A little 300 PRC update. With about 1300 rounds down the barrel and like a light switch it started losing accuracy...I decided to give the old tried and trued JB Bore Cleaning Compound a go on the old 300PRC Bartlein barrel. After a thorough normal cleaning...I hit it with the JB as per directions...well Speedy's directions anyways. I started pulled more stuff out eventhough I thought it was clean. Not worrying about damaging the barrel....I mean it is shot out right? I cleaned the ever living poo out of that barrel. Dry patched it...bore scoped it to make sure I didn't have any residue left...and put it away until this morning when I went to the range.
Today's range session was primarily focused on 308....and fun....beautiful 72F with not a cloud in sight...maybe a 2mph right to left wind. Flat range with berms at 100yds, 150yds and 242yds. Installed the Magneto speed and loaded a fouler shot that was a 250gr A-Tip that was damaged on the Ogive from pulling.....Hornady 6x brass..... a HOT load of VV N565 and a seating depth that was magazine feedable for a 250gr A-Tip...which btw...is WAY TOO OVERPRESSURE now for an action that isn't built like a tank.
First shot blew a primer. Brass is toast....but barrel is fouled. Shot hit 1/2" below POA...speed...2884fps....below what I expected...but this was the first time every...I had a very heavy bolt lift.
Now..the subject of this post. I proceeded to shoot two five shot groups with Hornady 6x brass, VV N565 loaded a little too hot, and a crappy bullet in the Hornady 225gr Match...not the ELD-M....the old BTHP 225 with the low BC. Here is a pic of the first 5 shot groups MagnetoSpeedV3 readings.
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The group measured 3/8ths and it was all horizontal...the vertical was almost unmeasurable. Now...granted...this load ruined the brass and it went straight into the recycle bucket....but I was amazed at the SD after some JB Bore compound. The second group was 1/2" and the speeds were about the same.
On the agenda today was testing out how close the Optimal Barrel Time listed in
Gordon's Reloading Tool was to reality. I think I nailed it. While the speeds were close...the group was small...and vertical dispersion was almost nothing....I know you can shoot a small group with really high SD's. Today, with the 308 and 'pot luck' brass....I shot a nice 1/2" group at 100yds with an SD of 37.5. 100 yards isn't long enough to show much of a vertical dispersion due to speed differentials. The 308 was also guestimated at using the OBT calculator on GRTools and changing the seating depth and powder charge accordingly.
The highlight of my day was NOT me shooting...but spotting for my shooting buddy. First shot 1/4" above POA....second shot I call "Same hole"...3rd shot I call "Same Hole"....he thought I was messing with him.....4th shot was a flier and opened it up to 1/4"....5th shot opened it up to 3/8ths. He thought I was messing with him...so I told him we needed to take a walk....he was Peacocking all the way back to the bench when he saw 3 shots in the same hole....but that's why we shoot 5
Summary....JB Bore Cleaning Compound has been used for years and years....and I finally saw the light...I may get another few long range sessions out of this barrel yet before the other one arrives.
I hope you guys enjoyed your day at work while I was at the range