There seems to be a lot of questions/interest in utilizing the JSD 80% insert for a 45 acp build. After multiple google searches on the differences between the small caliber (9mm, 40, 357 sig) models and 45 acp versions there was no consensus on the differences, or whether one insert could be used for the other.
To help answer the question I decided to dive in ad give it a go. I ordered a 45 acp build kit from Chris at F & F Firearms and set off. The below is a picture of the kit I received including FCU components from a 45.
Upon receiving the parts kit I examined all of the 45 acp FCU parts and compared them to the small frame version. The only difference I could discern from the parts was the takedown safety lever. As shown the picture below, the small caliber version has an extra tab (the arrow) that prevents smaller caliber magazines from being inserted.
Additionally, examining the inserts themselves, it appears that the ejector on the 45 acp insert is also shorter. This makes sense due to the longer length of the 45 case. The image below shows the ejector length from the factory 45 acp insert compared to the small caliber ejector length.
9mm, 40, 357 sig:
With the differences noted above the following steps would need to be followed to complete a 45 using the JSD insert.
The JSD 80% insert comes configured for the small calibers, so in order to build a 45 acp the ejector needs to be trimmed down to 0.470”. ‘This is completed easily using a dremel and file to trim to final length.
Additionally in order to complete the build the correct takedown safety lever must be used. If you purchased the FCU parts for a 45 acp, the correct takedown safety lever should be in the kit. If this is the case then you would just complete the FCU assembly as normal. If your FCU parts were procurred from a small caliber build, you will need to source the 45 acp takedown safety lever. All of the other parts would remain the same.
And that’s it folks. Assemble the insert with the 45 acp grip, slides, and mags and you should be good to go. I have put 500 rounds down my conversion without a hiccup and can say I prefer the P320 to my P220.