IMR sr 4756 in 9mm Luger

[Captainmerzlak]

Totally new to reloading but I need some help here!

I am trying to find the most accurate/consistant load for several bullets. I use plated 124g rn and am currently loading them to 5.2g and oal of 1.135 With so so accuracy.

I am now trying to find a good charge for 124g precision delta fmj. at the moment I am at 5.2 with an oal of 1.140. I was loading up some at 5.4 5.6 and 5.8 with an oal of 1.140 when I checked imr's reloading center, they list the max at 4.9 oal of 1.090.

I called imr and the guy told me to load 4.9 at 1.090 oal. Do these guys know what they are talking about or do they just read from their web page? A 124g at an aol of 1.090 would be stupid short and I can't imagine it would function well/be safe.

I was under the impression I could load a max of 6.3g in a 124fmj oal 1.125
Does a reduction in oal of .035 drop the max charge from 6.3 to 4.9g? Doesn't seem right to me.

Any help on this would be great. and if any of you have some pet loads for 4756, feel free to share them. It would save me a bunch of time

Thanks,

 

[Jesse Heywood]

Welcome aboard.

Rule #1 - Never exceed load data from a powder manufacturer. They have the most current testing data, and it is their rear on the line if something goes wrong.

You are correct about reducing a charge with a shorter oal. What is your source for the 6.3 gr. charge?

 

[Captainmerzlak]

Sorry I should have linked it the first time.

6.3g from the imr handbook. http://www.imrpowder.com/pdf/IMR_handgun.pdf

If you use the imr "reloading center" which takes you to the hodgdon website you get a max of 4.9g

The handbook is published by imr. If you call them or use the reloading center data you get 4.9 it seem to me that they have decided to farm out the load data and in this day and age, nobody wants to take responsibility for anything and everyone want to sue somebody. So the charge gets dumbed down. At least that's what it looks like to me.

 

[Jesse Heywood]

It's not that charges have been dumbed down, but that technology in measuring pressure has improved. With the use of computers and pressure metering the manufacturers are no longer going the feel in the seat of the pants. Some powders have shown pressure far higher than previously thought. The 9mm has always been loaded on the edge.

Stick with the current data. Reduce the charge if you shorten the oal, especially on 9mm. Work up to the maximum load. Keeps you and your guns functional and able to return and ask more questions.

And don't get too attached to 4756, manufacturing ends this year.

 

[wlkjr]

I have 3# of 4756 but have only tried it at max for the G42 and it wouldn't operate the slide. Had read good things about it but haven't tried it in 9mm yet.

 

[Captainmerzlak]

In my glock 17 (stock) it started functioning reliably at 4.8g at 1.135 with plated. I have shot a few 100 now at 5.2 (990fps) and have seen no signs of pressure. I know recoil doesn't = pressure but at 5.2g, recoil feels about 30% less than wwb to me.

 

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It works good with 147 grain bullets, but I have never tried it with 124 grainers. 1.090 is not unreasonable but its not set in stone. You can go longer and be ok, but you can have problems is you go shorter than reccomended. Where did you get your load data at and at what length did they use? Shorter COL=less case volume=less powder. If you dont have the exact bullet listed try to find data at the COL you want or need to use and work up from there.