These 174 grain bullets are the same length/weight.

[Ignition Override]

The title should read "Both 147 and 174 grain bullets are totally identical and are approx. the same weigh, if not exactly".
Just compared these two apparently different bullets:

The bag bought from a private seller has a printed label: " '.311' 147gr. Surplus Bullet", "MPB311". This old faded bag was sealed when it arrived.
The identical twins: "Hornady .303 CAL. .'312' # 3130 Interlock 174 GR RN". These two boxes of "174 GR RN" are from sporting good stores.

Just weighed both on a digital kitchen scale (Escali) and over six times with each bullet the scale indicated 9 grams, .30 oz., with no variation.
How can you trust the bullet labels as being different weights, when they generally weigh the same and have identical looks, lengths, with faded gray on tips? Maybe the old bag's label is wrong?
Was extremely fortunate to have bought 3,000 rds. of surplus Brit, Aussie, Italian and POF surplus .303 since April. The large expense in time finding this ammo was well worth it, and will easily cover me as I take months to get reloading (for just One caliber) figured out.

 

[ants]

Shoudn't you be using a reloading scale in Grains,
rather than a kitchen scale in Grams?

 

[Ignition Override]

ants: Good point, and I did this a few days ago, but the Lee Safety Powder Scale silver ball only goes to the '100' index, all the way to the left.
The tiny plastic slide on the opposite end near the small silver 'basket' (where grains of powder will go, one day... I hope) plus the bullet far out-weigh the opposite silver ball, no matter where the tiny plastic slide is put. No way to fine-tune such a bullet on the scales: "clunk" as the basket with bullet hits the table.

But the basic multiple results on the kitchen digital ('Escali) scale seem to indicate that bullets from different Indicated weights are pretty much the same: 147 AND 174 grain. The lengths and appearance of both bullets are identical, and both have the same concave shape in the base.
This is my very first reload kit and going very slowly.

 

[ArchAngelCD]

I agree, you should be using a scale with the correct measures to be sure of your readings. I don't think the scale you are using will give you accurate information. I'm questioning your results because a 147 grain bullet should weigh 9.53 grams, .336oz. A 174 grain bullet should weight 11.28 grams, .398oz. If anything the heavier bullet is mislabeled but, in any event, if your scale is correct both bullets weigh only 139 grains. I doubt your scale is giving you an accurate reading, sorry...

BTW, congrats of finding so many bullets during a time when everything is hard to find...

 

[Ignition Override]

Thanks.

It seems really strange that the bullets that are actually labeled 174 grain are in those two Hornady boxes, which were sealed until opened.

 

[Kernel]

O.I., try weighting 10 or 100 bullets at a time. Then divide to get an average bullet weight. Adjust your sample size. It's likely your scale has a "sweet spot". Maybe then you’ll be able to detect a weight difference in your bullets. Still, I doubt it’ll be accurate enough for reloading purposes.

 

[Ignition Override]

Kernel:
Right, I only used the less-precise kitchen digital unit because my Lee scales can not equal a .303 (.311) bullet's weight.
Will have more time late next week and my friend has equipment which can check.

 

[kanook]

Zero out you scale

Place one of the lighter said bullets on the far end closest to or on the ball

Place one of the heavier bullets in your pan and see if your difference is there.

Hope I explained it right. If they weigh the same your scale will zero out again

 

[Ignition Override]

Thanks kanook:
When back in a few days will let you know the results.