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Chaszel Chamber Half 18" Long

357 12 Gauge Shotgun Adapters

(12 customer reviews)


357 Magnum Shotgun Adapters for 12 Gauge Shotguns

Adapters come in 4 Lengths

2 3/4″ 5″, 11″ and 18″

All Adapters are Fully Rifled with a 1-12 or 1-18″ Twist.

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Select Length below: 


357 Shotgun Adapters for 12 Gauge Shotguns

357 Shotgun Adapters Allow a 12 Gauge Break Action Shotgun to use 357 Magnum in addition to 38 Special Ammo.

For 3″ as well as 2.75″ Chambers

Compatible with Break Action single as well as double barrel shotgun.


Rifled:  with a 1:16 twist rate for the 18″

with a 1:12 twist rate for all other lengths


357 Shotgun Adapters Rifled dimensions are .355″/.349″ with 6 lands and .125″ wide.


Black Oxide coating as a result provides notably better corrosion protection (for maximum corrosion protection keep a thin coat of oil on the insert)


Carbon Fiber (The Carbon Fiber is used for a cover in addition to added stiffness.  It is not a factor in the strength of the all steel construction).

Please Note:  Not all shotguns are the same!  While the majority of them are capable of handling high pressure rounds, some are NOT.  Only use these rounds in shotguns that are compatible.  I recommend on any shotgun to test the first shot in a vice while out of harms way and to always wear eye and ear protection.  If after testing you see the primer punctured in the round discontinue using this round and use a less powerful round. These high pressure rounds include: 45-70 gov., 357 Mag Shotgun Adapters, 327 Federal, 44 Mag, and 22 Hornet.  Please always be safe and aware.
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What are Shotgun Adapters?

Shotgun Adapters frequently called Chamber Reducers or Shotgun Barrel Inserts. Our shotgun adapters allow you to use other types of ammunition in a Break Action Shotgun. Including double barrel and over and under double barrels in addition to the popular single barrel break action. We offer several different versions to suit your preference in ammunition, as well as length. 12 and 20 Gauge shotgun adapters are our most popular adapters followed closely by the 410. 16 Gauge is something we plan on expanding in the future.


357 Shotgun Adapters are a High Pressure round

However, not all shotguns are capable of handling all of the shotgun adapters we offer. Low-pressure rounds work in any shotgun, whereas high-pressure rounds can cause problems in some shotguns. The problem is when the firing pin punctures the primer. This event causes the gases to escape and possibly damage the firing pin. All adapters chambered for high-pressure rounds have red text on the website, signifying that is is a high-pressure round. These adapters also include a pamphlet with more information about this concept. In addition These Shotgun Adapters also have a Low-Preasure round alternative.


357 Shotgun Adapters

Most of our shotgun adapters come in different lengths to suit your needs. Some like the secure storage and portably of Shell length adapters. Whereas some are looking to get the most fps (feet per second) or accuracy out of their adapter. Black Oxide has become our standard finish. We can offer unfinished adapters during our production if you have requested one.

FPS (Feet Per Second)

As a general rule, the longer the adapter, the more FPS it produces. However, with low-pressure rounds such as the 45 colt, the fps difference is minimal once past the 11″ length. If you are interested, here is an excellent website that gives a good idea of fps per inch BBTI. All of our shotgun adapters are entirely made in the United States and are an affordable addition to your break action shotgun. Thank you for you interest in our Shotgun Adapters or Chamber Reducers. We are working to make more adapters for more calibers, so you can sign up to be notified here
The video below gives a brief demonstration of how they work.

We are working to make more adapters for more calibers, so you can sign up to be notified here. Thank you for your interest.

If you like 357 Shotgun Adapters, check out our other Shotgun Adapters

Additional information

Dimensions24 × 3 × 3 in

18" With Carbon Fiber, 11", 5", 2 3/4"


Black Oxide, No Finish (Silver)

12 reviews for 357 12 Gauge Shotgun Adapters

  1. Peter W. (verified owner)

  2. Eugene (verified owner)

    Seems to fit well in a TRADITION 12 Ga. folder. Not had a chance to shoot yet.

  3. David Rickard (verified owner)

    Now I have a 12ga AND a .357mag/.38 spl in one device! Happy, happy, happy!

  4. Jesse d. (verified owner)

    Why not add variety to your single shotgun

  5. Jose Ramirez (verified owner)

    Well made love it.

  6. Brian Blanchette sr (verified owner)

    Good value for what it is.

  7. matthew green (verified owner)

    great adapter just wish they made them in 28 inch length.

  8. Doug M. (verified owner)

    You did great, product is awesome. Great company to work with.

  9. Robert Harwood (verified owner)

    Awesome quality and accuracy. Great machining and finishing

  10. Jeffery F. (verified owner)

    Perfect edition to my scavenger single shot set-up.

  11. John (verified owner)

    Great, worked just fine in 1910 era spanish shotgun, BUT I will use ONLY .38 SP and NON +P to avoid any overpressure. SHOT VERY accurate both wad cutter and copper coated ball …Great job… I really wanted the 18 inch version but you were out. However the 5 inch accuracy is quite good. Thanks again for fantastic service and delivery…. John

  12. Nader (verified owner)

    I received my product on time in a perfect condition but I did not get a chance to go out there and use it and shoot some round with it to see how is it doing but I really appreciate it thank you so much

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