12-27-2017, 07:44 PM
So, you've got a few things going on with poi shift. Simplest to see is the weight. This will effect harmonics to some unpredictable degree, less with a heavier barrel. It will also cause the barrel to flex, no different than resting the barrel on a barrier and seeing a shift, also less with a heavier barrel.
These are relatively small changes and extremely repeatable.
The other effect is bore concentricity (possibly spelled wrong), this has 3 factors, how parallel the bore of the barrel is to the can, how shifted, off center, the suppressor bore is from the barrel bore, and how straight the bore of the suppressor is (just like a barrel, there'll be a slight curve).
All three of these will effect the bullet in the same way, if the bullet passes too close to the bore of a baffle or the exit end, the high pressure area around the bullet will deflect it. You don't have to have a strike to send a bullet keyholing or way off course. Just like a passing truck will move your car, the bullet will feel that same force as it passes through each bore.
The tricky bit about this issue (since it's normally greater) is that it can be affected by many parts, so it can be very unrepeatable. If the suppressor doesn't index the same every time, if it is able to wiggle on the mount (we're looking at thousandths of an inch), or if things move with heat, you will see large poi shift. An oversized bore can help compensate at the cost of effectiveness.
Pretty much, heavy barrel, light suppressor, and keep everything straight, and you'll minimize poi shift. But repeatability is the more important factor.
These are relatively small changes and extremely repeatable.
The other effect is bore concentricity (possibly spelled wrong), this has 3 factors, how parallel the bore of the barrel is to the can, how shifted, off center, the suppressor bore is from the barrel bore, and how straight the bore of the suppressor is (just like a barrel, there'll be a slight curve).
All three of these will effect the bullet in the same way, if the bullet passes too close to the bore of a baffle or the exit end, the high pressure area around the bullet will deflect it. You don't have to have a strike to send a bullet keyholing or way off course. Just like a passing truck will move your car, the bullet will feel that same force as it passes through each bore.
The tricky bit about this issue (since it's normally greater) is that it can be affected by many parts, so it can be very unrepeatable. If the suppressor doesn't index the same every time, if it is able to wiggle on the mount (we're looking at thousandths of an inch), or if things move with heat, you will see large poi shift. An oversized bore can help compensate at the cost of effectiveness.
Pretty much, heavy barrel, light suppressor, and keep everything straight, and you'll minimize poi shift. But repeatability is the more important factor.