SJR型KP/-31“索米”冲锋枪，与普通版本索米相比多了一个枪口抑制器（suujarru，芬兰语的枪口制退器），枪长也要更长（枪口抑制器长度不属于枪管长）。但根据数据来说，该抑制器的效果并不是特别突出，不但索米的枪口上跳没得到立竿见影的改善（毕竟射速摆在那里，你跳一下十发子弹都没了），反而把这把枪的长度逼向了卡宾枪等级。
下面是该图片源网站的介绍，我懒得翻译了，因为这是一家军用古董出售网站，一共是399加元，弹匣弹鼓免费随枪送，有条件的可以考虑一下。
Suomi KP31 SJR Submachine Gun SPECIAL
Military use Finnish Suomi KP31 SJR model with muzzle brake. This uncommon version outnumbered slanted muzzle of the Kp31 by 10 to 1. Introduced in 1942, the SJR was used extensively in the Continuation War and well beyond by the Finnish armed forces. Most of the Suomi SMGs that we have had were reconditioned before being put into war stores. A unique opportunity to explore the fascinating military history of Finland in the 1939 to 1944 by owning an original Finnish submachine gun at what can only be called an amazingly low price. Supplied with deactivated drum mag, deactivated stick mag and sling. No licence required to purchase or own. For sale in Canada only. Supplied with stick mag, 70 round drum mag, sling. It is illegal to alter this deactivation in any way.
