What is the lightest charge of RED DOT ...

[Nostrum Damus SASS #110702]

... that will reliably push a .358" 125gr RNFP bullet out the muzzle of a 5.5" barreled pistol at 500 fps (and thus achieve a SASS-legal Power Factor of 62.5)?  I'm sure I load my .357 Mag cartridges "hotter" than they need to be, but I'm interested in knowing by how much.  I don't own a chronograph.

Thanks in advance if you have this information.

ND

[Larsen E. Pettifogger, SASS #32933]

No way to tell without a chrono.  Guns vary and the velocity out of two identical models can vary by quite a bit.

Edited October 14, 2025 by Larsen E. Pettifogger, SASS #32933

[Old Man Graybeard]

A chrono is a worthwhile investment. I was trying different loads for 45 acp. I was using a Springfield Mil-spec and an R-1 Remington. One was consistently faster than the other. And by about 50 fps. I found out that my loads were hotter than needed...by quite a bit.

[Sedalia Dave]

Years ago those that wanted to go fast fired tens of thousands of rounds searching for the ideal bullet weight and velocity. What they discovered is that if your loads were too light your split times actually increased.

 

Bottom line is that shooting loads at the minimum power factor is counterproductive.

[Stump Water]

I have no idea "how low can you go".  I use 3.5 gr in a .38 spl case.

 

13 minutes ago, Sedalia Dave said:

What they discovered is that if your loads were too light your split times actually increased.

 

Or, at a match some years ago, the gun went "pop", the spotters raised a finger, then the bullet hit the target.

[Nostrum Damus SASS #110702]

41 minutes ago, Sedalia Dave said:

Years ago those that wanted to go fast fired tens of thousands of rounds searching for the ideal bullet weight and velocity. What they discovered is that if your loads were too light your split times actually increased.

 

Bottom line is that shooting loads at the minimum power factor is counterproductive.

I'm not interested in shooting loads at the minimum power factor.  But I am interested in knowing approximately where on the spectrum from minimum to maximum my loads are.  Ballpark is good enough for now.  I load the same rounds for both pistol and rifle because ... I'm lazy?  I just don't need Bullion Rose getting two different .357 Magnum rounds mixed up and blaming you-know-who for whatever.  We both shoot Ruger NMVs, hers are 4 5/8" barrels and mine 5 1/2".  She shoots a JM Marlin 1894CB Cowboy Limited, I shoot a Browning B-92 (until I find another good .357 Mag JM Marlin 1894 for me -- I covet her rifle in a big way).  All of the guns are fed the same diet of RNFP 125gr coated pills over 3.2gr of Red Dot.  (I used to load 4.0gr and that was too hot.)  Do folks go much lower than 3.2?  

[John Kloehr]

A chrono is not that expensive. It and a good scale were two of my earliest purchases on the road to reloading (almost there). I trust the advice I was given so passing it on.

[Sedalia Dave]

2 hours ago, Nostrum Damus SASS #110702 said:

I'm not interested in shooting loads at the minimum power factor.  But I am interested in knowing approximately where on the spectrum from minimum to maximum my loads are.  Ballpark is good enough for now.  I load the same rounds for both pistol and rifle because ... I'm lazy?  I just don't need Bullion Rose getting two different .357 Magnum rounds mixed up and blaming you-know-who for whatever.  We both shoot Ruger NMVs, hers are 4 5/8" barrels and mine 5 1/2".  She shoots a JM Marlin 1894CB Cowboy Limited, I shoot a Browning B-92 (until I find another good .357 Mag JM Marlin 1894 for me -- I covet her rifle in a big way).  All of the guns are fed the same diet of RNFP 125gr coated pills over 3.2gr of Red Dot.  (I used to load 4.0gr and that was too hot.)  Do folks go much lower than 3.2?  

 

Without a chronograph you'll never even be in the ballpark. Barrel length, cylinder gap, throat diameter, bore diameter, temperature of the ammo, powder lot, primer lot, bullet hardness, consistency of your powder charge, brand of case, how tight the crimp is (impacted by the variations in case length) and many many more variables will impact bullet velocity.

 

EVEN IF you could hold the cartridge variables to a minimum,  two Ruger Vaqueros shooting the same ammunition will have  different velocities because no two are exactly the same.

 

[Nostrum Damus SASS #110702]

3 minutes ago, Sedalia Dave said:

 

Without a chronograph you'll never even be in the ballpark. Barrel length, cylinder gap, throat diameter, bore diameter, temperature of the ammo, powder lot, primer lot, bullet hardness, consistency of your powder charge, brand of case, how tight the crimp is (impacted by the variations in case length) and many many more variables will impact bullet velocity.

 

EVEN IF you could hold the cartridge variables to a minimum,  two Ruger Vaqueros shooting the same ammunition will have  different velocities because no two are exactly the same.

 

That's right -- there will always be variation even among my own loads because my case lengths differ, thus crimp force differs, and I use different brands of cases and primers, all in the same reloading session.  And I shoot in different weather conditions!  Yet there will always be a mean value and a median value of all of those different velocities.  I'm not planning a mission to Mars and don't need the sort of scientific accuracy required to do so.  If NO ONE here loads less than my charge of 3.2 grains of Red Dot in any .357 Mag case with any brand of primer, it's probably safe to guesstimate that I'm already at the low end of the scale.  If lots of folks load 2.5 grains of Red Dot in whatever case and with whatever primer brand they use, that is useful information, too.  Resist overthinking this. 

Maybe the better question I should have asked is this: if you shoot .358" 125 gr RNFP coated bullets over Red Dot in your pistols, what charge of Red Dot do you load?

[watab kid]

MHO is that when folks that have been doing this a long time give you a starting point they have found comfortable and reliable you can experiment a little but pretty much you will find they are within a tiny margin of what works , 

[I. M. Crossdraw, SASS# 8321]

5 hours ago, Nostrum Damus SASS #110702 said:

 Do folks go much lower than 3.2?  

I do.  I use 2.5 grains of RD with 125 grains lead projectile (coated and uncoated) with firm roll crimp, 38 specials, any primer.  I have been using this load for many years when I shoot smokeless during monthly matches.  I've chrono mine and it meets the power factor (as far as I can remember, it's been a while since I chrono).  I use NMV with 4.62 in. barrel.  It also works good in my 73 with 18 and 20 in. barrel.

 

Note: It is temperature sensitive during the cold season (winter), I have experienced erratic velocity but no squib (when I used to live in Ohio).  During the warmer months, no problem.  Now that I live in Florida, no problem (I hate snow).  If I do shoot in the cold, I up my load of RD to 3 grains.  Load at your own risk, stay safe. YMMV

Edited October 15, 2025 by I. M. Crossdraw, SASS# 8321

[Nostrum Damus SASS #110702]

6 hours ago, I. M. Crossdraw, SASS# 8321 said:

I do.  I use 2.5 grains of RD with 125 grains lead projectile (coated and uncoated) with firm roll crimp, 38 specials, any primer.  I have been using this load for many years when I shoot smokeless during monthly matches.  I've chrono mine and it meets the power factor (as far as I can remember, it's been a while since I chrono).  I use NMV with 4.62 in. barrel.  It also works good in my 73 with 18 and 20 in. barrel.

 

Note: It is temperature sensitive during the cold season (winter), I have experienced erratic velocity but no squib (when I used to live in Ohio).  During the warmer months, no problem.  Now that I live in Florida, no problem (I hate snow).  If I do shoot in the cold, I up my load of RD to 3 grains.  Load at your own risk, stay safe. YMMV

Thank you for this!  A club member is lending me his chronograph and I will experiment a little bit.  (It is purely coincidental that it will make my supply of Red Dot, currently unobtanium it seems, last longer.)  I used to live in upstate New York.  Here in Houston there is no cold season, just "wonderful season" (October through March) and "unbearable season" (April through September).

[Abilene, SASS # 27489]

2 hours ago, Nostrum Damus SASS #110702 said:

... Red Dot, currently unobtanium it seems,...

Natchez has Red Dot in stock (expensive 1 lb) or Promo (same thing, 8 lbs, better deal).

[Colorado Coffinmaker]

 

NOSTRUM,

 

Before you go in search of "The Lowest" I would strongly suggest you check ALL your Rugers for Cylinder Throat diameter.  Ruger is famous, or infamous for undersize throats.  Undersize throats WILL give you more felt recoil.  cylinder throats should be sized to .358 or .3585.  Drop a 357 bullet down the cylinder and you should be able to tap it thru with a tap from a pencil.  If the bullet sticks solid, the throats are undersize and need reaming.

[Cpt Dan Blodgett, SASS #75655]

16 hours ago, Nostrum Damus SASS #110702 said:

I'm not interested in shooting loads at the minimum power factor.  But I am interested in knowing approximately where on the spectrum from minimum to maximum my loads are.  Ballpark is good enough for now.  I load the same rounds for both pistol and rifle because ... I'm lazy?  I just don't need Bullion Rose getting two different .357 Magnum rounds mixed up and blaming you-know-who for whatever.  We both shoot Ruger NMVs, hers are 4 5/8" barrels and mine 5 1/2".  She shoots a JM Marlin 1894CB Cowboy Limited, I shoot a Browning B-92 (until I find another good .357 Mag JM Marlin 1894 for me -- I covet her rifle in a big way).  All of the guns are fed the same diet of RNFP 125gr coated pills over 3.2gr of Red Dot.  (I used to load 4.0gr and that was too hot.)  Do folks go much lower than 3.2?  

Don't use much red dot for years as years ago A2 a very similar but not identical powder in terms of performance was $2 a pound cheaper.  Have used 3.2 grains of A2 in either a .38 spec or .357 Mag case with bullets from 125 to 160 grains out of a Model 66 smith Taurus Cowboy .357 S&W M&P/10 .38 Spec and a Colt Army Special

[El Chapo]

I can run it through Quickload if you tell me what bullet it is and barrel length.  I have a feeling it's going to be below 3 grains, maybe more below that than any of us would be comfortable loading.  Quickload is an incredible piece of software.  If you really want it to be precise, measure the water capacity of your sized cases and it can be fine-tuned from there.

[Nostrum Damus SASS #110702]

1 hour ago, El Chapo said:

I can run it through Quickload if you tell me what bullet it is and barrel length.  I have a feeling it's going to be below 3 grains, maybe more below that than any of us would be comfortable loading.  Quickload is an incredible piece of software.  If you really want it to be precise, measure the water capacity of your sized cases and it can be fine-tuned from there.

Thanks, I'll get in touch if I want to try that.

[Blackwater 53393]

2 hours ago, El Chapo said:

I can run it through Quickload if you tell me what bullet it is and barrel length.  I have a feeling it's going to be below 3 grains, maybe more below that than any of us would be comfortable loading.  Quickload is an incredible piece of software.  If you really want it to be precise, measure the water capacity of your sized cases and it can be fine-tuned from there.

I’d like to take you up on that offer!  If I send you the information by PM, can you run a couple of loads for me?

[El Chapo]

1 hour ago, Blackwater 53393 said:

I’d like to take you up on that offer!  If I send you the information by PM, can you run a couple of loads for me?

 

sure, send me what you can and I'll try to get it done before I get on the road to Bordertown.

 

I'd be curious to see how it compares to real-world chrono data.  Make sure you send me as much information about your bullet as you can, and a COAL, cartridge, powder charge, and what barrel length you want me to test.

Edited October 15, 2025 by El Chapo

[Nostrum Damus SASS #110702]

8 hours ago, Colorado Coffinmaker said:

 

NOSTRUM,

 

Before you go in search of "The Lowest" I would strongly suggest you check ALL your Rugers for Cylinder Throat diameter.  Ruger is famous, or infamous for undersize throats.  Undersize throats WILL give you more felt recoil.  cylinder throats should be sized to .358 or .3585.  Drop a 357 bullet down the cylinder and you should be able to tap it thru with a tap from a pencil.  If the bullet sticks solid, the throats are undersize and need reaming.

I have a set of precision gage pins in 0.001" increments from 0.251-0.500" diameter.  I'll check the cylinder throats, thanks.

[Lead Monger]

I’ve gone as low as 2.8g of Red Dot with a 125g bullet. Dirty as heck and sensitive to the temperature. Produce a noticeable amount of unbent powder in the revolver cylinder and barrel.  3 grains is better but still dirty.

[watab kid]

i use 3 grn , and yes its a little dirty but its my red dot , another powder might be cleaner 

[Blackwater 53393]

El Chapo!

 

PM sent!

 

 

 

Can’t get any photos onto the PM, so here’s what it looks like. If this and the measurements I gave you will help, maybe we can get close…

 

 

Edited October 16, 2025 by Blackwater 53393

[Erasmus]

3.1 grains of Red Dot under a 125 grain coated bullet averages 550 fps out of some 5.5 inch Uberti 1873 SAA repos. Out of the holster thr first shot is often under 500, subsequent shots are closer to 600. 

 

 

Uberti SAA 5.5	Chey Cast coated 125 RNFP	CCI 500	Red Dot	3.1		478.1	542.3333333	57.57571826		Pistol A	First round from holster is slower
				3.1		589.3				Pistol A
				3.1		559.6				Pistol A
				3.1						Pistol A
				3.1						Pistol A
				3.1		503.6	581.2	55.18592816		Pistol B	First round from hlster is slower
				3.1		599.7				Pistol B
				3.1		588.1				Pistol B
				3.1						Pistol B
				3.1		633.4				Pistol B
							564.5428571	55.3112664		Composite
							594.02	26.57587252		Composite minus first round from holster

 

[Nostrum Damus SASS #110702]

21 hours ago, Nostrum Damus SASS #110702 said:

I have a set of precision gage pins in 0.001" increments from 0.251-0.500" diameter.  I'll check the cylinder throats, thanks.

OK, funny thing discovered at the bench.  Every cylinder throat in my two pairs of .357 Mag Ruger NMVs is perfect; my 0.358" ZZ minus gage pin slips into and through every one.  Just for ships and giggles, though, I took out my blued .45 Colt Ruger OMVs; I could not insert a 0.451 ZZ minus gage pin into a single cylinder throat!  Reaming cylinder throats is in my future!!

It is my understanding that other than light polishing, no cylinder throat surface treatment of any kind is required after reaming; in other words, the inside walls of the cylinder throats are not blued.  If anyone knows otherwise, please let me know.

[El Chapo]

To answer the original question:

 

According to Quickload, in a .357 Magnum case with a 125 grain Lee RNFP, 1.7 grains of Red Dot will make 493 fps out of a 5.5" barrel for a power factor of 61, assuming a COAL of 1.590".

 

I would not attempt this, pressure is 3,264 PSI.  But that's the answer to the question you asked.

Edited October 17, 2025 by El Chapo

[Nostrum Damus SASS #110702]

Thanks to all for the discussion.  I learned A LOT!

ND

[Sedalia Dave]

2 hours ago, El Chapo said:

To answer the original question:

 

According to Quickload, in a .357 Magnum case with a 125 grain Lee RNFP, 1.7 grains of Red Dot will make 493 fps out of a 5.5" barrel for a power factor of 61, assuming a COAL of 1.590".

 

I would not attempt this, pressure is 3,264 PSI.  But that's the answer to the question you asked.

 Does that take calculation take into account cylinder gap?

[El Chapo]

2 hours ago, Sedalia Dave said:

 Does that take calculation take into account cylinder gap?

 

You'd have to ask the guy who programmed the software that question.  That person is not me.

[Still hand Bill]

9 hours ago, Sedalia Dave said:

 Does that take calculation take into account cylinder gap?

Probably not.  I have not tried QL with pistol cartridges, just rifle.  For subsonic rifle loads it does not work well.  It overestimates velocity by quite a bit.  Seems drag from the bullet to barrel is not accounted for correctly at slower speeds and low pressures.  It may work fine for pistol loads, but it does not for slow rifle loads.  

[Blackwater 53393]

Thanks to El Chapo for his help! That program is news to me! I’ll be getting a copy of it soon.

 

The info he shared with me was reassuring.

 

Edited October 17, 2025 by Blackwater 53393

[Yohan]

I use 3.0 Grains of Red Dot pushing a 105 grain projectile in both pistol (3.75 barrel length and wife's 4.62 barrel length) and rifle (18 inch barrel) OAL around 1.47

never had a issue I dropped down to 3.0 from 3.5 almost 2 years ago.

[Blackwater 53393]

I got the opportunity to test fire the loads that I discussed with El Chapo and found that they worked very near to the predicted outcome.

 

I was unable to chronograph them, but they looked, felt, and sounded very much like other examples that I have test data on. They shot to point of aim and there was no evidence that they might be unreliable.

 

I’m planning to get the QL program in the near future.