Weighing internal case capacity

[Reloader000]

Let me start of by saying I will not be shooting 1000 yards maybe 700 time to time . So is it worth weighing internal case capacity with water . Will it make a noticeable difference?

Im using starline brass not the best but what I have on hand . #1 batch consist of 125.0-125.9 I can mixed these up since they are all with in 125gr water value and load them up for a load . Or I can try and sort as many I can to make a batch on .3gr variance from that branch ????


Batch # 126.0-126.9 variance in water weight .

Did I waste my time water weighing Since I’m not not using top line bras ?

I know I have a lot of variance here . Any input would be great .

 

[jepp2]

So is it worth weighing internal case capacity with water . Will it make a noticeable difference?

What accuracy do you load your powder to?

Did I waste my time water weighing Since I’m not not using top line bras ?

Probably more to gain from the brass you have than with brass that has less variation. But I usually just weight sort by case weight on new brass batches. Much quicker and I know "not as accurate as sorting by water weight" but I go with it.

I gr. of difference in water capacity is a LOT. Were your cases fired and unsized when you did the sort?

 

[big5ifty]

I think you're wasting your time.

Weight difference can be accounted for in the variance of the machining of the extractor groove.

Get a good load, and practice shooting.

But if it gives you more confidence to weigh and sort, do it.

 

[6.5 forever]

I think you're wasting your time.

Weight difference can be accounted for in the variance of the machining of the extractor groove.

Get a good load, and practice shooting.

But if it gives you more confidence to weigh and sort, do it.

I 100% agree.

 

[big5ifty]

I'll add that determining internal case volume by weight of water is error prone and unreliable.

The margin of error can larger than the variation in actual volume.

 

[JFrank]

I don’t believe case sorting is a waste of time at all, I sort by speed and case weight rather than water volume.

 

[Beiruty]

Pick 10 random cases, fill to the brim with water weight, compute the net water weight for each
Get the min, max and the average and if you provide a load for your rifle, I will estimate min, max and average MV.
Then, I can estimate min, max and average drop at 1K.
Here is an

 

[Beiruty]

 

[Beiruty]

 

[quest450]

Or if you want to get really deep into this bottomless rabbit hole get the Bison Armory case volumizer

 

[Coyotefurharvester]

Won't the brass internal height and inside diameter of the neck need to be the same because of the meniscus effect? Than you would know a volume difference.

 

[Doom]

EDIT: I SCREWED THIS UP.

So the real question is what is the end effect of variations in case capacity. Gordon's Reloading Tool is a way to estimate the effect of varying capacity on velocity and pressure. Using a 308 case with changing the volume from 56 gr to 55 gr (Fired capacity) the velocity increases about 20 fps and the pressure increases by a little over 2,200 psi. (168 SMK, 41gr N135). Smaller case will have greater effects and larger less.

If everything is the same on the brass (rim recess, length, sizing, etc) then a 10 grain change in weight of the brass is about a 1.2 grain change in water capacity or .12 gr H2O/gr Brass.

It's up to the shooter to decide if and what type of measurements and limits are necessary to achieve the level of accuracy they need. Weighing cases works pretty well if all the brass is the same lot and came off the same machines (Lapua seems to fit this description). It does not always work well with some other cases such a Winchester. At least that has been my experience. Measuring fired brass is actually a more accurate method if someone wants get really deep in the weeds.

The OP can estimate the velocity effect as

0.9gr H2O x 20fps/gr H2O x 177gr/125.5gr= 25 fps. (estimate of extreme spread of 0.9 gr H2O capacity)


The 177gr is the assumed weight of the 308 brass (Lapua).

 

[Beiruty]

+- 0.25gr of internal case volume would result in max of 2.5" of vertical spread at 1000 yards from 6.5 PRC load (see my spreadsheet posted earlier above).
Unless the shooter is using a scope with 0.128 MOA turret, that can not be adjusted for at 1000 yards.

 

[Mulligan]

Or if you want to get really deep into this bottomless rabbit hole get the Bison Armory case volumizer

View attachment 1432234

Now I am curious, do you use one of these gizmos? What has been your experience with it?

CW

 

[SKWERLZ]

I just get usable case volume for my internal ballistics program and mark cases (and cull them if needed) that seem to produce anomalies.

 

[Dave M.]

Let me start of by saying I will not be shooting 1000 yards maybe 700 time to time . So is it worth weighing internal case capacity with water . Will it make a noticeable difference?

Im using starline brass not the best but what I have on hand . #1 batch consist of 125.0-125.9 I can mixed these up since they are all with in 125gr water value and load them up for a load . Or I can try and sort as many I can to make a batch on .3gr variance from that branch ????


Batch # 126.0-126.9 variance in water weight .

Did I waste my time water weighing Since I’m not not using top line bras ?

I know I have a lot of variance here . Any input would be great .

Never weighed a single piece of brass or put water or alcohol in any of them to measure internal volume. I compete at the top of the 600 F open class in my state and near the top of the 1000 yard class. Not worth it if you ask me. If I was to do anything, it would be to measure case volume using alcohol and sort the outliers. Make sure all of the cases are trimmed to the same length before measuring internal volume. But at 700 yards max, you will never be able to shoot the difference of volume sorted brass vs normal prepped brass used from the same lot #.
Dave

 

[Dave M.]

View attachment 1432221

did you weigh the primers? I feel like there are so many other things you could measure or work on to improve that would return more on your investment. I feel this is a massive waste of time. Buy good brass and work on wind calls and rifle tracking…that is a far better use of time. Also, did you measure the extractor groove and primer pocket dimensions on each?? Another source of variation.

 

[quest450]

Now I am curious, do you use one of these gizmos? What has been your experience with it?

CW

I do use it and I like much better than using alcohol or water, it is repeatable, the pic in my post is actually a screenshot of a batch of my BRA cases prepped for a match, I'm basically looking for any outliers but I hardly ever find any that might make a difference punching paper at 600 yards, I think it helps knowing that my brass prep is uniform and it helps my mental game.....I guess
But at the end the Indian still has to pull the trigger

Take a look at utoobe video by Ben Triplett from Bison Armory

 

[Mulligan]

Different brass companies, different results for me.
Norma and Alpha brass for me is absolutely worth sorting by weight

Lapua by volume

CW

Edit

Shot at 600 yards

 

[Beiruty]

did you weigh the primers? I feel like there are so many other things you could measure or work on to improve that would return more on your investment. I feel this is a massive waste of time. Buy good brass and work on wind calls and rifle tracking…that is a far better use of time. Also, did you measure the extractor groove and primer pocket dimensions on each?? Another source of variation.

It is a case study to show, that the case volume variation in good brass is unaccountable for up to 1000 yards. That it is do not care, unless you are shooting bench rest, and you want to win a national match.