Standardized Moderator Testing (free), Discussion Thread

[WobblyHand]

How does one use masking tape to ensure concentricity?

GsT

It doesn't, at least not to machinist tolerances. However, it can serve as a crude indicator of how close to the edge one is.

Another indicator is a chip at the exit! That was when I didn't quite have enough clearance, fixed that with a slightly tapered hole. Even better is to true up all the mounting surfaces. It doesn't take much tilt error to result in clipping. I have turned the bottom surface of my moderators to minimize tilt error.

 

[OldSpook]

It doesn't, at least not to machinist tolerances. However, it can serve as a crude indicator of how close to the edge one is.

Another indicator is a chip at the exit! That was when I didn't quite have enough clearance, fixed that with a slightly tapered hole. Even better is to true up all the mounting surfaces. It doesn't take much tilt error to result in clipping. I have turned the bottom surface of my moderators to minimize tilt error.

A fellow I recently mentioned to you uses a magic marker to ring around the muzzle. If there is even the slightest drag across that it will show up as a lead wiping. Yellow or White seem to work best.

 

[WobblyHand]

• Range geometry done
• Parts ordered. Will be looking for advice.
• All instrumentation will be documented

I want to put together a range which anyone with a couple hundred dollars and minimal engineering skills could reproduce.

What metrics should we look at. I think @JungleShooter might have some thoughts on that.

Yes, he has collected a lot of moderator information as I recall.

Minimal engineering skills perhaps, but think we will need to generate a check list, so those without engineering background can follow the list and get good results. The idea is to get reproducible testing. Unfortunately, that means more documentation, which is no one's favorite thing to generate. Good docs are hard to write, which is hard, because people interpret things quite differently, especially if from different cultures or countries.

 

[OldSpook]

Yes, he has collected a lot of moderator information as I recall.

Minimal engineering skills perhaps, but think we will need to generate a check list, so those without engineering background can follow the list and get good results. The idea is to get reproducible testing. Unfortunately, that means more documentation, which is no one's favorite thing to generate. Good docs are hard to write, which is hard, because people interpret things quite differently, especially if from different cultures or countries.

Air Force Certified Instructor and curriculum developer. Taught at Goodfellow AFB, Joint Service Cryptologic Center and School when I was still sane.

 

[WobblyHand]

So you are familiar with checklists
And making things idiot proof. I'm sure you were exposed to some clever idiots though!

Don't know how to respond to "when I was still sane"
but I will leave it at that. Made me laugh.

 

[OldSpook]

So you are familiar with checklists
And making things idiot proof. I'm sure you were exposed to some clever idiots though!

Don't know how to respond to "when I was still sane"
but I will leave it at that. Made me laugh.

They can't catch me. When they wanted to I was young and too fast for them. Now I am old and they think I am harmless.

 

[bucketboy]

Good on ya! How much does that rifle cost?
Sub-12 fpe... Wouldn't that fall into the category of "guns that are already quiet"?
I'm thinking literally anything including a childs baloon could make that thing sound weally weally quiet...
but yeah I guess a moderator the same size as the one on my HW110 Weirauch would probably be as quiet as you suggest... if I tuned it to 600 fps or so...

No, even sub 12 make a crack without a moderator, the weirauch is an excellent moderator and is the standard by which all manufacturers try to emulate but mine are definitely better due the tighter tolerance in the baffles hole and I make my cages lengths random sizes to try and disrupt any uniform frequency.

I have 4 rapids and 2 raw, the are in the higher price band, , new Sub 12 and high power are exactly the same price here in the uk but s/h sub12fpe command a much higher price because unlike high power there are no legal hurdles to jump over.

 

[OldSpook]

No, even sub 12 make a crack without a moderator, the weirauch is an excellent moderator and is the standard by which all manufacturers try to emulate but mine are definitely better due the tighter tolerance in the baffles hole and I make my cages lengths random sizes to try and disrupt any uniform frequency.

I have 4 rapids and 2 raw, the are in the higher price band, , new Sub 12 and high power are exactly the same price here in the uk but s/h sub12fpe command a much higher price because unlike high power there are no legal hurdles to jump over.

How much more dead is a squirrel that has been shot with a $4000 rifle than one which was shot with a $400 rifle?

That's a nice stable. If I had that kind of money to spend I would spend it on test equipment.

I get more pleasure from studying these rifles than decorating myself with them as I am so ugly that no amount of high dollar rifle can make me look like I am an expert!

 

[Mike_OH]

Air Force Certified Instructor and curriculum developer. Taught at Goodfellow AFB, Joint Service Cryptologic Center and School when I was still sane

@OldSpook , I am a Goodfellow JSCCS graduate. Thank you for your service!

 

[OldSpook]

@OldSpook , I am a Goodfellow JSCCS graduate. Thank you for your service!

Oh HELL YEAH! Thank you, brother. Keep the faith.

 

[beerthief]

(old) just can't think of the name but there is a fellow in Mexico making air pistols and a mod with a membrane that closes exactly as the pellet exits trapping the "noisy " air inside ? have you seen that post ?

 

[WobblyHand]

User name Xolotl, Tequila Gun. Silicone valve of some sort. Interesting idea.

 

[Stubbers]

The testing standards need not only consider environmental conditions, but the rifle and its tunes condition, the energy output relative to the barrel length, state of tune, potential hammer bounce, shroud diameter and if its vented, air stripper efficiency/diameters, pellet weight and fps range...A 19" barrel making 50 fpe in .22 cal will be a lot louder than a 23.5" barrel making 50 fpe, even more if it suffers from hammer bounce, has a poorly designed air stripper with a skinnier shroud, and is tuned to keep the valve open longer than necessary.

Any change to the above variables can vastly alter the results/data obtained in a test, simply skewing results from one user to the next due to their rifle or its tune alone.

This is unless you only allow one guy, with one gun become part of the standardization which imo, not only reduces possible legitimacy of the results, the testers rifle would still be need to be dialed in to within the median users arrangement, but that by no means will guarantee one user with a 19" or 27" barrel will yield the same results as a tester does with a 23.5" barrel, no matter how standardized you make every other variable, as the 3 barrels may all benefit from different designs with different baffle arrangements, be them their shape or distance apart. The 19" barrel might have to deal with 1200 psi in the first set of baffles, where as the 23.5" may have to deal with 900 psi, and the 27" 500 psi, to that, one baffle design or spacing may be superior in the 19" barrel but inferior to another in the 27"...

-Matt

 

[IMADMAN]

(old) just can't think of the name but there is a fellow in Mexico making air pistols and a mod with a membrane that closes exactly as the pellet exits trapping the "noisy " air inside ? have you seen that post ?

Unfortunately the membrane only works for certain FPS.

 

[WobblyHand]

The testing standards need not only consider environmental conditions, but the rifle and its tunes condition, the energy output relative to the barrel length, state of tune, potential hammer bounce, shroud diameter and if its vented, air stripper efficiency/diameters, pellet weight and fps range...A 19" barrel making 50 fpe in .22 cal will be a lot louder than a 23.5" barrel making 50 fpe, even more if it suffers from hammer bounce, has a poorly designed air stripper with a skinnier shroud, and is tuned to keep the valve open longer than necessary.

Any change to the above variables can vastly alter the results/data obtained in a test, simply skewing results from one user to the next due to their rifle or its tune alone.

This is unless you only allow one guy, with one gun become part of the standardization which imo, not only reduces possible legitimacy of the results, the testers rifle would still be need to be dialed in to within the median users arrangement, but that by no means will guarantee one user with a 19" or 27" barrel will yield the same results as a tester does with a 23.5" barrel, no matter how standardized you make every other variable, as the 3 barrels may all benefit from different designs with different baffle arrangements, be them their shape or distance apart. The 19" barrel might have to deal with 1200 psi in the first set of baffles, where as the 23.5" may have to deal with 900 psi, and the 27" 500 psi, to that, one baffle design or spacing may be superior in the 19" barrel but inferior to another in the 27"...

-Matt

How do you suggest making testing more tractable? It's obvious that we can't test every possible variation in the universe. So, in your opinion, how can the testing regime scope be reduced intelligently to something practical. If you don't think it's possible, that's ok, but then I request you state so once, and then not contribute.

We are trying to make quantified measurements that could be reproduced by others with "reasonable" testing. So if you can offer some helpful constructive suggestions, or things to make this possible, we are glad to hear them. I can comprehend how different characteristics of the air packet might change the final acoustic output. I don't think many folks would like to drill their barrels and install fast responding pressure sensors, so what do you suggest? Sure we could make an adapter, but then we'd all end up in a discussion about whether that's the same system or not... Let's try to be solution oriented. The opposite approach is non productive.

 

[Stubbers]

How do you suggest making testing more tractable? It's obvious that we can't test every possible variation in the universe. So, in your opinion, how can the testing regime scope be reduced intelligently to something practical. If you don't think it's possible, that's ok, but then I request you state so once, and then not contribute.

We are trying to make quantified measurements that could be reproduced by others with "reasonable" testing. So if you can offer some helpful constructive suggestions, or things to make this possible, we are glad to hear them. I can comprehend how different characteristics of the air packet might change the final acoustic output. I don't think many folks would like to drill their barrels and install fast responding pressure sensors, so what do you suggest? Sure we could make an adapter, but then we'd all end up in a discussion about whether that's the same system or not... Let's try to be solution oriented. The opposite approach is non productive.

The thought experiment I was conducting is conducive to the conversation, if you wish to omit the sentiments logic and reasoning of rifle to rifle variability potentially skewing results, suit yourself. However its contribution here to this discussion is valuable, weather you deem it insightful, productive or not.

I am unsure how one could standardize moderator testing for all airguns, from short barreled .177 12fpe pellet shooters to long barreled .50 cal slug shooters and everything in between. If I had the answers I would happily provide them, I only bring to the threads attention the concerns of the aforementioned variables due to feeling those variables are a wrench in the gears of standardizing any and all moderator testing. One moderator may produce better results in a gun that exhibits no hammer bounce and is tuned incredibly efficient where another design may do much better in an airgun that is inefficient, and so on.

There is no need to integrate pressure sensors in ones barrels to estimate the pressure gradient from breach to end of muzzle, there's enough research done on this that one can napkin math it. I can't help but wonder that different designs will handle the parcel of air differently depending on that parcels pressure, and amplitude, which varies from caliber to caliber, tune to tune, gun to gun.

Bringing to light these variables and conditions which may alter end results of data collected isn't being unproductive, rather, its an attempt to bring these considerations to readers attention so we collectively can resolve it. It's called troubleshooting. Baffle spacing alone could have massive effects when altered on either a .177 or a .50 cal producing two entirely different energy levels.

If the test results are conditional, as in they pertain to a .22 cal making 40 fpe with a very efficient tune, an end user who is swayed to think the standardized test results will apply to his inefficiently tuned .357 making 170 fpe, well said user may be disappointed if his results don't line up with results found within an otherwise standardized test that conclude Moderator A1Z is the best there is (at reducing muzzle report in the .22 cal at 40 fpe), but upon their own personal tests they find their original moderator B2Y performs better.

-Matt

 

[WobblyHand]

@Stubbers Thanks for your rationale. Let's continue this a bit more.

There's always the issue of an inefficiently tuned gun. They waste air and are louder than they need to be, period. There have to be some assumptions made to make some testing program useful. I'd propose the AG's in question should be tuned to be efficient, for the test. Have to reduce the test scope to something practical. I realize not everyone's AG is tuned, but somehow the problem space has to be reduced, or testing becomes something that only well financed organizations can afford.

My motivation on the pressure sensors was to get a handle on the pressure time product, or some other metric like that. An idea might be to integrate that product to come up with the available energy. Perhaps that could be used to normalize the results (in a way that I haven't spent a 1/2 second thinking about). This might help make the problem space become more compact (or not). Napkin engineering has some benefit, but actual measurement data is often more revealing, sometimes contradicting what we thought.

Think baffle spacing is a deeper test, and that needs to be done by those who are designing their own, to see what works and what doesn't. It could very well be that the solution is "power-time" dependent. However, those particular designs could be tested using the yet to be developed protocol.

 

[bucketboy]

How does one use masking tape to ensure concentricity?

GsT

It doesn’t aid concentricity but it’s a good indication how centrally the pellet exits the endcap. Even if the pellet doesn’t clip the baffles, if it’s not going through the middle of the moderator it can cause inaccuracies. Ideally you want the hole in the baffles and endcap to be as small as possible, obviously this means the possibility of clipping becomes more likely, masking tape is a simple and effective test method.

Try it, you may be surprised how bad some moderator/shroud assemblies are, particularly those with a liner and compression nut.

How many recommendations have you seen that say “ if are shooting .xx calibre then select a moderator the next size up” this is only necessary to correct poor manufacturing tolerances.

Bb

 

[steve-l]

How does one use masking tape to ensure concentricity?

GsT

I think that is really the wrong way to check alignment with the barrel. It could give you a false reading if there was contact with a baffle before exiting the mod. The best way to test barrel moderator alignment is to use a rod turned on one end to the land diameter of the barrel for a length of about 2 inches. Then by simply slipping the test rod through the mounted mod. and into the barrel, alignment is easily verified.

 

[steve-l]

I enjoyed the back and forth of this thread, but I received a notice yesterday that discussions of mod. construction is now no longer permitted by moderators of this forum. Violations of this new restriction will be permanent suspension. I will be 80 years old this year and I have been building moderators all my life for my self. I do not sell them. I have given a few away to friends over the years of course. I think I can say that I have tried most ideas, materials and designs over the years. Yet, I still think I can do better. Building these mods. is a very large part of my air gun hobby. I enjoy sharing my knowledge and experience with others. I am fortunate in that I also possess a rather well equipped machine shop, so I can do this at my leisure because I am the number one customer of that machine shop. The many years of my experience has also taught me that testing of moderators is very subjective and impossible to effectively evaluate a moderator's meaningful performance in a comparison to other moderators so that the same results could be reproduced elsewhere. There are simply too many variables to be meaningful. Then there is the rule of diminishing return. I can also say that the design criteria for a PB is NOT the same for an air gun for the simple reason of gas temperature. What works well for one does not necessarily work well for the other. However, what really upsets me most is being told what to do, what to say, how to say it and lastly what to think. I have no intention of changing anything I do for anyone least of all, this forum. I have earned that right. I am open to private discussion accordingly.