Velocity Drop after cleaning (thoroclean)

[coldboreshot]

My first few rounds after cleaning are always slower, especially, especially the very first round. This freaked me out the first few times my Garmin revealed it; now I just accept it as what my barrel(s) do.
Garmin reveals a lot…

First 1 or 2 are blowing out residual solvents and/or oils. Its gonna slow velocity on those initial rounds. The product of physics.

 

[jthor]

You’re going to see velocity drop offs when using an abrasive. You’re going to smooth over the fire cracking and that will drop pressure. In 50-100 rounds the fire cracking with rough up and your see your velocity jump back up. The speed up seen when fouling and this are 2 separate things.

 

[goodi]

I agree with "jthor ".

Over many year using abrasive cleaners, regardless of calibre, i have found for the first fired shot or so, the registered velocity, is always slower and consequently shoots slightly lower, especially in LRBR .

Just my opinion , but I believe it is due the reduced (fouling) and friction in the barrel which contributes to slightly less pressure and consequent velocity.

Depending on the calibre, i add and extra
.3 grain to .5 grain powder for the 1st shot or so which seems to give the same point of impact as per the standard loads.

cheers

goodi

 

[Longtrain]

I’ve used abrasives for many barrels, currently Flitz Bore Cleaner with Iosso brushes gets the job done. Velocity is slightly lower after a clean until I get a few shots down. Clean barrel, lower pressure, as you shoot that changes obviously and pressures go up along with the velocities.

 

[Fast14riot]

My first round on a cold clean barrel is always a 6 o'clock 7 at 1000y. Second round is usually tight 8 or low 9, third creeps into the 10 ring and by shot 5 I'm confident its where it will stay.

Think of it like using moly, your bore is slick and clean, it requires less pressure to get it moving, so velocity is lower. Unlike moly, it's gone after just a couple rounds and builds pressure like normal again.

 

[ncageneral]

Where in Mississippi? If its a match I'd love to go watch the pro's shoot!

 

[6ShotsOr5?]

I always thought you needed to finish with some oil or lock-eaze patched out before sending a bullet down a clean barrel.

That’s what I thought too. When I got a Garmin I just started using it all the time. One thing I noticed is that when I run an oily patch last, the first shot after that is around 50-75 fps low, then back to normal on the next shot. Now I only run the oily patch when I’m through shooting that barrel for the day. Also a mentor pointed out that I could use a dry patch before a match starts instead of a bullet during the match to clear the oil, saving a sighter shot. If you extrapolate over several years of future matches, that adds up to a lot of time that can be spent picking the best shooting condition and a lot of money saved on components and barrel wear.