Opening a 9mm bolt for .40

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[ARCHIVED THREAD] - Opening a 9mm bolt for .40

Posted: 8/20/2017 11:58:35 PM EDT

I've got a Spinta blem bolt in 9mm and I am looking to convert it .40sw. I want to make it work with a Kaw Valley .40 barrel that's on it's way. Is it just opening the bolt face diameter or is there more that needs to be changed?

Posted: 8/21/2017 9:32:21 AM EDT

[#1]

I'm not sure what what point you have to start enlarging the ejection port. On the ARs in 45acp, that hole is hogged out to allow the fatter cases to fly out. I wouldn't be surprised to see the .40 and 10mm needing it, too.

I'm sure you already looked at the extractor and the ejector if that's in your bolt rather than fixed in the receiver.

Posted: 8/21/2017 10:28:11 AM EDT

[#2]

The ejection port doesn't have to be enlarged for a 40. If you contact Rudy at Macon Armory he can help you out on the bolt, he specializes in pistol caliber AR uppers.

Posted: 8/21/2017 8:42:59 PM EDT

[#3]

You'll need to modify the extractor hole and possibly the extractor to ensure it isn't restricted form clipping over the rim, and also make sure it doesn't hang onto the case when extracting.

Posted: 8/21/2017 10:55:03 PM EDT

[#4]

Quote History

Quoted:
You'll need to modify the extractor hole and possibly the extractor to ensure it isn't restricted form clipping over the rim, and also make sure it doesn't hang onto the case when extracting.

View Quote

Thanks! I didn't think about modifying the extractor hole but it makes sense. What do you suggest I open the bolt face diameter up to?

Posted: 8/22/2017 7:52:33 PM EDT

[#5]

Measure the rim, and add about .006 to .008 and you will need a VERY RIGID carbide tool, I have a selection of grooving tools I use that have been ground to cut like a boring bar.

[ARCHIVED THREAD] - Opening a 9mm bolt for .40

AR-15 » Rimfire and Pistol Calibers

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