Moderator Questions ??

[Trucker3573]

Just curious if this is normal. Awhile back I posted a thread about an fx impact mk2 700 .30 cal I was struggling to get below 18 fps ES. Accuracy was stellar. Fast forward to recently shooting a wildcat bt .30 cal th at was extremely consistent with shot to shot speed. It was very loud so I decided to throw an FX aluminum can moderator on it. Was a pretty good POI shift which I didn’t think was unusual. The accuracy was great so I don’t suspect clipping however the speed was very inconsistent. The can slowed the speed overall but also made it vary a lot. Took it off and the ES went way down and velocity went back up. The gun definitely doesn’t like that FX mod. I suspect that is the culprit behind the speed issue in the impact as I have never shot that gun without an fx stock moderator on it. I haven’t had a chance to find out. It’s just weird to me as I have two .25 cal fx guns that shoot consistently and great with that same type of mod on them. However the same doesn’t seem to hold true in .30 cal. Has anyone else experienced this? Does it sound normal ?

 

[bucketboy]

A moderator should not affect either speed or consistency (except on a co2 gun) and although accuracy may still be ok I wouldn’t rule out clipping.

A couple of years ago while testing a new moderator I had made for my extremely accurate and consistent.20 I was surprised to see the poi had dropped by an inch or two which was unusual so I chrono tested the gun to see what was going on, again a suprise to find it was a little down on power.
After a while I realised I had accidentally fitted calibre specific.177 baffles with a bore of 4.75mm instead of the the 5.25mm baffles. Every shot the 5mm pellet was being swaged down to size but it didn’t seem to affect accuracy too much

Bb

 

[Long_Gun_Dallas]

Moderators and the likes absolutely can affect velocities. In powder guns they tend to increase it slightly. The hollow fx mod is odd.... no baffles. So, I am imagining the muzzle blast is coming thru the large bore at the rear, going around the projectile, since there is little or no stripping taking place. Being contained in the can, and swirling around the exit trying to make its way out with the projectile. This could likely cause turbulence and interference. And your odd es. If we formulate a theory based off of the behavior of pressurized air, construction of the items in use, and the data you have collected.... it's easy to theorize this is the scenario

Also wouldn't rule out clipping

 

[Trucker3573]

Thanks for the replies. Yeah it was really weird to see the inconsistency disappear after taking that can off. I really would like to moderate the gun but have hesitancy spending 100-200 dollars on one that may not work for my set up.

 

[bucketboy]

Moderators and the likes absolutely can affect velocities. In powder guns they tend to increase it slightly. The hollow fx mod is odd.... no baffles. So, I am imagining the muzzle blast is coming thru the large bore at the rear, going around the projectile, since there is little or no stripping taking place. Being contained in the can, and swirling around the exit trying to make its way out with the projectile. This could likely cause turbulence and interference. And your odd es. If we formulate a theory based off of the behavior of pressurized air, construction of the items in use, and the data you have collected.... it's easy to theorize this is the scenario

Also wouldn't rule out clipping

I would doubt that a .30 cal pellet ther would be any noticeable velocity change with or without moderator.

Bb

 

[Long_Gun_Dallas]

Thanks for the replies. Yeah it was really weird to see the inconsistency disappear after taking that can off. I really would like to moderate the gun but have hesitancy spending 100-200 dollars on one that may not work for my set up.

So long as the gun and mod adaptor is straight/square, I can say for sure the huma mods are also all dead straight/square

I would doubt that a .30 cal pellet ther would be any noticeable velocity change with or without moderator.

Bb

Typically, yeah seems it would be almost nothing. But this isn't a normal moderator. The air charge is blowing past the projectile Inside the can. This normally does not happen due to baffles. But there is a tight exit. There would be a lot of turbulence there. And the projectile cannot move as fast as the air trapped behind it once it has ample room to move past it.

I would think a large part of it would be due to the projectiles profile. I seriously doubt a slug would be affected nearly as much.

 

[steve-l]

A moderator should not affect either speed or consistency (except on a co2 gun) and although accuracy may still be ok I wouldn’t rule out clipping.

A couple of years ago while testing a new moderator I had made for my extremely accurate and consistent.20 I was surprised to see the poi had dropped by an inch or two which was unusual so I chrono tested the gun to see what was going on, again a suprise to find it was a little down on power.
After a while I realised I had accidentally fitted calibre specific.177 baffles with a bore of 4.75mm instead of the the 5.25mm baffles. Every shot the 5mm pellet was being swaged down to size but it didn’t seem to affect accuracy too much

Bb

A properly working mod will attenuate the pellet velocity. This is caused by the air column in FRONT of the pellet is also attenuated reducing the net differential pressure across the pellet.

 

[bucketboy]

A properly working mod will attenuate the pellet velocity. This is caused by the air column in FRONT of the pellet is also attenuated reducing the net differential pressure across the pellet.

Well I must be doing something wrong, I have made at least 100 moderators of different size shape and design, in all the testing I have done I haven’t noticed any discernible difference in velocity or consistency and poi shift has always been minimal. What I do know is that all my guns are more accurate with a moderator than without

Bb