Three Letters Re: .40 S&W to 9mm Conversion Barrel for a Glock Model 23?

A question was posted on your site about the ability to use a Glock 23 with a 9mm barrel. It has been my (limited) experience that all that is needed to shoot the gun in 9mm is a replacement barrel and a 9mm magazine. I first heard of this from a friend of mine who is a part time gun writer. I was skeptical but, given the source, I gave it a try. I am not a Glock fan but my then girlfriend was. She shot her Glock 23 more as a 9mm than as a .40 because it was cheaper. In her experience the gun was fully reliable in 9mm. She used .40 for carry and in the home but most of her practice was 9mm. I would guess that in the time we were dating she fired 2,200-2,500 rounds of 9mm and only 300-350 .40. All without any failures. I believe the barrel was made by FAC (Federal Arms Corporation). To avoid any confusion she used the orange Glock magazines in 9mm so she wouldn’t confuse the 9mm mags with the .40 mags. – Jake

Hi Jim,
Enjoy the blog immensely. Read it every day. Regarding barrels for conversion from one model of Glock to another (i.e. .40 S&W model 23 to 9mm model 19), there are a number of manufacturers of barrels for such purposes. Topglock ( sells conversion barrels from several manufacturers. Federal Arms also makes them, but I don’t know if they sell directly or only through dealers. As I recall, from what I have picked up from the web, no change in slide or extractor is necessary for the conversion. The original .40 S&W mags will work for the 9mm, most of the time. But if I was going in harms’ way, I’d order the mags for the same size 9mm Glock to use in the .40 S&W.  I’m sure the staff at Topglock or Lone Wolf Distributors (
) could answer any questions people have. Thanks for the site, – Jim H.

There are barrels available to convert .40 to 9mm, but they are NOT 100% reliable. Bar-Sto and Jarvis make them
[JWR adds: So do Federal Arms and Olympic Arms], various places like Glockmeister carry them. You simply replace the barrel but use the same slide, and this is the cause for it not being 100%. There are ejector/extractor issues. These are okay to train with but not to fight with. To convert to 9mm with full Glock reliability requires you to simple swap slides with a 9mm gun. Thus the 23 can shoot both 40 stock and 9mm. The M23 frame is essentially the same as the M19, just beefed up to handle .40 cal. The downside is price, since a complete 9mm slide costs as much as the used trade-in Glock 19s now. This same “trick” is available for Beretta, SIGs and others. Drop a Beretta 92 slide on a 96 and you have a convertible gun, in fact Beretta sold this combo at one time. DO NOT take a 9mm frame and drop a .40 slide on it. It will function but it (the 9mm frame) isn’t beefed up enough to handle the .40. Almost forgot, .40 cal mags hold 9mm with no modification. Back in the High-cap magazine ban days [Sept. 1994 to Sept. 2004], you could always take a 10 round 40 cal mag and put 9mm in it to have a 12-13 round “high cap”, it functions fine in every case I have tried. HTH,  – Mike, M.D. in MO