doublegunshop.com - home Forums Thread Like Summary - Laser Cartridges

This stems from the mention of these devices in a previous post regarding the potential purchase of a Darne. The potential buyer mentions checking to see if the barrels are regulated through the use of the laser pointing cartridges. Somehow I always imagined a regulation problem would stem from something wrong at the muzzle end like chokes, etc. Does a regulation problem in a shotgun originate at the breach / chamber area? I have never used these laser pointer cartridges nor have I ever owned a shotgun that did not shoot to the same point of aim on a patterning board, so my question is an honest one. All answers appreciated.

Having regulated every shotgun I use, if I ever find one that does that it's gone as fast as I can move it. Over-convergence or under-convergence (which is a lateral issue with side by sides) can be dealt with by load testing. My last instance of proving this has been noted here in other threads but will be repeated here for emphasis. My 20 ga. Fox Sterlingworth ejector cross-fired very badly when I first patterned it, with 7/8 oz. loads at "something over 1200 fps", can't remember the exact stated velocity. Center of the patterns were 8" too far right, for the left barrel, and 8" too far left, for the right barrel. I had no idea changing loads could move it that much, and sent it to Dean Harris at Skeet's GS in OK, requesting he work his magic by honing the bore, just before the choke, to move the patterns for me. He called me and said the gun was now regulated perfectly. I happily asked how hard it had been for him to achieve this, and he said it was very easy. He just fed it some 1 oz. loads at 1150 fps and the patterns were dead atop each other. Eight inches movement at 25 yards is considerable, and this was a learning moment for me.

Happily, most guns I've patterned that have not been regulated had lateral issues, and were dealt with accordingly. Dean Harris is a genius when it comes to shotgun barrels and patterns, IMO.

the rifle laser cartridges that I used pointed to different points depending on the orientation when inserted into the chamber. In other words the laser wasn't leaving the cartridge from the exact center or was not parallel to the bore.

Can you explain how chamber convergency matters? Those laser cartridges will tell you where your chambers are pointing, not the barrels or patterns. If you think that does not matter why do we use eccentric chokes to correct a point of impact problem. They do not change chamber convergence. The only way to check for barrel convergence is to use a pattern plate, shooting the gun repeatedly to get as complete a picture as possible.

Dean Harris is a genius when it comes to shotgun barrel and patterns, IMO.[/quote]
I'll second that endorsement! Dean saved an abused 1894 FE barrel for me, the FE is now the PERFECT doubles shooter.
Lasers are nice to have in your tool box....if you have a cat.

None of the above will predict where patterns will land when the gun is actually shot. The reason is that recoil is not factored into the deal. Recoil is what causes side by side guns to need barrel convergence. And, different loads will cause the patterns to "over-converge" or "under converge". When the right load is found many guns will converge properly, printing right and left patterns dead on top of each other. Then, the gun is regulated, with that load. Regulation of side by side barrels is a complicated affair and subtle changes in loads can affect that regulation boldly.