i have no desire to do math beyond the check book balance and tipping the waitress... that's why i married an accountant.Well I got bored and did some math. The equation for the deflection of a cantilevered beam is deflection = Load x Length cubed divided by 3 times the Modulus of Elasticity times I. I of a tube = 3.14 times (OD to the 4th power - ID to the fourth power) divided by 64. E is 29,000,000 for steel (I did not try to figure out what type of steel this is for, it is probably a bit low for barrel steel). I used my P35 for an example. It has a barrel OD of about .526 and I assumed my 22 so the ID is .22 inches. For a 1 lb moderator I get a deflection of .000682 inches. That would be a heavy moderator so I also looked up my Tanto, it weighs about 4 ounces.
But how much would that move the POI? That is another potential math problem but I have an empherical example I used. I know that a barrel band that moved the end of the barrel by something less than .010 pushed my POI by at least 6 inches. The 1 lb moderator would move the POI by 0.4 inches using this example. But my Tanto would shift it by .1 inches.
Based upon this I still don't think a moderator will move the POI on my P35s by enough to be obviously apparent but for heavier moderators with barrels that are unsupported for longer lengths I think it is possible there could be a noticable effect. Especially if you use a heavy moderator. I gave you the equations in case anybody wants to do this for their gun and so you could see how different parameters affect things. The weight is a simple linear effect. The unsupported length is quite short for the P35 at 6 inches and it gets cubed. So it is much more important. The diameters (internal and external) get raised to the fourth power so they are very important.
Putting on a barrel band would effectively reduce the unsupported length to near zero and greatly reduce the effect. The support added by the airtube is not infinite so it would not strictly speaking be a zero unsupported length but the I would get pretty complicated to come up with.
My phone is not very fancy but it has a calculator that can raise values to the fourth power which is the most complicated part of this so you probably have a tool that could do the calculation.
this is a QA issue in the way the barrel interfaces with the moderator or is attached, or machined imperfectly.Almost everytime I have accuracy issues the moderator is the problem.
The pellet will touch the moderator on its way out of the barrel, or whatevr else happens.
I usually solve this by using a moderator for a larger caliber.
Sometimes that does not work and then I use a completely different moderator design.
It helps if you can 3D print your moderators![]()