Shotgun Boresights

I have four of the Sightmark laser boresights - the 12 gauge, 9mm, 7.62x39mm, and .223.I had used a Bushnell laser boresight before getting this set of chamber loaded laser boresights. The Bushnell is the kind that you stick into the muzzle end of the gun, fitted with an arbor matched to the barrel size. The problem with this device was that the arbors never fit quite right - they were always either too tight or too loose, plus you had to try to seat the body of the boresight in the center of the opening of the barrel (or muzzle brake) in order to properly align the center axis of the boresight with the center axis of the barrel. This rarely if ever happened just right as the slightest tilt in the seating of this boresight in the barrel would take it off the center axis so that rotating the laser would cause the laser light to mark out a small circle that was several MOA in diameter rather than being dead centered. Ugh.Of course with these chamber loaded laser boresights, there is also the potential for the lasers to be mis-aligned off the center axis. Plus there is the potential for the boresight to not fit the chamber properly. The key is to find a brand that has a measure of quality control so that you aren't stuck with these problems.I read through a lot of reviews before deciding on Sightmark. It is definitely not the cheapest out there. There are so many different brands and generic versions of these chamber loaded laser boresights now that almost look alike, with many much cheaper than the Sightmark. However, it was clear from reading the reviews that as the prices went down, so did the quality control. Several of these cheaper brands came with complaints that the lasers were not aligned to the center axis (resulting in the laser painting a circle as it rotates in the chamber) or that they did not fit properly in the chambers and so would either get stuck or wiggle.I have this theory that the really cheap laser boresights must be factory seconds or some such.I considered the Osprey line with the adjustable arbors, which saves money by allowing you to use one laser bore sight for different calibers. But, the reviews indicated that hassling with arbors would have an effect on accuracy and reliability.I almost got the Firefield, which seemed to have a similar number of decent reviews. Ultimately I decided against it because the entire line is made of an aluminum shell, and I think the brass shell of the Sightmark will hold up better.It should be noted, however, that the 12 gauge Sitemark is made out of aluminum, unlike the others, and is only painted a brass color.The biggest complaint against all of these laser boresighters are the frequent DOA batteries and poor battery life. The Sightmarks all come with alkaline button cell batteries. The small caliber ones (9mm, 7.62mm, .223) come with two AG5 batteries while the 12 gauge came with three AG13 (LR44) batteries.To get you all confused, the printed information on the back of the packaging for the 7.62mm and .223 says you can use 3 AG3 batteries in place of the 2 AG5 batteries (since the AG3 is a thinner battery with the same 7.9mm diameter), while the printed info for the 12 gauge says you can use 2 AG5 or 3 AG13 batteries. This is flat out incorrect since 2 AG5 batteries are too small to fit into the 12 gauge Sightmark battery chamber.Confused? Go to wikipedia and look up the article "List of battery sizes". Scroll down to the section titled "Silver oxide and alkaline cells". The table lists all the different names for each battery, their dimensions, and their mAh power rating. Note how the silver oxide batteries contain 1-1/2 to two times as much energy as the alkaline batteries.So the key is to go out and get some silver oxide button batteries, size SG5 for the AG5 powered Sightmarks and SG13 for the AG13 powered lasers. And don't go to your nearest retail store, since that will cost you an arm and a leg. Google shop for these batteries online. I found two Made in China "brands" one called Vinnic and another by Chung Pak Battery Works which were pretty cheap. The names aren't important, since I'm sure they will change rapidly. Just remember to get some silver oxide batteries online at the same time you are getting these Sightmark bore sights.How well did these Sightmarks work? The very first time I used one (the 7.62x39mm), I plugged in the included AG5 alkaline batteries and the resulting laser light was exceedingly weak. My initial reaction was that this was a bad laser. Then I remembered the silver oxide batteries I had gotten. When I switched out the batteries, the laser suddenly glowed brightly. Later, when this set of silver batteries finally wore down, the laser light faded again. That's a sign to change batteries.The larger AG13 alkaline batteries for the 12gauge shotgun boresight worked reasonably well and are still working as of this writing. Not surprising, since these batteries pack a lot more energy than the small AG5 batteries.As many have noted, the Sightmarks do not have an on-off switch. Once the batteries are screwed in the laser light is on! This is just as well, since the bore sights have to flush fit inside the chamber of the barrel and endure having the bolt and firing pin slammed into them. But you do have to have a plan of action ready so as to not run down your batteries. With one pair of SG5 silver oxide batteries, I was able to adjust the sights for about four guns, each taking about 5-10 minutes. So I am guesstimating a battery life of about 30 minutes with a fresh pair of SG5 silver batteries (the Sightmark packaging claims up to an hour of battery life - hah!).All of the Sightmarks have fit in well, none have gotten stuck (so far), and none have had off-center lasers.These chamber loaded Sightmark boresighters make it easy to dial in a scope, and for fixed sights, they help confirm the aim points. They are much better than the muzzle loaded bore sights, although the total cost is a lot more since they are ammo caliber specific.

I own several different laser bore sights by Sightmark, in a number of different calibers. I also have one of their universal laser bore sights. I've found all of their products to work quite well so far.I've found these in the chamber type of laser bore sights to work much better than the universal types which hang out from the muzzle. The machining on these in the chamber types by Sightmark is quite good. With the firearm firmly mounted in a heavy bench rest, I've rotated the sight to several positions in the chamber and seen very little change in the point of the dot even at 100 yards, which indicated to me not only a very good machining, but also a very good adjustment of the laser within the brass body.One thing to bear in mind with these sights are that while they do feature a rim like a standard cartridge, the sight is not meant to be removed from the chamber by means of the extractor and bolt. While you will get best results by gently letting the bolt close and push the sight snugly into the chamber, the sight will not simply fall out upon opening the bolt and again, it is not meant to be extracted like a standard cartridge. to remove it is best to open the bolt and keep it open while using a cleaning rod from the muzzle end to gently push the sight out from the chamber.While very well made and adjusted, these devices still have very slight variations from true center, which becomes more noticeable with distance as does the increase in the size of the dot. Yes, it is a laser but it is a laser diode, not a high end gas or sapphire rod laser, so the coherence of the beam is not 100% and the diameter will increase with distance. That isn't a negative though as it helps you to see the dot at distance with the naked eye. Try seeing the period of a sentence on a newspaper page 25 yards away with the naked eye and you'll get what I mean. Even with the increasing dot size at distance and a good spotting scope though it is best to use the laser bore sight in less than full daylight light levels.These laser bore sights are truly ideal for a shotgun though, as they give outstanding results at distances under 50 yards. With a 12 gauge shotgun you really aren't likely to be trying to hit dead center of a bullseye as you would with a rifle or pistol, let alone would you be doing so for a distance of 100 yards. If you are using this to set ghost ring sights, reflex/holographic or laser sights for use on a defensive shotgun however, the distance required is considerably less and the results of using this bore sight will be as close to perfect as you should want.Due to its size this laser bore sight probably could have used a single CR123 battery rather than three small AG13/357A, or LR 44 batteries that it requires, but it's not likely to be used often enough for that to be an issue. It also would be nice to have an on/off switch rather than having to remove the batteries, but again due to infrequent use it is not really much of an issue. It could have used a green laser which would have greater visibility at long distance or in full daylight, but for a shotgun the distance isn't an issue and a green laser would have driven the cost up to more than double what it is.

I got it primarily to help train me in shooting from the hip at close range in the house.I already discovered now after just an hour that my unguided tendency is to aim a little high. So now I will compensate. To keep from "cheating", I throw several layers of fabric over the muzzle and then try to aim. I keep the gun still and pull off the fabric. Voila! I see what I was really pointing at.If you use for long range, I would check the centering of the beam. If its at an angle of eben a fraction of a degree, it will not be on target at 50 yards. If you put a fabric over the muzzle you can see if the beam is centered. I found that there was some variation, depending on how I chambered it. So try it several times. Maybe my remington is overboard and the thing has some wiggle room. I don't know. But the fabric trick works since you don't want to look directly into the beam.

I have Sightmark and other similar lasers for 10 or more calibers and cringe when I see where some butt head gives it a 1 star because its not a 1 shot dead on for their scope. You need to sell or give your gun away, your gonna hurt somebody someday.1) Laser bore sights are to save you time and ammo and get you on the paper.2) You scope has range and windage marks below/beside the cross hairs that will need to be tuned in by a COMPETENT shooter.3) Laser light is perfectly straight line without bullet drop. Are you sighting in at 20 or 500 yards... Big difference. If this is too much for you, go back to playing golf.So before you whine that it's not dead on after the first shot go back to Steps 1-3 above and pay close attention to "Competent Shooter and Playing Golf".