I've loaded 40s in the past but it's been awhile and were just run of the mill 40s. I have a Glock 40 (10mm long slide) that a bought a KKM 40mm barrel for a while back. It shoots standard 40s just fine but are pretty anemic. I'd like to load some hot 40 about as close to 10s as I can get safely. The gun is obviously designed for 10mm pressures but of course the 40 case has much less volume so there's that. Anyone played with max 40 loads in fairly strong guns? Yes I still have the 10mm barrel but I don't have much 10mm brass. 40 brass I have.

Interestingly enough, .40 brass is inherently stronger than the original 10mm brass because the .40 S&W always used a small pistol primer and classic 10mm has always used the large pistol primer, leaving more brass in the case head with the shorter round.

In theory, if you can safely load the bullet long (and yet maintain bullet pull), you can also safely load the .40 closer to 10mm if you can mimic the space.

Approaching cautiously (and already using a 10mm pistol), this isn’t anywhere near as “DANGEROUS!” as far too many will try to make you believe.

I load my 40's on the hot side but never over max COAL (1.135").

The 10 Auto's max COAL is .125" longer than the 40S&W's at 1.260".

By my volume calculator you'll gain 19.8% more case volume if you seat a 165gr JHP (Zero) bullet out to 1.260", which is right at 10 Auto case volume.

That'll leave you with only .150" of the bullet seated in the case, -vs- .275" with a COAL@ 1.135".

Don't know if the available leade/freebore on your 40S&W barrel will accommodate that extra length.

If you're using 40S&W magazines that additional length might be a problem too.

I'll take issue with our friend Sevens though on one thing. As far as the case having a small pistol primer making the case stronger that was the logic when Dick Casull went with a small rifle primer in his hyper magnum 454 Casull.

That was ultimately debunked. If it was true then all the hyper magnums that came after it (460 Mag, 500 Mag, etc.) would have all used small rifle primers too, which they don't.

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Haha but look at the SIZE of the .460 and .500 Magnum, plenty of brass there. With a 10mm, the large pistol primer appears to be the focus of the significantly smaller case head.

Anything the .40 can do, the 10mm can do better and well beyond. I load for both and load all my 40 SD ammo at max pressures, however they cannot compare with my 10mm max loads, not even close. You've got the 10, so why not just get more brass? 10mm brass

The 40 is fun. I have a couple, my S&W pushes a 175 at close to 1000 fps, recovers easy for a fast second shot. 10 years ago brass was almost a give away. I bought a large flat rate box full for $40 shipped. It was de-glocked and well over 3500 pieces of brass. I like Power Pistol, a 175 gr bullet and just under the max listed in the manual.
You can oad the 10 mm down but why since you already have the bbl.

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My carry ammo for both my M&P 2.0 40c and my 229 in 40 is a hornady XTP over 9.3 gr of longshot at 1.120". it is a great round that is wonderfully accurate and flat shooting. A bit noisy but recoil is very manageable.

I don't shoot that as my regular range round but have shot plenty so I could get the feel. In a gun built for 10mm I might shoot it more often

I run my M&P40c 2.0 on the warm side, but it has perfect case head support - so don't try this with your Glock. I use Longshot and Hodgdon's load data. I use a COL of 1.16" instead of the SAAMI 1.135". My HiTek-coated 155gr lswc from MBC runs 1350fps from the 4" barrel.

Reloading Tips for 40sw - Christian Ed and Hobby info

Your running SWC through your semi. Interesting... I have been wanting to try but didn't think it would work. In hindsight I bet it will feed nicely considering the ogive on the coated 180 gr coated RFN bullets I have been using are kind of extreme.

Going to order a small batch and see how it goes

I load my .40S&W right on the hot side with no sign of over pressure... pushing plated projectiles... I load power pistol exclusively in the .40, because I want to shoot the .40 as it should be....

Power Pistol no matter the load or caliber has an inherent crack that I love its a rather loud boom and makes quite a fire ball out of the CHP4006TSW/Shorty.40 (note I do dial loads back spficly for the shorty given its alloy frame...

Best advice I can say is work loads up to what you want and air on the side of caution... the .40 should be fine in a gun ment for 10mm...

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This is the way....

...to begin with.

As such, increasing the OAL by that 0.035" should certainly increase the volume in the case, and correspondingly lower the pressure. How, using Hodgdons MAX Longshot load of 9.3gr (for an XTP) at 1.125", you get more velocity out of the same length 4" barrel than their reported 1,283 fps does not seem logical to me...? The other problem would be in how this much longer a 40 would fit in the magazine and chamber.

If it was a typo, and your OAL was really 1.116" I can see where a reduction in case volume could generate more pressure and more velocity. How safe a load PRESSURE WISE in a 40 case that would be is a question that, IMHO, might deserve further consideration? Nobody wants a KABOOM, regardless of how stronger the Glock in 10mm may be over the 40.

As far as the OP's query is concerned, loading to anything over the suggested MAX loads in 40 S&W cases just makes me want to ask why, when the 10mm option is right there? A lot of the (mostly unavailable?) 10mm factory loads (excepting Underwood & Buffalo Bore) are not that dramatically higher than the hotter 40 S&W MAX loads.

Just wondering...

Cheers!

The 0.025" COL reduced the start pressure, i.e. the MAP. My magazines work nicely with a COL of 1.17" so I chose 1.16" for feeding reliability.

The increase in velocity could just be lead versus jacketed - it's not uncommon to see higher velocities with lead.
And of course it is possible that I might have a fast barrel.
My chronograph and I get along, so I trust the velocities.

Thanks for the responses.

I have plenty of 40 brass (It was the Dept. standard for a good while) and a very limited 10 supply. To make matters worse, my recovery rate for my 10 brass is abysmal. The loss rate for hot 40 might be bad too but not an issue at this point. Out of my Glock 40, standard .40 falls right at my feet, but with no function issues. I should probably get a KKM barrel for 10 also, for cast bullets, as Glock barrels aren't supposed to like cast.

When I ordered the KKM 40 barrel I asked them about being a fully supported barrel. It's been awhile but I believe their response was to the effect that you couldn't make a fully supported barrel for a Glock due to the design. I'll try and post a couple of pictures but they might not show much.





I'm thinking the KKM is a bit more supported but maybe not enough to make a difference. The finish on the Glock barrel makes it harder to compare.

Focus? Never heard of any head failures in the 10 Auto & their SAAMI max is 2.5K psi more than the 40S&W.

I load my 10mm Magnums with near 41 Magnum charge weights.

Other than some case separations, no problems with the heads.

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Waiting for the break of day

KKM Glock barrels do provide more case head support than Glock gen 3 and earlier barrels, but I don't think there is a big difference between aftermarket barrels and gen 4 or later barrels in terms of case head support. I am not in favor of hot rodding an already high pressure cartridge like the 40 S&W. Yes, you can play games with longer OAL's and gain some velocity, but don't try to turn the 40 S&W into a 10mm Auto. You may end up with a spare parts pistol.

Large primer vs small primer has nothing to do with case head strength. The reason for the large primer in the 10mm is for more uniform ignition of a long column of the relatively slow burning powders used in full power loads. The 40 S&W uses a small primer because the powder column is shorter and the powders used are typically in the medium burning range. It has nothing to do with case strength.

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I admit I don't care about the .40 as a cartridge; it does not do anything enough better than the 9mm and 45ACP to be worth the hassles I would experience with the supply chain.

HOWEVER: the Glock 20 has some appeal to me as a woods gun, and a local cop has THREE barrels for it, which allows for shooting 9, .40, and .357Sig in addition to the 10mm with only barrel changes (and maybe a mag change for the 9mm; don't recall). In today's weird ammo crisis and the repression we may face in the near (and long) term, that has some real appeal.

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NHI, 10-8.

I surprised the 9mm works. A wouldn't think a 9mm magazine would fit and the only 9mm mags I have are 19s so would be too short to try. The 40s work in the 10 mags as the cartridges are just a bit shorter and the 357 would probably work as well. But the nine is both shorter and skinnier so I can't see 9s working and I don't think any other mags would fit. 10, 40 and 357 are a likely go but I never got into the 357s.

I haven't really been into 10 all that long, just a year and a half or so. I expected the 10 (Sig JHP for example) to have more felt recoil than the 40, which I personally consider pretty mild, but I was surprised how much more felt recoil it had over 45ACP duty rounds.

Not that the 10 is in hot 44 mag snub nose category, which it isn't, but it is hot enough to take me noticeably more time to reacquire my sights, even out of my 40 long slide.

Granted, a lot of factory 10s aren't much more than 40s. Last year I qualified with my G40 for S & Gs. I used the Sig ammo. Not a problem at all but there were a few fliers and I punched a hole in the Depts automated target controller pipe doing the 1 second double tap from the 3. Yeah, it blew right through the galvanized pipe. No, I don't know what the gauge was but it looked fairly stout. That was with the Sig rounds.

I'm not saying the Sig ammo is super 10 or anything but the other stuff I've had is PPU and S & B. They both feel like I'm shooting 40s through the KKM barrel and the brass flies about as far. The Sig brass, unfortunately, has about a 30% recovery rate. I'm rambling again.

oink, I've pushed a 165gr XTrm RNFP HPCB plated to over 1,200fps and a 180gr Brazos Prcsn FP NLG to just over 1,100fps, both with Longshot in an M610. I haven't shot them in my 40S&W semi-autos yet. If I'm pushing them hard and fast in 40S&W or 10mm, Longshot does it for me.

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Back in the mid 1990's some of us were building 40 caliber guns on the then new STI/SVI/Para frames for the new USPSA "Limited division".

The first problem we ran into with those early designs was getting a short 1.135 length cartridge to feed in a platform designed for the much longer 1.260 of the 45acp. Since these frames worked in 10mm, the solution was to ream the chamber throats longer to allow a over all length of our 40 ammo closer to 10mm length.

Most of us were loading 180gr or 200gr bullets out to between 1.180-1.250 to get reliable feeding. We also discovered, in order to get our bullets going fast enough to meet the power factor, we had to load our ammo closer to 10mm reloading data. Which lead us to hypothesize that the only major difference between our new hybrid 40 round and real 10mm was the small primer pocket in the 40 case.

Some of us experimented with seeing just how close we could get to real 10mm velocities with our new Hybrid 40 round and discovered the 40 S&W case is made with a much thinner web, (to increase powder capacity) and would blow out at the web or the case head would completely separate when we got close to max 10mm loads.

Today, it's quite common for 10mm owners that handload, to have a 40 S&W barrel with a long throat fitted to their Glock 20 or 1911 10mm guns and be able to shoot close to full power 10mm ammo without worrying about how much expensive 10mm brass they'll lose.

Hope this helps.

Jeff

Not a fan of running over pressure in a caliber to gain performance. The cade will likely fail before the gun does. Just go with the 10mm.

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Most glocks will feed swc, but ebery caliber is a bit diff. I have no issues in 9 or 40, 45 in a full size g21 are fine, not so much in the g36.

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NRA Cert. Inst. IDPA CSO

Save those small pistol primers. Load the 10’s!

Thanks, that's good information. Unfortunately my powder selection is limited. I have plenty of W231 and H110 but I'm pretty poor otherwise so I guess my options are fairly limited at the moment.

Thanks, I'll have to check the throat depth on my .40 barrel. I don't need to shoot full power 10s out of the .40 barrel but I would like more zip than what normal .40s are.

I guess I can take a fired 40 casing and then loose fit a bullet of my chosen design and then plunk it in the barrel to seat the bullet to depth and then load a bit shorter than that measurement. Hopefully I'll get more length than expected. Does that sound reasonable? Maybe I'll do a test fit that way tomorrow. Otherwise I'll have to find someone with a reamer although I suppose KKM might do it. Any suggestions on throat depth to have it reamed to?

+1;

I also think that the first step would be to see how long a OAL your magazines will accept....
and if the bullets will feed, w/o any problems.......

before loading to a maximum load.

Stay safe.

To determine your max OAL for any given bullet, I use this method:
To lengthen your chamber throat, you need to use a throating reamer. I have a Mason reamer (avail here:https://mansonreamers.com/) chucked up in a drill press or end mill.

I would only deepen the throat .050-.0110 depending on what the customer wanted to load his ammo to.
For example, on the Bar-Sto barrel in my Limited gun, I only cut it to allow ammo loaded to 1.200 OAL. Because, that's all the longer the ammo had to be to feed reliably.
On the 40 barrel I have for my RIA 10mm, I cut it for ammo loaded out to 1.250 so I can duplicate my favorite 10mm accuracy load, substituting 40 brass that I don't mind losing.

Hope this helps.

Jeff

Thanks, that looks easy enough.