no baffle strikes, he said patting himself on the back.
A bore (and endcap) bored tighter to the bullet most definitely has a positive impact on suppression. Silencerstudent, on Youtube, ran a test of two cans, identical except that one was a dedicated 556 and the other bored for 30 cal and there was a measurable advantage by going dedicated. If I felt like digging through Silencerstudent's old videos, I could give you what that number was. I'm thinking 3-5dB.

 

[akmtnrunner]

By “enough”, what does that mean? .338 bullet through a .340 hole etc?

It's about .353" give or take a couple thousandths

 

[wyld3man]

I would guess that as a couple others stated it has to do with heat, pressure and the blast. Not all baffle construction are created equally.

As far as clearance I use a suppressor alignment rod to verify everything is GTG whenever I get a new suppressor or remove the muzzle device.

https://geissele.com/tools/suppressor-alignment-gage.html

 

[Mordamer]

It's about .353" give or take a couple thousandths

That's very, very close. Everything about the suppressor manufacturing, and your muzzle threads has to be near perfect for that to work. It is possible you would still never have an end cap or baffle strike, but I think you are so close it would be very likely to have a strike. You will likely void any warranty offered by the manufacturer if you did have a strike. You have to decide if the risk of destroying the suppressor is acceptable. I might actually try it if I were you, but I have lots of suppressors and I don't mind buying more.

If there isn't a strike you likely will retain good precision. You may get into a situation where every once in awhile you get a strike that just barely rubs the end cap and throws a shot wild.

 

[Ledzep]

(.353-.338)/2=.0075" per side...

I do some redneck stuff occasionally under the guidance of "Can't take it with me when I die!"... And I would not attempt this one.

Fwiw, I've seen .338 bullets clear a .380" '.30 cal' can without issue. .353 is tight.

 

[Yondering]

While you do have enough clearance for the bullet to drop through the hole, the biggest issue is accuracy. Just allowing the bullet to come close to a baffle on one side without contact can affect accuracy, due to air/gas pressure differences as the bullet passes, and your combination doesn’t have any room for error at all.

Also with long high-b.c. bullets you can have minor baffle contact that ruins accuracy without seeing any baffle damage. It doesn’t take much.

Your combination doesn’t even have the minimum necessary tolerances if it was perfectly aligned, and you can’t count on perfect alignment. Even minor stuff like some powder fouling on the thread shoulder can mess with your alignment enough for this to go wrong. Don’t do it.

 

[Red_SC]

There is already enough physical clearance, but I am still wondering if the above second mechanism would spoil the accuracy?

Yes, I’ve seen tests that showed accuracy loss if the bore was too tight, even without baffle contact. IIRC, the minimum was .040 over to avoid accuracy problems. I’m sure different baffle designs would affect that.

 

[akmtnrunner]

Thanks, everyone, I appreciate all of the responses. I'll forego squeezing the tolerances.