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How much bullet momentum (bullet weight x velocity) needed to reliably knock down targets?


Mysterious Stranger

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I think it is generally accepted that it is a bullet's momentum (weight x velocity) that knocks down a knock-down target.

 

How MUCH momentum is needed?

 

I am asking because the only powder I can get for my CAS loads right now is TiteGroup, and testing loads with one of my two handguns seems to show that the preferred load for accuracy is one that delivers a 158g Hornady swaged bullet with only about 680 fps velocity. In fact, the testing seems to show that the HOTTEST load that Hornady recommends for this bullet weight with TitGroup generates 900 fps , BUT my handgun (a) only egnerated a bit over 800 fps with it, and seems to HATE that load (really poor accuracy).

 

Will 158g x 680 fps = 107,440 power factor be sufficient to knock down the targets?

 

Jim G

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That’s a heavier load than a number of shooters run. More than a few are running around that speed, or even a bit slower with 105 or 125’s. 

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Just now, Buckshot Sheridan said:

That’s a heavier load than a number of shooters run. More than a few are running around that speed, or even a bit slower with 105 or 125’s. 

 

And those lighter loads still knock down the targets? Wow, then I should be ok! I would personally PREFER a stronger load that woudl be more "in the spirit" of real Old West cartridges, but if it works, I guess that's fine.

 

Jim G

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SASS says knockdowns should go down with a factory .38 Spcl.  That would be 158gr at I don't know what velocity.  But most knockdowns I've seen around these parts tend to go down easier.  Most people's regular main match .38's which are much lighter, take them down if hit center or higher.  Some people have "knockdown loads" in their guncart.  My 125gr bullets with 3.2 gr of various powders have no problems.  But if you travel much and/or are a serious shooter, it might pay to be prepared for tougher knockdowns.  My 125gr with FFFg BP knock them down with authority.  

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IIRC the general consensus was a 158 gr LRNFP bullet at 750 - 800 f/s hitting a popper mid height

in the round part was the calibration standard.

 

I might be off by a few f/s or so but generally I think that would work . . .

 

SC

 

 

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Your question is impossible to answer.  No one knows the height, weight, condition, wind direction and strength, etc. of the falling target you are shooting at.  If you think someone can say a 158 grain bullet at 650 fps is not sufficient but a 158 grain at 675 fps is sufficient you are mistaken.

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2 hours ago, Jim Gnitecki said:

...

Will 158g x 680 fps = 107,440 power factor be sufficient to knock down the targets?

 

That would be a power factor of 107.44

Quote

Power factorBullet weight (in grains) times the velocity (in feet per second); divided by 1000. The minimum standard in all SASS matches for smokeless categories is not less than 60 and no velocity less than 400 fps. Maximum velocity for revolvers is 1000 fps. Maximum velocity for rifles is 1400 fps.

SHB p.44 Glossary of Terms

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It's been my experience that at bigger matches knockdown targets will be fairly well calibrated and people can feel comfortable that if they're making minimum power factors and place their shot appropriately the knockdown will fall.

 

When you step down to a monthly you are likely to encounter knockdowns that will fall over in a slight breeze or knockdowns that won't go down unless hit by a fairly hot .45 round, so at that level there are no 'guaranteed' knockdown loads.

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A few years ago I got tired of carrying a separate stash of heavier bullets just for knockdowns so I switched to 125s loaded to the mid range of load data.  I use those for everything and haven't had any problems at all.  Those big pills you're shooting should handle any knockdown out there with ease.   

 

This is reminiscent of the age old 45 ACP vs 9 mm debate.  Which is more effective, fat and slow or light and fast?  I will forever live in the fat and slow camp.  (Lumpy Grits should have a field day with that one. :lol:)

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7 hours ago, PaleWolf Brunelle, #2495L said:

 

That would be a power factor of 107.44

SHB p.44 Glossary of Terms

 

PaleWolf said that the rules call for "The minimum standard in all SASS matches for smokeless categories is not less than 60 and no velocity less than 400 fps. Maximum velocity for revolvers is 1000 fps. "

 

So the power factor of the minimum load would be 60g x 400 fps / 1000 = 24, and maximum power factor for that 60g bullet would be 60g x 1000 fps / 1000 = 60! That's REALLY low! IF that is true, and IF clubs actually do abide by that apparent rule, my potential 158g x 680 fps / 1000 = 107 power factor should be fine. That's IF  .. . 

 

Anyone ever see a club, especially a small local one, test it's knockdowns?

 

Hmm . . .

 

Jim G

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14 minutes ago, Jim Gnitecki said:

So the power factor of the minimum load would be 60g x 400 fps / 1000 = 24, and maximum power factor for that 60g bullet would be 60g x 1000 fps / 1000 = 60! That's REALLY low!

Not the bullet weight, the minimum power factor is 60;) (which is low). Btw, there's no maximum PF, just max velocity, 1000fps/1400fps.

 

* Example: a 105 grainer has to leave the revolver's muzzle with > 572fps (but always use enough margin!)

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21 minutes ago, Jim Gnitecki said:

ever see a club, especially a small local one, test it's knockdowns?

I test knockdowns that I set for local or state matches with the calibrated hand test.   Bump KD with heel of hand (or bottom of clenched fist).  If it falls over, it's good.  If expected wind for the day will blow it over, it's bad.   If I hurt my hand, it's a bad, bad, bad target!

 

Calibrated that hand against the KD's set for EOT, WR and Bordertown.  Have helped set targets for all of those matches.  B)  You don't always have the capability to fire the "standard .38 special factory load" at targets during setups, even at some big matches.     Have to get practical.

 

good luck, GJ

 

 

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16 minutes ago, Equanimous Phil said:

Not the bullet weight, the minimum power factor is 60;) (which is low). Btw, there's no maximum PF, just max velocity, 1000fps/1400fps.

 

* Example: a 105 grainer has to leave the revolver's muzzle with > 572fps (but always use enough margin!)

 

Oh, ok! A power factor of 60 is VERY low, and your 105g bullet example clarifies for me HOW low! On that basis, my 158g bullet at 680 fps, with a power factor of 107, is almost 80% higher than the minimum PF!  So, yeah, I should be fine even if a knockdown target is set to fall at a somewhat "stiff' setting.

 

Jim G

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10 minutes ago, Garrison Joe, SASS #60708 said:

I test knockdowns that I set for local or state matches with the calibrated hand test.   Bump KD with heel of hand (or bottom of clenched fist).  If it falls over, it's good.  If expected wind for the day will blow it over, it's bad.   If I hurt my hand, it's a bad, bad, bad target!

 

Calibrated that hand against the KD's set for EOT, WR and Bordertown.  Have helped set targets for all of those matches.  B)  You don't always have the capability to fire the "standard .38 special factory load" at targets during setups, even at some big matches.     Have to get practical.

 

good luck, GJ

 

 

 

Is your hand a "regular" hand or a "Magnum" hand? :D

 

Jim G

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All of the science is well and good. However, the biggest factor is where you hit that knock down target. It won’t matter what your pf is if you hit the kd on the bottom it probably won’t go down. 

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Just now, Too Tall Bob said:

All of the science is well and good. However, the biggest factor is where you hit that knock down target. It won’t matter what your pf is if you hit the kd on the bottom it probably won’t go down. 

 

You raise a great point! It is very relevant to me personally right now since BOTH my revolvers shoot to the left at 25 yards, one by 2.3" and the other by 4", as proven by consistently repetitive laser boresighter test results, and they also shoot LOW! I need to fix that.

 

Jim G

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Ellie's loads are 125gr. 38s with 2.8 gr. of Clays. For the rare occasion we encounter pistol knock downs,they always go down. Certainly not a hot load, but haven't chronoed it.

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58 minutes ago, Shooting Bull said:

A few years ago I got tired of carrying a separate stash of heavier bullets just for knockdowns so I switched to 125s loaded to the mid range of load data.  I use those for everything and haven't had any problems at all.  Those big pills you're shooting should handle any knockdown out there with ease.   

 

This is reminiscent of the age old 45 ACP vs 9 mm debate.  Which is more effective, fat and slow or light and fast?  I will forever live in the fat and slow camp.  (Lumpy Grits should have a field day with that one. :lol:)

sounds like you are just shooting the bull to me. LOL

 

TM

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BOTH my revolvers shoot to the left at 25 yards, one by 2.3" and the other by 4"”


why don’t you pattern on paper at nine or 10 yards. This will tell you where you’re at plus, that is probably the farthest distance you will be shooting KD’s at with your Revolvers anyway.

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Too Tall Bob:

 

Your alias really struck me when I read it because of a coincidence:

 

In Canada, under Federal law, each province has a Chief Firearms Officer, whose job, as the Feds see it, is to enforce Federal firearms laws, which in Canada right now, are very, very strict, and the Federal Government is despite that trying very hard to make them even stricter. For example, they just used a cabinet order mechanism to temporarily halt the sale or transfer of all handguns, while they try to muster enough votes in Parliament to make that permanent. I had to buy my 2 Peacemaker replica handguns in a hurry last September before this occurred, or be forever locked out of CAS.

 

But our Province, Alberta, is a major opponent to the Federal initiative, and our provincial CFO, appointed by the province, is a lady named Teri Bryant. Teri is VERY tall, and a very public enemy of The Federal Government, taking every opportunity and every legal approach available to her to blunt the Federal over-regulation.

 

Teri is also a CAS shooter!

 

Her alias is "Too Tall Teri".

 

You are in fine company with your alias! :D

 

Jim G

 

 

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18 minutes ago, Jim Gnitecki said:

Oh, ok! A power factor of 60 is VERY low, and your 105g bullet example clarifies for me HOW low! On that basis, my 158g bullet at 680 fps, with a power factor of 107, is almost 80% higher than the minimum PF!  So, yeah, I should be fine even if a knockdown target is set to fall at a somewhat "stiff' setting.

As @Abilene, SASS # 27489 already wrote, reactive targets should be set to fall when squarely hit with no more than a "standard .38 Special factory load" (SHB p.20). I guess that factory loads are considerably above 60 PF, so you cannot expect a knock down to fall if you load to minimum. Some could consider that a flaw in the rule book... As I only shoot .45 with at least 225gr, I personally don't care much about PFs.

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6 minutes ago, Too Tall Bob said:

BOTH my revolvers shoot to the left at 25 yards, one by 2.3" and the other by 4"”


why don’t you pattern on paper at nine or 10 yards. This will tell you where you’re at plus, that is probably the farthest distance you will be shooting KD’s at with your Revolvers anyway.

 

I do realize that most handgun targets in CAS are at very close ranges. But I subscribe to "Only accurate guns are interesting" school of thought, and it bothers me to have revolvers that shoot THAT far off POA, and I dislike having to remember to shoot to the right, and by differing amounts for the 2 revolvers, on critical targets.

 

Jim G

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5 minutes ago, Equanimous Phil said:

As @Abilene, SASS # 27489 already wrote, reactive targets should be set to fall when squarely hit with no more than a "standard .38 Special factory load" (SHB p.20). I guess that factory loads are considerably above 60 PF, so you cannot expect a knock down to fall if you load to minimum. Some could consicer that a flaw in the rule book... As I only shoot .45 with at least 225gr, I personally don't care much about PFs.

I don’t consider that a flaw in the rule book.  Targets set to fall at minimum PF might fall down themselves during a light gust.  I’ve seen that and dislike having to shoot over the top of downed targets.

 

My wife has knockdown loads for her .32s and for her shotgun.  I carry some shotgun game loads for difficult SG targets.  These were put to use at EOT recently.

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Some time around 2000 or '01 I was at a Butterfield Regulators Match and there was one stage that was all knockdowns.  Before the match and even during the shooter's meeting, somebody was down at the stage trying to get the targets adjusted and having a hard time.  Well, the only person to knock them all down was shooting the new Ruger .32 H&R magnums.  I think he was using store bought ammo (Black Hills maybe?).  I was shooting a .38 and 44 Spcls, and I knocked them all down but missed a shotgun target (no makeups).

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All of this meaningless if the knockdown are not calibrated. I always walk the stages before a match and actually tap a few knockdowns over . My cart always has a few hotter loads just in case. Be Prepared .

 

Best Wishes

 

TJB

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Jim reading this and your post about POA it appears you are overthinking everything.  Fall back, calm down, regroup.  SASS is not bullseye shooting.  Pistol targets are not at 25 yards.  At any match above the local club in East Buttcrack, Montana that is snowed in 10 months of the year and the two members come out twice a year to shoot, the pistol targets are going to be less than ten yards.  In many cases way less than ten yards.  If you wanted 25 yard bullseye accuracy you should have gotten a gun with adjustable sights.  SASS is not minute of angle shooting.  It is minute of pie plate.  If you can hit near the middle of a pie plate at ten yards you are good to go.  I would not even file down the front sight for elevation corrections but that can be a different discussion.  Look at this video of how they make Uberti revolvers.  Skip to about 2:45 where they install the barrel and notice the precision bench vice with leather pad and scientifically designed wooden stick they use in the frame to tighten the barrel.  Notice how the craftsman eyeballs the front sight alignment.  After you have shot a couple of dozen matches then worry about this stuff.  In the meantime learn and enjoy.  I could not find the factory video.  The dialog in this was added by someone as a joke although the factory narration was not much better.

 

 

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19 minutes ago, Abilene, SASS # 27489 said:

Some time around 2000 or '01 I was at a Butterfield Regulators Match and there was one stage that was all knockdowns.  Before the match and even during the shooter's meeting, somebody was down at the stage trying to get the targets adjusted and having a hard time.  Well, the only person to knock them all down was shooting the new Ruger .32 H&R magnums.  I think he was using store bought ammo (Black Hills maybe?).  I was shooting a .38 and 44 Spcls, and I knocked them all down but missed a shotgun target (no makeups).


These are good knockdown loads.

 

95BD8123-7E5B-48D8-8FFB-9FF026DE9478.thumb.jpeg.84e1b80f1a59b350bf2c7d23aa7c32d9.jpeg

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22 minutes ago, Larsen E. Pettifogger, SASS #32933 said:

Jim reading this and your post about POA it appears you are overthinking everything.  Fall back, calm down, regroup.  SASS is not bullseye shooting.  Pistol targets are not at 25 yards.  At any match above the local club in East Buttcrack, Montana that is snowed in 10 months of the year and the two members come out twice a year to shoot, the pistol targets are going to be less than ten yards.  In many cases way less than ten yards.  If you wanted 25 yard bullseye accuracy you should have gotten a gun with adjustable sights.  SASS is not minute of angle shooting.  It is minute of pie plate.  If you can hit near the middle of a pie plate at ten yards you are good to go.  I would not even file down the front sight for elevation corrections but that can be a different discussion.  Look at this video of how they make Uberti revolvers.  Skip to about 2:45 where they install the barrel and notice the precision bench vice with leather pad and scientifically designed wooden stick they use in the frame to tighten the barrel.  Notice how the craftsman eyeballs the front sight alignment.  After you have shot a couple of dozen matches then worry about this stuff.  In the meantime learn and enjoy.  I could not find the factory video.  The dialog in this was added by someone as a joke although the factory narration was not much better.

 

 

 

The video is hilarious, and you raise valid points. But, being a former engineer, I am required by engineering tradition to INSIST on getting the best possible precision and accuracy out of any firearm I own, or face humiliating disgrace and perpetual disdain from my peers.. I have no choice . . . :(

 

Jim G

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I just looked up the specs for that Federal 95g 32 H&R cartridge. It has a muzzle velocity of 1020 fps.

 

Therefor, its power factor is just 95 x 1020 /1000 = 97.

 

And it is described as "a good knockdown load"? Well, Hell, my 107 power factor should be really "good to go"!

 

Jim G

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Simple answer, load toward the upper end of what the rules allow.  The targets will fall and you will be employing a round with potential value beyond the game.  When I was doing CFD I preferred to hit quickly rather than miss blazingly fast.  Some practical considerations can be taken into account.

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26 minutes ago, Jim Gnitecki said:

 

The video is hilarious, and you raise valid points. But, being a former engineer, I am required by engineering tradition to INSIST on getting the best possible precision and accuracy out of any firearm I own, or face humiliating disgrace and perpetual disdain from my peers.. I have no choice . . . :(

 

Jim G

No one says you have to tell your engineer buddies that your guns shoot a couple inches left at 2 to 4 times the normal target distance! You won't even notice in the excitement of an actual match. Most pistol targets are between 5 & 10 yards, you'll be off by less than an inch. Just go play and enjoy.

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Knock down targets are a small part of cowboy shooting.

Most will go down with a center hit from a 158 grain bullet 650 FPS

 

Many shooters use a 105 grain TC bullet at mild velocity 600-700 FPS

Sass minimum:

roughly =   105 grain @ 575

60.3 power factor

 

I prefer a 125 grain @ 700-750 FPS for knockdowns 

main match ammo 105 gr poly coated bullet loaded with 2.7 Grains of N-310 in 38 Short Colt brass  (700-720FPS)

38 Special 3.7 Grains of N-320 

925-1000 FPS from a 20” rifle 

 

Good Luck 

3GC

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