I posted this on another forum as well, but wanted to see what some of you guys on here thought...

Is it common for a barrel to gain velocity after proper breakin?

Last summer, I put a new Shilen Barrel on my .270. I finished it at 24.75". I put approx 100 rounds down it (Barnes, Accubonds, Partitions) to break it in and develop a load for 2016 fall hunting season.

I ended up settling on 55.0 grains of IMR 4831 W/ 129 Barnes LRX. The book showed this to be around 3150, but my chronograph was showing an average of 3075 - so I ran with that. The velocity was questionable as I had a tad longer barrel than the book, but it wasn't enough for me to care too much and accuracy was what I was looking for.

FAST FORWARD - This spring I have brought out the 270 for two separate range visits - one about a month ago in 50 degree weather and one today in 75 degree weather.
NOTHING HAS CHANGED on the rifle or the loads, in fact I was shooting the same loads I developed last fall that have been sitting in the safe all winter.

In my first range visit a month ago, the velocity average for the 15 rounds I shot was right at 3140 FPS. POI stayed exactly the same and group size was 3 shots in .5-.6 range which is what this load has always done. Overall an average velocity increase of approx 75 FPS over the last time I shot the rifle in the fall.

Today, I get out and I shoot 24 rounds - 6 4 shot groups. POI is same. Was shooting .5-.6 4 shot groups (Super Stoked about that) but Velocity average was 3217 FPS. Highest Velocity was 3240, lowest was 3180.

Will a barrel normally speed up like this? By now I consider the barrel broke in as I can shoot quite a few barnes loads with minimal fowling. Again, these are all the same loads from a batch of 60 I whipped up last fall. I know it was hotter today, but the speed increase has came every range session.

I am mainly curious because I shot today to get a final chrono speed to submit for my Leupold CDS Dial. I was going out to verify 3150 ish, and now I am averaging 3200. I wont be shooting far enough for it to really matter (5-600 max) but I still want to be as accurate as possible.

Thoughts? Do barrels speed up?