Gunsite XLR class

[CoryT]

The latest class is in the books. Only three clients, some last minute cancellations due to the Florence debacle on the coast. This was the first class to use the new Shotmarker target system, which is going to be a great help during these classes. We get not only the shot location but the velocity at the target displayed on a laptop. With the target at 1000 yards and the Labradar setup at the shooter, we can calculate very precise BC's with just a couple of groups. With this class, we were able to illustrate a variance in BC due to barrel/muzzle brake/suppressor. Two shooter using the same lot of Hornady 285 ELD's had two different BC's, as the velocity decay difference showed. For example, one shooter starts the bullet at 2896 and it arrives at the target at 1921, the other shooter initial velocity is 2827 and the target velocity it 1919. This trend continued so that one ended up with a BC of .78 and the other with .83, both BC's provided correct trajectories the next day from 600 to 2000 meters. Changes in the departure angle of the projectile due to the muzzle brake and suppressor affect BC.

The next class will be using the target at 500, 1000 and possibly 1250 for multiple downrange velocities. This is a great system and a big time saver as well, since we won't have to go back and forth downrange to collect paper targets. If you have not seen it yet, go to Shotmarker and take a look, well worth the investment.

Scope calibration revealed a cant problem, even in a Spuhr mount. The scope was actually fine, but the level attached to the scope tube (the mount level is almost invisible on this setup) was off WHEN VIEWED FROM THE SHOOTERS POSITION. It was placed from behind the butt, and the parallax from viewing by the left eye caused a shift of about .6 mil at 1450 yards, not good. Once corrected for viewing angle, there were no further difficulties.

The Magnetospeed target flashers work great, we'll add more of those as well.

The 'UKD' targets provided some challenges. Using a LRF at these ranges requires some practice and knowledge of the actual beam size and location versus the aiming point. Some ranges were off by 10-14 yards, and at 1600 that results in shots going high/low rather that getting the hit, then people start to question the software solution. Once we illustrated the problem and corrected the range, it was clear that just having a great LRF like a PLRF 15 is not the entire solution to the rangefinding problem.

A great time was had by all, and I look forward to the next one in the Spring!

 

[Unknown]

Shotmarker looks like a really cool system, even if other toys are higher on my priority list at this time. It sure would make running a match easy though.
Murphy's law says that just like people shooting their old style chronographs, someone is eventually going to shoot one of the sensor units.

The advance of technology this system uses is really neat, and I would love the chance to try one out, or even see one working at one of the local Precision rifle series matches, or practical rifle matches.

 

[CoryT]

The good news is a replacement sensor is pretty cheap and can be kept on hand ($40). the cables are simple 3.5mm audio. The expensive part is the sensor hub, but it's small enough to be easily protected, I've got an AR500 plate bolted in front.

 

[one shot ST]

The latest class is in the books. Only three clients, some last minute cancellations due to the Florence debacle on the coast. This was the first class to use the new Shotmarker target system, which is going to be a great help during these classes. We get not only the shot location but the velocity at the target displayed on a laptop. With the target at 1000 yards and the Labradar setup at the shooter, we can calculate very precise BC's with just a couple of groups. With this class, we were able to illustrate a variance in BC due to barrel/muzzle brake/suppressor. Two shooter using the same lot of Hornady 285 ELD's had two different BC's, as the velocity decay difference showed. For example, one shooter starts the bullet at 2896 and it arrives at the target at 1921, the other shooter initial velocity is 2827 and the target velocity it 1919. This trend continued so that one ended up with a BC of .78 and the other with .83, both BC's provided correct trajectories the next day from 600 to 2000 meters. Changes in the departure angle of the projectile due to the muzzle brake and suppressor affect BC.

The next class will be using the target at 500, 1000 and possibly 1250 for multiple downrange velocities. This is a great system and a big time saver as well, since we won't have to go back and forth downrange to collect paper targets. If you have not seen it yet, go to Shotmarker and take a look, well worth the investment.

Scope calibration revealed a cant problem, even in a Spuhr mount. The scope was actually fine, but the level attached to the scope tube (the mount level is almost invisible on this setup) was off WHEN VIEWED FROM THE SHOOTERS POSITION. It was placed from behind the butt, and the parallax from viewing by the left eye caused a shift of about .6 mil at 1450 yards, not good. Once corrected for viewing angle, there were no further difficulties.

The Magnetospeed target flashers work great, we'll add more of those as well.

The 'UKD' targets provided some challenges. Using a LRF at these ranges requires some practice and knowledge of the actual beam size and location versus the aiming point. Some ranges were off by 10-14 yards, and at 1600 that results in shots going high/low rather that getting the hit, then people start to question the software solution. Once we illustrated the problem and corrected the range, it was clear that just having a great LRF like a PLRF 15 is not the entire solution to the rangefinding problem.

A great time was had by all, and I look forward to the next one in the Spring!

hello Cory,

one question, you have used the labradar to catch muzzle velocity and the shotmarker for down range velocity, have you used any protocol or test to calibrate LB and shotmarker ?
I’m thinking to buy the shotmarker, in your opinion is a good tool ?
my idea is to use the two velocities for BC calculation using FFS, and also to have group statistic at the FFP.
But I need to be sure about velocity down range is linear with muzzle velocity, and If different I can take it in account for BC calculation.

 

[CoryT]

It seems to work quite well. It matches the PVM-21 at 300, where I can easily shoot through both. I've done exactly what you want to do, use both velocities to correct the BC in FFS and it provides an excellent solution. You do need to be careful with the setup, make sure the target is square to the trajectory, if you are off angle you can get some bad results. You can check by using a known bullet and the downrange velocity should match closely to the estimate provided by FFS.

 

[one shot ST]

It seems to work quite well. It matches the PVM-21 at 300, where I can easily shoot through both. I've done exactly what you want to do, use both velocities to correct the BC in FFS and it provides an excellent solution. You do need to be careful with the setup, make sure the target is square to the trajectory, if you are off angle you can get some bad results. You can check by using a known bullet and the downrange velocity should match closely to the estimate provided by FFS.

thanks for replay

 

[LastShot300]

It seems to work quite well. It matches the PVM-21 at 300, where I can easily shoot through both. I've done exactly what you want to do, use both velocities to correct the BC in FFS and it provides an excellent solution. You do need to be careful with the setup, make sure the target is square to the trajectory, if you are off angle you can get some bad results. You can check by using a known bullet and the downrange velocity should match closely to the estimate provided by FFS.

Cory can you share more about your setup to calculate BCs? Can it work up to what distance? In other words, would you consider the Shotmarker somewhat an alternative to the Oehler System 89?

 

[CoryT]

The current setup works like this. Labradar at the rifle, using the recoil trigger or the airgun microphone trigger for muzzle velocity. A 3' square Shotmarker target at 500 yards and an 8' square Shotmarker at 1000 yards. The 1K target can be place farther out if need be, you'd like to be at about 1.3-1.2 Mach range. The only thing this lacks that the System 89 should deliver is time of flight. It seems however that the three velocities provide a very good BC number as calculated in FFS or Coldbore. If you have elevation data and the range permits, you can line up the two Shotmarkers with the mid range unit elevated so the bullet passes through both at the same time. I was on the list for the 89, but at this time I can't see it being an improvement on what I'm using.

 

[ZiaHunter]

Attended the XLR class this past September and used Cory's system for calibrating a 338LM and a 375 SnipeTac. Used the 338LM in two previous classes and was pretty well dialed in but the 375 needed to be calibrated. Compared to how rifles were calibrated in previous classes this system is far superior. The rounds ran through the 375 prior to the class were for fire forming and load development only and at shorter distances. By using this system we had the rifle dialed in by the second day. I was so impressed by the system that I ordered the Shot Marker as soon as I got home. Going forward will calibrate all my rifles using this system.

 

[LastShot300]

The current setup works like this. Labradar at the rifle, using the recoil trigger or the airgun microphone trigger for muzzle velocity. A 3' square Shotmarker target at 500 yards and an 8' square Shotmarker at 1000 yards. The 1K target can be place farther out if need be, you'd like to be at about 1.3-1.2 Mach range. The only thing this lacks that the System 89 should deliver is time of flight. It seems however that the three velocities provide a very good BC number as calculated in FFS or Coldbore. If you have elevation data and the range permits, you can line up the two Shotmarkers with the mid range unit elevated so the bullet passes through both at the same time. I was on the list for the 89, but at this time I can't see it being an improvement on what I'm using.

Thank you Cory, very detailed review of the procedure, will have to get now a Shotmarker

 

[CoryT]

The trick to the Shotmarker is building the frame. It must be flat and square. I used square Al tube and Al T bar, drilled on the milling machine, leveled and squared with a laser. Don't skimp on the build and it will work well and last.

 

[LastShot300]

The trick to the Shotmarker is building the frame. It must be flat and square. I used square Al tube and Al T bar, drilled on the milling machine, leveled and squared with a laser. Don't skimp on the build and it will work well and last.

Good advice, thanks again!