44 spl reload groups fly high

[rockquarry]

Can anyone name or cite a reference that explains the science behind the "hang time" or "dwell time" theory?

Sounds like sterile textbook esoterica rather than something useful, but I'll not criticize something I'm unfamiliar with. While they may have true worth, I doubt they are among the most important aspects of developing a good load.

 

[geekeye]

Can anyone name or cite a reference that explains the science behind the "hang time" or "dwell time" theory?

not needed. just balance your revolver upside down on its sights and look at the barrel; it will not be parallel to the table, it will be higher at the front sight than the rear. this is because, unlike a delayed blow-back semi auto, revolvers start to rotate from recoil immediately after ignition (before the bullet leaves the muzzle).


it's possibly misleading to attribute this to dwell time or muzzle velocity, but certainly heavier bullets causing more recoil will hit higher, while lighter bullets causing less recoil will hit lower.


in my 442 with fixed sights the difference in POI between 110 grain bullets and 158 grain bullets is pretty extreme (even with the short barrel). i'm talking about 3" at 7 yards (with the 110s hitting low).

 

[Forrest r]

Can anyone name or cite a reference that explains the science behind the "hang time" or "dwell time" theory?

Sure, how about the watered down version.

Hang time is for farts, they can be up to 30* methane. Hence the more methane, the longer the hang time in the room.

Dwell time is the amount of time the bullet spends in the bbl.

 

[STORMINORMAN]

Hang time...?

Sure, how about the watered down version.

Hang time is for farts, they can be up to 30* methane. Hence the more methane, the longer the hang time in the room.

Dwell time is the amount of time the bullet spends in the bbl.

"Hang time" sounds like what you don't want to hear the deputy say when he brings you your breakfast...?

Hang Ten! on your board is Kool!

Cheers!

 

[scattershot]

Great thought - thanks! On the other hand, I was thinking the opposite - that the heavier bullet should drop more quickly and group lower than the lighter commercial rounds. Just want to be sure I'm not doing something wrong in the reloading process. If the rise of the groups is consistent with this load, it will be easy enough to adjust my aim point.

It has to do with dwell time in the barrel. It’s normal, just adjust your sights.

 

[pasound]

With fixed sight revolvers, front sight up or down is important to learn when changing ammo weight.

 

[k22fan]

Can anyone name or cite a reference that explains the science behind the "hang time" or "dwell time" theory?

While we've explained it apparently you are not convinced. How about a little simple evidence. 4" Model 19s & 66s use 0.145" rear blades. 4" Model 15s and 67s use 1.10" blades, 0.035" lower. The higher blades on the magnums raise bullet impact. With the same blades and same up & down sight adjustment the faster magnums would hit lower than the .38s.

After the revolvers are sight in then the longer the range the more import bullet trajectory becomes but the original poster was only asking about short range.

 

[Rogeronimo]

Can anyone name or cite a reference that explains the science behind the "hang time" or "dwell time" theory?

Don't take our word for it, slow the powder down, and speed the bullet up ... report back.

 

[Jellybean]

While we've explained it apparently you are not convinced. How about a little simple evidence. 4" Model 19s & 66s use 0.145" rear blades. 4" Model 15s and 67s use 1.10" blades, 0.035" lower. The higher blades on the magnums raise bullet impact.

k22fan, thank you for taking the time to help me through this.

The purpose of the sights are to put the line of sight at the point of impact at a given range, they don't really change the bullet impact. If the magnums need higher sights wouldn't that indicate the point of impact is higher than the specials in relation to the bore axis instead of lower?

Raising the velocity of a bullet does make it leave the barrel faster, but it also increases the velocity of the revolver in recoil so there is not that much difference in the angle of departure at the time the bullet leaves the bore. The formula I've seen for calculating muzzle jump doesn't include velocity data for this reason, only the weight of the bullet, revolver and powder charge and distance the bullet and powder charge passes through the bore.

I'm not saying this formula is perfect and that's what I'm trying to find out, is there some real science or not?

 

[k22fan]

[...] If the magnums need higher sights wouldn't that indicate the point of impact is higher than the specials in relation to the bore axis instead of lower? [...] I'm not saying this formula is perfect and that's what I'm trying to find out, is there some real science or not?

Remember, when we are not sighted in we move the rear sight in the direction that we want our group or POI to move. Firing magnums a Model 19/66 with the sight rear blade from a .38 special would have hit low. S&W went to taller blades on the magnums to get them sighted in with the rear sight in the middle of its adjustment range. Probably that was done by trial and error. It's more mechanical engineering than science. There's so much variation in shooters' grip and muscular resistance to muzzle rise that I doubt there could be a formula that deserves to be called science.

 

[dogdoc]

Can anyone name or cite a reference that explains the science behind the "hang time" or "dwell time" theory?

This is common knowledge among serious handgun users evidenced through simple use. Try it on a ransom rest if you think different or even off sandbag rest. If you just think about it, it makes sense. No “study “ needed. Slower heavy loads allow more recoil(muzzle rise) before bullet leaves barrel. Recently had to put higher front sight on a ruger super Blackhawk so I could shoot midrange loads to point of aim.

 

[Jellybean]

k22fan,
I thought about the sight blade height difference this morning and realized you were right about the magnums shooting lower instead of higher. It's going to be awhile before I can dig a .357 out of the safe and get to the range but it will be interesting to see.
Thanks again for your time.

dogdoc,
I wish I had a ransom rest. It's been about 25 years ago, but when I did test shooting different velocity loads using the same bullet and focusing on holding the revolver the same way each time, there was little difference in vertical spread. Heavier bullets compared to lighter ones did make a noticeable difference as expected.

Thanks to everyone that responded to my question.

Waxter60, I didn't mean to hijack your thread, just trying to find some good reading material.

 

[nbedford]

My Ruger BH 41/2" shot near the top of the target - load was a 240 grain Speer swaged SWC - .430" and using 6.5 grains of Unique. I did not do all the formulating as indicated above; just upped the powder charge to 6.8 grains. Shot to point of aim then. It is called dwell time. The longer it is in the revolver the more it will shoot high. BTW with 6.8 grains it was running 894 fps.

 

[rockquarry]

k22fan,
I thought about the sight blade height difference this morning and realized you were right about the magnums shooting lower instead of higher. It's going to be awhile before I can dig a .357 out of the safe and get to the range but it will be interesting to see.
Thanks again for your time.

dogdoc,
I wish I had a ransom rest. It's been about 25 years ago, but when I did test shooting different velocity loads using the same bullet and focusing on holding the revolver the same way each time, there was little difference in vertical spread. Heavier bullets compared to lighter ones did make a noticeable difference as expected.

Thanks to everyone that responded to my question.

Waxter60, I didn't mean to hijack your thread, just trying to find some good reading material.

Regarding a Ransom Rest, just one opinion...I bought one years ago, along with a windage base and a number of inserts. I used it a lot, at first.

I found that learning good benchrest technique and using good equipment will allow a shooter to duplicate at twenty-five yards what a Ransom Rest is capable of at fifty yards. The late Al Miller, long-time editor of HANDLOADER and RIFLE magazines mentioned this in an article. I was skeptical until trying the procedure and verifying that Miller knew what he was talking about.

The big advantage of the Ransom Rest is that it will never suffer shooter fatigue, something that unfortunately affects us all. Group sizes enlarge without us realizing that we are tired when we shoot from a benchrest. Best to quit before this happens if we're interested in meaningful groups.

 

[Waxster60]

k22fan,
I thought about the sight blade height difference this morning and realized you were right about the magnums shooting lower instead of higher. It's going to be awhile before I can dig a .357 out of the safe and get to the range but it will be interesting to see.
Thanks again for your time.

dogdoc,
I wish I had a ransom rest. It's been about 25 years ago, but when I did test shooting different velocity loads using the same bullet and focusing on holding the revolver the same way each time, there was little difference in vertical spread. Heavier bullets compared to lighter ones did make a noticeable difference as expected.

Thanks to everyone that responded to my question.

Waxter60, I didn't mean to hijack your thread, just trying to find some good reading material.

No worries, we're all learning together - thanks!

 

[dogdoc]

Regarding a Ransom Rest, just one opinion...I bought one years ago, along with a windage base and a number of inserts. I used it a lot, at first.

I found that learning good benchrest technique and using good equipment will allow a shooter to duplicate at twenty-five yards what a Ransom Rest is capable of at fifty yards. The late Al Miller, long-time editor of HANDLOADER and RIFLE magazines mentioned this in an article. I was skeptical until trying the procedure and verifying that Miller knew what he was talking about.

The big advantage of the Ransom Rest is that it will never suffer shooter fatigue, something that unfortunately affects us all. Group sizes enlarge without us realizing that we are tired when we shoot from a benchrest. Best to quit before this happens if we're interested in meaningful groups.

Same with me. I used my ransom rest a lot years ago and now not so much. I have a 4 inch 29-2 with an orange front sight insert that my older eyes cannot focus on well. I think I will dig it out for some load testing with that revolver! Great to have one when you want it

 

[Jellybean]

The purpose of the ransom rest is to remove the biggest cause of error, the human element. When developing loads for my varmint rifles I could shoot them from the bench with the only contact between me and the rifle being the tip of my finger. I couldn't do that with the handguns so I'd shoot more loads for each step in working up a load to help weed out errors caused by my holding the handgun.

On the issue of the blade height, I finally pulled a model 19 and a 67 out of the safe and compared them side by side. I never noticed how short the 67's sight blade was before, but that didn't explain why it was shorter and haven't found anything else that explained it.

Then I thought about k22fans comment:

...4" Model 19s & 66s use 0.145" rear blades. 4" Model 15s and 67s use 1.10" blades, 0.035" lower. The higher blades on the magnums raise bullet impact. With the same blades and same up & down sight adjustment the faster magnums would hit lower than the .38s.

...and decided to take a closer look at the sight blade heights of the "other" magnums compared to their non-magnum counterparts since their sight blades should be higher also for the same reason.

According to my S&W Parts List Manual, the model 29 and the model 24 both use .146" sight blades for the 4" and 6" revolvers. The model 48 uses a .126" sight blade on the 4" revolver while the 4" model 18 uses a .136" sight blade, while the 6" and 8 1/2" model 48 and 17 both use a .146" sight blade.

Also, the 2" model 15 and 2 1/2" model 19 both use a .146" sight blade so I don't believe the shorter sight blade on the 4" model 15 and 67 has anything to do with "dwell time".

 

[STORMINORMAN]

What ever happened to the o'l Kentucky windage...?

Up or down, left or right...?

Cheers!