moderators need to be defined for particular caliber groups following certain parameters:
1. define loosely around case capacity, ( although bare in mind high intensity cartridges using fast burning powders may need catagorising a step or two above a larger case of a slower burning, more plodding caliber, as its always the exception that proves the rule)
2. the bore size of the maximum bullet diameter that will fit through the bore of the baffles, plus some clearance. Bare in mind you need to allow enough clearance for the machining capabilities of every gunsmith and lathe that is likely to be tasked with threading a rifle barrel.
3. Material from which the moderator, in particular the baffles are made of ( and there are large variances in the spec types of materials, its not possible to just say, alloy is alloy, titanium is titanium and steel is steel, close attention needs to be paid to the exact molecular structure and properties of the material)
4. Baffle shape, subtle differences in baffle shape lend them selves better to dealing with different ranges of velocity in the propellant gasses and amount of propellant gasses.
You could go down the road of designing a mod to suit the exact particulars of every caliber, but with so many it would take forever.
The way to do it is define a range of popular calibers commonly in use and design a mod that will work as a happy medium from the smallest, least intense, to the largest and most intense. Paying regard to ease of manufacturing and the logistics of thousands of parts, one needs to find a design that will keep most of the calibers happy most of the time. Of course here and there you loose a little or gain a little efficiency when it comes to sound suppression. It is no mean feat and the scientifics involved are quite interesting to say the least, But with the right research and developement, the right scientific and manufacturing input, computer simulation capability and a team of bofins the whole process is a lot easier and without that the process is purely trail and error.
Most moderators currently on the market achieve a minimum required level of sound suppression, they vary greatly in ergonomics, size and price as well as material and design catagory.
When it comes down to the efficiency of the moderator, size is not always the answer. You could probably use a mod the size of a dustbin, but without the right baffle geometry, spacing and number it would be no quiteter than one the size of a large mag light.
What is the use of a large over barrel rearwardly extending expansion chamber when the baffle shape does not take advantage of the space available, and what is the use of baffles with a shape that forces gases backwards if you don't have an expansion chamber to recieve them.
The beauty of a modular system is that you can tailor the mod in question to particular calibers or to a particular type of use.
Take a 5 baffled all alloy modular mod for example. while it will happily plod on all day with a .260 rem, put the same mod on a 6.5x68, although the 5 baffles will give adequate sound suppression just watch the baffles burn out quickly. Replace however the first 2 or even 3 baffles with steel, stainless steel or even titanium, you will combat the higher intensity of the 6.5x68 and its side effects.
If the same moderator design is possible in a selection of materials, you can choose the material that suits your use, for a stalker firing a few hundred rounds per year in a fairly standard caliber like a .308win, and walking up hill and down dale with a light handy rifle, an all alloy mod will suffice and will not interfear with the balance and ergonomics of the rifle, the user can add a baffle for more sound suppression or remove a baffle for lighter weight and less length. Should however the use be on a .300win mag range gun, firing a few hundred rounds every weekend, you can opt for a heavier all steel or stainless version, and the few hundred grams more probably wont bother you, and still doesn't effect the balance of the rifle, which is probably shot off a rest anyhow.
As far as seeing bullet strike goes, here you have to consider the 2nd and 3rd employment of the moderator,
Recoil Reduction and muzzle flip reduction are bye and large a byproduct of a moderator, with the 1st employment bieng sound suppression.
However, with the correct geometry in baffle design it is possible to increase recoil reduction and control muzzle flip.
The difference in weight of lets say 250g between an all alloy version or an all steel version of a mod when added to the recoiling mass of the rifle weight will make little difference in the generated recoil. a 250g barrel weight doesn't make much differnce to the felt recoil.Now if the baffles in the mod are designed with maximum recoil reduction in mind, they may not provide maximum sound reduction. By using a simulation program, and backing that up with actual tests on prototypes to verify, its possible to provide maximum recoil reduction as a parameter of sound suppression. Its a case of ballanceing the desired effects.
Adding lets say a 600g weight to the end of a barrel will certainly alter the muzzle rise or flip. but at the expence of ergonomics maybe, likewise the 250g difference between an alloy and a steel mods effect on muzzle flip are minimal,they do however exist but if muzzle flip was such a worry, its more a product of stock design than mod design, and one needs to get the line of recoil in a straight line between the muzzle and the shoulder. Adding a 1kg scope like a S&B PMII ontop of the rifle will also alter the muzzle rise to some extent.
Anyhow, all these factors can be considered by anyone wishing to design or to purchase a moderator.
When it comes down to a modular moderator or not, the end user like i said above can by choice taylor the product to his - her use. With a non modular mod you are pretty much stuck with what the designer or manufacturer considered best sorted to your use.
A happy medium would be a moderator design in which the expansion chamber and baffles are designed to cope with the range of calibers commonly found in hunting - target rifles, lets say from .222 up .458 win mag. that provided good sound suppression and recoil reduction, has the capability to be added to to cope with the increased amount of propellant gasses from larger cases of higher intensity cartridges, and is available in a choice of materials taylorable to suit a variety of usage. be it a super light version for mountain region stalking or a heavier version for higher and more frequent rates of fire.
Added to that it needs to be well made and affordable and affordable and titanium are 2 words that don't often fit together.
now to go back to answer the original question. will a smaller light weight mod be rubbish on a .308win. The simple answer is: if you put something the size of a parker hale .22 mod on there then yes, most likely. But if the mod you chose has enough volume to cope with the amount of propellant gasses generated then no, there is no reason it should give any less performance than a larger heavier model, and as I mentioned before, size isn't everything.
The right baffle design combined with adequate volume will give you excellent performance.
Just dont expect to put a super light weight mod of 200g onto a beast like a .338 lapua or 458 winmag and be happy.
But with a .308win ive found its quite possible to go down as far as 160g, with 4 baffles and still be happy with performance, reliability and robustness. with the same performance of a steel 4 baffle unit weighing 420g. If i put the same 2 mods on a .300 Ultramag I would probably get different results.
as far as invisible goes, you got me stumped there mind, but maybe one of the coating companies will ablige,
know what realy would be cool. a rifle coating that worked like a camelion and changed to suit the background, now that would make a million over night.
Hope thats food for thought.
rgds. Pete
