308 Win Projectile Comparisons

[Drop shot]

G'day;

Over the last 3 years, we've been doing projectile comparisons for a number of different cartridges in different barrel lengths.

Attached is the 308 Winchester data we have collected.

These are all verified loads which includes a jump test.

Standard atmospherics apply;
Temp = 20°C
Pressure = 30 inHg
Humidity = 50%
DA = 660ft or 200m

Black cells indicate trans - We determine this to be the limit of the predictable flight path for bullets generally speaking. Some bullets make it through trans ok, some make it all the way to sub ok, but we have to choose a limit so for comparison purposes, we choose trans.

The wind is a 3 O'Clock, 10kph wind - for comparison, whilst drop is interesting, it's not necessarily relevant to hit probability and therefore we use wind drift as the great divider. As such, the figures in the cells next to each range and below each projectile type are drift in tenths of mils.

Some important things to note.

Your gun might attain a different muzzle velocity with the same projectile, the comparison will be the same across projectiles. Eg, if you get a faster MV out of the 155s, you'll get a faster MV (generally speaking) out of the other projectiles. The exception to this is the heavies that can't go longer (eg in the AR10 Mags) or where the throat is stopping the projectile.

All rounds were at least .75 MOA accuracy - most were .5 for an average - the SMKs short range accuracy tends to be better.

Twist rate varies across the barrels. Faster twists tends to keep the bullets stable for a longer distance. This can be seen in some of the results where in a shorter barrel may have less wind deflection or longer range than a longer barrel. We have tested down to 12.5" but this is under legal limits and was not included here.

Longer barrels with faster twists tend to deform bullets with the 6mm Creedmoor blowing up 108gr ELD-Ms at 3050fps with a 1/7 twist.

We can see concentricity issues spinning the bullets too fast, and a reduction in accuracy as the bullets jackets are stressed.

We measure each lot of projectiles, and we measure 100 rounds from each lot. There are variations between lot numbers. Berger is particularly guilty of this - so if you input this information into your BA of choice and get a different result, measure your projectiles.

We have also found that it is common for Digital tools like GRT and applied ballistic analytics'/kestrels to have different information pre-loaded in them and using the custom curves is not always the best way forward. Mil spec ammunition like the Mk248 series and M118 series are the exceptions which are generally about 98% correct with most of the variation occurring in the tips.

When assessing the projectiles we measure 100 rounds per lot, runnout is typically;

OAL;

Sierra = 8 Thou
Hornady = 3 Thou
Berger = 3 Thou

BTO;

Sierra = 2 Thou
Hornady = 3 Thou
Berger = 2 Thou

Boat Tail;

Sierra = 7 Thou
Hornady = 3 Thou
Berger = 2 Thou

We used to measure weight but there's no point as the distribution of that weight along the bullet's length is more important than the weight itself. As we don't have the tools to assess where in the bullet the weight is added/missing, and because we are unable to ascertain any discernible and repeatable results on targets for bullets that are heavier or lighter, we no longer bother.

Where the fields are white is simply where we don't have that particular projectile to test.

This information was collected by us for analytical purposes and provided to select groups/organisations.

Some of this data has previously been shared, in this forum, in part, by a member here who took it from that closed group and posted it here without permission. At the time, we felt that the nature of the post and the fact that this information was posted without our permission, was inappropriate and we asked the moderators here to take the post down, which they did. We want to say thankyou to Graeme for his support on the matter.

In retrospect, and in discussion with the rest of the team, considering the popularity of 308 in F-Class, we have decided to share the data in it's entirety.

It'll hardly blow anyone's mind to see where some projectiles stack up, given the experience in this forum, but some might find it interesting - particularly for use outside F-Class.

[John Weigel]

Sorry to show my ignorance. What is half-node max? I think it is the crux to seeing the patterns here, but not sure if a bigger value or smaller value is best - and more importantly, what it is rating. Sorry about that! But very interested in seeing what the tables show.

[Drop shot]

Sorry to show my ignorance. What is half-node max? I think it is the crux to seeing the patterns here, but not sure if a bigger value or smaller value is best - and more importantly, what it is rating. Sorry about that! But very interested in seeing what the tables show.

No ignorance to show mate.

This was just short hand for us to say where we found accuracy in the charge weights relative to the case capacity.

There's debate over whether nodes are a thing - in our cases we are more on the side of they do, but it's not a hill we'll die on.

Once we have found the accuracy point, we run a series of ladder tests across the accuracy point.

If it gives us a region or "node" of <5 tenths of a grain, we consider this a half node. If we get a node 5> we consider this a full node.

The max part is just we are close to max case capacity. Low is we are quite a way under max capacity but couldn't find accuracy and consistency pushing the bullet harder.

[Frank Green]

"Longer barrels with faster twists tend to deform bullets with the 6mm Creedmoor blowing up 108gr ELD-Ms at 3050fps with a 1/7 twist."

The problem here more than the bullet itself is the twist rate and velocity with the length of the barrel coming in at the end of the equation but you also have to figure in type of rifling and the round count on the barrel as well.

The bullet is coming out at 313,714rpm. The hard line in the sand is 300k or if you will as you approach 300k rpm bullet failure rate is going to go up. Sierra's, Bergers, Hornady's etc...your on borrowed time. The RPM wants to tear the bullet a part.

Type of rifling plays a part as well. The 5R rifling distorts/upsets the bullet jacket less vs a 4 groove or 6 groove barrel. So the 5R will help fight bullet failure.

Also how many rounds are on the barrel? The more worn/rougher the throat the bullet will take more of a beating when it makes the jump into the rifling. Couple that with the high velocity along with twist rate... and again bullet failure is going to show it's ugly face.

Also from test data that I got access to in Aug. of 2022 where 6 groove barrels where tested along with 5R rifled barrels.... I can't say the caliber but the velocity was 3000+fps along with high pressure. I didn't know we made all the barrels for the test and didn't even get the data till after the test was done. We made 7 barrels with 6 groove rifling and 5 barrels with the 5R rifling. So a total of 12 barrels where used in the test. Bullets tested where match bullets, high end hunting bullets and solid bullets. Same test was done twice. Two weeks apart to confirm the data from the first test and everything tracked. Every bullet fired was photographed right after it left the barrel. 10 shot groups for accuracy data. A total of 320 rounds fired. 11 hours to shoot and record the data for 160 rounds fired. Not one bullet fired out of the 5R rifling put a burr on the side of the bullets jacket. The burr on the bullet was as big as a 1/32" or if you will .031". This affected the bc of the bullet by as much as 5%. Accuracy was recorded at 200 yards only. The 5R rifling overall shot the smaller group avg but by only a .100". My comment to that was repeat the test but record the accuracy at 500 yards or further. That 5% in BC variation will show up even more.

[Drop shot]

"Longer barrels with faster twists tend to deform bullets with the 6mm Creedmoor blowing up 108gr ELD-Ms at 3050fps with a 1/7 twist."

The problem here more than the bullet itself is the twist rate and velocity with the length of the barrel coming in at the end of the equation but you also have to figure in type of rifling and the round count on the barrel as well.

The bullet is coming out at 313,714rpm. The hard line in the sand is 300k or if you will as you approach 300k rpm bullet failure rate is going to go up. Sierra's, Bergers, Hornady's etc...your on borrowed time. The RPM wants to tear the bullet a part.

Type of rifling plays a part as well. The 5R rifling distorts/upsets the bullet jacket less vs a 4 groove or 6 groove barrel. So the 5R will help fight bullet failure.

Also how many rounds are on the barrel? The more worn/rougher the throat the bullet will take more of a beating when it makes the jump into the rifling. Couple that with the high velocity along with twist rate... and again bullet failure is going to show it's ugly face.

Also from test data that I got access to in Aug. of 2022 where 6 groove barrels where tested along with 5R rifled barrels.... I can't say the caliber but the velocity was 3000+fps along with high pressure. I didn't know we made all the barrels for the test and didn't even get the data till after the test was done. We made 7 barrels with 6 groove rifling and 5 barrels with the 5R rifling. So a total of 12 barrels where used in the test. Bullets tested where match bullets, high end hunting bullets and solid bullets. Same test was done twice. Two weeks apart to confirm the data from the first test and everything tracked. Every bullet fired was photographed right after it left the barrel. 10 shot groups for accuracy data. A total of 320 rounds fired. 11 hours to shoot and record the data for 160 rounds fired. Not one bullet fired out of the 5R rifling put a burr on the side of the bullets jacket. The burr on the bullet was as big as a 1/32" or if you will .031". This affected the bc of the bullet by as much as 5%. Accuracy was recorded at 200 yards only. The 5R rifling overall shot the smaller group avg but by only a .100". My comment to that was repeat the test but record the accuracy at 500 yards or further. That 5% in BC variation will show up even more.

Yeah mate you are spot on. There's a lot of variables that come in - this was just a base line for information purposes. It's hard to incorporate everything. The throat and bore wear and the quality of the barrels plays a big part agreed, but yeah, the 5R is the way to go. Good to see a lot more manufacturers offering this rifling.

Agreed on RPM as well - though there's some exceptions to purely focusing on RPM - we use 300k as the cut off as well. The 1/7 twist 6mm was for heavier bullets initially but we ended up not getting a consistent supply and tried other bullets, so blowing up the 108s wasn't a surprise. We run these at 2895fps for short range pennant.

Solid info though mate - well put - thanks for including.

Carso