DonH, I personally believe you're correct about the development of the coil spring being pursued to facilitate the takedown feature. The actual lock time may even be a little slower with the coil spring vs the 2nd-model flat spring, I've heard that opinion in the past. Pete, I agree about the origin of the Mann-Neidner conversion. From what I've read, a blown or severely cratered primer was a common occurence with the old soft primer cups, sloppy fits and early smokeless powders. These guys HAD to be concerned with the gas-handling properties of their rifles, and the Mann-Neidner conversion proved it would positively prevent gas blow-by back into the shooter's face. It wasn't until around WW2 that John Buhmiller established the actual upper limit of the high wall's strength and gas-handling abilities with the original design, and the earlier smiths quite naturally tended to err on the side of caution. I also believe that Winchester altered Browning's original design intent by increasing the over-travel that's built into the linkage dimensions, thereby ensuring that none of their actions would be what I call properly timed. Some amount of overtravel is necessary in any toggle linkage so that it locks up solidly and doesn't open under pressure, but I believe Winchester intentionally made SURE theirs had enough overtravel! Karl, my definition of a floating firing pin is a pin that's too short to reach the primer when the hammer is fully down, a perfect example is the Colt Government Model 45. When provided with a retraction spring it's known as an inertia pin because it relies upon inertia to be able to strike the primer against the resistance of the spring. This was Ackley's major objection to the M-N type conversion, the fact that some conversions used inertia or floating pins that allowed the primer cups to blow. I first encountered this phenomenon while using the then-new Armalite AR-180 5.56/223 back in the '60s. My very early model had a very strong f/p retractor spring, it was actually strong enough to force the firing pin to the rear against the pressure of the hammer spring. This allowed the primer indentation to be forced to the rear, into the firing pin hole, causing that portion of the primer cup to 'disc' or break out around the edges. The resulting disc was pushed back into the f/p hole and jammed the f/p when the next shot was fired. My ammo obviously had primer cups that were too soft to stand an unsupported f/p hole. I cut two turns off the retractor spring and changed ammo, no more problem. To give a little more background, I've been rebuilding single shot rifles and SA Colts since the late '60s and over the years have encountered just about every example of ill-fitting parts that you can imagine. When pressures are below ~20K psi as in the 44-40, 45 Colt, 38 Special, 44 Special, etc, I dont really worry too much about f/p fit since I've seldom had a primer even crater enough to prevent OK functioning, much less blow out. However the noticably higher pressure (~35-40K) loads in cartridges like the 30-30, 30-40, 357 Magnum, 25-20 High Speed etc require a snugger fit for the f/p nose to prevent cratering and its resultant malfunctioning, or even primer rupture in extreme cases. These cartridges in my experience usually won't blow a primer even if unsupported, unless the f/p fit is GROSSLY loose or the f/p nose is rough or sharp. In 25-20 walls I have found that a large f/p nose will allow the primer cup to actually push the f/p to the rear enough to cause discing/cratering, even when the large f/p nose is a snug fit in its hole and the mainspring tension is high. Also found the same thing in small Martinis when using cartridges with SR primers. Apparently or at least in my experience the small primers are much much worse in this area, almost demanding that they be bushed to a much smaller diameter while the LR primers can be used with f/p noses as large as 0.100" with few if any problems, again in my experience. I personally have found that some unsupported primer cups will blow or disc beginning at ~45-50K according to my best SWAG. In my experience the SR cups are more prone to discing than the LR ones but both will do it. Now, I don't have any pressure-testing apparatus so those figures are merely SWAGs, but they should be pretty close. Most of the old SS rifles I've worked on have had some sort of mechanical f/p retractor. Examples that come to mind are the Winchester, Borchardt, Ballard, Martini-Henry and Remington roller. The trapdoor Springfield does not, and that is a major design/safety flaw. Only one of my Whitney rollers had a retractor, but Whitney was a less-expensive knock-off of the Remington. IMO Frank de Haas' books should be required reading for all single shot enthuiasts. There's more good solid info in just two of his books than in all my dozens of other single shot rifle books put together. EZXs, Joe
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