20ga to 357 text

357 Mag 20 Gauge Shotgun Adapters

(98 customer reviews)


357 Magnum Shotgun Adapters for 20 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.

Select Length below: 


357 Mag Shotgun Adapters for 20 Gauge Shotguns

357 Mag Shotgun Adapters Allow a 20 Gauge Break Action Shotgun to use 357 Magnum or 38 Special Ammo.

For 3″ as well as 2.75″ Chambers

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

Comes with multiple O-ring configurations.  As a result,  easily achieving a good fit for 20 gauge shotguns.

Rifle 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)

*357 Magnum rounds should only be used in capable shotguns with SB1 or SB2 or equivalent receivers.
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.
Thank you for reading.

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.


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 Mag 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 this product, check out our other Shotgun Adapters

Additional information

Weight N/A
Dimensions N/A

2 3/4", 6", 11, 18"

98 reviews for 357 Mag 20 Gauge Shotgun Adapters

  1. Rocky (verified owner)

    A high quality product !
    Finish is surprisingly nice and gauge / cartridge is clearly marked, so anyone can see and understand what it is.
    Tested with 38 special +p and 357 mag. Accuracy, at least with this 11 inch adapter, seems to be very good. I’m very pleased with it. Thinking about buying one for 12 gauge now !

  2. Dickson Skipper (verified owner)

    The 18” .357 mag 20 ga. insert is great! Well made, accurate, and easy to use. Great customer service.

  3. Benny (verified owner)

  4. Scott B. (verified owner)

    Fits the gun nicely. Functions well. So far only fired with 38 sp.

  5. Karl Bartlow (verified owner)

  6. kevin walker (verified owner)

  7. Shelley Burk (verified owner)

    Very happy with our purchase, on the wait list for two more. We were sent the wrong one at first but was corrected in less than a week. I am still waiting on a response on how to return the incorrect item.

  8. LARRY (verified owner)

    Great company good on thier word

  9. Steven Oppermann (verified owner)

    I have sights on the shotgun I intended to use the adapter in. Maybe I had unreasonable expectations, but, with sights from a bench, the best group I could get was around 5-6 inches at 25 yards. I found the adapter would rotate a little with each shot, I assume from the torque generated from the bullet engaging the rifling. The adapter is very well made, but I won’t be using it due to the very poor accuracy of this particular adapter in my particular shotgun.

  10. Richard Harrison (verified owner)

  11. Barry Holland (verified owner)

  12. LUIS A. (verified owner)

  13. anthony winkler (verified owner)

  14. Scott (verified owner)

    I have not fired any rounds through the insert as of this writing. But insert fits nice and tight into shotgun, its easy to remove, i like the bold lettering on the side of insert, makes it easy to identify caliber if you have more then one insert. Shipping was fast. Website is a bit plain, but navigating was fairly easy. Caliber availability and options is lack luster.. it seams certain calibers are never available for purchase.. thats unfortunate cause i would like to purchase other caliber’s.. overall i like the insert, hopefully it fires great and have no firing pin issues, when i get the chance to do so..

  15. Joe O. (verified owner)

    Very Very happy!!!!!!!!

  16. Johnny Ryals (verified owner)

    I am well pleased with the adapter and fast delivery after purchase. The adapter is well made and a quality product

  17. Joel G. (verified owner)

    This barrel insert is a steal for the money. It appears to be a precision machined piece.

  18. Verified Buyer (verified owner)

    Perhaps this review is premature. Not as accurate as I’d hoped, but beautifully constructed and finished. Based on my other .357 long gun, I was hoping this 20-ga.-to-.357 insert would deliver 1.5″ groups at 50 yards and 3″ at 100. Not the case, sadly, although I only tried it with three different (reasonably powerful) loadings and have yet to attempt the experiments with the included O-rings that Chaszel suggests might help with accuracy. (Removing spent cases requires only the flick of a fingernail.) I’ll try it again later, but right now I’d say 5 stars for construction, function and finish, 3 for price, and 2 for accuracy.

  19. Verified Buyer (verified owner)

    Quality product

  20. Osbourne S. (verified owner)

    Actually, I haven’t used it yet, but I really appreciate the prompt shipping and an almost immediate response to a question I had. I’m confident the adapter will perform as advertised and I continue to look forward to the availability of the 12 gauge to 30-30 adapter.

  21. Roland S. (verified owner)

    Makes a light weight fast handling single shot

  22. Verified Buyer (verified owner)

    Great quality, communication and shipping!

  23. Harold Zeitler (verified owner)

    Great piece. Sighted it in the other day with a red dot sight. Great groups at 25 yds. Using it for the MN deer firearms season in a couple weeks.

  24. Richard (verified owner)

    Great way to make your own .357 single shot rifle!

  25. Richard Mastenik (verified owner)

    I love Chaszel products, I’ve purchased three 18″ shotgun adapters so far. The quality is incomparable. My only issue is that they make such a fine product they’re often backed up for a very long time. I still hope to buy a 20 gauge to .30/30 Win. And a 20 gauge to .45 Colt – both at 18″. The good news is that the high quality of their product makes it worth the wait. 5 stars !

  26. Verified Buyer (verified owner)

    357 not compatible with shotgun – primer penetration. 38spl quality made, fast economic shipping, and accurate.

  27. Verified Buyer (verified owner)

    Quick ship, nice product.

  28. Verified Buyer (verified owner)

    This is my 4th Chaszel adapter and they all have been excellent. They have repeatable accuracy with consistent placement in the barrel even with just a bead front sight.
    I will have a couple more as discretionary funds allow.

  29. Carl (verified owner)

    This barrel insert is top notch. Beautifully finished inside and out. I used it with all manner of .357 and .38 sp ammo without any extraction or leading problems. Hard to check accuracy with no more than a bead for sights but easy enough to get used to.

  30. Mitchell Young (verified owner)

    Great product and very fast shipping

  31. Eric Grant (verified owner)

    Great transaction. Fast shipping.

  32. Verified Buyer (verified owner)

    Item seems well made, fits well in my single shot, and it is relatively accurate with just a bead sight. Oh, it is a blast to shoot also.

  33. Verified Buyer (verified owner)

  34. Cody Elmy (verified owner)

    Fantastic accuracy. Best adapter you can buy in my experience.

  35. Cody Elmy (verified owner)

    (11″ 20 gauge to 357 magnum)
    Waited for one to become available, but finally messaged and was very lucky they had one available in the warehouse that wasn’t listed online. So happy with it, went out and shot it today out of my Stevens 301 turkey shotgun and it shoots so well. Very accurate.

  36. Quintin B. (verified owner)

    Works great in my cz shotgun

  37. Arcy Swopes (verified owner)

    You guys have the best shotgun adapters in the business,hands down 👌👍.

  38. peter b. (verified owner)

    Now, after a test in my new Henry 20 ga single shoot, all 38spl/357mag find it’s way into a 6.0″ target @ 25 yds without any problem when free standing.
    Next week I plan a bench test @ 25 yds, so I expect a
    all inside a 2.0″ circle…………………

  39. Stephen (verified owner)

    Great piece, fit and works, accuracy better than expected

  40. James (verified owner)

    Great product and great communication with you folks. Insert works well! Hope to purchase more in the near future! Keep up the QUALITY work!

  41. Carl (verified owner)

    fabulous!! Chaszel adapters are great!!

  42. Richard E. (verified owner)

    Haven’t used yet but fit is good. Machining is excellent. I do wish more selections for 20 gauge. Like where’s the .22 lr caliber? One other thing, I would like the choice when purchasing to specify if you want effector cut out on any length adapter. I had to file off rim myself, which takes away from the beautiful machining job.

  43. Joseph L. (verified owner)

    Great item. Fair price. Quality Product.

  44. James S. (verified owner)

    Have not had a chance to try it yet but quality seems to be top notch. It fits the weapon good and tight. Shipping was very fast and got it 3 days after ordering. Can’t wait to get a chance to try it out.

  45. David (verified owner)

    I recently purchased the 357 20 adapter. It fit perfectly in my H&R Tracker. I’m ready for the range.

  46. Anonymous (verified owner)

    Excellent 20 GA shotgun adapter. Carry it in my game vest when hunting with my single shot 20 ga. More accuratre than me

  47. DOUGLAS G. (verified owner)

  48. Mike Grills (verified owner)

    Love your adapters. They make my shotgun more versatile. Thank you.

  49. Anonymous (verified owner)

    Exactly as I expected, good grouping at 25 to 50 yards very quick shipping cool products if that Day ever comes that your in a pinch,or even wanna take an animal without having to use buck shot I believe I could take down a Deer at 20 yards with the 357 adapter or the 45 . Don’t hesitate grabbem if you can .

  50. Anonymous (verified owner)

    Good customer service. Quick response time. Product appears to be excellent quality. Not used it much but seems to pattern well. Hope it holds up over time.

  51. Andrew H. (verified owner)

    Cannot believe a drop in adapter can be so accurate! 38spc 125 gr FMJ busting 4″ plates at 50 meters with stock bead sight! Excellent craftsmanship!

  52. Anonymous (verified owner)

    Very easy to order and once available delivered quickly.
    Looks to be well made and finished. I fired only 2 rounds so far so I don’t have a group to share.
    Looking forward to find out what groups will be like out to 50 meters.

  53. jsaladna (verified owner)

    Looks good and fits like a glove. Shipping is very fast. My big fingers have no issue extracting spent brass. I have not checked accuracy yet but expect it to be at least reasonable given the tight fit.

  54. kenneth moores

    i put this insert in my savage 301 turkey gun with a cheap Tasco 3×9 scope and some hand loaded 357 158 grain lead hollow points i had kicking around 75 yard groups were amazing more then enough for hog n deer

  55. John (verified owner)

  56. Anonymous (verified owner)

    works good but I want the longer one when they become available

  57. david s. (verified owner)


  58. Josh M. (verified owner)

    Couldn’t ask for better. .38 and .357 Mag out of a CBC single shot with bb front sight. 3in grouping at 50ft. Can’t ask for better than that. I want the 11in one when stock come in. Would be a great deer gun with a scope.

  59. Anonymous (verified owner)

    Have not used them yet, but feel tight in gun…glad they are blued and marked with calibre’s….may buy some 12’s, 28, and .410 adapters soon…..Thanks….I like them..Great Price…..!!!!

  60. Anthony P. (verified owner)

    My Chaszel shotgun adapter is a perfect fit in my chamber/barrel. I am pleased with the accuracy of this rifled adapter. Ordering and delivery were efficient and quick. Now, I own two Chaszel products and will purchase more as they become available.

  61. Andrew P. (verified owner)

    Fast shipping, great product!

  62. Dale C. (verified owner)

    I am very happy with my .357/20 ga Adapter. Shoots good out of my H&R single shot.

  63. Wendy T. (verified owner)

    Received the wrong adapter at first, but they sent me out the right on as soon as I told them. I would definitely recommend this company.

  64. sumatracarbine25 (verified owner)

    Love the 11 inch 357 barrel accurate easy to install and remove if need be

  65. Greg H. (verified owner)

    awsome product and super accurate..will buy more as money allows..thank you

  66. Mark Renfrow (verified owner)

    Was going to attach picture of target to review, wouldn’t post. 2 1/2″ group @ 30 yds. I’m happy.

  67. Stephen P. (verified owner)

    Another well made product. Would buy again!

  68. James (verified owner)

    This is a happy update. I installed larger o-rings in the three grooves on the muzzle and installed better sights. I also discovered that my barrel does not particularly like cast lead bullets.

    Using copper plated 125 gr JHP bullets I was able to get a 1″ group at 20 yards and a 3″ group at 50 yards. These meet my expectations.

    The liner is semi permanently installed in the left barrel because the oversize o-rings are very tight. I carefully reduced the portion of the rim so the ejector does not try to eject the insert.

    Now the only issue is to remember that the barrels are not regulated and to make appropriate “Kentucky windage” adjustments when shooting. This SxS shotgun/rifle is a formidable weapon.

    Thanks for the fine product.


    So far I have been unable to get an acceptable small grouping. I installed a Marbles bullseye rear sight and a post front sight on my Stevens 20ga. SXS shotgun. The 20 yard target was a 4″ group and the 50 yard was all over the target.

    I put a beeswax thread shim under the two forward most o-rings to get a tighter fit to see if that will tighten the group.

    I intend to leave the insert in the shotgun as a “permanent” rifled barrel to augment the other shotgun barrel.

    • Chaszel (store manager)

      Good Afternoon, I am sorry to hear that the adapter is not grouping well. With the 18″ adapters try to keep the muzzle as tight as possible as you are doing. Will the 3rd o-ring install or does that make it too tight? Also after each shot make sure the adapter is indexed to the same location every time. If you planning on leaving the adapter in permanent I would recommend filling away just enough of the rim on the adapter so that the extractor in the shotgun does not move the adapter when opened. If you are not happy with the adapter you can return it for a full refund. Thank you.


  69. Chris Kostelansky (verified owner)

    Looks great, works perfectly. Thanks

  70. Kevin K. (verified owner)

    Works good at 25 yards 50 yards shoots high hornady amo seems to work best used open sight just a brass dot on end of barrel . May take to gun smith and have riffel sights put on .

  71. Anonymous (verified owner)

    Haven’t had a chance to shoot it yet but looks of good quality and with a few of my own O-rings managed a nice tight fit.

  72. Thomas Prather (verified owner)

    Love the insert and customer service was great.

  73. Carl (verified owner)

    great for my truck gun!!

  74. Kevin (verified owner)

    I’m highly pleased with the barrel insert I received. The workmanship is top-quality. Your service was excellent. I’ve fired this insert in my H&R single, and the accuracy is even better than I had hoped. You get five stars for this one! I do recommend your company to others.

  75. Mark (verified owner)

    I’m hesitate to give you this rating and not a lower one. At this point in time I have not received my order. I don’t know if the blame is on you or the Post Office, UPS, FEDEX, or some other service. I will say this, the order process went OK.

    • Chaszel (store manager)

      Good Afternoon, We really appreciate your business and understand the frustration of having a shipment take so long to arrive. Your package was shipped Priority Mail the day after you ordered it. The Post Office has been very behind on a lot of there delivery’s due to Covid-19. Your tracking say it is arriving late but is still on its way and was updated yesterday. We realize the inconvenience of these delays and have now offered UPS as a shipping option. Sorry again for the inconvenience.


  76. Mitch W. (verified owner)

    have not used it yet is a Christmas gift but looks good and feels well made

  77. Anonymous (verified owner)

  78. Patrick M. (verified owner)

    It looks great fit both single shot and double barrel shotgun good haven’t had chance to shoot it yet.

  79. Weldon P. (verified owner)

    Beautifully made adapter. Good price and functions as it should. I will by from Chaszel again. Happy with my purchase. Thanks

  80. James Allegre (verified owner)

    Excellent craftsmanship fitment is perfect! Unfortunately I haven’t been able to use the product yet but I expect you shortly. Dealing with Chad was a pleasure.

  81. Riley B. (verified owner)

    Cannot wait time deer hunt with this!!!!! (I already have another insert for my O/U, this completed the gun)

  82. Kevin H. (verified owner)

    I wanted to try the inserts out before reviewing . The purchase and delivery was simple and quick . Items were well made , well packaged and worked just as advertised .

  83. William Trader (verified owner)

    very accurate out to 100 yrds.

  84. Paul R. (verified owner)

    Outstanding company and products I thus far have a 20ga-.357 12ga-9mm 20-9mm and just picked up 12ga-45-70 all are great quality and shoot as they should. Can’t beat them for multitude of scenarios.This .357 model gives boosted carbine performance from my handgun sidearm loads in my survival NEF 20GA with minimal extra weight .

  85. John D. (verified owner)

    Fast shipping,nice fit and finish.Will buy again.

  86. Riley B. (verified owner)

    The insert is accurate and was delivered quickly. I can’t wait for more calibers!

  87. Riley (verified owner)

    I purchased a 357 Mag 20 gauge adapter and this product really exceeded my expectations. I wanted an 18 inch adapter, but that wasn’t available. The 11 inch adapter was and it is excellent. I set up a target at 55-60 yards (the area around the 50 yard mark was muddier than normal), I put four shots within a 6 inch circle on the paper. I need to practice more and I’m sure accuracy will go up. I moved the target to 100 yards. At 100 yards, it should be known I have a Stoeger Conder 20 ga O/U. So in terms of bead placement, the bead covered the entire target. My first shot was a flyer as it was high and right. The last three shots were more or less just outside a 6 inch target. It was all to the right, but I was using a bead, not rifled sights. The 11 inch insert went 8/8 for shots on paper, it is consistent and easy to use. I know changing sights will make an impact and I will explore some of those. I can’t wait for more caliber to come out! I plan on using this for deer season this fall, I just need to practice more first.

  88. steve (verified owner)

    excellent workmanship

  89. Dean Santomango (verified owner)

    Excellent quality

  90. Anonymous (verified owner)

  91. John (verified owner)

  92. Anonymous (verified owner)

    Quick delivery and on checking up the adapter, the machining looks excellent.
    I did put a note in the Graybeard forum about the product.

    • Chaszel (store manager)

      Thank you for your product Review, We really appreciate it.


  93. James Ballou (verified owner)

    Chaszel makes a super high-quality, well designed and finely machined product, they mail the orders right away, their prices for these types of products simply cannot be beat, and in my experience their customer service is outstanding.

  94. Amanda McGowan (verified owner)

    I could not be more pleased with this product. It has breathed new life into my topper jr. I plan on purchasing more calibers when they are available.

  95. Mark Wilson (verified owner)

    quick reply, i like the interaction, overall great experience, would recommend again

  96. Jeremiah wimmer (verified owner)

    Awesome product works amazing it is as they said

  97. Troy D. (verified owner)

    I have not used the 357 insert yet, the bore for the bullet casing seems a little large. mic’d at .3805. Measurements on the 357 cartridges I have are .3755 so have a little play when placed in the insert. Bore is correct and the lands and grooves look great..

    • Chaszel (store manager)

      The loose fit is normal. Saami specifications call for .381″ at the opening. If you have any other concerns or questions feel free to let me know. Thank you very much for your business and your feedback.


  98. Corey W. (verified owner)

    Sent me the wrong one. When I emailed them they immediately returned my email and sent me the correct one. Great product and great customer service.

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