Thread: Ogive variance between batches (Sierra TGK .270)

I have one packet of Sierra bullets 140gr in .270 which came with the rifle I picked up off TardMe. I recently bought a second packet. There was a difference of up to 0.024” in measuring to the ogive between packets.

The newer box was all the same ogive measurement, and the overall length within 0.002” of each other.
The older box had a difference (compared to the newer box) of between -0.019’ and -0.024” for the ogive measurement, yet the overall length within 0.005” (including with the newer box).
Both packets had a consistent .277 diameter.

So even though the lengths were similar, and acceptable. And, of course, it’s expected to have differences between batches. This caught my eye as a rather unexpected jump in measurements.

I am new to this. I guess this is why people say not to mix your batches

Not uncommon with lead core bullets although I think it's not so much an issue now as it has been years ago. I remember being mystified somtimes at COAL changes when seating supposedly the same bullets but from different batches until discovering that between batches that ogives had subtly changed position or shape.
You're right, it doesn't pay to mix bullet batches at least until you have test seated and compared some to ensure everything is consistent. It's also a good policy when finding a good performing bullet to buy several boxes of the same Lot Number to negate any necessity for die changes when making handloads.
I would note that while this can also occur with monometal bullets I have never had similar issues with any that I have used.

Shouldn't matter much, load em up and send them. Check zero if you are worried

Originally Posted by Nick-D

Shouldn't matter much, load em up and send them. Check zero if you are worried

True, it may not affect accuracy but agree it should be tested.
Where it affected me was due to COAL changing the rounds were a tad too long to fit the magazine. Not a massive issue but a bit annoying nevertheless.

After experiencing this once (same lot of projectiles just a big variation in the profile of the ogive on those pills) I now work out what the max overall length is to fit the mag and check each round is less than that. Hasn't caught me since...

Adding the disclaimer there - for the hunting ammo I'm using it's more important to fit it into the mag than have perfect freejump to the lands. Some rounds it might make a heap more difference than for a dirty old interlock with the exposed lead tip!

As above, its a mid price cupped hunting projectile.
Sierra projectiles tend to be pretty tolerant of big jumps to the lands.
Don't beat yourself up over it unless you are shooting 1000m PRS matches (unlikely with a .270).

Originally Posted by 30.06king

True, it may not affect accuracy but agree it should be tested.
Where it affected me was due to COAL changing the rounds were a tad too long to fit the magazine. Not a massive issue but a bit annoying nevertheless.

Must have had quite a different ogive profile. Seating dies touch the ogive so it has to be quite a big change in geometry to significantly alter your jump or coal, you would typically just end up with a bit more bullet in the case.

Originally Posted by Nick-D

Must have had quite a different ogive profile. Seating dies touch the ogive so it has to be quite a big change in geometry to significantly alter your jump or coal, you would typically just end up with a bit more bullet in the case.

I remember it was one of the Hornady bullets and likely a 30 cal something. I assume the change in bullet shape / ogive was to a slimmer, more streamlined profile. This would make the seater cup contact the bullet further down the ogive causing the COAL to be longer and too long for my magazine as it was at the time.
Also had another incidence of changed bullet shape as another time but don't remember the cal or consequences. No repeats since though.

Originally Posted by 30.06king

I remember it was one of the Hornady bullets and likely a 30 cal something. I assume the change in bullet shape / ogive was to a slimmer, more streamlined profile. This would make the seater cup contact the bullet further down the ogive causing the COAL to be longer and too long for my magazine as it was at the time.
Also had another incidence of changed bullet shape as another time but don't remember the cal or consequences. No repeats since though.

Yeah the 150 gr SP Interlocks... Still got the old bastards, well away from the newer ones.. that threw me as to why same loads were different POI...
Thats when I found out the comparator and a set of digi verniers were such an asset in reloading..

Sierra hpbt from twenty years ago the projectiles overall lengths were all over the show as jacket folds etc at tip varied.but the olgive was in same place on them all( near as eyeteometor could tell) if they shoot straight stop stressing.

Originally Posted by Nasty Factory Trigger

Yeah the 150 gr SP Interlocks... Still got the old bastards, well away from the newer ones.. that threw me as to why same loads were different POI...
Thats when I found out the comparator and a set of digi verniers were such an asset in reloading..

Quite likely Interlocks. I shot quite a lot of those for a few years.

Originally Posted by Micky Duck

Sierra hpbt from twenty years ago the projectiles overall lengths were all over the show as jacket folds etc at tip varied.but the olgive was in same place on them all( near as eyeteometor could tell) if they shoot straight stop stressing.

I agree, though I once decided to batch my primers due to thickness... (pun intended)

Originally Posted by Micky Duck

Sierra hpbt from twenty years ago the projectiles overall lengths were all over the show as jacket folds etc at tip varied.but the olgive was in same place on them all( near as eyeteometor could tell) if they shoot straight stop stressing.

Overall bullet length variance was more of a thing with lead tipped bullets when they were pretty much the standard. But that's hardly a factor affecting accuracy so mostly not worth grieving over. I liked when plastic tipped bullets became common allowing reliability in COAL measurements.

Originally Posted by 30.06king

I remember it was one of the Hornady bullets and likely a 30 cal something. I assume the change in bullet shape / ogive was to a slimmer, more streamlined profile. This would make the seater cup contact the bullet further down the ogive causing the COAL to be longer and too long for my magazine as it was at the time.
Also had another incidence of changed bullet shape as another time but don't remember the cal or consequences. No repeats since though.

Ahh right a design change rather than tolerance variation. Makes sense