Loads for Destroyer Carbine

[Larry Gibson]

The ratio of a cartridge case capacity to bore capacity is expressed as the expansion ratio (ER) and is a measure of a cartridges ability to do well with slower burning powders with a smaller ER being better for slower burning powders.

The 30-30 for example has an ER of 10.6 to 1 with a 20" barrel.

The 22 Hornet has an ER of 18.8 to 1 in a 22" barrel.

The 25-20 WCF has an ER of 12.6 to 1 in a 20.25" barrel.

The .38 Super has an ER of 40 to 1 in the 21.4" barrel of the Destroyer.

While 4227 are usually very good powders in the 22 Hornet and 25-20 WCF because they are at 100%. Since the load density of 4227 is very low (around 50 60%) the ER shows us 4227 is not the best powder in the 30-30 and a slower burning powder would perform better.

In the .38 Super in the Destroyer the very high ER tells us, in theory, that a faster burning powder is needed than 4227. And so it works out in reality. A case at 100% load density under a 90 gr jacketed bullet is a very poor performer during the internal and external ballistic phases.

Larry Gibson

[bruce drake]

Jeff,

Here is a little bit of information on the Destroyer Carbine. I wish you luck on the search. THey are a cute carbine. I had one a few years back that had a bad extractor. I had to file one out of barstock and heat treat it (I actually had to file two. I didn't heat treat the first one and it cracked a few months later and I had to make another)

http://www.9mmlargo.com/destroy/index.htm

Bruce

[batjka]

Well, in my quest to find good 9mm long-barrel loads I went to KTOG page. There are loads there listed for Sub 2000, which are blowback carbines with 16" barrel. I found some info there that I would like the experts to check out. Would same load but in bigger Largo case be safe in a Destroyer?

"I chronographed ten rounds of the new 9mmSUB loads that had 9.2 gr of Longshot powder pushing a 90 grain Hornady V-Max JHP achieved an average of 2020 fps, with a maximum of 2060 fps, which I'm claiming on behalf of crazy people everywhere as a new SUB speed record. That equates to 848 ft lbs of kinetic energy, For comparison purposes, this far exceeds the PLR-16 kinetic energy, but is a bit less than an M-4 carbine.

The same load of 8.6 grains of Longshot that averaged 1883 fps last time had a single shot of 1888 fps this time. I had a few issues setting up the chrono, so only chronoed a single round from the previous record load."

Please do comment. It seems pretty awesome to get rifle velocities out of a blowback pistol-caliber weapon without exceeding pressure limits. I think I need me some Longshot.

[batjka]

Larry Gibson,

Any comments on the Longshot load I listed above? It looks great, but I would like an expert's opinion on it. It seems to me like the chamber pressure for 9mm Largo would be lower than for 9mm Para with the same load. That due to Largo case being larger. Would it be safe to fire in a Destroyer?

[Larry Gibson]

Well......that seems awefully warm for a 9mm sub gun. Might get that velocity but what is the bolt velocity coming back and how long with the subgun sustain that without breakage? Anyones guess?

As to Longshot working in the Destroyer? Probably would be a good powder to try. I haven't though so I don't know. I would certainly start at starting loads for the 9mm or the 38 Super and work up carefully though. Longshot's burning rate is just slightly faster than BlueDot so it is in the ball park for good performance in the Destroyer. However, I've not used it and have no idea of the loading density.

Let me say this about pushing the pressure limits of any cartridge in the Destroyer. What the quality of the steel used to make them or what the heat treating was is anybody's guess. While I have pushed the performance level slightly above the 38 Super +P levels I'm not sure I would want to "on behalf of crazy people everywhere as a new SUB speed record for the Destroyer. I really don't think a 90 gr HP at 2000 fps is going to explode any quicker than the same at 1800 fps considering the velocities they are made for. Same goes for most any 9mm, 38 SPL or even 357 magnum bullets. Just suggesting anyone be judicious and careful in pushing this little cartridge in the Destroyer.

Since initially playing around with and working up those HV loads all of the loads fired out of my Destroyer have been a mild 3 gr of Bullseye or WST under the Lee 356-120-TC cast bullet for a sedate 965 fps and excellent accuracy.

Larry Gibson

[Gtek]

That is what pushed me to 45 A.C.P.. Leaving the 28-30K psi world down to 17-18K. The top radius was kind of close front to rear bridge, cleaned up for scope bases. The receiver I have appears to be just harder than butter. Run a good file on bottom and ask yourself how fast do you want to go. Gtek

[batjka]

Can you give us more details about the conversion? I'm curious on how you've done the magazine well, barrel, etc. Photos would be nice, too.

As far as the receiver goes, could one heat treat it to bring it to the appropriate hardness level?

I'm still toying with the 2400 idea. Larry, if you had tried it, can you tell me what the velocities were? I know you've said the loads weren't good, but still.

Thanks

[Gtek]

Conversion- Some completed, some still in head. Barrel was straight forward, straight wall rec makes removal / install a lot easier. I have most tools so that makes things a little smoother. First was to modify bolt, cutting off handle for low scope mount and to allow fitting in lathe. Machine bolt face to .482", then fit extractor. I then cut a .125" wide by .125" vertical into bolt handle stub for fab of bolt handle which I plan on machine screw attach. Match thread cut on barrel leaving .200" to bolt face for a.c.p., straight forward barrel job. Top radius of bridges were off, rather than spend time chasing radius with fixture, I just black sharpie top and 600 wet on plate- slow and low and measuring off bottom flat of rec I am within a couple, drilled and tapped for weaver steels. Cut stock off at front band line, wrapped barrel with sand paper and fitted channel. Mag well is still to be done, I am leaning toward a poly strip in rear for make up of smaller mag dimension. Magazines will be easy, just cut slot on rear wall. Still need to cut chamber and tighten barrel. The plan is to finish mechanical, epoxy bed stock and shoot ugly. If all goes well, barrel is at 1 inch, remove and flute, green park everything, paint stock this really cool speckled green Krylon I saw and screw thumper tube on and sight in. With the other eight bizillion projects, maybe Xmas- who knows. Gtek

[Artful]

Conversion- Some completed, some still in head. Barrel was straight forward, straight wall rec makes removal / install a lot easier. I have most tools so that makes things a little smoother. First was to modify bolt, cutting off handle for low scope mount and to allow fitting in lathe. Machine bolt face to .482", then fit extractor. I then cut a .125" wide by .125" vertical into bolt handle stub for fab of bolt handle which I plan on machine screw attach. Match thread cut on barrel leaving .200" to bolt face for a.c.p., straight forward barrel job. Top radius of bridges were off, rather than spend time chasing radius with fixture, I just black sharpie top and 600 wet on plate- slow and low and measuring off bottom flat of rec I am within a couple, drilled and tapped for weaver steels. Cut stock off at front band line, wrapped barrel with sand paper and fitted channel. Mag well is still to be done, I am leaning toward a poly strip in rear for make up of smaller mag dimension. Magazines will be easy, just cut slot on rear wall. Still need to cut chamber and tighten barrel. The plan is to finish mechanical, epoxy bed stock and shoot ugly. If all goes well, barrel is at 1 inch, remove and flute, green park everything, paint stock this really cool speckled green Krylon I saw and screw thumper tube on and sight in. With the other eight bizillion projects, maybe Xmas- who knows. Gtek

You should definitely document your build - this is even more work than converting SMLE to 45 ACP - as I remember the .gov bought some destroyers that had been converted to 45 for Vietnam issue.

[Hugo Stiglitz]

Got two of them. had the firing pin rebuilt on one. That gunsmith is no longer able to do that do to macular degeneration. Here are mine. Yes I still have them ans shoot them often! https://www.smithandwessonforums.com...e-9-largo.html

[Stephen Cohen]

I have never seen one in such fine condition let alone two, fine looking firearms Sir. Regards Stephen

[abunaitoo]

I've been playing with my Destroyer in another thread.
Started with Unique, tried W231, and now on HS6.
So far HS6 seems to be the best powder.
I'll be trying some SR7625 and HS7 next.
Probably some Blue dot then 2400 next week.
Had to make shells out of 9mm Mag because the chamber is so long.
Longer shells made a big difference.
Fun little rifle.