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+--- Thread: My Grendel Barrel is "Slow?" (/showthread.php?tid=23137)
My Grendel Barrel is "Slow?" - mv1arms - 03-30-2021
Hey everybody, I wanted to see what people think about this.
The barrel is a 6.5 Grendel SAAMI Spec chamber PROOF Research 20" steel barrel.
Bedded with green loctite. Running a Dead Air Nomad Silencer. Superlative arms adjustable gas block that is adjusted 6 clicks away from closed (no gas) and will cycle but not lock the bolt back without the can. These are my desired gas settings because it's not too gassy.
Groups are 0. 5 to 1.5 moa 5 shot groups with factory and handloads.Not too worried there. 2 to 3 moa with wolf 100gr factory ammo. Again no surprises.
Velocities were recorded with a ProChrono DLX about 2.5 yards from muzzle.Velocities were after break in, cleaning, and approximately 100 to 150 rounds down the pipe total. Elevation was about 1k feet. Temp 50 degrees F.
Velocities:
123gr Hornady Black ELD - velocity 2401 sd 8 for 16 shots.
123gr Hornady SST - velocity avg. 2421 sd 36 for 23 shots
Wolf 100gr - velocity avg. 2565 sd 13 for 5 shots
Seems like a slower barrel ~ 50 fps slow compared to others I've seen on this forum.
Thanks!
My Grendel Barrel is "Slow?" - VASCAR2 - 03-30-2021
Some barrels are just slower, my 16 J&T has a generous size chamber on the loose side of tolerance and produces less velocity than most reported velocites from 16 6.5 Grendel. My Faxon 16 Monster barrel produces velocities closer to what I see reported.
Verify the spacing is correct on your chronograph sky screens. Most new chronograph sky screens are already mounted to a bracket but not all. Some chronographs have optional sky screen spacing so verify your using the correct distance setting. Lighting conditions can affect the angle of the bullet shadow cast on the sky screen creating less or more than the true velocity.
Shooting at an angle and not square over the chronograph screens can have an effect on recorded velocity.
I know people that use a Magnetospeed chronograph at the same time they are using an optical chronograph to try to avoid erroneous readings or no recorded velocity.
My Grendel Barrel is "Slow?" - mv1arms - 03-30-2021
Do you think there's more room on the higher end of load development to match advertised or would I likely hit pressure at the same spot?
Thank you, this is kind of what I was expecting to hear but I was a bit surprised when I saw the chrono numbers.
My Grendel Barrel is "Slow?" - VASCAR2 - 03-30-2021
Normally the cooler temperatures produce less pressure/velocity. Recent lots of Hornady Black show less velocity than the earlier production 6.5 Grendel 123 grain A-Max. Without shooting two rifles on the same outing using the same chronograph with the same ammo it is hard to know for sure using an optical chronograph. I think Id trust a lab radar or Magnetospeed chronograph more than an optical chronograph.
Your velocities seem a little low for a 20 barrel but if the ammo looses about 1 FPS per lower degree of temperature your still getting low velocity for factory ammo. In my 20 Shilen I got right around 2500 FPS with 123 grain SST on a 70 degree day using a magnetospeed chronograph.
With my 16 J&T the velocities were lower than expected regardless of ammo.
My Grendel Barrel is "Slow?" - kmon - 03-30-2021
You might find the velocity will increase some in 100 to 200 more rounds down the pipe.
My Grendel Barrel is "Slow?" - Bigs28 - 03-30-2021
You might be too close to the chrono. My Caldwell manual states it needs to be much further away then what your shooting.
My Grendel Barrel is "Slow?" - mv1arms - 03-30-2021
Bigs28 Wrote:You might be too close to the chrono. My Caldwell manual states it needs to be much further away then what your shooting.
I'll push it back a few yards next outing. Thanks!
My Grendel Barrel is "Slow?" - Bigs28 - 03-30-2021
I just read their manual and it states muzzle blast can affect readings and they recommend 10-15 feet from muzzle for rifles.
Page 6
My Grendel Barrel is "Slow?" - mv1arms - 03-30-2021
Bigs28 Wrote:I just read their manual and it states muzzle blast can affect readings and they recommend 10-15 feet from muzzle for rifles.
Page 6
I'm going to try 5 yards. I was using a can for all the measurements but I'll go by the book. Thank you!
My Grendel Barrel is "Slow?" - mv1arms - 03-30-2021
kmon Wrote:You might find the velocity will increase some in 100 to 200 more rounds down the pipe.
I'm about 200 rounds down the pipe so I thought it would have sped up by now a little. But I really didn't see that.
My Grendel Barrel is "Slow?" - kmon - 03-31-2021
One of mine did not speed up until about 300 rounds, then again some barrels are slower than others. one with minimum dimensions for chamber and barrel internals will be faster then ones at the upper end of tolerances
My Grendel Barrel is "Slow?" - mv1arms - 03-31-2021
I hit the range after work today. Chrono pushed back to 5 yards from the muzzle. Velocities for factory hornday sst were 42 fps faster average velocity than previous based on 20 rounds fired. Velocity for 100gr wolf was approximately 21 fps average faster. I think it's possible the barrel is still speeding up or I am using my chrono correctly now or a combination of both.
My Grendel Barrel is "Slow?" - Klem - 03-31-2021
mv1,
Good chance it's the chrono. Optical chronos are notoriously fickle. I have a folding optical Chrony and gave up using it in the daytime. I use it at night with LED strips under the skyscreens. The difference in reliability was chalk and cheese, no more odd readings and lost shots.
I upgraded to a LabRadar but the nighttime chronying works fine.
My Grendel Barrel is "Slow?" - mv1arms - 03-31-2021
Interesting I may have to try that, I don't have a night time "range" so it may take me a while before camping season to do that method.
My Grendel Barrel is "Slow?" - Double Naught Spy - 04-01-2021
Optical chronos can be fickle, but usually if you are too close to the chrono, velocities get shown as being higher than normal because the chrono is reading gas/debris from the powder instead of the bullet.
My Grendel Barrel is "Slow?" - kmon - 04-01-2021
When I was using a optical chrono, I got more reliable reading with it on overcast days and make sure you are shooting straight through it not angled.
My Grendel Barrel is "Slow?" - Zeneffect - 05-04-2021
if given the choice between a magnetospeed and optical chrono, which would you choose? Im having a hate-hate relationship with my optical.
My Grendel Barrel is "Slow?" - A5BLASTER - 05-04-2021
Zeneffect Wrote:if given the choice between a magnetospeed and optical chrono, which would you choose? Im having a hate-hate relationship with my optical.
Magnetospeed hands down 100% of the time over a optical chronograph.