[ChrisLCR]

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?

 

[LAGun]

It is all in the heat treating of the cylinder.The older cylinders were not treated to withstand the new ammunition pressures...

 

[ikar]

I checked with S&W about using +P ammo in a model 15 I was looking at. They said it could be used but only a small amount. Maybe a box and not all at the same time.

 

[ozo]

My personal view.....
I see all +P ammo as a marketing gimmick
more than an improvement in the product.
Not just from a safety factor in older guns.
I have reloaded since 1970 and when I buy a
new gun that I load for, I make 5 rounds, bump
the charge up a hair, make 5 more, etc. and
work up an accuracy load.
Sometimes more powder means less accuracy,
and in short barrels, it doesn't always mean more
energy and speed.
In a snub-nosed .38 I see no benefit in +P ammo
and the regular ammo is more than sufficient.

 

[ExArmy11b]

I can't believe S&W told you that only a small amount of +P should be used in a Model 15?!?! That Model 15 will handle all the +P you care to feed it......

S&W maintains that any "model number" revolver can handle any +P .38 Special, but I think they use this as a "CYA" cutoff. I see no reason why, for example, a S&W M&P .38 made in 1956 can't take .38 +P but a Model 10 made in 1957 can.......

The early S&W M&P's, made approx. 1920 and prior, did not have heat treated cylinders.

The fact is, ammo has been downloaded over the years due to lawyer CYA stuff, so I would wager that a so-called .38 Special "+P" round made today is probably only a little hotter, if at all, than the standard .38 Special made in the 1950's.

I had some Super Vel 110 gr. HP .38 Special, from the 1960's (before Super Vel was bought by another company) and this stuff is hot, more like a light .357. It's not even branded as "+P", it's just .38 Special. My gun dealer had some old boxes of it, so I bought 2.......I saved one full box for my .38 ammo collection and shot up the other box, except for 6 rounds that I use for CC occasionally. Since it's HOT, and uses a 110 grain bullet it's horrible for forcing cones, so I wouldn't shoot too much of it.

This stuff is gold if you can find it, but I don't like to trust ammo this old for life and death scenarios........it's more collectible and "vintage" now. I do want to try some of the .357 if I can find it, I bet that stuff is spicy

I love the "Police Only" mark on the box, I collect and own a LOT of ex-police revolvers, so this ammo would fit great into my collection.

My point is, factory ammo is no where near this hot these days, so the whole designation of ".38 Special +P" more or less means ".38 that's just a little hotter", but many people think it means .38 that's much more powerful.

My dealer had a box of the .38 +P+, I would imagine it to probably be on par with the Super Vel .38. I think I fired some .38 +P+ years back, through my S&W 67-1 but without a chronograph, all I could tell is that it seemed pretty hot but not .357 power levels.

 

[Iowegan]

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.

 

[kingpins9]

Don't forget about metal fatigue also. Metal actually becomes weaker after many years and more rounds downrange.

I only carry +P ammunition for SD in a revolver. Not to target practice, etc.

 

[ChrisLCR]

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.

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.

 

[Iowegan]

ChrisLCR, Yes, 38+P ammo is more effective in a snubby. There are several factory loads especially designed for snubbies. Most use a 135~140 gr bullet and pack quite a wallop. I guess it's up to you .... is the extra benefit of more power worth more recoil and muzzle flash???

Here's a good example: Speer Gold Dot Short Barrel Ammo 38 Special +P 135 Grain Jacketed

This ammo is too expensive and not too comfortable for casual target practice but is a great load for self defense.

 

[gfw1985]

Since my wife purchased a new S&W Airweight 38 Special today, I read the owners manual and +P can not be used in K frame revolvers made prior to 1958. +P+ should not be used in S&W firearms period. Their words, and barrel is stamped 38 Special +P.