Variance in Velocity

[RedHawk357Mag]

Been testing loads in 357 to see effects of bullet hardness. During the ten round sets I noticed an unexpected trend on chronograph results. I tend to believe that 40 fps is probably the minimum acceptable spread for a ten round set. BUT, a series of ten rounds that consistently print exceptionally well groups would move extreme spread to the back seat. I consider ES a kind of unofficial indicator of the level of quality of rounds coming off the press. With repeated consistent loads trumping velocity information. I haven't really found a specific list of things to check for to reduce ESs.


Things I think will have effects on ESs.


Variance in bullet weights, individual powder charges, headstamps, load history of individual cases, case trim length, variance in seating depth/air space probably side effect of trim length.


Equipment related, specs of dies used, tolerance in resizer, expander, and crimp. Ability of scale to determine accuracy of charges. Level of accuracy and lighting available to chronograph to include it being set up correctly and staying in chronograph optimal bullet path. If leading is present or happening during course of fire causing different pressure levels. Different abilities of individual powders used to limit velocity spreads. Brands of primer or consistency of primers to maintain level of heat.


Anything else to consider to reduce ES?



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[OS OK]

I think about the crimp, it's consistency which can vary with age of the worked brass or it's length...I'm thinking 'starting pressure' before the cast ever leaves or moves within the case.
Starting pressure to me is...in a crude way of thinking...how well the fire is stoked before the process of internal ballistics really gets started.

Or, something like that...given all other variables are minimized as best as possible. I'm trying to think of just one of the factors that might have the greatest amount of influence on the 'ES's & SD's'.

[RedHawk357Mag]

I think about the crimp, ...

I share that idea as well. I have tested the Redding Profile crijjjjjmp with better results. I have compared it to the standard Redding bullet seater and crimp die, Lee CARBIDE and COLLET. My brass is trimmed and segregated by headstamp and length. I think I might need to relook at test protocol as I am certain that I didn't stick to the same brass for the different crimp dies. BUT I also agree case tension plays a big part in this as you mentioned in your post.

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[Dusty Bannister]

I would have a difficult time discounting a good group at 50 yards with a handgun based upon a chronograph reading. The target proves the load.

Quote: Variance in bullet weights, individual powder charges, headstamps, load history of individual cases, case trim length, variance in seating depth/air space probably side effect of trim length.

While there is usually a variance in handgun bullet weights being casually produced unlike rifle bullets, I would think that the bullet diameters would be of greater effect due to adequate gas seal in the throat and bore. Individual powder charge variation is very common and is usually a factor when selecting a powder (easy metering). Head stamps, age and trim lengths all affect the amount of crimp and neck tension. Neck tension probably more than amount of crimp, unless crimp reduces bullet diameter. Trim length has no affect on the seating depth so I would not consider that a factor, especially in a revolver where the cartridge head spaces on the rim. Dusty

[OS OK]

I share that idea as well. I have tested the Redding Profile crijjjjjmp with better results. I have compared it to the standard Redding bullet seater and crimp die, Lee CARBIDE and COLLET. My brass is trimmed and segregated by headstamp and length. I think I might need to relook at test protocol as I am certain that I didn't stick to the same brass for the different crimp dies. BUT I also agree case tension plays a big part in this as you mentioned in your post.

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An aside to neck tension...I have an old Green Machine that loads exclusively the .38S. FWC. Once I had to de-mil a few rounds...I was new at the operation of an inline progressive and I thought I may not have charged those cases.
I noticed that one of the cases was a longer trim length and it tucked well into the crimp groove and the roll crimp tucked it in tight whereas the others were a bit shorter cases, not by much just a minimal amount so as not to be noticed when they're empty and they too roll crimped into the crimp groove but the ends of the cases were not tucked tight into the topmost part of the groove.
Those shorties released the FWC with a few taps of the inertia puller...don't get me wrong, they tried to hang onto those FWC's but let them slip out a little with each tap...on the other hand the case that was a smidgen longer and was crimped tight up in the top of the crimp groove had more case material bent over, roll crimped...it withstood my every effort to get it out of the case with the inerta hammer...it just wasn't happening.
That tells me that some longer cases can hold those casts with much more vigor than the shorter ones...from the time that the primer is ignited and builds sufficient pressure to actually start to move that cast where-by volume in the case increases as the pressure rises...I think the difference could be substantial & adding to the variance in ES's within the batch.
When we roll or taper crimp into crimp grooves we increase the neck tension of the case hanging onto that cast...were increasing starting pressure and I think that may lead to a more complete burn within the barrel.

I don't have any proof really...just some random thoughts from a lot of years mulling on the matter.

[country gent]

Neck tension, crimp, powder orientation or air space in the case all affect the ES and or Standard Deviations. I also believe mechanical things that have an effect are firing pin strength and size shape of pin as this affects ignition. burrs around the flash hole n the case can also have an effect as does the flatness of the primer pocket it self.

Finding the right load that's optimized makes a big difference some combinations have a point where everything is balanced or optimum for the given conditions.
I have tested the above on primer pockets I loaded new brass as is and chrono graphed. then same load same brass with the pockets uniformed and got lower es and sd. THis was done several times. Same with deburring the flash holes.
Air space in a case is a variable to powder position and ignition. Another is the slower powders when used for light to midrange loads, most powders need a certain pressure range to burn clean and efficiently. Below that and complete burns and fill burns become iffy.

I have found with the big BPCR cases heavy bullets and black powder that when working up a load. Your numbers ( ES and SD) slow drop as compression of the powder charge goes up. I have several BP loads for rifles that give 12 fps ES over 10 rds.

It can take a lot of testing and experimenting to get the best numbers. as so much affects it.

[popper]

Have you considered the tolerance of the chrony? The pulse over both sensors has to be the same to get really good numbers, lighting the same, path of boolit the same. Your numbers are ~ 3% variation. I don't pay much attention to SD, but ES shows up on the target Lots of factors but don't forget this one.

[garandsrus]

I did some quick math and the difference between a 900 and 1000fps at 50 yds is 1" of vertical spread. It would result in a little over 4" vertical at 100 yds.

With a velocity of 1400 and 1500fps, the difference is .3" at 50 yds and 1.1" at 100 yds.

With a velocity of 1900 and 2000fps, the difference is .1" at 50 yds and about .5" at 100 yds.

I would be happy with a 1" group at 50 yds with a handgun!

[RedHawk357Mag]

I did some quick math and the difference between a 900 and 1000fps at 50 yds is 1" of vertical spread.


Grandsrus, I think you are on the precipice of learning me something here. I just need for you to show your work. Or point me in the direction of the concept you applied here. Thank you.


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[RedHawk357Mag]

Countrygent, powder orientation is something I forgot to account for and list above. Thank you.

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[Larry Gibson]

Many of us really don't think getting the best load we can is "silly" even in a "relative way". Adjusting our loading techniques to get the lowest ES and relevant SD is worthwhile. Even from field positions good ammunition will shoot well and bad ammunition will shoot badly for all shooters. Excellent shooters can not make bad ammo shoot better. Poor shooters can learn to shoot better from even "field positions" with good accurate ammunition. They can not learn much of anything with poor inaccurate ammunition. The only thing an excellent shooter can learn from shooting poor inaccurate ammunition is that it is poor inaccurate ammunition.

[country gent]

Over the years I shot NRA High power, I saw a few loads that performed well at 200 yds but at 600 fell apart. I also saw 600yd loads that wouldn't perform at 1000 yds to the same level. ES doesn't just affect trajectory but also the barrel harmonics and the point in such where the bullet leaves the muzzle in its oscillations.
Doing a ladder test over the chronograph can be an eye opener. as the charge is slowly increased velocity goes up and groups tend to tighten SD and ES go down to a point then start to increase, in some cases they may shrink in again.
Good numbers indicate correct ignition, efficient complete burns, and an all around balanced load. Cases that vary in volume can skew results. uneven crimps can also raise these numbers. The one not mentioned and obvious is variations in powder charges, a high energy powder that's producing 100 fps every .5 grn increase that's varying by .1 grn +/- may be a big part. A lot throw charges and consider +/- .1 grn good. With BP that produces very small increases even with a 1 grn jump a small variance probably doesn't matter, but with the modern smokeless powder to get the best numbers charges must be weighed exact.

[JoeJames]

I have been interested in velocity differences myself lately. Even though as someone said on pistol and revolver reloading "it ain't precision bench rest shooting". Anyhow, for more consistency and less variation, here's another thought. I noticed somewhere that in a situation where there is a large volume case and a small amount of powder (like say 357 magnum case and Bullseye powder) the ammo companies often have a protocol where the cartridge is tilted vertically before firing for pressure and velocity testing.

[Larry Gibson]

44MAG#1

Come on now, you come on a thread and denigrate what the OP was talking about and then get sensitive?

You put your "2 pennies" worth in and so did I. The OP made no claims about wanting to be a "phenom". The OP simply stated he wants to see if he can lower the ES in his 357 loads.......I see nothing wrong with that. Neither did I say you said anything regarding about poor ammo. I said my "2 pennies" worth. I agree there is "no magical ammo" but there is, indeed, excellent ammo, okay ammo and poor ammo. As to what I know; this is what I said and what I stand by regardless of your inference otherwise; " Poor shooters can learn to shoot better from even "field positions" with good accurate ammunition. They can not learn much of anything with poor inaccurate ammunition."

No where did I put words in your mouth. I took issue with a couple things you inferred and simply stated my own opinion. We all know from your numerous posts on the subject of chronographs you haven't much use for chronographs. We get that. That is your prerogative. However, it is our prerogative, in this case the OPs, to want to use the chronograph for further load development. Doesn't matter what kind of shooting he does, bench rest, "field positions", cowboy action, looooooong range or shooting outhouses ala Keith......if he wants to learn how to lower the ES of his 357 loads then more power to him. Doesn't matter what you let drive how you spend your time. It's how he wants to spend his time.

Thus if the OP wants to load better ammunition. You said; "Me, i will work up a "good" load, get up and practice from many positions and improve myself."......maybe you should consider that just might be exactly what the OP is trying to do........work up a good load........


RedHawk357Mag

Go for it, be glad to help where ever I can.

[JoeJames]

"If I am checking factory ammo as I sometimes do I realize it is the results I obtain at that time with that gun and that box of ammo." I agree on checking factory ammo. I had gotten a box of HSM cowboy 44 Special loads, and they were just not accurate at all. Turned out they were running about 730 fps. Because of that I miked them and they were about .429", and my Ruger SA likes at least .430". The chronograph kind of underlined the problem.

[Winger Ed.]

[QUOTE=Anything else to consider to reduce ES?[/QUOTE]

Something not mentioned yet is the gun itself as being a variable.
We've all seen loads that one gun 'didn't like'.

The assumption here is that without variances in the ammunition, the gun will shoot to one hole at any distance.
Even the test barrels mounted in concrete won't do that.

[Traffer]

Have you considered the tolerance of the chrony? The pulse over both sensors has to be the same to get really good numbers, lighting the same, path of boolit the same. Your numbers are ~ 3% variation. I don't pay much attention to SD, but ES shows up on the target Lots of factors but don't forget this one.

Yup, First thing I thought was to check out the chrono WELL. Sounds like at least SOME of the discrepancy is coming from there. Could be a little of this and a little of that added to each other is giving a very perplexing outcome.

[garandsrus]

Grandsrus, I think you are on the precipice of learning me something here. I just need for you to show your work. Or point me in the direction of the concept you applied here. Thank you.


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Sure! There are only two formulas that you need to use,
R * T = D (rate * time = distance) so written a different way,
T = D/R

Drop = 1/2ATT (Drop = 1/2*Acceleration due to gravity*time*time)
Make sure you use consistent units, such as seconds, feet, and feet/second. The acceleration due to gravity is 32ft/sec*sec (seconds squared) and is always the same.

Starting with these numbers:
Velocity low (rate) = 900f/s
Velocity high (rate) = 1000f/s
Distance = 50yds = 150ft (use feet)
Solving for the 900f/s velocity:
t = d/r
t = 150 f /900 f/s
t = .16666 s - This is the time it takes for the bullet to travel 50 yds (150 ft) at this velocity.

Solve for drop due to gravity:
drop = 1/2att
drop = .5(32)(.16666)(.16666)
drop = .444 ft
.444ft * 12 in/ft = 5.333 in - This is the drop of the bullet shot from a horizontal barrel, ignoring friction, drag, etc.

Solving for the 1000f/s round gives you a time of .15 sec to the target. Note that it is a shorter time since the velocity is higher.
drop for 1000f/s = .36ft * 12 in/ft = 4.32 in.

5.333 - 4.32 = 1.013" difference in drop between the two loads.

You can enter any velocity and distance and compare the results. Try 1000 yds (3000ft) and a typical black powder velocity of 1250 and 1275fps and the vertical difference is huge. A 25fps difference results in over 3 feet of drop difference!

Bullet drag and ballistic coefficient does matter, but is WAY beyond the scope of this example.

[RedHawk357Mag]

I am sorry if I have offended the OP or anyone of the fine individuals on here. .

Absolutely no issues buddy. I appreciate all that you have contributed. If it doesn't fit my reality l shelve it, no harm no foul. I didn't really find any resource specifically listing what areas to consider when faced with greater variance than expected. So I figured to ask it here. If your information doesn't exactly speak to me, it doesn't mean it doesn't speak to the next guy looking for information. Also information provided may also spark the cognitive process for some other issue folks may not even be thinking about. I respect ALL information and time spent in sharing what you find true for you in your experience.

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[RedHawk357Mag]

Grandsrus, thank you for sharing and typing that out. I will definitely add that to my notes as I think this is what the Wizard behind the curtain does at JBM ballistics when I am tinkering with 308 data. Again much appreciated.

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[Larry Gibson]

Got agree with 44Mag#1, go with the ballistics program.

Also when you set up the chronograph try to be as consistent as you can with distance from muzzle to start screen. You probably know that just thought I'd mention it.

[RedHawk357Mag]

https://www.amazon.com/Competition-Electronics-538002-SSI-ProChrono-Chronograph/dp/B0028MTBJ4/ref=sr_1_3?keywords=Chronograph&qid=1551403617&s=gateway&sr=8-3

Great points about chronograph accuracy points. I have been pretty successful taking data from this and making come ups for my 308 out to 800 yds. It tracks pretty consistent in 40 and 45 load work ups. I have a couple different checklists that I use to follow setting up, one from PACT and I think I still got one Iowean from one of the Ruger forums. I might drag those out and do a review. If I ever got a weird reading it was always a clear bogus number. Good points all. Thank you .

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[garandsrus]

Here I am being stupid again but wouldnt it be just as good for practical purposes to use something like JBM trajectory program instead of using all that mental gyrations unless one gets a kick out of doing them

Two simple formulas don’t count as mental gyrations to me, but if they do for you, by all means use the software and don’t try to understand anything about what is actually going on. If you do use a ballistic program, you need to set the “zero” at 1 ft (or yard) to see the actual drop at 50 yds and then run it twice, once for each velocity. Unfortunately, you will still need to do subtraction to see the difference in drop between the two velocities.

You do realize that you are shooting “upwards” out of the barrel for any zero distance other than 0, right? Gravity always works and starts working as soon as the bullet leaves the barrel.

The ballistic programs are what I would use if I was trying to find the real trajectory of a known bullet with a known ballistic coefficient, zeroed at a given range, etc..... That wasn’t what the OP asked. He was surprised that his groups were still very good with a large extreme spread in a 357. I explained why!

[Traffer]

Sure! There are only two formulas that you need to use,
R * T = D (rate * time = distance) so written a different way,
T = D/R

Drop = 1/2ATT (Drop = 1/2*Acceleration due to gravity*time*time)
Make sure you use consistent units, such as seconds, feet, and feet/second. The acceleration due to gravity is 32ft/sec*sec (seconds squared) and is always the same.

Starting with these numbers:
Velocity low (rate) = 900f/s
Velocity high (rate) = 1000f/s
Distance = 50yds = 150ft (use feet)
Solving for the 900f/s velocity:
t = d/r
t = 150 f /900 f/s
t = .16666 s - This is the time it takes for the bullet to travel 50 yds (150 ft) at this velocity.

Solve for drop due to gravity:
drop = 1/2att
drop = .5(32)(.16666)(.16666)
drop = .444 ft
.444ft * 12 in/ft = 5.333 in - This is the drop of the bullet shot from a horizontal barrel, ignoring friction, drag, etc.

Solving for the 1000f/s round gives you a time of .15 sec to the target. Note that it is a shorter time since the velocity is higher.
drop for 1000f/s = .36ft * 12 in/ft = 4.32 in.

5.333 - 4.32 = 1.013" difference in drop between the two loads.

You can enter any velocity and distance and compare the results. Try 1000 yds (3000ft) and a typical black powder velocity of 1250 and 1275fps and the vertical difference is huge. A 25fps difference results in over 3 feet of drop difference!

Bullet drag and ballistic coefficient does matter, but is WAY beyond the scope of this example.

Why does my head hurt when I try to read this?

[JBinMN]

Why does my head hurt when I try to read this?

LOL You are not alone...
;)

[OS OK]

Been testing loads in 357 to see effects of bullet hardness. During the ten round sets I noticed an unexpected trend on chronograph results. I tend to believe that 40 fps is probably the minimum acceptable spread for a ten round set. BUT, a series of ten rounds that consistently print exceptionally well groups would move extreme spread to the back seat. I consider ES a kind of unofficial indicator of the level of quality of rounds coming off the press. With repeated consistent loads trumping velocity information. I haven't really found a specific list of things to check for to reduce ESs.


Things I think will have effects on ESs.


Variance in bullet weights, individual powder charges, headstamps, load history of individual cases, case trim length, variance in seating depth/air space probably side effect of trim length.


Equipment related, specs of dies used, tolerance in resizer, expander, and crimp. Ability of scale to determine accuracy of charges. Level of accuracy and lighting available to chronograph to include it being set up correctly and staying in chronograph optimal bullet path. If leading is present or happening during course of fire causing different pressure levels. Different abilities of individual powders used to limit velocity spreads. Brands of primer or consistency of primers to maintain level of heat.


Anything else to consider to reduce ES?



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How does any of this mathematical gymnastics address the OP’s question?

Have you even bothered to read it...no really...have you guys bothered?

[Forrest r]

Well here goes, IMHO:

I didn't catch if the op was using a revolver, rifle, tc, etc, it really doesn't matter. Same principals apply but I'll be using a revolver in this post. A chronograph can pickup on the outlaying issues with reloading and accuracy. The user of the chronograph has to have the ability to break down & target/test those different area's and then combine what they've learned to make an overall picture/testbed looking for accuracy.
Cylinder fit is huge & is where the accuracy game is won or lost. Some people like to use bullets 1/2 thousands undersized to the throats in the cylinders. I like to use the same size or slightly larger diameter bullets along with letting the bullet tell me the oal of the load. 2 bullets in a cylinder cut-a-way, the top bullet has a small gap/air space around it in the leade/throat area of the cylinder. The bottom bullet is out far enough to fill this area. Doing this is huge for accuracy.
https://i.imgur.com/99pBGCP.jpg

These 38spl's are loaded long/crimped in the bottom crimp groove to move the bullet forward into the leade/throat of the cylinder. Typical 6-shot accuracy @ 50ft
https://i.imgur.com/AL4WBux.jpg

Same firearm but testing loads in 357 cases @ 50ft. No matter what powder I tried I kept getting 4 shots into a bughole and 2 out.
https://i.imgur.com/7yITG2Q.jpg
Sat back and thought about it & realized I made a rookie mistake. The brass I was using was junk. It was a combo of mixed brass that was once fired to don't know how many times they were fired to so old that it looked like the puppy played with them and split the ends. Couple that with the fact that I was using a 110gr wc that has a short body/limited case neck tension and wasn't seated out into the leade/throats of the cylinders. The small wc is the bullet on the left.
https://i.imgur.com/NN4tThP.jpg
In contrast the 2nd bullet from the left pictured above (h&g #50) seated in 38spl cases so that they sit tightly in the leade/throat of the cylinders of that same 357's cylinders.
https://i.imgur.com/h3YS3YJ.jpg?1

Alloys and lubes are always the great equalizer when it comes to accuracy. Their job is seal the leade/throats/bbl and have enough elasticity to stay intact when hitting the forcing cone, survive the rotational torque & the compressions of the lands. Several years ago I did a little head to head testing with plinking loads in a 44mag using traditional cast/lubed bullets VS the same cast bullets and pc'ing them. The accuracy standard was set @ 1 1/2" 6-shot groups @ 25yds. I did ladder tests with 5 different bullets and 7 different powders. At the end of the tests the pc'd bullets had 13 targets that did 1 1/2" 6-shot groups compared to just 3 targets for the traditionally cast/lubed bullets. 13 Vs 3 is huge Note the 5-shots in 1 bughole and 1 shot out on the 13 targets. It's that junk mixed brass thing again.
https://i.imgur.com/BAyAIIY.jpg

Myself I'm a firm believer in crimping my 357 reloads along with everything I reload for. It's my belief the crimp aids in taking some of the differences of the brass's neck tension out of the picture along with alloying the powder to get a better/more even burn.

If you break your reloads down to test different parts of the reloading components a chronograph can be extremely useful. Ladder tests and components over a chronograph can be an eye opener. A short bullet like the h&g #41 seated in cases deep enough so that they are not in the leade/throat of the chambers will test the quality of your brass (neck tension) along with your crimp. After you test/find out if your brass is up to snuff you have a base line of chronograph data to feed off of. Change the alloy, lube, etc and re-test looking for the same accuracy or better accuracy along with noting any increase/decrease in velocity & if the es/sd's were lower or higher. Test different powders after you have your alloy/lube/brass sorted out looking for extreme accuracy & consistently low sd/es's.

A short bullet in a long case like the 357 will easily show the reloader huge swings in chronograph #'s along with group sizes. A chronograph isn't an answer all for accuracy. But it will aid in telling you when you have found consistence with your components/combo of components. A good example of this is when your running test loads & have cut your sd in 1/2 but still don't have any accuracy. Use the same cases/powder/primers & start different alloys/lubes/bullet designs. Soft alloy's & pc'd bullets tend to take the alloy/lube thing out of play when looking for accuracy, it's that 13 vs 3 thing.

Anyway sorry for being long winded. Accuracy is a combination of things and a chronograph is most useful when testing 1 thing at a time.

Just another opinion

[RedHawk357Mag]

Anyway sorry for being long winded.
Just another opinion

Excellent! I appreciate the effort to express your findings. Thank you

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[RedHawk357Mag]

Forrest, quick question how long have you been PCing Vs traditional lube?

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[fredj338]

I think many get all tied up in chasing numbers on their chrono. The final word is always how do they group? Lead bullets with unique is a good example. Often SD & ES are pretty high compared to some other powders but the groups are smaller. Paper targets don't lie, just go with that.

[Forrest r]

Forrest, quick question how long have you been PCing Vs traditional lube?

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Haven't been pc'ing bullets that long, started in dec 2013 (5 years+).

I still use traditional cast/sized/lubed bullets in the hp rifles. I also like to use 45/45/10 lube or a combo of traditional lube + 45/45/10 along with pc + 45/45/10.

100% of my pistol/revolver bullets are now pc'd.

[Hi-Speed]

...I find even with well matched components best equipment, etc that powder type and amount plays the biggest role in getting low ESs. Power Pistol for instance literally cuts my ES’s in half compared to Unique in 38-44 and 357 Mag mid range loads. In 38-44 and 158 gr SWC’s, 2400 ES’s don’t behave until heavier charges are thrown, 11.0-12.0 grs. Try looking at your powder would be my humble recommendation.

[MostlyLeverGuns]

Back to reducing ES, I find uniforming primer pockets and deburring flashholes makes a difference. Case length uniformity and case neck tension also count. Annealing case necks in a consistent manner assists in uniform case neck tension and crimp 'tightness' where crimps are required. In rifles, case weight(powder capacity) can make a difference. In most cases, the farther you shoot, the more you will notice vertical stringing due to velocity variance. Sometimes primer strength can make a difference, stronger primer/weaker primer depending on powder. Powder position, using a powder that 'fills' the case or filler to keep the powder in place also helps reduce ES. I don't normally fuss at primer pocket uniforming for pistol or revolver cartridges, but I seldom shoot handguns beyond 50 yards on targets, though I still find accuracy of a good handgun surprising at longer ranges (150,200,300 yards).
I just enjoy getting my 'saddle and brush guns' to go MOA or better at 200 yards and beyond. Some would say I am wasting my time and should run a bolt gun??

[JoeJames]

There's lead and then there's lead. Hard cast vs soft cast (swaged):

Test of new Speer 158 grain 38 cal. lead swaged SWC’s

Old load of hard cast 160 grain swc’s, over 3.8 grains of Bullseye: 823, 833, 830, 820, 849, 820 = avg: 830 fps.

New load - Speer swaged swc’s over 3.8 grains of Bullseye, = Model 15 & Model 67: 763, 782, 773, 774, 760, 784, 783, 792, 791 = average 778 fps. Using a Model 15 4" and a Model 67 4". No appreciable variation in velocity between the two revolvers this time. Same powder charge (3.8 grains of Bullseye), and same primers (CCI 500 small pistol). Only variable is the hardness of the boolits. Hard cast vs. swaged soft lead Speer. Still shoots to point of aim.

237788

[Black Jaque Janaviac]

Crimp seems to be mentioned quite a bit. I have a question:

If crimp is critical for consistent velocities, then isn't case length a critical factor in making consistent crimps?

I reload a lot of .357s and I've never really heard of anyone checking case length of these straightwalled cases. But when I think of how a Lee FCD depends on the case length - I wonder if it makes for uneven crimps.

[JBinMN]

Crimp seems to be mentioned quite a bit. I have a question:

If crimp is critical for consistent velocities, then isn't case length a critical factor in making consistent crimps?

I reload a lot of .357s and I've never really heard of anyone checking case length of these straightwalled cases. But when I think of how a Lee FCD depends on the case length - I wonder if it makes for uneven crimps.

IMO, Yes.

OSOK touched on that issue early in the topic on how he had some 38Spec. rounds he needed to pull, and found that the one round that was crimped deeper into the crimp groove was much more difficult to remove from the case than the other shorter cases & where they were crimped. The location of the crimp seems also to have an effect.

There may be others that mentioned such things, but OSOKs post stuck in my mind better due to the related info given about his observations in that "anecdotal evidence".

Thinking about the pressure increasing inside the case from the expanding gases. If the pressure builds to a certain point before the projectile is released from the crimped case and it is different than the pressure(more) reached by a round that has a tighter crimp, the amount of pressure would likely cause the "push" that propels these projectiles from the cases to reach different velocities, with the lighter crimp reaching less pressure before release & thus less velocity than the one with the heavier(tighter) crimp where pressure could have a chance to build even more than the ones with the less tight of a crimp.

Length of case determines just where the die is set for crimping, and once the die is set for one case length it would not be in the same place as other length cases. If a shorter case is use to set the die, and then a longer case is run thru the die, the longer case will have a tighter crimp than the shorter one & make release of the projectile more difficult, thus more pressure required to get the projectile moving than the shorter case. Pressure in the case is one of the factors that determines velocity of the projectile & if the pressure in the longer case is higher than the pressure in the shorter case, more velocity is likely the result for the longer cased projectile that had more pressure pushing it, if all the other factors(bbl. length, bore size, components, case length etc.) remain the same.

I have been trying to think of an analogy or example to help explain and while I thought about levers & moving the point of pivot to change pressure(weight) needed to lift, I thought about garden hoses & how much thumb you put over the end changes things, even popguns with a cork & shaken bottle of soda pop with a cork, but I just could not nail down a good one to share to try to help out. "Brain freeze" time for me on that it seems...

Anyway... Others may give a better description than I have, but I tried to help anyway.

[Black Jaque Janaviac]

You explained it well enough JB. I'm just perplexed that I don't read more about people minding case lengths with revolver cases. In fact I gave up trying to trim them when I got a Lee .357 Mag trimmer and tried a bunch of cases - well the trimmer length appears to be set for a maximum because the cutting teeth hardly touched the mouth of any of the cases I tried to trim.

I measured the case lengths and they had a pretty good amount of variation - but I couldn't figure out how to trim them all down to the shortest length with the Lee trimmer. And I just didn't find much reading about guys who bothered with this sort of thing.

I recently picked up a Lee collet crimper which may be different - the crimping indexes off the shell holder - so maybe this gives a more even crimp?

[JBinMN]

You explained it well enough JB. I'm just perplexed that I don't read more about people minding case lengths with revolver cases. In fact I gave up trying to trim them when I got a Lee .357 Mag trimmer and tried a bunch of cases - well the trimmer length appears to be set for a maximum because the cutting teeth hardly touched the mouth of any of the cases I tried to trim.

I measured the case lengths and they had a pretty good amount of variation - but I couldn't figure out how to trim them all down to the shortest length with the Lee trimmer. And I just didn't find much reading about guys who bothered with this sort of thing.

I recently picked up a Lee collet crimper which may be different - the crimping indexes off the shell holder - so maybe this gives a more even crimp?

I am glad I help out a bit.
:)

I think the reason most folks do not trim straight walled pistol cases is due to the shorter ranges usually shot. (or perhaps apathy/laziness, LOL who knows for sure.) I have both the Lee trimmers & a Lyman Univ. case trimmer & I have not yet "needed", IMO of course, to use them for handgun cases, since I am not yet to a point where I think it necessary.
Simply because most of my handgun shooting is at 25yds or less, and I do not compete against anyone, unless it is just for fun & they are usually using my firearms. IOW, even without trimming, my groups are satisfactory enough to me to not need go into any more efforts to improve them at this time.

EveryoneMMV/YMMV, regarding the need for trimming straight walled pistol case, of course. I am not going to argue with anyone if it is "right or wrong', is basically what I am saying.. ;) I currently don't but anyone else is free to do so if they prefer.
:)

I think some time in the future, I may just do some experiments to see if I can find a good reason to trim the handgun cases for the calibers I have, just to see if it makes any difference off sandbags for accuracy & thru a chrony for velocity. Just for ****s & giggles & my own personal research. I have not heard or read of anyone doing so & I think it would be interesting to find out.

I may also just take a steel straightedge like a ruler to a row of cases just to see how much variance I have in them based on headstamp. I 99% of the time use the same headstamp & rarely used mixed case, as well as I keep track of times fired as well. So I think it would be interesting to check that as well & then perhaps, using the Lyman with the adjustable setting rather than the Lee with a "set" length setting & compare the results of non trimmed headstamps to trimmed ones of the same headstamp, just to see what results might be found & possibly differ...
{ I really like testing different things related to shooting & handloading when I find the time, even if others have already done so; Just so I can see if my results are the same or not. It is just one of those things I like to do. ;) }

Anyway... Once again, glad to have been a little help, BJJ!
:)

I hope this little sidetrack from the topic subject is not frowned upon. It was not meant to be something bad, I assure ya.
;)

[Messy bear]

The crimp thing you guys been hashing. Good point on case length. I used to shoot silhouette with jacketed and with small and shallow crimp groove, I found that trimming for uniform length helped consistent " pull " and therefore helped consistensey that was measurable over the chronograph.
But I don't know if it's all that helpful with cast because of the generous crimp groove that we usually haveto work with. If your groove is small and shallow I would say it might help.
Try different primers. I have found certain brands will ignite powder differently and you can close up extreme spreads by experimenting with them.

[Black Jaque Janaviac]

I went and searched up one of the threads about trimming revolver cases - and most of the replies indicated that people don't bother.

However, now I'm wondering if velocity spreads are more deleterious for rifle shooting than pistol. And if that's the case, maybe the guys shooting .357 mag out of a rifle might trim the cases for uniform length - and consequently uniform crimp. I'll go start a thread in the levergun section. . .

[Larry Gibson]

With regards to trimming straight walled pistol cases.......

Yes, it does sound very good in theory that trimming cases to a uniform length gives a more consistent crimp and should give a more uniform pressure better velocity SD/ES and thus provide better accuracy.

However, as good as the theory sounds I have not been able to measure any better improvement based on velocity measurements, psi measurement or accuracy. Having tested the theory in the 357, 41 and 44 magnums and recently in the 45 Colt I do not trim straight walled pistol cases as it has proven to be a waste of time.

In a recent test of a 252 gr cast bullet in the 45 Colt I used Starline cases that had been fired several times with mild level I loads in my SSAs and M1873 carbine. The trimmed cases were trimmed to the "trim to length" (1.275") in the CBH #4. The untrimmed cases were about .005 longer. The load was 6 gr of Bullseye and the primer was a WLP. The test firearm was a Contender with a 10" barrel. Velocity and pressure measurements were by the Oehler PBL. Accuracy was based on the 10 shot group at 50 yards with widest CTC shots.

With untrimmed cases;
Velocity 930 fps, SD 13 fps, ES 42 fps
Pressure; 12,900 psi, SD 500 psi, ES 1,500 psi
Accuracy; 1.8"

With trimmed cases;
Velocity; 923 fps, 10 fps, ES 35 fps
Pressure; 13,000 psi, SD 800, ES 2,600 psi
Accuracy; 1.8"

As with tests with the other cartridges there was essentially no difference ( any noted difference is well within the test to variation of the same load) between trimmed cases and untrimmed cases.

[RedHawk357Mag]

The last set of used brass I purchased was around 300 pieces of 357. I am a reluctant brass trimming camp guy. This is a picture of how this brass broke down. 1.280"-1.291". I bought a lot of mixed brass once that was around 1k in pieces unfortunately it was like 970 nickled brass and I don't do nickled brass. Some of it had been prepared for loading to the point of being expanded. It was so trumpeted that it would not fit in mouth of resizer. Alot of the cases had to be rolled on the bench under a block of wood to close case mouth so they could be resized. In that lot I remember lots of 1.293 and several 1.295". The short ones were in mid 1.270"s. Unfortunately I never really payed attention to new brass sizes but I did just order 100 Sig Saur 357 mags from Midway to test. I will post breakdown of them when they come in. Starline is my most common purchased brass. I resize all five hundred cases, then measure and sort by .001". I form lots of same sized brass and trim minimum pieces of brass to complete boxes.

Problems I see with untrimmed brass. Resizing no issues. Expanding, cases either not expanded enough or expanded too much. With not enough expanding I would think bullet shaving, misaligned seating, and interruption of the loading process in a progressive loading operation would be likely. With too much expansion, excessive working of case mouth leading to premature case wear, potentially interrupting progressive loading process. Bullet seating, variance in airspace in cartridge leading to variance in pressure. Where this could be a real issue is where "stacking of tolerances" works against you. Small case capacity, fast powder, heavy side of acceptable powder throw, a minimal diameter bullet loaded in a case with lower amount of case tension with minimal crimp force applied smacking a feed ramp COULD lead a within safe load into a pressure event. Crimping or removing of case belling, short cases not being crimped or belling remaining to the point of not allowing cartridge to chamber. Long cases, uneven crimp pressure, excessive working of case mouth, reduction in effective case tension due to cartridge walls pulling away from bullet sides due to cartridge being pushed down by crimp ring, deformed bullets by being pushed too far into die.

I can barely stand trimming brass but I find it necessary to make the best load I am capable of producing. I believe tired worn brass is the culprit in accuracy and velocity variance that led to this post. Preliminary test results with new brass showed reduction in overall group size and velocity variance. Waiting on weather to determine if results are repeatable.https://uploads.tapatalk-cdn.com/20190314/64c01d78d1826efc77941284c6b209e5.jpg

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[gareth96]

I just started PC'ing bullets.. I loaded some with just 'range brass' and my Unique load & 230gr boolits that I developed using 45-45-10. Accuracy was spot on.. with a rest was a little over an inch at 15 yds, but ES was in the 70's. Then I tried the same boolit (same 'lot' PC'd at same time) in brass that I was anal on processing. All trimmed to same length, pockets uniformed, etc, and loaded with True Blue. It was only 5 shots, but my ES was 3, I was stunned... However, the group opened up to about 3".. fwiw.. I loved the ES, but not sure I'll load any more because of the group.

[RedHawk357Mag]

I loved the ES, but not sure I'll load any more because of the group.

I tend to approach this a little differently. I would definitely want to know if this is reproducible. If I am not getting the results that I expect I definitely want to know why.

I make note of things that don't work and try to find out why. For instance leading, I check off the usual suspects, bullet too small, lube insufficient in some way, not enough pressure, too much velocity, throats/barrel mismatch diameter, expander/brass wall thickness/alloy hardness affecting bullet diameter, crimping die/technique changing bullet diameter. Lot's of things to be learned by analysis of less than expected results.

The results of Mr. Gibson inspires me to evaluate what I think I know. That's why I ordered some virgin brass to see if I have similar results with untrimmed brass. But I still maintain that his results may have been different using brass with variance that I had in the new to me brass in picture. I know that people maintain that they never trim straight wall brass and load random headstamps and shoot groups half the size of mine at double the distance. I don't doubt it is possible but I want to see if I can replicate it. It is said proof is in the pudding

Also I fully agree with you an accurate load trumps any numbers from a chronograph. But it must do it more than once and a third time isn't that outrageous before I load a hundred of them.

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[Jayhawkhuntclub]

I've seen loads with spreads over 100 fps consistently shoot sub moa at 100 yards. Velocity variation generally has little impact on accuracy until the distance is far enough for bullet drop to become a factor. I chrono anything that is for shooting past 300 yards. For pistol rounds, I have rarely used a chronograph.

[Silvercreek Farmer]

Following. I'm working on a economical and accurate load for my Ruger 77/357 to use mostly for field position practice. So far the Lee 120 TC, HF Red PC, over Promo for 1500 fps looks promising, but they are showing a bit of vertical spread my ES is higher than I think it should be. I don't remember off the top of my head, but perhaps 70-80 fps. I started with a goal of 3 MOA, but I think 2 MOA might be possible.

[TRM]

You are so right.

[Silvercreek Farmer]

You explained it well enough JB. I'm just perplexed that I don't read more about people minding case lengths with revolver cases. In fact I gave up trying to trim them when I got a Lee .357 Mag trimmer and tried a bunch of cases - well the trimmer length appears to be set for a maximum because the cutting teeth hardly touched the mouth of any of the cases I tried to trim.

I measured the case lengths and they had a pretty good amount of variation - but I couldn't figure out how to trim them all down to the shortest length with the Lee trimmer. And I just didn't find much reading about guys who bothered with this sort of thing.

I recently picked up a Lee collet crimper which may be different - the crimping indexes off the shell holder - so maybe this gives a more even crimp?

Sand a little off of the end of the guage pin. Go slow, measure often. Only takes a few scratches on some 200 grit paper.

[country gent]

The Creighton Audette ladder work up for working up loads was meant to find the "sweet" spot in the barrels harmonics where the variation in velocity didn't matter as much whether powder, capacity or crimp induced . His method was to load one round every .2 grain from starting to max and shoot using the same target sight picture position keeping each shot the same. You end up with a string running up the target with the occasional clusters of 2-4 shots in a group. For this to work you need to accurately plot the shots as fired on a target besides you also. You then go back and test at the mid point of the clusters. This finds the point where the bullet is leaving the muzzle at the dead point of the harmonics. The wife and I worked up our 223 loads in this way. When done the loads charge could vary from 23.2 - 23.6 and still go into the group.

ES or velocity variations show up more as the ranges increase. Ive seen loads perform in testing at 200 yds that fell apart at 600

[jimb16]

I may have missed it in this long thread, but if I'm trying to get the absolutely most consistent/smallest ES I try to make certain that all of the brass that I'm using is from the same batch. Even from the same maker, batch differences can exist due to slight changes in the material used for the cases. The walls can be thinner, or thicker. The neck tension can vary due to material difference. Just sayin'......

[JoeJames]

Kind of a personal interest in variables: fixing to run out of CCI 500 primers, but did some digging in my storage tub and found a carton of new Winchester small pistol primers. Wondering if y'all had noticed any variation in accuracy or velocity between CCI 500's and Winchester small pistol? Being as how a carton of primers is rather expensive, I'd just as soon use the Winchester.

[RedHawk357Mag]

JoeJames, I have used both, I don't think there is much difference between the two. I have read Winchester provides a bit more heat. If I recall it says on the sleeve that they are for both standard and magnum loads. I used them when dinking around with HS6 for awhile. I kinda just gravitate to CCI for no particular reason other than I have always used them. I was gifted 1k of Remingtons but used them only for blasting rounds. I never seriously tried to actually develop any loads with them. I have never bought Remingtons but I would purchase Winchester if CCI wasn't available and would not feel handicapped.

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[country gent]

In my high power rifle rounds and BPCR Remington primers shine with the best numbers and accuracy. I have used Federal gold medal, 210s. CCIs standard, Winchesters and Remington's. I

[JoeJames]

JoeJames, I have used both, I don't think there is much difference between the two. I have read Winchester provides a bit more heat. If I recall it says on the sleeve that they are for both standard and magnum loads. I used them when dinking around with HS6 for awhile. I kinda just gravitate to CCI for no particular reason other than I have always used them. I was gifted 1k of Remingtons but used them only for blasting rounds. I never seriously tried to actually develop any loads with them. I have never bought Remingtons but I would purchase Winchester if CCI wasn't available and would not feel handicapped.

Sent from my XT1650 using TapatalkThanks for the input on Winchester primers. I figure I was going to use them anyhow; since I have found a new carton with 1000 primers in it, but a little reassurance don't hurt a bit. Course I will chronograph them to make sure I am getting about the same velocity as I get with the CCI 500's.

[JoeJames]

Winchester makes a small pistol standard and a small pistol magnum. It is the large pistol primers that are a hybred between standard and Magnum.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.Learn something new every day, I reckon. I have a quantity of Winchester Large Pistol Primers, the exact description is "Large Pistol (MAG)", and I wondered about that. I have been reloading some 30 or 40 years, and just had not run across that. And now I know. Thanks.