40 S&W barrel in 10mm

[fltbed]

OR, Who wants to shoot 10mm ammo but tired of losing 30%+ of their 10mm brass.

This story starts back in the mid 1990's when some of us were building 40 caliber guns on the then new 2011 STI, SVI and Para wide body frames for USPSA "Limited division".  The 10mm/40 bore offered a 5+ round capacity advantage over the then standard 45acp and since these guns worked in 10mm, it seemed logical to chamber them in 40 S&W and take advantage of the abundant and CHEEP brass.

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-220gr bullets out to between 1.180-1.250 to get reliable feeding. We also discovered, increasing the combustion chamber of the powder charge, decreased the chamber pressure and velocity.  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 case head and case 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.

And that story brings us back to the present.

The only advantage to the current Chinese virus shut down and quarantine is, I have the time to go through all the boxes I have stored here.  Some of them I haven't opened since I packed them up eleven years ago when I got divorced and moved here.
In one of those boxes, I found a 5 1/4" stainless KKM gunsmith fit match 1911 bull barrel short chambered in 40 S&W.  I'm not sure when I picked up this barrel.  Probably sometime between 2000 and 2004 when I was competing a lot and traveling to major matches frequently.  I'm not sure if I bought it cheap off a vendor table or picked it up off a prize table but I remember thinking at the time, I would use it for my next Limited gun build...that never happened.

I noticed this barrel had the same Clark/Para ramp cut as my 5" 10mm RIA 1911 and that got me thinking back to my experience with long OAL 40 ammo I told you about earlier and that got me wondering if I could duplicate my favorite 10mm load, substituting it with 40S&W brass that I wouldn't mind losing.    
(My favorite 10mm load is, any good 180gr bullet loaded with 10.4gr of Blue Dot because this load shoots the most accurate in every 10mm I've tried it in.  Not exactly a max load but not really wimpy either as it still chucks brass into the next bay and I lose about 30% on average.)

I found the box with all my old reamers and mill bits and discovered some dampness somehow got it there and rusted almost everything to one extent or another, including my 40 finishing reamer.  I sent it back to Mason Reamers to see if it could be salvaged and they ended up sending me a new one at a discount.  Thankfully, my old 40 throating reamer was still in it's sleeve covered in a congealed layer of oil and cleaned up nicely.

Most of you know whats involved with fitting a 1911 barrel so I won't bore you with any of the details only to say, it took longer that I thought it would using only hand tools and no milling machine.  Chambering and throat reaming were also uneventful and went as expected.

I now have test loads ready consisting of:
once fired FC headstamp brass
CCI 550 SPM primers
180 gr Star JHP bullets loaded out to 1.250
test loads of Blue Dot of, 9.2, 9.6, 10.0 and 10.4
As soon as the current cold, snow and rain blows out of here, I'll be able to head to the range to test.  Hopefully by this weekend.

If your still reading this I'm sorry it's so long and without pics.  In my old age, I can be a bit long winded and since Photobucket started charging, I still haven't found a free pic hosting site I'm happy with.
I wasn't sure where on the forum to post this but since it involved fitting a new barrel, I chose the gunsmithing section.  Mods can move it to wherever seems appropriate.

Jeff

[sqlbullet]

Good write up.  I made it through even without pictures.

Excited to hear the results.

[Kenk]

Hey Jeff, a great write up to be sure. For me, and my range of choice, it's 40 acres of woods and hayfields (mainly hayfields) and would guesstimate I lose 50 to 70% of my 10mm brass, and Yes, an expensive and unfortunate fact, however I love this location, and the only cost is, right, the loss of my dandy new brass. I am currently working with my good friend and property owner on a plain to clear a 30 x 30 area, still possibly to small, and then put sand down. The best of success with your endeavors

Ken

[fltbed]

Test results
It was a beautiful clear day today here with temps in the mid 50s no clouds and next to no wind.  When I got to the range I realized I forgot to bring any targets.
Oh well, this was more of a chronograph day anyway.

I found some of my old competition ammo from back when the power factor was 175, then some more from later, when the power factor was lowered to 165.  So, I packed up my old FrankenPara Limited gun to compare them as well.

This ammo is all loaded to 1.200 OAL
Date: 1997
180gr Montana Gold
6.1gr WSF
Win Small Pistol Primer
Velocity:  FrankenPara 1010f.p.s. PF 181.8   RIA/KKM  1053f.p.s. PF 189.5

Date: 1998
200gr Star FMJ
5.4gr WSF
Win small pistol primer
Velocity:  FrankenPara  901f.p.s. PF 180.2  RIA/KKM  948f.p.s. PF 189.6

Date: 2011 (current load)
180gr Bear Creek TC coated lead
4.8gr WST
Rem 1 1/2
Velocity:  FrankenPara  955f.p.s. PF 171.9   RIA/KKM 1001f.p.s.  PF 180.2

The velocities were a little higher due to WSF, and more so WST, being reverse temperature sensitive.  If the temps were in the mid 90s, all those velocities would be about 30-40f.p.s. slower and much closer to the minimum Power Factor.
Also, don't read into the velocity differences between the new KKM barrel in the RIA and my old Limited gun.  The Bar-Sto barrel in my FrankenPara has around 60K rounds through it.

Now, what you all have been waiting to hear.  I'm gonna stamp this Barrel 40XL because it's just a SAMMI min spec 40 S&W chamber with the throat cut extra long.
Following loads are using once fired 40 S&W FC cases,  a Star 180gr JHP loaded to 1.250, with a CCI 550 mag primer and Blue Dot powder.  5 rounds of each.

9.2gr   1049f.p.s. ES 162 SD 68
9.6gr   1135f.p.s. ES 64 SD 24
10.0gr 1189f.p.s. ES 23 SD 11
10.4gr 1243f.p.s. ES 21 SD 10  OVER MAX! 

These numbers were all a bit confusing and I'm gonna do this ladder test over again with weighed charges in 0.2gr increments on my Chargemaster vs thrown charges on my progressive.  The 10.4gr load was a bit unsettling as three cases had Really flat, cratered primers and the other two were pierced.  I'm also concerned about bullet set back while feeding.  I saw no indications of it when testing them here at home, but I'm gonna hold off on more testing till I can get a LEE undersized sizing die.

I'll check back with more results.
I hope you've enjoyed this journey as much as I have.

Jeff

[Kenk]

For sure Jeff, Thanks for your continued efforts. As always, many can / will benefit from data such as this

Ken

[my_old_glock]

http://10mm-firearms.com/general-discussion/40-sw-deep-throat/



.

[gnappi]

Funny...

" I found a 5 1/4" stainless KKM gunsmith fit match 1911 bull barrel short chambered in 40 S&W.  I'm not sure when I picked up this barrel. "


I did the same thing!!!

[fltbed]

http://10mm-firearms.com/general-discussion/40-sw-deep-throat/.

Oh dear Lord, I forgot all about this thread.   I even posted in it!

You win.  I'm stamping the barrel 40 DEEP THROAT!

[The_Shadow]

Thanks for the story and testing Jeff!   

[fltbed]

UPDATE:
The weather finally broke this week with temps today at 70 degrees so, I re-ran the Blue Dot test with weighed charges from 9.8gr-10.4gr loaded with 180 gr Star JHP, lit with CCI 550 SP mag primers, at an OAL of 1.250, loaded in once fired Federal cases.
As always, gun was shot from a rest and targets were at 50 yards.

Chrono results:

9.8gr   1215 f.p.s. / ES 27 / SD 11   7" group
10.0gr  1227f.p.s. / ES 68 / SD 25   5.5" group
10.2gr  1237f.p.s. /ES 24 / SD 10      2.3" group  * 4 into 1"
10.4gr  1236f.p.s. / ES 15 / SD 6 (Primers starting to flatten. Slight tail on firing pin indent.)  5.2" group

With 180gr 10mm loads, Blue Dot seems to have a "sweet spot" of 10.4 gr.
With the 40 Deep Throat, it appears to like 10.2gr.

I don't often post pics anymore but I just had to show off this fluke of a group.


Jeff

[PCFlorida]

Yep, too bad that flyer didn't make it into the group

[Kenk]

Nice job on this Jeff!

[tommac919]

Plus 2 on good job...
Yes 10.4 bd is a sweet spot for 10, soi can see slightly less in 40 as BD has always liked to be near the high end.