Best Moderator for Karma SLS compact .25

[Surefire]

Hi Everyone, I am usually an Impulse Air guy for my moderators yet I reached out to Donnyfl about a moderator due to them having a part in designing this airgun. Some-1 got back to me & sent me a link to a Ronin.. I did ask for something shorter/fatter seeing how it's a compact & id like to keep it that way. But I figured that I'd ask this community about they're knowledge on this subject. I like the gun a lot & don't intend to pull the mod on & off a whole lot, rather set it & forget it. I also don't know much or understand why on some of the moderators have a .177/.22 or .22/.25 my IA 1350 that's on my .30 FX Panthera Hunter Compact is a straight .30 & quites the bark down quite well.. I would like something that is designed specifically for .25 only to avoid clipping... I just can't see something that's designed for two different pellet sizes working as good as one that's designed for One projectile size. Also I know that this gun is made in China (now) not usually one to go for such things but if they work & are reliable than well you know.. lol all relevant thoughts & comments are greatly appreciated! Thanks, -SF

 

[subscriber]

You can shoot .177 pellets though a .30 mod and it will work much better than you expect, for two reasons:

Airgun power is roughly proportional to bore area. So, there is no way that a 20 FPE .177 is louder than a 60 FPE .30; when fired through a .30 rated mod. The same principle applies to a .22 fired through .25 mod, or a .25 fired through a .30 mod.

The second reason why, is the predicted loss in performance is incorrectly estimated . This is because the baffle bores represent a small percentage of the overall internal length of a mod. However, with the flat baffle designs such as DFL uses, some air and part of the shock waves can overtake the pellet and leak out ahead of it, even with the correct for caliber mod. Consider that, as the pellet traverses the open spaces between baffles it is as if a .25 mod is baffled for a .75" diameter projectile.

Certainly, if the caliber correct baffle bore ran the full length of the mod, then pellet to tube clearance would matter more. But then, the large OD of the mod would not add functional value. The total volume works precisely because the air is able to expand radially, away from the pellet path. Most of that air slams into the baffle wall, and so cannot leave the baffle bore directly. Ditto for the shock waves reflecting off the baffle wall. The baffle bore area is small compared to the baffle wall area. So, increasing the baffle bore diameter by 1 mm changes the ratio of baffle bore to baffle wall area very little - unless the mod is unusually skinny.

If you shoot a .25 from a .30 moderator that is up to the job for the .30, then unless the .25 is tuned for more power than the .30, or has a very short barrel, the .25 will still be quieter than the .30. The reason to get a dedicated .25 mod is that it will probably be smaller and lighter than the .30. Not because the .30 mod would be louder.

Depending on how your mod attaches to your airgun barrel; directly or via a shroud, making the baffle bores too small may cause just enough clipping to double groups; or may turn your PCP into a shotgun. Worse, would be the occasional wide flier.

There are a small number of very loud folks on the forum that swear that anything over 0.01" radial pellet to baffle bore clearance is a criminal wasting mod performance. There are many more that use one moderator to shoot multiple calibers, that are happy with the sound reduction and grouping ability of their smaller caliber airguns, when fired through a mod intended for 1, 2 or 3 calibers larger than what they are shooting.