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Old February 25, 2013, 06:37 PM   #1
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.38 Special Derringer Load Suggestion

Just bought a Lyman -Ideal 358-72 dbl cavity mould,bought a 2 shot deringer for backup and wish to load the 115gr RNPB bullet it casts with wheelweight aloy at .362,this is a Cobra 38 Spl deringer so no +P loads can or will be a choice,presures must be kept at factory psi for the 38 Spl. and cant seem to find a listing for the bullet I have chose to cast,they will be lubed with Lee liquid alox,have 2400,Bullseye,Unique,H-110 and a few more .
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Old February 26, 2013, 12:17 PM   #2
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I would suggest starting with Bullseye for a couple of reasons. One is that derringer barrels are so extremely short, it's one of the few cases where small ignition inconsistencies in slower powders can result in very irregular muzzle velocities because of the bullet's exact location at the pressure peak varying. The same issue comes up in snubnose revolvers and requires either faster powder or a benchrest shooter's level of attention to using matching cases with matching case load histories, how primers are seated, how cases trimmed to get exact crimp consistency, not to mention getting cylinders reamed so the chambers match. A lot of bother. Quick powder is less affected by performance variation issues.

The second reason is the light weight of the bullets. A light bullet, even at .38 Special pressures, will accelerate pretty quickly. That causes rapid space expansion that can cause a slower powder to fail to burn efficiently. As a result you get a lot of muzzle flash and blast but may not get good velocity consistently.

To get any further requires more information. How long is that bullet? How much of it will stick out when seated so the front edge of the crimp groove is just a crack over level with the case mouth, where it should be for a good crimp? Without that information, I can say with good confidence that 3.0 grains of Bullseye will be safe, as it is safe even with flush seated 148 grain Wadcutters. I'm going to guess that an upper load of 4.5 grains would be safe, based on it being a maximum in 125 grain lead SWC loading data. How much higher you might go depends on the details.

Also, with Bullseye, as with other fast powders, once it nears maximum pressure, very small changes in the charge weight have bigger effects on pressure than is the case at lower pressures. The number of additional psi you get grows exponentially with the charge weight. So if you are going to load right up to maximum with one, rather than middling, you should consider weighing the charges individually.
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Old February 27, 2013, 02:02 AM   #3
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Thank you,verry helpful information,depending on my type of mix and most likely will use strait wheelweights will determine bullet weight but little is said for a cast roundnose plain base bullet in 115grs and as you stated short barrel and getting a good burn the faster powder is a good idea for starting !
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Old February 27, 2013, 04:54 AM   #4
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Yes, a relatively fast powder with a mild to mid charge, is what I would use. Win 231 would be another good choice, even Titegroup, if you have some.
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