oal for 40 in glock 10mm mags?

[durdy1]

I am building a Glock 20 10 mil with 40 conversion barrel 6 inch long slide for USPSA limited with major power factor. How far out can I load the OAL and still be safe? I will be ordering a KKM barrel and thought about having them ream the chamber to what my oal will be. Thanks

[durdy1]

Sorry might help if I threw in what bullet. Bullet is bayou bullets 180 gr. Still researching powders.

[Justsomeguy]

The issue here is the use of 10mm magazines. The "standard" length for 40S&W is more or less 1.125 or so, while that for the 10mm is 1.255 or thereabout, so the magazines are presenting the round to the barrel with a longer jump than 40cal mags are. Chambers are chambers and throats are throats. The chamber size is pretty much fixed, but the barrel could be throated to accept a longer than standard 40S&W round to allow you to use the 10mm magazines without some feeding issues though that would have to be worked out. In other platforms 1.165 or so is used a lot of times as a good compromise when using a platform not originally designed for the shorter length cartridge. Throating too long will affect accuracy though, so there is a limit. You might want to talk to your gunsmith or whoever is building this gun if it isn't you and see what they recommend. STI and Infinity as well as some other 1911 type pistols have confronted this issue before, but few go from 10mm magazines.

Edited December 21, 2013 by Justsomeguy

[durdy1]

I have been searching some forums and found some guys loading out to 1.180, and one was loading 1.200. I know I am asking a lot out of the gun this way. I am just trying to lay out everything before I start putting it together.

[notfast]

I am using a similar setup. Glock 20 with a LWD 40SW conversion barrel. I have been using the conversion barrel in the G20 for about 18 months. That would be a minimum of 5500 rounds. I know. I need to shoot more.

I am not having any feeding issues with the 10MM mags (4 with Arredondo 5 round extensions installed) running standard 40SW OALs of 1.120" to 1.135". I have used these OALs with Speer 165GR TMJ (1.120 and 1.125), Precision Bullet 170GR RNFP (1.120 to 1.135), and Xtreme 180GR RNFP bullets (1.125).

I have loaded out to 1.175" with an Xtreme 220GR RNFP I received in error. I had ordered 200GR bullets. I decided to keep the 220s and play a little.

Experimenting with the 220GR bullet indicated a max OAL of 1.185 in my barrel chamber. I backed off 0.01" for reliable chambering.

With my pistol, conversion barrel, and magazines, I have not had any issues shooting 40SW loads with OALs anywhere from 1.120" to 1.135" for the 'normal' weight 40SW bullets, and out to 1.175" with a 220GR bullet out of the G20 magazines.

Durdy1, if you are considering reaming your chamber for a longer OAL due to feeding issues, you may not need to.

I have run most of my loads over a chrono and have no problems making major PF using WSF with standard book loads.

If you are reaming the chamber for increased OAL in order to use what would be too fast of a powder at normal 40SW OALs to safely make major PF, then ignore my post.

Edited December 22, 2013 by notfast

[Justsomeguy]

Here, Notfast has experience with your combination and so the old adage of "If it ain't broke, don't fix it" applies. If feeding is reliable with standard length 40cal OAL's using 10mm magazines then perhaps it's not a problem with your platform. There is certainly no issue with making major with a .40 with a variety of powders at almost any OAL.

Edited December 22, 2013 by Justsomeguy

[durdy1]

Thank you for the info and experience. The reliability during competition was my concern mostly. I was reading a thread on using Allianzt E3 powder cause it burns cool and very clean. I have titegoroup and win231 on hand now. I will also call kkm and see what they recommend when I get ready to order the barrell.

[WilliamDahl]

I have a Glock 20 and 29. I have had no problem shooting .40SW rounds in the 10mm barrel. I have found no need to purchase the .40 conversion barrel and I have used the 10mm barrel for both handloaded and commercial .40SW rounds. Since 10mm brass is a bit more difficult to find, I decided to experiment with .40SW brass loaded to 10mm lengths. I had read that this was possible with the Glock 20 and 29. I have loaded many rounds this way and have not had a problem with them. When loaded to the 10mm OAL, the bullets stick a bit further out of the brass than with a regular .40SW round, but the space between the powder and the base of the bullet remains the same as when you are using 10mm brass.

[Justsomeguy]

Though I have heard of this practice of shooting the shorter round in a 10mm barrel, I would not recommend it. You are shooting off the extractor as it is what is keeping the casing from going further down into the barrel. Better to have a chamber made for the round where it headspaces on the shelf in the chamber and not on the extractor.

[WilliamDahl]

Though I have heard of this practice of shooting the shorter round in a 10mm barrel, I would not recommend it. You are shooting off the extractor as it is what is keeping the casing from going further down into the barrel. Better to have a chamber made for the round where it headspaces on the shelf in the chamber and not on the extractor.

From what I've read, the Glock has a more heavy duty extractor and it allows you to do this. It is not necessarily something that you can get away with on other 10mm handguns (e.g. Colt Delta Elite and such). One disadvantage is that in order to load a round in the chamber, you need to load it from the magazine and you can't just drop the round into the chamber without a magazine present. I don't remember this being an issue on any of the M1911s that I've owned over the years, but I have noticed it on the Glocks.

[jmbaccolyte]

If you're going to load longer than SAAMI, I suggest you use the "plunk" test to ensure that the bullet isn't jammed into the rifling which will cause pressures to jump.

[WilliamDahl]

I did a bit of testing with my Glock 29 (10mm) and some .40SW handguns the other night and came up with the following conclusions:

1. To load a normal length .40SW round into a 10mm chamber, you must load it from the magazine. You cannot just drop it in the camber with the slide pulled back since the extractor will not grab it.

2. A .40SW loaded to 10mm length (and pressures) can be dropped into the chamber directly and does not need to be first loaded into a magazine.

3. A .40SW loaded to 10mm length will not chamber in .40SW handguns, even if you load it directly into the chamber. Or to be more precise, the slide will not fully close.

Shooting a regular .40SW in a Glock 10mm is a non-event as long as you are loading the rounds from the magazine.

[durdy1]

I am going to order a Kkm Barrel in a 40 conversion for Uspsa.. I just want to load the bullet far enough out to be 100% reliable in a 10mm mag. I was thinking 1.180 to 1.20 oal. I will also call kkm soon to see what they recommend.

[coordinator]

I have loaded the 180 grain MG JHP out to 1.20 with Universal Clays and a 13 lb recoil spring. I too am using the KKM barrel.

[durdy1]

Cool. That's re assuring. That's kinda what I was leaning towards...is the universal clays clean burning ? Have ya ever tried the Alliant e3?

[jmbaccolyte]

I did a bit of testing with my Glock 29 (10mm) and some .40SW handguns the other night and came up with the following conclusions:

1. To load a normal length .40SW round into a 10mm chamber, you must load it from the magazine. You cannot just drop it in the camber with the slide pulled back since the extractor will not grab it.

2. A .40SW loaded to 10mm length (and pressures) can be dropped into the chamber directly and does not need to be first loaded into a magazine.

3. A .40SW loaded to 10mm length will not chamber in .40SW handguns, even if you load it directly into the chamber. Or to be more precise, the slide will not fully close.

Shooting a regular .40SW in a Glock 10mm is a non-event as long as you are loading the rounds from the magazine.

William- I try to always load from the magazine anyway because an old timer once told me its hard on the extractor to make it jump up onto the case rim.

Edited January 2, 2014 by jmbaccolyte

[WilliamDahl]

William- I try to always load from the magazine anyway because an old timer once told me its hard on the extractor to make it jump up onto the case rim.

I've always loaded the +1 by dropping it in the chamber instead of loading from the magazine and have never had a problem with any of my extractors. Then again, this doesn't happen that often, so maybe I've just not done it enough for a problem to have shown itself.

I've noticed on the years that some handguns will not allow you to load a round directly in the chamber unless you have a magazine also inserted and others will not allow you to load a round in the chamber if you have an empty magazine inserted. Probably has something to do with respect to the manufacturer's design decisions on whether to lock the slide back upon when a magazine is empty. I switch between firearms enough that I really don't remember which do what anymore.

[chevyoneton]

I've always loaded the +1 by dropping it in the chamber instead of loading from the magazine

Interesting, in 40 years of shooting I don't think I have ever dropped a bullet in the chamber of a semi-auto pistol to load it, or even considered doing it. I have always loaded the chamber from a magazine, even if just "barneying up".

[G29SF]

I did a bit of testing with my Glock 29 (10mm) and some .40SW handguns the other night and came up with the following conclusions:

1. To load a normal length .40SW round into a 10mm chamber, you must load it from the magazine. You cannot just drop it in the camber with the slide pulled back since the extractor will not grab it.

2. A .40SW loaded to 10mm length (and pressures) can be dropped into the chamber directly and does not need to be first loaded into a magazine.

3. A .40SW loaded to 10mm length will not chamber in .40SW handguns, even if you load it directly into the chamber. Or to be more precise, the slide will not fully close.

Shooting a regular .40SW in a Glock 10mm is a non-event as long as you are loading the rounds from the magazine.

The reason that works is because the bullet is hitting the rifling and stoppinig the cartridge from dropping further into the chamber. This sounds dangerous to me due to potential pressure spikes when fired. In this situation, the cartridge is headspacing on the bullet-and-rifling... rather than the case mouth in a properly mated barrel-and-cartridge.

I load and shoot 40 S&W out of my glock 10mms (20 and 29) all of the time... but I use their respective 40 S&W barrels.

I won't bother with the plusses and minuses of shooting 40 S&W through a 10mm barrel, however situation #2 above is not something I would do.

NOTE: My issue with item #2 above is not a 40 with a 10mm OAL. My issue is dropping the slide on a 40 chambered round with 10mm OAL which causes the round to slam into the rifling. As long as there is enough neck tension, loading a 40 to 10mm OAL should be fine when used with a magazine.

For the record, I don't drop my slide on a chambered round in any sitiation.

[jmbaccolyte]

Different model guns have different distances to the start of the rifling. I have a .40 caliber pistol (Tanfoglio/EAA Witness Match) that allows me to load to 1.23" OAL (I'm using 10mm mags) and I have not had the barrel throated. I'm using 180 grain BBIs and Bayou bullets. I haven't tried 1.26" OAL, just because the 1.23" OAL was the first longer than SAAMI length that I tried and it feeds perfectly (there hasn't been a single failure to feed through several thousand rounds).

Edited January 13, 2014 by jmbaccolyte

[G29SF]

My point above was...

If a 40 OAL round in a 10mm barrel swallows the round when dropping the slide on it (and the extractor does not hop over the rim), the 40 case mouth is not reaching the end of the chamber (as expected)....

-- and --

If a 40 round with 10mm OAL in a 10mm barrel DOES allow you to drop the slide on it and the extractor DOES hop over the rim, the only thing allowing this is the bullet bottoming out. This is NOT a desireable thing.