Author Topic: Load Testing: IMR 4756 powder  (Read 359 times)

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Offline Wobbly

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Load Testing: IMR 4756 powder
« on: November 29, 2019, 06:23:20 PM »
From IMR...
Quote
Fine-grained and easy-metering SR 4756 has long been a favorite of upland and waterfowl handloaders, not to mention that it’s legendary for delivering great [shotgun] patterns. Like Hi-Skor 800-X, SR 4756 performs extremely well in the big handgun cartridges.

Equipment List
Caliber:     9x19 Luger
Bullets:     Precision Delta 124gr JHP
Brass:       Mixed
Powder:    IMR 4756
Max Velocity:  1060 fps
Primer:     Federal Small Pistol
OAL:        1.110"
Pistol:      SP-01 Tac
Qty:        10 rounds each, slow fired
Weather:  60F and clear
Chrono:    ProChrono DLX
Load data from IMR: 6.3gr Max @ 1.135"

Load      Avg Vel           SD
5.5gr        1021              29
5.7           1057              37
5.9           1095              40 Above Max Load

NOTES
• Seems to track Bullseye velocities very closely
• This is a single-base powder
• This is not a very efficient powder in 9mm


« Last Edit: November 29, 2019, 06:51:12 PM by Wobbly »
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Offline jwc007

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Re: Load Testing: IMR 4756 powder
« Reply #1 on: November 29, 2019, 07:50:35 PM »
Very Interesting!   8)

I know I have an old Canister of it in my loading room, I just don't remember why I bought it.
I may have to consider using it up.
"Easy is the path to wisdom for those not blinded by ego." - Yoda


For all of those killed by a 9mm: "Get up! You are not dead! You were shot with a useless cartridge!"

Offline timetofly

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Re: Load Testing: IMR 4756 powder
« Reply #2 on: November 29, 2019, 10:09:58 PM »
Great report on the 9mm.  It is some very good info. 

The revolver part of me was wondering how it shot in your GP100?  Is it like VV N-350 or N-3N37?  I just started loading 38 SPL and I like N-3N37 so far, but I'm always looking for something better or what to stay away from. ;)

Offline ReloaderFred

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Re: Load Testing: IMR 4756 powder
« Reply #3 on: November 30, 2019, 10:06:57 AM »
SR 4756 is an excellent powder in the .38 Special, and I've been using it for factory duplication loads since about 1965, or so.  I'm still working off a 12 pound keg from when you could buy powder in 12 and 20 pound kegs. 

I've used it in 9x19, but I prefer it in .38 Special and 158 grain cast bullets for some reason.  It just works in that combination.  I've also used it in near maximum loads with cast bullets in .45 acp, where it also works.  With a full load of SR 4756, and a 230 gr. cast bullet, recoil is stiff, and it lets you know you're throwing a chunk of lead downrange, but it's going to hit where it's aimed.

Hope this helps.

Fred
After a shooting spree, they always want to take the guns away from the people who didn't do it. - William S. Burroughs

Offline Wobbly

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Re: Load Testing: IMR 4756 powder
« Reply #4 on: November 30, 2019, 01:33:52 PM »
I just started loading 38 SPL and I like N-3N37 so far, but I'm always looking for something better or what to stay away from. ;)


SR4756 is an obsolete powder no longer offered for sale. I wouldn't get started on it now unless you have an 8lb can laying around.
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Offline Pistolet

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Re: Load Testing: IMR 4756 powder
« Reply #5 on: December 02, 2019, 12:28:17 AM »
Equipment List
Caliber:     9x19 Luger
Bullets:     Precision Delta 124gr JHP
Brass:       Mixed
Powder:    IMR 4756
Max Velocity:  1060 fps
Primer:     Federal Small Pistol
OAL:        1.110"
Pistol:      SP-01 Tac
Qty:        10 rounds each, slow fired
Weather:  60F and clear
Chrono:    ProChrono DLX
Load data from IMR: 6.3gr Max @ 1.135"

Load      Avg Vel           SD
5.5gr        1021              29
5.7           1057              37
5.9           1095              40 Above Max Load

NOTES
• Seems to track Bullseye velocities very closely
• This is a single-base powder
• This is not a very efficient powder in 9mm

If I understand well, are you saying the 5.9 load is above max because the 1095 velocity is higher than the IMR data of 1060?  If so, how dangerous would it have been to go all the way to 6.3gr, almost a half grain?
« Last Edit: December 02, 2019, 08:17:38 PM by Wobbly »

Offline Wobbly

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Re: Load Testing: IMR 4756 powder
« Reply #6 on: December 02, 2019, 08:40:26 PM »
If I understand well, are you saying the 5.9 load is above max because the 1095 velocity is higher than the IMR data of 1060?  If so, how dangerous would it have been to go all the way to 6.3gr, almost a half grain?

Yes, there is a 1:1 correlation between speed and chamber pressure (within the loading range). So when you shoot a new-to-you load, you can use your chrono and the Max Velocity to warn you.



Going to 6.3gr would be a huge leap. Powder burns more efficiently at higher chamber pressures. Which is to say it may take 0.3 or 0.4gr to make the difference at the LOW end that you can achieve with 0.1 at the HIGH end of the load range. (It's NOT linear, it's a curve.) So what you'd want to do is drop back and check out 5.8gr. If those were low, then you could shoot a 5.9gr again. I'm not saying my numbers are gospel, I'm only reporting what my chrono told me. I have very reason to believe my test was done correctly, but on another day I might get another answer. 

Additionally, Velocity and Chamber Pressure loose their 1:1 correlation somewhere north of Max Load. So even if you have a chrono it's not going to be of much help. Notice that Pressure zooms upward while Velocity flattens out. More than one gun has been blown up chasing "that last 10 fps".

Bottom Line....  once you pass the Max Load all bets are off. If you need more velocity, then the thing to do is change your powder. Max Load then is like the red line on your car engine tachometer. You don't bury the tach in the red zone just to "see what happens" or to go 3mph faster. No, you shift from 3rd into 4th. So moving on to the next slower powder is equivalent to shifting gears.

Follow all that ?

« Last Edit: December 02, 2019, 08:51:34 PM by Wobbly »
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Offline Pistolet

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Re: Load Testing: IMR 4756 powder
« Reply #7 on: December 02, 2019, 10:11:13 PM »
Yes, got it. You are really making a case for getting a chronometer.

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Offline Wobbly

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Re: Load Testing: IMR 4756 powder
« Reply #8 on: December 03, 2019, 12:18:09 PM »
You are really making a case for getting a chronometer.


• For the 75% of shooters who just want cheaper plinking ammo for their friends and family members, then "No". They are working at about 92-93% of Max Load, and they are happy with their "bunny fart" loads. No problem. Their focus is on process refinement so that they can make thousands of identical and safe cartridges to have on hand when shooting friends drop by. We all make and have loads in this area.

• But if you are pushing a powder to get maximum performance*, or using a powder with very little load data, or trying to design a cartridge that works in your revolver and your lever action, or trying to keep a bullet sub-sonic, or any number of other "fringe" activities, then "Yes" it is almost a requirement.

* By "maximum performance" I don't mean seeing which 357 loads make the biggest bang. I'm thinking about testing N320 to achieve PF for competition, where the VV load manual suggests that 4.0gr is Max Load while the chronograph proves it is closer to 4.2gr in an SP01.

Hope this helps.
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Offline Pistolet

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Re: Load Testing: IMR 4756 powder
« Reply #9 on: December 03, 2019, 08:25:39 PM »
Yes this helps. I am one of the 75 percenters.

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Offline Wobbly

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Re: Load Testing: IMR 4756 powder
« Reply #10 on: December 04, 2019, 06:06:32 PM »
Yes, so your focus is much more concerned with obtaining accuracy. For that simply order a 500 pack of small individual targets, like TQ-2. Shoot your "incremental ladders" at those and see what your gun likes.



In God we trust; On 'Starting Load' we rely.

Immature reloaders ask: What's wrong with this gun?
Mature reloaders ask: What did I do wrong?

Check out my reloading equipment for sale CLICK HERE

 

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