just recently got my first suppressor out of jail and went and tried it out with just factory ammo for the time being. We had limited time, so I didn't get to gather as much data as I wanted. I let my wife shoot it and she was hitting 1.5" low. I have not confirmed this to be the actual POI shift with the can attached, but I adjusted for it anyway. The first few shots were dedicated to adjusting the gas to cycle correctly. I didn't get velocity data either (I think this would have been a hard data point needed to figure out what's going on). Here's where things get interesting. I run Strelok and had my reload data pulled up instead of factory ammo. I have gathered all data needed previously for factory ammo and I have a load for this rifle worked up without the suppressor, which is about 100fps faster than factory rounds. So we stretch it out to 775 yards. Impact, center hit. Now to 1100. Impact, hitting about 5-8" high. My ballistic calculator was giving me come ups for my reloads, not factory rounds, but I was shooting factory rounds. A few things could be going on here, but the main two I'm thinking of are my factory rounds velocity has increased dramatically with the can on or my BC number needs to be increased (not that likely). I checked the angle we were shooting at and it was level, maybe a slight positive angle, but neglible. Is there anything else I'm missing? Can a suppressor really increase muzzle velocity that much?

yes it can, it is like adding barrel length.

The suppressor allows some of the gas to continue pushing on the base of the bullet without having the friction of rifling to slow the acceleration.

It varies from rifle to rifle, and even from 1 can to another.

I shoot Dead Air, and my 6.5Creed bolt gun picked up about 80Ft/sec with a Sandman K, and only about 60ft/sec with a Sandman S.

Verified with Magnetospeed V3 over about 30 rounds on each. I wound up making new DOPE cards for each can, and had to number the cans because I have 2 Ks and 2S, but i only tested one of each.

My gas gun was similar, with a smaller gain.

I only ask this because it has happened to me and I know it has happened to others.  Were you accounting for temperature differences?  I live in a state that goes from -40 F (worst case scenario, but happened the last couple years), to over 100 F in the summer time.  Temperature is a huge factor.  Even "temperature insensitive" powders are not perfect.

If temp wasn't to blame, ALL other variables were held constant, and there was no major zero change prior to stretching it out, then it has to be coming from the can.

I haven't seen a huge boost, ~ 40 fps tops, usually less.

What bullet, powder and BC were you using? Have you checked your drops with that load out to 1,100 yds before? You're basically talking a 0.1 - 0.2 mil discrepancy at that range, I'll see something like that sometimes at 1k just from weather changes.

Edit: re-read and saw that you were using factory ammo, not reloads. Did you chrono with and without the can? What's on the box doesn't always mean a whole lot. How many shots to establish your POI @ 1,100? I'd put the chances of variable factory ammo or conditions way ahead of your can adding lots of velocity.

No temp swings. All variables were constant, so I'm assuming it is the can that's increasing the MV. I thought about tweaking BC, but that takes it from a G7 of .312 to .353. And I've already verified the data was solid without the can out to 1000 yards with the factory ammo and reloads.

I've chronoed everything without the can and have made consistent hits out to 1000 yards. I did not chrono with the can on, which is going to tell me a lot. Bc of time constraints, we only put 2 rounds out to 1100 which were both hits at about 5 to 8" high. Not enough to make a solid judgement, but I'm afraid if it has increased the MV that much, I'm going to have to workup another load for suppressed shooting.

I usually note a 0-10fps increase with my suppressors on the chronograph, but this is also something that could get lost in the SD of most ammo I shoot.

It is just a POI shift, usually it's down, but NOT always. Your velocity is likely statistically insignificantly different.

You would need to chrono with and without, using the same loads to answer the question.

THIS. I've never personally seen a velocity decrease, but also don't recall it being a massive increase whether bolt guns or AR platforms, only the chrono will tell you for sure how your setup is effected.

I plan on doing this at the end of this week to know for sure. Whoever mentioned freebore boost above, I've been reading about that. Could be what's going on.

The other thought I had was about barrel time and whether or not it would be worth it to drop my established unsuppressed load by a couple tenths to achieve the same velocity node if there were an increase in velocity with the can on.

Went out today and tested everything. I noticed a few things:

1. First shot on a cold can had a big increase in velocity. After warming up the can, velocities tended to normalize.
2. Did a Satterlee test and accuracy nodes have not changed at all. As a matter of fact, the repeatability of the test compared to a previous test without the suppressor was impressive and damn near identical.
3. I took the suppressor on and off a lot and still had consistent hits out to 1100 yards.
4. When testing factory or reloads for velocity numbers, I noticed an increase in velocity by about 15-30 fps.
5. Shooting suppressed is less forgiving of a lapse in fundamentals.
6. Tighter groups
7. Dirty as shit!

Thanks for sharing your testing results and they appear in line with what I and many others have experienced.

Dramatic increase....nope.   More like 20 fps on average.    It depends on the caliber, silencer and powder used.

My understanding (such as it is) is that POI shift is mostly due to the added weight of the suppressor changing the barrel harmonics, and thus the nodes for any given load.

Not exactly. At least with my combo of parts. The first round out of my suppressor increased the velocity by 60 fps. I have no idea if that is correlated with FRP or I read something about the actual density of gas is thicker on the first shot than the subsequent shots after heating up. I can't explain it, but I tested it.