First shot suppressed

[BjornF16]

Fellers

Went to the range today with new MagnetoSpeed V3 to check various muzzle velocities. One of the Grendel guns I checked included using my 308 suppressor. I noticed that the first shot of my string of 5 Hornady 123 SST factory ammo was noticeably lower velocity than the remainder of the string.

I know that the sound suppression of a suppressor increases after the first shot.

Will the first shot of a suppressor typically be lower velocity than the following shots in a short period of time?

Shot 1 mv = 2516
Shot 2 mv = 2576
Shot 3 mv = 2579
Shot 4 mv = 2590
Shot 5 mv = 2582

[SG4247]

Hmmm,

I've been having flier issues with my 308 suppressed Grendel. I have noticed the first round was often a flier.

I do not generally chrony my loads until I find one particular charge weight that groups well.

After 500 test rounds, I still haven't found a load that is better than 3/4 MOA.

Good info Bjorn, I need to check my rig for this behavior using the chrony.

SO, I too am interested in others experiences.

[am4966]

Haven't got my Surpressor out of jail yet. But my theory and I'm not not a expert. Is that the can fills ups with gases and such and so you have a 1st round pop and a slower bullet. Then you fire and it's shot out and so faster bullet and quieter can.

So that's my thoughts on it and someday can report back with actual shots and chrony

[cory]

Where all 5 rounds from the same lot #?

[motoxxx_ryder]

Haven't got my Surpressor out of jail yet. But my theory and I'm not not a expert. Is that the can fills ups with gases and such and so you have a 1st round pop and a slower bullet. Then you fire and it's shot out and so faster bullet and quieter can.

So that's my thoughts on it and someday can report back with actual shots and chrony

to rule this out you can empty a nasal spray container (this kind http://www.medidose.com/Nasal-Spray-Bottles.aspx) and fill it with water. It atomizes the water in a way to replace the oxygen and stops the FRP.

i need to test my suppressor on my 65.

[lead chucker]

Iv been using my AAC Cyclone on both my grendels and haven't noticed any FRP or strange groupings. All my velocities from chrony seem ok. What can are you using? I do have some rifles that show the first round to be lower in velocity, I believe due to the barrel being cold then heating up as shot leading to higher velocities as fired. I have found no difference in this from suppressed to unsuppressed.

[Klem]

Given the same ammo bullet velocity exiting the muzzle and entering the suppressor will be the same. The suppressor will then actually increase the velocity slightly. The phenomenon is called 'Free-bore boost'. It is only a couple of fps more than if there were no suppressor and is because pressure is maintained behind the bullet for longer.

If it was the first round through that suppressor from the factory then perhaps there was some contact with the baffles creating a 'brush fit', similar to shoot-through rubber baffles. The friction of the slight contact may have slowed the bullet slightly but not enough to cause it to yaw and baffle-strike. Subsequent bullets now have a clear path to travel.

Other than that the reason is something other than the suppressor.

[BjornF16]

Where all 5 rounds from the same lot #?

Affirmative...same box

YHM .308 suppressor.

[SG4247]

Affirmative...same box

YHM .308 suppressor.

Hmmm..

Mine is a YHM Phantom 308.

[BjornF16]

Hmmm..

Mine is a YHM Phantom 308.

That's the one...