I have been working on this project for some time now and thought it might be interesting for the forum to hear the report.

I have wanted a 10mm for a long time, but I did not want a glock, I already had a 1911, and did not trust Tanfoglio.

After some searching, I learned about the 40 super, which is a wildcat cartridge that uses common 45 acp platforms with a barrel and spring change. I did not have a Sig, and learning that the Sig 200 45 acp was one of the original platforms for the conversion, I decided to go that direction.

I bought a used West German 220 on gunbroker for $550; it was in excellent, almost new shape. I then asked www.efkfiredragon.com about conversion barrels. They keep the 400 corbon conversion barrel in stock for $190, but they used to produce the 40 super, so they agreed to prepare the 40 super for $245. Not bad for a very high quality stainless barrel. It is extended and ported. It took about 60 days for the production.

Starline makes the brass, and Redding makes the dies ($68 at Midwayusa).

The EFk Firedragon barrel dropped right in. I used the same recoil rod but used the strongest recoil spring for the 220.

It actually took a long time to work up the loads. The available information suggests using slow pistol powders such as Accurate #9 and h110, but these proved too slow. I tried HS longshot, 800x, and finally settled on HS-7, a powder no longer in production. This is the same powder that I had great success with on my other bottleneck experiments--7.62x25 and 32 NAA.

Using 165 grain fmj and Golden Sabres, I slowly worked up the loads. I used CCI small rifle primers. The HS-7 power curve or burn rate seemed just right. It did not recoil abruptly like the longshot or #9, but had a slow workup, more like the 45 acp than my other 40 s&ws.The recoil was less than my CZ 40s and slightly sharper but less perceived recoil than with the 45 acp barrel in the 220. The porting makes a big difference.

I ended up with a load of 14.2 grains with the 165 gr golden sabres. This load averaged just under 1400 fps, with a fairly low standard deviation. That makes for about 700 foot pounds of energy, lots of momentum, and a high KO number. When I pushed the load up above 1400 to 1425, I began to get some pressure signs with the primers. This performance is equal to or slightly above the 10mm. I have achieved my goal.

I have not done accuracy tests, but they should be fine.

Here are some pictures.

sounds interesting.

bltmonty, to 10mmTalk!

Very nice write up on your conversion of the SIG West German 220 to 40Super.

Congradulations with the project!

I was under the impression that the West German Sigs used the lighter sheet metal slides vs. heavier milled slides on US made Sigs.

Would the lighter slide be a safety or reliability issue for P220 10mm conversions ?

This will be an interesting question, and I am watching it carefully. I am not sure if the American slides are milled or not, but I do know that I had to choose between the alloy frame and stainless frame. I chose the alloy because I want to carry it. I am guessing that the steel frame also has steel slides.

I am not sure how the slide wear will be a factor. I am shooting lighter bullets than 45 acp, and the porting reduces the recoil significantly. In addition, the starline 40 super brass is incredibly strong, much like rifle brass, and 2-3 times stronger than 45 acp brass. So the porting, lower bullet weights, and strong cases means that the gun should be both safe and not cycle too hard. The slide is not ramming hard when shooting. I am also not using maximum loads--just enough to reach some ballistics goals.

Ejection distances has been somewhat inconsistent, but functioning has been 100 percent so far.

I think the slower pistol powders for 40 super might help--HS-7 instead of W231 or #5, which I use for the 45 acp.

I actually plan to practice using the 45 acp most of the time, but use the 40 super for hunting and ccw situations needing better penetration and power.

Nice write up. But no pics.

For reference purposes, here is a link to a Sigforum thread that shows pictures of the sheet metal manufacturing process.
http://sigforum.com/eve/forums/a/tpc/f/430601935/m/30710801

If .40 Super is used sparingly with light bullets the sheet metal slide should hold up. Although a milled slide with its extra mass would provide a higher safety margin for hot and/or heavy loads, and probably make the ejection distances more consistent.

Fun-to-none.......I have several Sig pistols and seldom shoot the P-226 model in a 40 cal. I was wondering if this conversion would indeed work on my American made Sig? I have a couple of Glocks in 10mm but want a Sig more so than a Kimber in a 10mm caliber pistol.

This is a follow-up on my p220 sig conversion. I have put about a thousand rounds and see no unusual wear. It is very accurate and 100% reliable. I could push the numbers of the 40 super load higher but don't need to. I don't know the differences between w german and american sigs, but my german one is doing great.

I have plenty of 40 Super load data if you need it. I developed it for Triton when they brought out the cartridge in 1998.
It's the same data that Triton had listed on their website when they were in business.

HS-7 works OK for lighter bullets, but AA#7 is really the ticket for the 40 Super. It's dirty but it performs the best.

Shoot me an e-mail at Rumore@Tromix.com if you want the data.

Tony Rumore
Tromix Corp