Inaccuracy of a Rail Mounted Laser

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kcofohio

kcofohio

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I have an M&P40 (full size) and a Viridian C5 (green laser) that I have tried mate off and on for a few years.

The first couple of tries may have been mounting issues.

This time I know I have it mounted solid on the frame rail.

At 10 yds., I can get a hit near bullseye, then I'm on the edge of the paper. Comparing with the sight, the laser may be as much as 5-6" off around the 10-11 o'clock position.

Could it be the slide isn't repeating back to home position by that much? I don't think the gun has that much rattle to it.

It this a common problem with mounting a laser on semi-auto pistol rails?

Thanks!
 
So you cannot get the laser to zero? Or it won't hold zero?

I don't have a whole lot of experience with lasers, but I've always just zero'd them to match my point of aim with the iron sights at whatever distance I want them on.
 
I think you've discovered the dirty little secret of frame mounted lasers (grips & rail mount) as the slide to frame fit tends to be a bit generous for reliability reasons. The barrel to slide fit is largely what determines accuracy in tilting barrel auto loaders. Its kind of like the way fixed barrel blowback autos can be very impressive in a Ransom Rest and not so great when aimed as the sights are on the slide and the barrel fixed to the frame making slide to frame fit the dominate factor for accuracy, which again tends to be generous for reliability reasons.

I've Crimson Trace Laser Grips on my SC360 J-frame, when I sighted it in off sandbags on the second shot I though I'd totally wasted my money thinking the damn thing couldn't stay on the paper after only one shot (the SC360 firing 158gr JHP is pretty brutal recoil wise) then I realized the hole in the target was "oblong" making essentially a one-hole two shot group.

You can check by clamping the frame and shining the laser at a distant target and "wiggling" the slide. My BG380 with factory laser (frame mounted) will move the laser ~2-3" across the room (~15'), which is acceptable as an alternative to the very short radius sights for its intended purpose.

Edit: Brain Fart, you need to clamp the slide and wiggle the frame, but I think the gist of the test came through :)
 
Last edited:
gotboostvr said:
So you cannot get the laser to zero? Or it won't hold zero?

I don't have a whole lot of experience with lasers, but I've always just zero'd them to match my point of aim with the iron sights at whatever distance I want them on.
Click to expand...

Won't hold zero. I should have clarified that. :)
 
wally said:
I think you've discovered the dirty little secret of frame mounted lasers (grips & rail mount) as the slide to frame fit tends to be a bit generous for reliability reasons. The barrel to slide fit is largely what determines accuracy in tilting barrel auto loaders. Its kind of like the way fixed barrel blowback autos can be very impressive in a Ransom Rest and not so great when aimed as the sights are on the slide and the barrel fixed to the frame making slide to frame fit the dominate factor for accuracy, which again tends to be generous for reliability reasons.

I've Crimson Trace Laser Grips on my SC360 J-frame, when I sighted it in off sandbags on the second shot I though I'd totally wasted my money thinking the damn thing couldn't stay on the paper after only one shot (the SC360 firing 158gr JHP is pretty brutal recoil wise) then I realized the hole in the target was "oblong" making essentially a one-hole two shot group.

You can check by clamping the frame and shining the laser at a distant target and "wiggling" the slide. My BG380 with factory laser (frame mounted) will move the laser ~2-3" across the room (~15'), which is acceptable as an alternative to the very short radius sights for its intended purpose.
Click to expand...

Thanks wally! Thought that may be the case. Will test it out.
I don't take it out to shoot much. But with sights, I can have decent accuracy. I have given thought of possibly selling the gun for the right offer. But I wouldn't feel right about selling laser with it, if it's not accurate.

If it is as you say, I may try the laser on 2 other guns that have rails on the frame.

Again, thanks!
 
I use the Crimson trace Green on a Colt 1911 .38 Super. The Crimson grip laser Green is fully adjustable and very dependable. I have encountered problems with the different rails and laser mounts.
The lasers and mounts are made in two different types and not interchangeable. One is the Weaver and the other is the Picatinny rail. I unknowing mounted a Picatinny laser mount on an AR 15 Weaver rail. The laser would not zero and exhibited an improper alignment. None of the mounts were so noted.

This is based on my personal experiences only. :) It maybe incorrect.:oops:
 
Dog Soldier said:
I use the Crimson trace Green on a Colt 1911 .38 Super. The Crimson grip laser Green is fully adjustable and very dependable. I have encountered problems with the different rails and laser mounts.
The lasers and mounts are made in two different types and not interchangeable. One is the Weaver and the other is the Picatinny rail. I unknowing mounted a Picatinny laser mount on an AR 15 Weaver rail. The laser would not zero and exhibited an improper alignment. None of the mounts were so noted.

This is based on my personal experiences only. :) It maybe incorrect.:oops:
Click to expand...

The C5 laser came with, I believe, 3 different clamps that you match the clamp to the gun, per their chart.
 
I did not intend or state the mismatched laser and rail brand. The laser was not a Crimson Trace.
Sorry for not explaining the post more accurately.:)
 
Dog Soldier said:
I did not intend or state the mismatched laser and rail brand. The laser was not a Crimson Trace.
Sorry for not explaining the post more accurately.:)
Click to expand...

I didn't take what you said in any bad way. But it reminded me of the procedure of mounting the Viridian and clarity. :)
 
That is OK. I am rather new to the current generation of lasers. The first ones were lacking. I bought the Crimson Laser Red and Green during their promotions. They sold for $368 dollars for the 2 sets.
The Green Crimson Trace is far better than the Red. That is my experience of late. :)
 
Dog Soldier said:
That is OK. I am rather new to the current generation of lasers. The first ones were lacking. I bought the Crimson Laser Red and Green during their promotions. They sold for $368 dollars for the 2 sets.
The Green Crimson Trace is far better than the Red. That is my experience of late. :)
Click to expand...

I agree. My wife's SR22 came with the red. Last year I put the green laser on it. Man, what a difference.
 
pintler said:
"Won't hold zero."

I'd look into a warranty repair.
Click to expand...

I think the warranty has expired. Though I have thought of contacting them to see what they would do for it.

But 1st, I may try it on one of our ARs. If it won't hold there, then I will call or email them.
 
Yes, I was surprised at the Crimson Green. It also draws more energy from the batteries. Crimson Trace will provide free of charge a new set of batteries each year for the Green laser.
 
I never had problems with a laser holding zero on a pistol and that was for thousands of rounds. Sounds like a lemon. Back when I had a laser on my EDC my morning routine was check its loaded, check the laser aligned with the sights.
 
I have the same model with the light (C5L) on my carry pistol. It has been there for years, taken on and off several times for cleaning, and it has never lost zero. Viridian has a 7 year warranty from date of purchase and they have very good turn around times. I sent my C5L in because one of the activation switches was sticking and annoying, but still functional. I had it back in less than 2 weeks.
 
OP, as others have indicated, something must be wrong. For reference, here's 14+1 through my P-01 with a Crimson Trace CMR-203 at 11 yards. POI remains the same every time I take it out. The reason that all of the shots aren't in the dots is my not-so-great shooting, not the gun or the laser. :)

I'm a big fan of the CT green lasers. I have the CMR-203 and the new CMR-206 that has replaced the 203. The 206 is a good bit more compact, the beam source is directly under the barrel instead of lower and to the right, and supposedly draws less current due to the diode vs the so-called DPSS. Not to start a re-hash, but I find a laser (green is the only one I've ever used on a gun) far superior to night sights in low light conditions such as inside my home at night.

P%2001%20Target_zpsp7fegw2u.jpg
 
Last edited:
herrwalther said:
I have the same model with the light (C5L) on my carry pistol. It has been there for years, taken on and off several times for cleaning, and it has never lost zero. Viridian has a 7 year warranty from date of purchase and they have very good turn around times. I sent my C5L in because one of the activation switches was sticking and annoying, but still functional. I had it back in less than 2 weeks.
Click to expand...

I will try the laser on another gun. If that doesn't work, I will contact Viridian.

I had assumed, or thought I read, that they carried a 3 yr. warranty.

Thanks for all the input guys! Hoping I can give an update by next weekend.
 
As for battery consumption green lasers operate a bit differently, using a more powerful emitter then filtering the light to only show the green wavelength. They are known to be much less efficient and power hungry in comparison to red lasers. The benefit is that green hits the human eyes "sweet spot" for reception on the cones and rods making it appear much more visible.

If or when they come up with an actual "green" laser instead of simply using the closest thing and stripping out the other colors it will improve.

I have a S&W TSW model with riveted rail, and yes, it's Weaver not Picatinny. The '80's/'90s commonly did that, one hint on the older guns is that there is only one cross slot commonly machined on it, where Picatinny usually has more.
 
Watch a slow-mo vid of a Glock.

Note the nose of the frame flexing and jiggling like a chinese AK47. I suspect your pistol does the same. You might want to try a railed 1911.
 
Another point to think about is how far above or below the gun's bore-axis the LASER is mounted. I have a Streamlight, TLR-2 light/LASER combo which holds zero pretty well (on a Glock!)

But, because it's mounted on an accessory rail which is lower than the bore axis, the LASER dot and bullet points of impact can only be aligned to match at one distance. (I have mine set for the red dot/bullet point of impact to align at about 25'. If the target is closer than 25' I basically can't see the dot.

I may adjust it for a closer match in the future -- knowing that it will be off (causing a lower point of bullet impact than the dot's position at greater distances.)
 
wally said:
I think you've discovered the dirty little secret of frame mounted lasers (grips & rail mount) as the slide to frame fit tends to be a bit generous for reliability reasons. The barrel to slide fit is largely what determines accuracy in tilting barrel auto loaders. Its kind of like the way fixed barrel blowback autos can be very impressive in a Ransom Rest and not so great when aimed as the sights are on the slide and the barrel fixed to the frame making slide to frame fit the dominate factor for accuracy, which again tends to be generous for reliability reasons.

I've Crimson Trace Laser Grips on my SC360 J-frame, when I sighted it in off sandbags on the second shot I though I'd totally wasted my money thinking the damn thing couldn't stay on the paper after only one shot (the SC360 firing 158gr JHP is pretty brutal recoil wise) then I realized the hole in the target was "oblong" making essentially a one-hole two shot group.

You can check by clamping the frame and shining the laser at a distant target and "wiggling" the slide. My BG380 with factory laser (frame mounted) will move the laser ~2-3" across the room (~15'), which is acceptable as an alternative to the very short radius sights for its intended purpose.

Edit: Brain Fart, you need to clamp the slide and wiggle the frame, but I think the gist of the test came through :)
Click to expand...


If the laser is mounted to the frame - how does moving the slide affect the light?
 
Merle1 said:
If the laser is mounted to the frame - how does moving the slide affect the light?
Click to expand...

Most experts suggest that barrel to slide fit (with consistent, precise lockup) is critical with aimed fire -- when the sights are on the slide. Then, barrel/slide fit (and consistent lockup) is far more important than slide to frame fit.

If the sighting system is attached to the frame, barrel/slide fit is still critical, but slide to frame becomes more important. And, if the slide has some slop -- for reliability, perhaps -- or if the frame can flex or move (as might be the case with some polymer-framed designs), the alignment of the sighting system and barrel can be inconsistent from shot to shot .( I suspect that's why we see some polymer guns with their sighting systems mounted on the slide rather than the frame.)
 
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