Insert conversion barrels and mag-fed guns.

[Uniquedot]

I believe accuracy could be improved by machining a couple of grooves in the insert to hold rubber O-Rings that would be a press fit in the chamber. That would take up all the manufacturing tolerance mis-match, and prevent the shakes & wobbles in the chamber.

Even a wrap or two of vinyl electrical tape might make them fit well enough to not rattle.

I have owned and used the long inserts with attached o rings and auto extractors and they are better, but they require grease on the o rings everytime they are removed from the chamber and in his situation he would have to remove the insert every shot.

True - but take a relook at that video and that is what you see - it IS off center.

If the video is showing a rimfire insert it will have to be bored off center in order for the centerfire firing pin to light off the rounds on a rimfire case.

 

[oneounceload]

That would depend on the size of the firing pin - one large enough might not need to be

 

[Zoogster]

One problem with accuracy is it being moved each time by the extractor/ejector. O-rings or anything really, even some paper sandwhich between it and the bore would keep it from moving if it was designed so it would not be extracted.

A pump gun one could have a smooth groove lengthwise on the adapter that you lined up with the extractor where the extractor could slip back and forth with little reistance or disturbance of the adapter. Then you could try to feed one round at a time through the ejection port with the action open.



Another advantage beyond adding versatility to your shotgun is these things firing .22lr almost work as an unrestricted suppressor. The 18"+ barrel provides such a large area for the .22 gas to expand into that by the time it reaches the surrounding atmosphere as a pressure wave to make sound it has dropped signficantly in pressure.
With what remains of the gas directed forward.
It sounds like a loud airgun.
Something you cannot capture on video that well.

 

[Uniquedot]

Another advantage beyond adding versatility to your shotgun is these things firing .22lr almost work as an unrestricted suppressor. The 18"+ barrel provides such a large area for the .22 gas to expand into that by the time it reaches the surrounding atmosphere as a pressure wave to make sound it has dropped signficantly in pressure.
With what remains of the gas directed forward.
It sounds like a loud airgun.

This is true and not just with shotguns and rimfire adapters. I put a semi permanent .32 acp adapter in an old .308 enfield and even that arrangement was no louder than an high power spring piston air rifle.

That would depend on the size of the firing pin - one large enough might not need to be

It would have to be a firing pin so large that the gun would be useless as a centerfire weapon. If the portion of the rim that holds the priming compound isn't struck solidly the priming compound will break up with out igniting rendering a useless round. Those guns that have interchangeable centerfire/rimfire barrels are also bored off center in the rimfire calibers.

 

[jmorris]

Even if centered, bullets rise then fall over the the shooting distance. Take a bullet exiting the converter, it still has to go over 20" before it is free of the barrel - it is possible it is slightly striking the barrel causing the keyhole

Are you saying the converter is machined so the "bore" is not parallel with the outside? The reason bullets rise then fall is because you aim the barrel up. Sight in for long range you are aiming further up so the bullet rises more. If the bore is level and a bullet pops out it is going nowhere but down at a rate close to 32 feet per second per second.

Solid line is the bore, the dotted one is the bullet.




A link on the subject.
http://hyperphysics.phy-astr.gsu.edu/hbase/grav.html

 

[DM~]

The only rimfire inserts that i've seen that are of good enough quality to depend on are the Krieghoff inserts,



And although they are expensive, they do NOT cost a couple thousand dollars to buy one. All of mine ARE accurate and they do go back to the sights of the gun they are in EVERY time i put them in.

I have numerous cheapo adapters of different mfg. that i've bought over the years too. Some i've moded to make them better and some are better than others.

They do go bang, but that's about all they do too well! You just can't get something for nothing!

BTW, i've never seen any of mine hit the shot bbl. before leaving the bbl.!!

DM