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Old May 3, 2018, 06:09 AM   #1
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12 Ga to 45 ACP converter

Recently I bought two 8 inch rifled 45 ACP converters for my stoeger double defense. These really do seem like a good design because they have adjustable o rings at the muzzle to keep it centered in the shotgun barrel.

Anyway, I've mounted glass and made very consistent reloads for it and I just cannot get the accuracy that others have gotten. From 25 yards its grouping about 4 to 5 inches firing just the right barrel. Accurcy doesn't really change if I fire both barrels. I've messed with the o rings, taken the scope off, and changed the handloads but its still just all over the place.

Anyone here have experience on these things?
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Old May 3, 2018, 03:42 PM   #2
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I didn't know that such a thing was made, although shotgun conversion tubes, say 12 to .410 have been around, one such called "the four-tenner".

Honestly, I cannot see how any rifled tube, that seats by rubber or synthetic O-ring, that can flex, will ever be stable or consistent enough, even from one barrel alone, to provide any type of usable accuracy. My only thought would be to reduce the .45 acp load way down, with light bullet and light charge, and hope the give and take of the seating system is reduced enough with minimal recoil, to allow some type of consistency.
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Old May 5, 2018, 05:12 PM   #3
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youre tying to get bullet accuracy in a shotgun barrel. that's the problem.
nothings consistent with a rubber o ring AND youre bbls are regulated to x for shot or slug.
this is the trap of do all guns. sure...they can do all.....but do none of them well.
snake oil is snake oil.
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Old May 7, 2018, 03:50 PM   #4
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I think your results are better than what I would have predicted.

They are an interesting product...or maybe amusing is a better term / accurate - no !! ( I don't own one of the kits ...but some of the guys at my local range had one they were fooling around with didn't work .../ they couldn't predictably hit a 12" square target at 12 - 15 yds...
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Old May 7, 2018, 04:14 PM   #5
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For any still interested.....

I did further testing with the converters. One in the Side by side. And another in a single shot with rifle sights. I bought factory S&B 230 gr as well as made some more handloads with a light charge of a different powder (power pistol).

All shots were taken from a braced sitting position at 25 yards in 5 shot strings.
- side by side with optic
- factory loads; 4 inches
- hand loads; 3.5 inches
- single shot with rifle sights
- factory loads; 3.5 inches
- hand loads; 3.0 inches

I didn't go into this thinking that I would get quarter MOA groups at 1000 yards (feel that sarcasm). However the goal of this project was to be able to give some purpose to a rather forgotten shotgun in my collection. The accuracy just needed to be good enough to hit soda cans from 25 to 50 yards (this is our most common type of shooting amongst my group). All of my research prior led me to believe this was attainable. But at this rate I'm just
Going to be frustrated with the inconsistancy and be missing my pop cans.

All in all, it is ABSOLUTLEY a ton of fun to load and fire a double barreled 45 ACP. I won't take that away from this. But for my purposes, this just ain't gonna cut the mustard.
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Old May 7, 2018, 11:58 PM   #6
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I was thinking about the problem ( not always a good thing with me ), when I realized the 45 slug doesn't touch the barrel so that's not the problem, but after 8 inches the gas from the cartridge stops pushing the bullet and joins it, the bullet spends the rest of the trip being buffed by the escaping propellant gas , both the bullet and the gas trying to shove each other out of the way so both can exit the barrel at the same time . Do you think that might have something to do with accuracy?? I really don't know but I would think so.
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Old May 8, 2018, 09:21 AM   #7
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Not necessarily. "Bloop tubes" are very popular with some competitive shooters and it doesn't seem to be an issue with those.

If I were to make a WAG, I'd say there just probably isn't enough consistency despite the o rings.

Have you contacted the manufacturer?
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Old May 8, 2018, 12:00 PM   #8
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I've used rifle adapters in an over/under Mossberg I have and I only used the iron sights. At 25 yards with .32 H&R Mag reloads I made, I was able to get I think 1-2 inch groups.

I think you should try different ammo, try rotating the adapter, sometimes there's a certain position it shoots best from and try shooting from whichever barrel shoots best. The one for each barrel concept isn't going to work, the regulation does affect where the bullets go IMO as for my Over/Under, if I switch the adapter from one to the other, the POI will be higher in the lower barrel and lower in the upper barrel.

Really, I think the best shotguns for rifled adapters is single barrels, but when Midland and Thompson Center are making single shot platforms that can have entire barrels replaced, the shotgun adapter concept is quickly becoming a poor choice. The only benefit would be is you can have a pouch with a bunch of the 3 inch adapters and have a lot of choices for ammo in the apocalypse and not have it weigh a lot.
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Old May 8, 2018, 12:21 PM   #9
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Adapters to convert shotguns to other shotguns seem to work well. Such as a 12 gauge to 20 ga or .410 adapter. Don't have to worry so much about accuracy.

I've seen plenty of adapters from Europe that use set screws and such to index them properly in the chamber, and I believe they're probably fit to a specific gun/barrel. I'd expect better accuracy from those.

My solution was to simply buy a German Drilling (triple barrel), so I can fire shot or rifle bullets without loss of accuracy or fiddling with inserts.
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Old May 12, 2018, 05:59 AM   #10
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Shotgun chamber adapters for rifle and pistol cartridges are not intended for precise shooting. They are for survival purposes, a way to have one gun in hard times and have some choices when ammo may be hard to find. The groups that you are getting are good enough for taking a rabbit at 25 yards. Closer is better.
Also better accuracy can be obtained by using longer chamber adapters. My son has an 18 inch 45-70 adapter for a 12 gauge. He has used it to take wild pigs. He is a good shot, no wounding.
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