special and magnum loads, same point of aim

[someguy2800]

I thought I would share some of my experience in finding two loads that shoot same point of aim in the same revolver.

The gun is my favorite companion when I am out tooling around my small property and when hunting. I bought this Ruger SP101 with 4.2" barrel a couple years ago. I slicked up the action by polishing all the internals and shaved on the transfer bar, installed a wolf spring kit and did a trigger job on it. I also customized the front sight as I hated the fiber one it came with.

This is exactly what I was looking for in a "kit gun". Being an SP101 is extreamly compact compared to say a smith K frame, yet its heavy enough to comfortably shoot stout 357 loads and has the sights and sight radius to hit what you want with it. I love it.



Now the goal was to find two loads for it that I could shoot without sight adjustment between the two. I wanted a non expanding 38 special load for plinking and hunting small game such as rabbits and grouse, and a stout expanding 357 load for backup duty deer hunting, or whenever I feel like making some noise.

I started out shooting 158 grain hard cast RNFP for 38 special and 158 jacketed soft points for 357 but found point of aim at 25 yards was a foot apart. After experimenting with different bullet weights in both 38 and 357 loadings to see how changing bullet weight affects point of impact I eventually found the right combo.

The 38 special load is a 125 grain berry's flat point loaded with 4 grains of 700x and a S&B primer which gives 800 fps in this gun. The 357 load is a 140 grain hornady XTP loaded over 18 grains of Win 296 and a federal magnum primer which gives an average of 1225 fps. The 357 load could go higher based on pressure signs and is just under max book loads but this load gives great accuracy and the two loads are exactly the same point of aim at 25 yards.

The 38 special load and the 357 load will both easily group 2" at 25 yards off a rest and I have no problem hitting a 4" steel offhand with either of them at 20 yards. When I practice for deer season I can keep the 357's in a 4 or 5 inch circle at 50 yards with the barrel resting on something. I have taken 1 rabbit with the 38 special load with no meat damage and two deer already with the 357 load. The first deer was a 4 point buck that my wifes uncle shot and we had to blood trail through a willow thicket. I shot it in the back of the head as it was trying to get up from about 15 yards away and dropped it. I also shot a 2 year old doe with it this last year resting on the side of my stand at about 40 yards. Clean shot through the lungs and the bullet passed through. She ran about 100 yards and went down and I put her down with another shot to the head.

Anybody else done any experimenting with this? Post your results

 

[FullClip]

I get a pretty pronounced change in POI when going between .44Mag/Spcl or 357/38. The specials hit higher. But I'm shooting off hand, and not sure if that has any effect. Longer time in the barrel and thus recoil has brought muzzle up higher at time of exit??

 

[gotboostvr]

In my 4" M19 my 125gr TC plated 38 load matches up with my 158gr LSWC 357 load very closely. I don't have the data at hand but it's a pretty standard 38 load and a mid range 357 load velocity wise

 

[Jim K]

When police officers went to +P .38 Special loads, they found that their shots went low, seemingly contradicting the belief that high velocity loads will shoot high, something that every "ballistic table" seems to confirm. Some cops had a theory that the new loads were intended to hit the bad guy in a very sensitive spot between the legs, and render him less, well, rambunctious, in the future. In fact the change was due to less barrel time for the faster bullet, allowing the gun to recoil more and the bullet to strike higher.

The same thing can happen in such a way that a relatively slow bullet will strike higher while a faster bullet will go lower. I think that is what you are seeing here.

Jim

 

[someguy2800]

I get a pretty pronounced change in POI when going between .44Mag/Spcl or 357/38. The specials hit higher. But I'm shooting off hand, and not sure if that has any effect. Longer time in the barrel and thus recoil has brought muzzle up higher at time of exit??

What weight bullet is that with in each load? When shooting 158 grains in both in my sp101 the difference in impact was huge, something like 16 or 18 inches lower for the 357 at 50 yards. This was with a very heavy, very hard recoiling load for an sp101.

When I bench shoot i rest my wrist on a bag and the barrel of the gun rests lightly on a rest. Just enough to steady the gun but not really resting on it so it still recoils naturally.

 

[someguy2800]

When police officers went to +P .38 Special loads, they found that their shots went low, seemingly contradicting the belief that high velocity loads will shoot high, something that every "ballistic table" seems to confirm. Some cops had a theory that the new loads were intended to hit the bad guy in a very sensitive spot between the legs, and render him less, well, rambunctious, in the future. In fact the change was due to less barrel time for the faster bullet, allowing the gun to recoil more and the bullet to strike higher.

The same thing can happen in such a way that a relatively slow bullet will strike higher while a faster bullet will go lower. I think that is what you are seeing here.

Jim

That's exactly what it is. If you put a straight edge on the sights of a revolver, the barrel actually points down from the straight edge to compensate for the barrel rise, unlike a rifle where the sights intersect with the axis of the barrel.

I always wondered about the old pistols you see such as the broomhandle Mausers and SAA's with detachable buttstocks. They must have a totally different point of impact with the stock on I would think.

 

[Rock185]

That is a neat kit gun. Wish my 3" SP101 had adjustable sights. I've never tried to get two loads to shoot to the same POA/POI at 25 yards. Any of my revolvers or semi-autos will shoot to different POIs by 2-3-4-5" at 25 yards just changing bullet weight,design or velocity within the same caliber. To get the 38 Spcl. @ 800 and 357 @ 1200+ to shoot to the same POI at 25 yds.,I just gotta say you must be livin' right

BTW, what grips are those?

 

[Jack B.]

I've always been told and from the slow motion video's I've seen the bullet is long gone from the barrel before recoil starts.

 

[FullClip]

What weight bullet is that with in each load? When shooting 158 grains in both in my sp101 the difference in impact was huge, something like 16 or 18 inches lower for the 357 at 50 yards. This was with a very heavy, very hard recoiling load for an sp101.

When I bench shoot i rest my wrist on a bag and the barrel of the gun rests lightly on a rest. Just enough to steady the gun but not really resting on it so it still recoils naturally.

Oh heck...it's a total mish-mash of everything from powder puff 148 grain wadcutters to fairly hot magnums. It seems the most pronounced in my 8 3/8 Mdl 629, as you said the difference is a foot or more. I just adjust the hold and seem to do OK enough when plinking away at the gravel pit. I leave the sights so the normal mag loads hit at POA and use a little Kentucky windage on the Specials. Guess if I were doing serious target work I'd be more detailed.

 

[buck460XVR]

I've always been told and from the slow motion video's I've seen the bullet is long gone from the barrel before recoil starts.

Dwell time and recoil is why for most handguns, heavy magnum loads impact higher than lighter bullets traveling at the same velocity. It's a very common and well known occurrence. In short barreled CWC guns shooting @ 7 yards, it's negligible, as opposed to long piped revolvers @ 50 yards. Why is it that most fixed sight guns are regulated to a certain bullet weight and velocity? It has nuttin' to do with bullet drop after it leaves the barrel, but the barrel rising from dwell time.

 

[Jack B.]

Dwell time and recoil is why for most handguns, heavy magnum loads impact higher than lighter bullets traveling at the same velocity. It's a very common and well known occurrence. In short barreled CWC guns shooting @ 7 yards, it's negligible, as opposed to long piped revolvers @ 50 yards. Why is it that most fixed sight guns are regulated to a certain bullet weight and velocity? It has nuttin' to do with bullet drop after it leaves the barrel, but the barrel rising from dwell time.

I thought the dwell time phenomenon only occurred in auto and semiauto guns and not in revolvers. Oh well live and learn.

 

[someguy2800]

That is a neat kit gun. Wish my 3" SP101 had adjustable sights. I've never tried to get two loads to shoot to the same POA/POI at 25 yards. Any of my revolvers or semi-autos will shoot to different POIs by 2-3-4-5" at 25 yards just changing bullet weight,design or velocity within the same caliber. To get the 38 Spcl. @ 800 and 357 @ 1200+ to shoot to the same POI at 25 yds.,I just gotta say you must be livin' right

BTW, what grips are those?

I am lucky enough to live in the country so I just have to walk 100 yards from my loading bench to my shooting range which allows me to do a good amount of testing.

The grips are just cheap ones from Thailand I bought on ebay. If you do an ebay search for "jaruwan sp101" you will find them. They fit perfect and are really nice quality but the fitment is for a smaller hand than mine. Oh and it will take a month and a half to get them!

 

[someguy2800]

I've always been told and from the slow motion video's I've seen the bullet is long gone from the barrel before recoil starts.

I've never really looked at them in detail but I bet the muzzle does rise just a mm or two while the bullet is still in the barrel which if you think about it would be enough to move the point of aim by quite a bit.

 

[MrBorland]

I've never really looked at them in detail but I bet the muzzle does rise just a mm or two while the bullet is still in the barrel which if you think about it would be enough to move the point of aim by quite a bit.

Correct. It'd defy the rules of physics otherwise.

Also, the ever popular "dwell time" is a red herring. It's true the lower-velocity bullet stays in the barrel for a longer period of time, but it's also true that the muzzle rises with a correspondingly lower velocity; the result is that muzzle rise between a fast and slow bullet of the same mass is the same. In other words, when considering normal handgun distances, neither velocity nor dwell time affect POI - mass of the bullet (as well as gun mass and barrel length) does, with the heaver bullet hitting higher.

At longer distances, external ballistics comes into play, of course, so velocity will affect POI if you're taking, say, 50+ yard shots.

 

[someguy2800]

neither velocity nor dwell time affect POI - mass of the bullet (as well as gun mass and barrel length) does, with the heaver bullet hitting higher.

Then why does a 158 at 38 special velocity and a 158 at 357 velocity have a totally different point of impact?

 

[Jack B.]

I've never really looked at them in detail but I bet the muzzle does rise just a mm or two while the bullet is still in the barrel which if you think about it would be enough to move the point of aim by quite a bit.

I've been looking at slow motion videos all morning to see if buck460XVR is right about dwell time. Bullet gone before recoil starts in all videos I've looked at auto's and revolvers both.

 

[MrBorland]

Then why does a 158 at 38 special velocity and a 158 at 357 velocity have a totally different point of impact?

I'd not be surprised that some might find some small difference in POI with some ammo and/or some guns, but you're finding a foot difference at 25 yards. Something's ain't right.

Here's a relevant vid on the subject:

 

[someguy2800]

I have 6 or 7 different 357 bullet on hand, if I get a chance this weekend I will do some comparative testing at 20 yards or so.

 

[FullClip]

I'd not be surprised that some might find some small difference in POI with some ammo and/or some guns, but you're finding a foot difference at 25 yards. Something's ain't right.

I wonder if it may be in part caused by unconsciously taking a firmer grip on the magnum loadings?? May be a good self test to have a buddy load the cylinder with a mix of rounds and see what happens.

 

[Jack B.]

I've never really looked at them in detail but I bet the muzzle does rise just a mm or two while the bullet is still in the barrel which if you think about it would be enough to move the point of aim by quite a bit.

Take a look. Lots on youtube . I think flinching is the biggest culprit. I stand by my observations.

 

[MrBorland]

Bullets of the same weight should theoretically print to the same POI, but some find they differ by a bit. I personally haven't found they do. If you find they don't, but worked up some matching loads for hunting, great. No reason not to go with that, though the large POI shift you observe at 20 yards does raise my eyebrows.

When testing, keep in mind it can be tough to get 2 successive groups with the same ammo to print to the exact POI, and this can bias our conclusions when shooting different ammo, particularly if the number of groups shot is fairly small. What you might do, then, is randomly mix 3 .38spl and 3 .357 mags in each cylinder, then note if 3 rounds consistently group differently than the other 3.

Bullet gone before recoil starts in all videos I've looked at auto's and revolvers both
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Take a look. Lots on youtube . I think flinching is the biggest culprit. I stand by my observations.

The movement is small, and our eye isn't particularly good at seeing it. Plus, a lot of these shots involve guns clamped down to steady the muzzle for a good slo-mo shot, so of course the muzzle won't move.

It's also important to recognize that while we perceive recoil after the bullet leaves the barrel, movement while the bullet's still in the barrel (I call it "intrinsic recoil") is real but very small and very quick. Immediately followed by very obvious perceived recoil, it's not likely we'd even be aware of it.

Flinching can, of course, be an issue, and can easily affect the POI between bullet-matched .357mag and .38spl loads.

 

[Jack B.]

Bullets of the same weight should theoretically print to the same POI, but some find they differ by a bit. I personally haven't found they do. If you find they don't, but worked up some matching loads for hunting, great. No reason not to go with that, though the large POI shift you observe at 20 yards does raise my eyebrows.

When testing, keep in mind it can be tough to get 2 successive groups with the same ammo to print to the exact POI, and this can bias our conclusions when shooting different ammo, particularly if the number of groups shot is fairly small. What you might do, then, is randomly mix 3 .38spl and 3 .357 mags in each cylinder, then note if 3 rounds consistently group differently than the other 3.



The movement is small, and our eye isn't particularly good at seeing it. Plus, a lot of these shots involve guns clamped down to steady the muzzle for a good slo-mo shot, so of course the muzzle won't move.

It's also important to recognize that while we perceive recoil after the bullet leaves the barrel, movement while the bullet's still in the barrel (I call it "intrinsic recoil") is real but very small and very quick. Immediately followed by very obvious perceived recoil, it's not likely we'd even be aware of it.

Flinching can, of course, be an issue, and can easily affect the POI between bullet-matched .357mag and .38spl loads.

If the gun recoiled while the bullet was still in the barrel, any heavy recoiling gun would shoot high. I sometimes shoot a 480 Ruger with full house 355 gr. bullet loads at 50Yds. If the gun recoiled while the bullet was in the barrel, how can I even hit the black much less the center of the target, airplanes would be in danger. Think about it. All those big bore handgun hunters would go hungry. But they don't . I stand by my opinion , bullet is out of the barrel before recoil starts.

 

[someguy2800]

Well the laws of physics state that the gun must be recoiling the instant the bullet moves at all. Equal and opposite reaction. The question is how much does it move before the bullet leaves the muzzle for a given load. The sights point up relative to the muzzle very slightly on a handgun to compensate for this.

I was just doing some math and if the muzzle of a 4" revolver rose by just 10 thousandths of an inch the point of aim at 25 yards would change by 2.25 inches.

 

[MrBorland]

If the gun recoiled while the bullet was still in the barrel, any heavy recoiling gun would shoot high. I sometimes shoot a 480 Ruger with full house 355 gr. bullet loads at 50Yds. If the gun recoiled while the bullet was in the barrel, how can I even hit the black much less the center of the target, airplanes would be in danger. Think about it.

You should give Ruger engineers a bit more credit: "Intrinsic Recoil" has been factored into the design. If you look at a revolver from the side, draw a horizontal line between the top of the front and rear sights, you'll see that the barrel is actually pointed down. Think about it.

 

[someguy2800]

Bullets of the same weight should theoretically print to the same POI, but some find they differ by a bit. I personally haven't found they do. If you find they don't, but worked up some matching loads for hunting, great. No reason not to go with that, though the large POI shift you observe at 20 yards does raise my eyebrows.

When testing, keep in mind it can be tough to get 2 successive groups with the same ammo to print to the exact POI, and this can bias our conclusions when shooting different ammo, particularly if the number of groups shot is fairly small. What you might do, then, is randomly mix 3 .38spl and 3 .357 mags in each cylinder, then note if 3 rounds consistently group differently than the other 3.

No flinching and not a small sample size test. I have shot 2 or 3 thousand 38 specials from this gun and probably 600 or so 357 magnums. One other variable I don't think I mentioned is that I don't shoot the same bullets in both loads. My 38 special 158 load is using a commercial hard cast bullet and 357 158 loads are various different jacketed bullets.