Accuracy Test with Different LDCs

[mrbulk]

So initially I started a thread about sound testing LDCs:

https://www.gatewaytoairguns.org/GTA/index.php?topic=180075.0

and in it a discussion came up about whether using a moderator changed a gun's point of impact (POI) when the gun was zero'd for another moderator, or maybe none at all.

So I first took the 5 quietest LDCs from the other test (with presumably more complex/involved pellet pathways) and tried this out with 5-shot groups, and the photos of the results are below.

Four of the LDCs grouped similarly, meaning no notable change in POI and fairly tight dime-sized groups from 25 yards. I used unsorted pellets pulled directly out of a factory tin and magazine loaded, no shot tray or nothing, as I was not going for ultimate accuracy, just general comparisons.

But it turned out I had to re-test one unit because of a glitch (see second photo of re-test below). Due to this unit being constructed of four separate screw-together pieces, I suspected clipping so I disassembled the pieces and screwed them back together as tightly as I could. As you can see, the retested group still exhibited slightly angled vertical stringing afterwards.

Will be testing the others for grouping soon.

[Long_Gun_Dallas]

Hmmm.... the relationship between pressure waves and barrel harmonics is a complicated one.   Wish I had as many to test.

I've got a TKO, several 30mm huma mods, a 40mm one, a modified FX moderator, GEO, froggy, home-made, and a factory SPA mod.  I used to have an old STO mod as well.

I've noticed on my 30mm humas, just changing the configuration (length) of them will alter POI.  Switching to the FX mod will alter again.  And switching to the TKO will once again. 

Tempted to print some groups like this as well.  I've got a number of .22s I can fit almost all of them to using 1/2"x20 thread

[ranchibi]

A friend picked up a new/used Crown, brought it to my place to dial it in as I have a chrony and I also installed a Sumo on it to quiet it down and the POI was definitely different but very consistent.

[mrbulk]

Yeah I’m gonna see what the rest will do POI-wise. All I know so far is that I zeroed with the Tanto first and made sure I spun on each successive LDC snug and tight for consistency.

Whatever shoots well from my (and I mean My) Avenger set at these pressures and hammer spring settings Should be repeatable later, so then I’m gonna retest the ones I already tested without changing a thing on the gun and see if they remain consistent and if so, I will have at least One set of repeatable circumstances and, hopefully, one set of repeatably consistent accuracy, even if unique to just this one gun and perhaps despite having to re-zero said gun each time I switch to a different moderator.

[mrbulk]

Hmmm.... the relationship between pressure waves and barrel harmonics is a complicated one.   Wish I had as many to test.

I've got a TKO, several 30mm huma mods, a 40mm one, a modified FX moderator, GEO, froggy, home-made, and a factory SPA mod.  I used to have an old STO mod as well.

I've noticed on my 30mm humas, just changing the configuration (length) of them will alter POI.  Switching to the FX mod will alter again.  And switching to the TKO will once again. 

Tempted to print some groups like this as well.  I've got a number of .22s I can fit almost all of them to using 1/2"x20 thread

Interested in seeing what the homemade one is like. 

[subscriber]

Good to see so little to be concerned about, Charlie.

[Rallyshark]

Seems like I remember some of the Humas being pretty snug for caliber, and Huub at Huma recommending going up a caliber at one point.  I don't know if they changed that though.  You could also remove the sound deadning from the first chamber, or even remove a section to see what the result will be with it.  It would be interesting if you measured the opening on the end of the LDCs to see what variation there is there.

It does appear to have some clipping going on there I'd say. 

[CraigH]

Seems like I remember some of the Humas being pretty snug for caliber, and Huub at Huma recommending going up a caliber at one point.

Whether or not it was completely necessary, DonnyFL recommended the same to me - .22 --> .25.

[Earl]

Good information.
Thank you mrbulk.

[Long_Gun_Dallas]

Hmmm.... the relationship between pressure waves and barrel harmonics is a complicated one.   Wish I had as many to test.

I've got a TKO, several 30mm huma mods, a 40mm one, a modified FX moderator, GEO, froggy, home-made, and a factory SPA mod.  I used to have an old STO mod as well.

I've noticed on my 30mm humas, just changing the configuration (length) of them will alter POI.  Switching to the FX mod will alter again.  And switching to the TKO will once again. 

Tempted to print some groups like this as well.  I've got a number of .22s I can fit almost all of them to using 1/2"x20 thread

Interested in seeing what the homemade one is like. 

Looks like what would happen if you ran down to ace hardware    haha.  I don't have any tools to get anything precise or center yet.  I need a lathe and 3d printer! 

Best I've been able to do use get someone to spin up some real precise delrin for me, and use some thin wall tubing as spacers.  Insert a bit of felt and a cage from huma.  Works a treat.  But cone baffles really do a number on airflow thru a mod.  Even on my 177, the one I have with 3d printed cones in it is clearly superior for it's size and weight  (and large baffle bores).

I do hope to get a lathe first, and a 3d printer later this year.  Pair that with a new living space, and I'll be set.  I'm smack in the middle of a city, and pay too much for where I'm at.  Or rather for what I'm missing which is more land, and a garage.

Seems like I remember some of the Humas being pretty snug for caliber, and Huub at Huma recommending going up a caliber at one point.  I don't know if they changed that though. 

I just received a new one that is 7mm bore and 7.1mm on the end cap.  For .22.....  Their old models were 6.5mm bore throughout.

[Long_Gun_Dallas]

...  duplicate post

[mrbulk]

I just received a new one that is 7mm bore and 7.1mm on the end cap.  For .22.....  Their old models were 6.5mm bore throughout.

Hmmm, verrry interesting...thanks Dallas!

[subscriber]

I had heard the proper bore clearance for a suppressor is 1.18 times the caliber.  For a 5.5 mm that is 6.5 mm.  I had also heard that caliber + 1.5 mm was the right number.  That would be 7 mm.

Either way, erring on the larger side is less likely to cause any kind of trouble; at the expense of a slight increase in sound. 

As a data point, stock Gen2 Marauder baffles have a bore diameter of 8 mm.  The same baffles are used for .25, .22 and .177.  The larger calibers have more air to deal with, but less leakage past the pellet.

[Long_Gun_Dallas]

I had heard the proper bore clearance for a suppressor is 1.18 times the caliber.  For a 5.5 mm that is 6.5 mm.  I had also heard that caliber + 1.5 mm was the right number.  That would be 7 mm.

Either way, erring on the larger side is less likely to cause any kind of trouble; at the expense of a slight increase in sound. 

As a data point, stock Gen2 Marauder baffles have a bore diameter of 8 mm.  The same baffles are used for .25, .22 and .177.  The larger calibers have more air to deal with, but less leakage past the pellet.

Indeed.  I threw the new .22 caliber 7mm unit on my .25 pistol.  It's super quiet, haha.  I need to test accuracy.  No clipping, though.

Hmmm, verrry interesting...thanks Dallas!

👍

[mrbulk]

I had heard the proper bore clearance for a suppressor is 1.18 times the caliber.  For a 5.5 mm that is 6.5 mm.  I had also heard that caliber + 1.5 mm was the right number.  That would be 7 mm.

Either way, erring on the larger side is less likely to cause any kind of trouble; at the expense of a slight increase in sound. 

As a data point, stock Gen2 Marauder baffles have a bore diameter of 8 mm.  The same baffles are used for .25, .22 and .177.  The larger calibers have more air to deal with, but less leakage past the pellet.

Missed this, Sub. Good info as usual, and something to emulate by future LDC makers.

[subscriber]

Charlie,

I think your 7 mm hole for a .22 is a good value.  I know I was greedy in the past with 6.5 mm for a .22, and saw some aerodynamic steering effects.  That said, it is not just the minimum diameter of the through hole that matters.  The average diameter of the passage also has an effect.  To put it differently; A very narrow projectile clearance is worse for "steering", if the total passage at that diameter is also long.

From a clipping perspective, just one instance of the passage and projectile meeting is too much - no matter how short that section...

As a counterpoint, the Marauder uses the same baffles for .177, .22 and .25 - with a 5/16" hole.  So, there you have the full range of tight to loose projectile clearance that all work rather well.  The "loose" .177 probably still works well because it has less air to deal with, assuming typical power levels.

Perhaps there might be a metric for dry firing loudness.  That would be linked to through hole size, with no projectile to narrow the gap.  Yes, dry firing is louder, but it might still be a useful metric.

[KnifeMaker]

I have a DonnyFl for my .257 Talon/Dor that is 8mm. I put it on the Raptor in .257, .250 and .222. Oddly, it is still quieter on the .222 than any other ldc I have even with the larger passages.  It is the Shogun version.


A few posters spoke about poi shift between units. Of course there is. Different weights/harmonics. It makes zero difference. Only group size matters and sound of course.


For those I have not bothers with this target before, here is the target at 80 yards with the DonnyFl in place. Raptor, 22" barrel, 1=20 twist, 930+ fps. 11 shots. One to settle reg, and 10 on target.    The target dot is one inch.  
For what it is worth, the new FX barrel (1-16 twist)  in it is evermore accurate. Way less fliers. 


Knife

[Ribbonstone]

Vibrationally...does not seem an worst than strapping on random lengths/weights of hollow (unbaffled) tubes. BIG negative for anything with the slightest "wiggle".,but I'll ignore POA/POI shift so long as it groups well (scopes go "clicky-clicky" for a reason).

[Earl]

I have a DonnyFl for my .257 Talon/Dor that is 8mm. I put it on the Raptor in .257, .250 and .222. Oddly, it is still quieter on the .222 than any other ldc I have even with the larger passages.  It is the Shogun version.


A few posters spoke about poi shift between units. Of course there is. Different weights/harmonics. It makes zero difference. Only group size matters and sound of course.


For those I have not bothers with this target before, here is the target at 80 yards with the DonnyFl in place. Raptor, 22" barrel, 1=20 twist, 930+ fps. 11 shots. One to settle reg, and 10 on target.    The target dot is one inch.  
For what it is worth, the new FX barrel (1-16 twist)  in it is evermore accurate. Way less fliers. 


Knife

WOW !!!