Can someone explain to me why an older, well made, all steel frame .38spl revolver are not rated or recommended for +p ammo, but the newer, smaller and lighter aluminum ones can?
Thank you for all the info! Is the higher velocity with .38spl+P really effective out of a short barreled snubbie? I'm curious because I'd rather not deal with the extra recoil and muzzle flash if there is little benefit.I can see there are a lot of misconceptions about the 38 Special. Here's some history that might help ... The 38 Special was introduced in 1902 and for the first several years, it was loaded with black powder and 158 gr LRN bullets. By the time SAAMI was organized in the mid-'20s, all ammo manufacturers had converted to smokeless gun powder in all handgun ammo. SAAMI rated the max chamber pressure at 18,900 CUP back then and that pressure standard remains the same today. When converted from the old CUP pressure measurements to the new psi pressure measurements, a standard 38 Special is now rated for a max chamber pressure of 17,000 psi and a 38+P is rated at 18,500 psi, which is about 10% higher. That doesn't mean the pressures are lower ... just a different way to measure.
What has changed over the years is the availability of different burn rate powders and different bullet weights. If you look in any reloading manual, you will see lighter bullets can be driven to much higher velocities than heavier bullets without exceeding the max allowable chamber pressure. That's why the 110 gr Super Vel ammo above are much "hotter" ... meaning much higher velocity, not higher chamber pressure.
Again if you look at any reloading manual, you will see some powders will produce higher velocities than others. The basic concept is ... faster burning powders develop high initial chamber pressure but because they burn very quickly, bullets do not achieve as much velocity. Slower burning powders maintain pressure longer and increase muzzle velocity without exceeding max pressure ratings.
38+P loads use more powder than standard loads so they will achieve higher muzzle velocity but at a higher chamber pressure. It's not a sales gimmick ... it's a fact. Herein lies the problem with older 38 Special revolvers. All cylinders are heat treated and always have been ... however the alloys used in modern revolvers are much stronger than the same thickness cylinders found in older guns with regular steel cylinders. As such, the older cylinders can not safely be used with +P loads. S&W's change in metallurgy started after the Korean war so to be safe, any 38 Special S&W revolver with a model number stamped in the yoke (started in 1957) have cylinders strong enough for +P loads. As with most manufacturing companies ... S&W used up old cylinder stock so any gun made before 1957 could have a standard steel cylinder but by the time model numbers were issued, all old stock was used up.
ChrisLCR, it's all in the metallurgy.
ikar, Not a problem ... your Mod 15 will safely digest 38+P ammo.
ozo, You need to try a chronograph ... they don't lie and will tell you that more powder always increases velocity ... not necessarily better accuracy though.
ExArmy11b, Don't blame the lawyers on this one ... the older 38 Specials with a 158 gr bullets (smokeless powder loads) only had a MV of 750 fps whereas newer ammo can easily achieve 850 fps with the same weight bullet and barrel length. It's all about modern powder burn rates.