Actual Bullet Weight Range: What is acceptable?

[Falloutboy89]

Since I just bought 147 gr. FMJ FN bullets from RMR I thought I'd do some random pulls and check weight.

 

I pulled over 100 and had some variance (see image). I'm wondering what is an acceptable range? Should I be doing this more often with all bullets?

 

Let me know what your procedures are when starting with a new bullet/weight.

 

Thanks

 

Edited July 15, 2019 by Falloutboy89

[HesedTech]

Get the average of say 10, lower it a little bit and make that number your standard for measuring PF.  If you “need” the PF to be that close to minimum then your over thinking the process. 

 

Personally I think most load so that PF is at least 5 higher than min, 130, 170.  What I do then is adjust powder for accuracy, which normally means bumping the average speed up some. My minor PF load averages 133.

 

Looking at your numbers I’d use somewhere in the 146.5 range for my standard.  You know at the Chrono stage the three they pull will be the lowest ones in your entire batch. 

 

 

Edited July 15, 2019 by HesedTech

[RAP]

What I do is take the lowest weight as my bullet weight in the formula to determine PF. Example, I recently purchased Brazos 145 coated round nose Bullets. I checked 20 Bullets the lowest weight was 145. That’s the weight I used.


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[zzt]

It depends on what you are shooting at.  For Steel Challenge and USPSA, bullet weight variance of 1 gr low to high is acceptable.  For bullseye, it is not.  If you load to 132PF with a 147 and they pull a 146gr bullet, you only drop to 128PF, so as long as your SDs are good, you'll have no problem.

[Falloutboy89]

I'm shooting USPSA and Steel Challenge. Not into Bullseye - at least not yet.

 

46 minutes ago, zzt said:

If you load to 132PF with a 147 and they pull a 146gr bullet, you only drop to 128PF, so as long as your SDs are good, you'll have no problem.

Makes total sense. Thank you.

 

1 hour ago, HesedTech said:

You know at the Chrono stage the three they pull will be the lowest ones in your entire batch.

Thanks for the info HT - I have definitely been "over thinking" it. I agree 100 with the above too. 

[Hi-Power Jack]

You'll find that everything has variance = OAL, powder charge, etc.

 

For USPSA and SC, none of it matters.      

[N3WWN]

Sample as many as you're comfortable weighing, calculate the average and the SD. You can then determine a "confident weight" with:

Wc = avg - (2*SD)

That will tell you the minimum weight for 99.5% of all bullets.

Do the same for your chrono numbers to get confident velocity, work up your confident PF using those two values and you won't worry at chrono ever again! [emoji6]

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[BallisticianX]

Dont overthink it. Not that uncommon to see a 1 grain swing in a batch of bulk bullets. Ive seen more!  Just load for 6-7 pf points above the floor based on the advertised weight and you have a built in buffer where a +/- 1 grain variance wont be a concern at chrono. After that as long as the load is accurate your good to go. With typical handgun yardages that 1 grain swing wont be the reason if the the load sucks either.  I personally run RMR 147 FMJ that have a 1 grain swing over A#2 in my ICORE revolver and its my money load...nothing has out shot that combo yet!

Edited July 16, 2019 by BallisticianX

[Yondering]

Agreed, for bulk bullets like that, a ~1 gr range of variation is not a big deal for pistol ammo. If you were shooting 1,000 yard rifle competition it would be worth addressing, but for our application it'll work great.

 

I'm more interested in your graphic actually. It's a nicely laid out presentation of the data. What software did you use to generate that? (I am one of those weenie engineers that likes numbers and stuff too. )

Edited July 16, 2019 by Yondering

[Falloutboy89]

Thanks to everyone that commented. Great info that gives me a plan moving forward.

 

1 hour ago, Yondering said:

I'm more interested in your graphic actually. It's a nicely laid out presentation of the data. What software did you use to generate that? (I am one of those weenie engineers that likes numbers and stuff too. )

I'm a designer by trade (who appreciates info graphics, data, etc.). I made it from scratch - used Adobe Illustrator. It's where I spend most of my time. Thanks for commenting and appreciating it.