ucrt
03-05-11, 00:20
.
I don’t know if this has any interest but I have seen some discussion on QD mounts ability to repeat POA and POI. I have been wanting to test the repeatability of my American Defense Base for my Aimpoint T-1 at 100-yards.
I did a similar test to this one, 8 or 9 months ago where I shot at one 50-yard Target. I shot 5-shots, remove this same RDS setup, tap it on the bench, remounted it, and repeated unmounting/tapping/remounting/5-shots until I shot 20-shots. That was 3 unmount/remounts for a 20-round 1.75" group. I thought that was good but I figured 100-yards would be a better test...
but...
I probably picked a crummy day to do this test but sometimes you just have to take what is available. Oh well…
My job is less than 2-miles from the gun range and our weather station indicated the wind to be 12-18 MPH average with 40-MPH gusts…Heck, I went anyway.
Background Info
- Aimpoint T-1 on ADM QD Mount w/ Hensoldt 2X Magnifier on a Burris XTR Mount.
. NOTE: The Hensoldt is a Cold War relic Tank Sight that LaRue has modified. It works very well, especially for the $60 I paid for it.
- Used a front tripod and rear sandbags on a heavy wooden bench.
- The Targets were placed at 100-yards
- The Target is one that I make with a 7” black bullseye. 7” is perfect for a T-1 at a 100-yards.
- I had 6 Targets set up and shot 10-shots at each Target.
- The 10-shots at each target were fired in less than 60-seconds
- PMC Bronze 55g Ammo
- RECCE 16” Chrome-Lined barrel with 1-7” twist.
- Barrel has not been cleaned in 2000+ rounds.
- Round count for this test were rounds #2062 to #2122.
- The barrel was cooled between each set of 10-shots. One good thing about the high winds...cooled the barrel pretty fast.
- The wind was 90 degrees left to right with 12-18 MPH average with 40-MPH gusts.
- I tried my best to shoot in between the gusts-fairly successful??
My Rifle and Sight Setup for the Test:
Aimpoint T-1 on an ADM QD Mount w/ a Hensoldt 2X Magnifier on a Burris XTR Mount
http://i52.tinypic.com/2iu29n9.jpg
.
Modifications
One note, I like the ADM Mount BUT sometimes when you adjust it, if you feel you need to go one more “flat” tighter, it feels like you’ll break the lever if you try and close it. So, I experimented with different O-Rings under the screw head to give a little springiness to the clamping.
The best O-Ring I found was a soft Buna 1/16” wide X 7/16” OD X 5/16” ID. I have had the O-Ring that I used during this test installed for about 6-7 months and probably have unmounted/remounted my RDS about 60+ times. This O-Ring idea works and holds up really well.
If you use an O-Ring, you have to be careful the flats of the screw are lined up with the flats of the hole or you can booger both of them up.
The O-Ring Setup:
http://i54.tinypic.com/2556syo.jpg
.
Real-Life
To induce a little real life into the test, while the T-1/ADM was removed, I knocked it around some. This was the procedure I followed:
After each set of 10-shots, I installed the T-1’s rubber “bra” lens caps, removed RDS, drop the RDS on the wooden benchtop from 7”, tapped the RDS on the benchtop on all six-sides, re-installed the RDS with finger pressure forcing RDS forward in slot, allowed the barrel to cool, fired 10-shots at the next target and the repeated the process.
Extreme spreads were:
Target 1 – 2.8”
Target 2 – 4.3”
Target 3 –4.3”
Target 4 – 4.4”
Target 5 – 4.4”
Target 6 – 2.9”
The Targets:
Target has a 7” black bullseye
http://i56.tinypic.com/2lbe635.jpg
.
Analyzing
Using drafting software I have at the Plant, I did, what I’m sure will be considered a weak imitation of “Molon”, try to analyze the groups. Not any sophisticated charts or computers or anything, just a stab at analyzing the info. I didn’t have time to figure the “mean radius” of each group but I did figure out the each target’s group center and plotted them out on a separate target.
Group Centers for all Six Targets:
Group Centers Extreme Spread was 1.7"
http://i55.tinypic.com/30iw51c.jpg
.
Summary:
What does all of this indicate…well, to me, the ADM seems to be pretty good at repeating the POA and POI. Overall, I would guess that all 60-shots had a 6" grouping. The "extreme spread" of the six Target's group centers was 1.7”.
Feel free to give me your thoughts, ideas, experiences, etc.
If I get a chance later this month, I’ll try and repeat the test with a clean barrel, better ammo, and hopefully, no wind.
Considering the negatives; wind, dirty barrel, cheap ammo, and probably my shooting, it seems like the ADM is very repeatable.
But maybe it's just me...
.
I don’t know if this has any interest but I have seen some discussion on QD mounts ability to repeat POA and POI. I have been wanting to test the repeatability of my American Defense Base for my Aimpoint T-1 at 100-yards.
I did a similar test to this one, 8 or 9 months ago where I shot at one 50-yard Target. I shot 5-shots, remove this same RDS setup, tap it on the bench, remounted it, and repeated unmounting/tapping/remounting/5-shots until I shot 20-shots. That was 3 unmount/remounts for a 20-round 1.75" group. I thought that was good but I figured 100-yards would be a better test...
but...
I probably picked a crummy day to do this test but sometimes you just have to take what is available. Oh well…
My job is less than 2-miles from the gun range and our weather station indicated the wind to be 12-18 MPH average with 40-MPH gusts…Heck, I went anyway.
Background Info
- Aimpoint T-1 on ADM QD Mount w/ Hensoldt 2X Magnifier on a Burris XTR Mount.
. NOTE: The Hensoldt is a Cold War relic Tank Sight that LaRue has modified. It works very well, especially for the $60 I paid for it.
- Used a front tripod and rear sandbags on a heavy wooden bench.
- The Targets were placed at 100-yards
- The Target is one that I make with a 7” black bullseye. 7” is perfect for a T-1 at a 100-yards.
- I had 6 Targets set up and shot 10-shots at each Target.
- The 10-shots at each target were fired in less than 60-seconds
- PMC Bronze 55g Ammo
- RECCE 16” Chrome-Lined barrel with 1-7” twist.
- Barrel has not been cleaned in 2000+ rounds.
- Round count for this test were rounds #2062 to #2122.
- The barrel was cooled between each set of 10-shots. One good thing about the high winds...cooled the barrel pretty fast.
- The wind was 90 degrees left to right with 12-18 MPH average with 40-MPH gusts.
- I tried my best to shoot in between the gusts-fairly successful??
My Rifle and Sight Setup for the Test:
Aimpoint T-1 on an ADM QD Mount w/ a Hensoldt 2X Magnifier on a Burris XTR Mount
http://i52.tinypic.com/2iu29n9.jpg
.
Modifications
One note, I like the ADM Mount BUT sometimes when you adjust it, if you feel you need to go one more “flat” tighter, it feels like you’ll break the lever if you try and close it. So, I experimented with different O-Rings under the screw head to give a little springiness to the clamping.
The best O-Ring I found was a soft Buna 1/16” wide X 7/16” OD X 5/16” ID. I have had the O-Ring that I used during this test installed for about 6-7 months and probably have unmounted/remounted my RDS about 60+ times. This O-Ring idea works and holds up really well.
If you use an O-Ring, you have to be careful the flats of the screw are lined up with the flats of the hole or you can booger both of them up.
The O-Ring Setup:
http://i54.tinypic.com/2556syo.jpg
.
Real-Life
To induce a little real life into the test, while the T-1/ADM was removed, I knocked it around some. This was the procedure I followed:
After each set of 10-shots, I installed the T-1’s rubber “bra” lens caps, removed RDS, drop the RDS on the wooden benchtop from 7”, tapped the RDS on the benchtop on all six-sides, re-installed the RDS with finger pressure forcing RDS forward in slot, allowed the barrel to cool, fired 10-shots at the next target and the repeated the process.
Extreme spreads were:
Target 1 – 2.8”
Target 2 – 4.3”
Target 3 –4.3”
Target 4 – 4.4”
Target 5 – 4.4”
Target 6 – 2.9”
The Targets:
Target has a 7” black bullseye
http://i56.tinypic.com/2lbe635.jpg
.
Analyzing
Using drafting software I have at the Plant, I did, what I’m sure will be considered a weak imitation of “Molon”, try to analyze the groups. Not any sophisticated charts or computers or anything, just a stab at analyzing the info. I didn’t have time to figure the “mean radius” of each group but I did figure out the each target’s group center and plotted them out on a separate target.
Group Centers for all Six Targets:
Group Centers Extreme Spread was 1.7"
http://i55.tinypic.com/30iw51c.jpg
.
Summary:
What does all of this indicate…well, to me, the ADM seems to be pretty good at repeating the POA and POI. Overall, I would guess that all 60-shots had a 6" grouping. The "extreme spread" of the six Target's group centers was 1.7”.
Feel free to give me your thoughts, ideas, experiences, etc.
If I get a chance later this month, I’ll try and repeat the test with a clean barrel, better ammo, and hopefully, no wind.
Considering the negatives; wind, dirty barrel, cheap ammo, and probably my shooting, it seems like the ADM is very repeatable.
But maybe it's just me...
.