Optimal bullet length

[Lemonaid]

https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

[Rosecrans1]

There is a huge link to accuracy based on the bullet used, case length and OAL length. But I think you'll find it is mostly on how the bullet aligns with the rifling of the barrel and not as much on how it is seated into the powder. (compressed or not).
OAL varies from gun chamber to gun chamber. Especially in an AR.
2.280 is 0.020" over what the max is for what most manuals call "the max" for a Grendel.

[grayfox]

Hello all, I thought I'd spark up a conversation about the optimal bullet length in an AR Grendel.
Here is my thinking:

Cartridge overall length of 2.280“ (max)
Bullet being seated to bottom of neck.
best length = 1.0106“

This brings up more questions to me than answers...
1. Why 2.280", what data or studies establish this, or is this just an assumption? Why assume that? Bolt actions... and some AR mags, can go upwards of 2.300".
2. There are both bolt-action and AR styles, how do we know that an "optimal bullet length" exists for the one action, or both actions, and how do we know whether it should be the same or a different length?
3. Please define "optimal bullet length" and what precisely are the advantages of said length. How do we know that this quality is actually useful, and for what?
4. Which part of the bullet is seated to bottom of the neck, and why can we conclude that any deeper of seating "intrudes" into powder column? This may sound funny but bear in mind that different mfrs of cases each has a different internal powder volume, and powders have differing densities, AND not all "best accurate loads" require 100% case fill... not to mention that some compression can be allowed for some powders. So, not sure why you can conclude this about powder column intrusion.
5. Where is the study that "shows" (or in your terms "seems") the link between bullet length and accuracy. I have not seen any studies that show that. Maybe I missed them?

Anyway, no offense, but such a sweeping generalization out of nowhere begs substantiation.

Right now, I'm planning on using my gold dots in my creedmoor.

[LR1955]

There is a huge link to accuracy based on the bullet used, case length and OAL length. But I think you'll find it is mostly on how the bullet aligns with the rifling of the barrel and not as much on how it is seated into the powder. (compressed or not).
OAL varies from gun chamber to gun chamber. Especially in an AR.
2.280 is 0.020" over what the max is for what most manuals call "the max" for a Grendel.

R1:

Yes, how the bullet aligns with the rifling is important but not as important as the right twist and velocity. Fixing a problem with the bullet going straight into the barrel is way easier than trying fix stability problems resulting from trying to shoot a bullet that is too long for the rifling twist.

As for an 'ideal' length, I am sure there is a way of calculating an ideal length but it really means nothing if the bullet is poorly designed and won't stabilize.

LR55

[Jimla]

Anyone got the length of the 120 Speer Gold dot?

I measured ten 120gr Speer Gold dot bullets:

Average Length 1.1210
Median Length 1.1213

1.1175 - 1.1235 range

[Jimla]

https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

[Sinclair]

R1:

Yes, how the bullet aligns with the rifling is important but not as important as the right twist and velocity. Fixing a problem with the bullet going straight into the barrel is way easier than trying fix stability problems resulting from trying to shoot a bullet that is too long for the rifling twist.

As for an 'ideal' length, I am sure there is a way of calculating an ideal length but it really means nothing if the bullet is poorly designed and won't stabilize.

LR55

Berger had a good explanation about the problems of optimal bullet design and how difficult it was to design when they announced their AR hybrid bullet. Lots of complicated number crunching to optimize the BC, SD, and mag length all in one design. Add to that is the problem that what my rifle shoots best doesn't work in yours at all pretty much rules out a one design fits all. Great concept just not achievable, at least that is my 2 cents worth.

After had said that, there are some bullets that seem to work at least so so in everyone's rifle. Flukes of nature or did someone almost get everything right?

[Lemonaid]

I measured ten 120gr Speer Gold dot bullets:

Average Length 1.1210
Median Length 1.1213

1.1175 - 1.1235 range

Thanks Jimla!

[SightedIn]

Just some personal data here. I used to always shoot 123 SST/Amaxs then one day out of boredom i loaded some 140SSTs meant for my creedmoor and to my chagrin, they shot better than the 123s ever had. Always hover around .5moa.
Handloaded 123's were usually around .7-.9 depending on barrel. Not that's that bad, just surprised how well the 140s did. Also surprised me how much the recoil increased

[Lemonaid]

This brings up more questions to me than answers...
1. Why 2.280", what data or studies establish this, or is this just an assumption? Why assume that? Bolt actions... and some AR mags, can go upwards of 2.300".
2. There are both bolt-action and AR styles, how do we know that an "optimal bullet length" exists for the one action, or both actions, and how do we know whether it should be the same or a different length?
3. Please define "optimal bullet length" and what precisely are the advantages of said length. How do we know that this quality is actually useful, and for what?
4. Which part of the bullet is seated to bottom of the neck, and why can we conclude that any deeper of seating "intrudes" into powder column? This may sound funny but bear in mind that different mfrs of cases each has a different internal powder volume, and powders have differing densities, AND not all "best accurate loads" require 100% case fill... not to mention that some compression can be allowed for some powders. So, not sure why you can conclude this about powder column intrusion.
5. Where is the study that "shows" (or in your terms "seems") the link between bullet length and accuracy. I have not seen any studies that show that. Maybe I missed them?

Anyway, no offense, but such a sweeping generalization out of nowhere begs substantiation.

Right now, I'm planning on using my gold dots in my creedmoor.

RE: #1 2.280 is just a in-between number, 2.260 is fine, 2.300 is fine, .040 difference won't make much difference in general (IMO).
RE: #2 in my OP I said "In the AR Grendel", so I excluded bolt, single shot or others from question.
RE: #3 I need help with this one, that's why I am asking for input. My thinking is that a bullet that is very long is not optimal due to it's having to be seated deep in the case so as to fit in an AR mag. From forum posts it looks to me that best accuracy is being had in bullets like Speer 90 TNT, Sierra 120's, Hornady 123's and others in the shorter side of the spectrum. There is a point where you can't put enough powder in the case for decent velocity with the longest bullets. Short bullets are great but lack high B.C's for long range. There is a happy medium (optimal) somewhere that can be useful when selecting bullets to try out. This can save money (useful).
RE: #4 the bottom of the bullet, the part that will first touch powder. If I understand correctly, that is the end of the powder column. Any deeper and you reduce the amount of powder that can be in the case and still have a bullet all the way into the neck. Case volume or powder density are not a factor at this point nor compression.
RE: #5 I know of no study. Should there be one? Gathering info and opinions. Is there a link? Are the longest bullets doomed to dissapoint? Where is the cut off point on how long a AR grendel bullet should be?
No offense from anyone taking the time and thought to post. I hope the same applies to me

[Lemonaid]

[QUOTE=Sinclair;231904]Berger had a good explanation about the problems of optimal bullet design and how difficult it was to design when they announced their AR hybrid bullet.

I would very much be interested in reading that, and may answer some of my questions. Where can I read that?

[Lemonaid]

Just some personal data here. I used to always shoot 123 SST/Amaxs then one day out of boredom i loaded some 140SSTs meant for my creedmoor and to my chagrin, they shot better than the 123s ever had. Always hover around .5moa.
Handloaded 123's were usually around .7-.9 depending on barrel. Not that's that bad, just surprised how well the 140s did. Also surprised me how much the recoil increased

Dang! Now I have to try the Sierra 142 Match kings I bought for my 6.5x55.
Were you satisfied with the velocity, and do you count that load as one you will keep on using?
Thanks for your post. More data!

[A5BLASTER]

RE: #1 2.280 is just a in-between number, 2.260 is fine, 2.300 is fine, .040 difference won't make much difference in general (IMO).
RE: #2 in my OP I said "In the AR Grendel", so I excluded bolt, single shot or others from question.
RE: #3 I need help with this one, that's why I am asking for input. My thinking is that a bullet that is very long is not optimal due to it's having to be seated deep in the case so as to fit in an AR mag. From forum posts it looks to me that best accuracy is being had in bullets like Speer 90 TNT, Sierra 120's, Hornady 123's and others in the shorter side of the spectrum. There is a point where you can't put enough powder in the case for decent velocity with the longest bullets. Short bullets are great but lack high B.C's for long range. There is a happy medium (optimal) somewhere that can be useful when selecting bullets to try out. This can save money (useful).
RE: #4 the bottom of the bullet, the part that will first touch powder. If I understand correctly, that is the end of the powder column. Any deeper and you reduce the amount of powder that can be in the case and still have a bullet all the way into the neck. Case volume or powder density are not a factor at this point nor compression.
RE: #5 I know of no study. Should there be one? Gathering info and opinions. Is there a link? Are the longest bullets doomed to dissapoint? Where is the cut off point on how long a AR grendel bullet should be?
No offense from anyone taking the time and thought to post. I hope the same applies to me

There isn't and can't be a optimum bullet length for the grendel.

Reason being is just because you feel a bullet is to long and takes up too much powder space and can't reach the velocity you like doesn't mean someone else feels the same.

Case in point I use the 127 lrx very long bullet, yep it eats up powder space, others deem it too long and slow. Me I'm going too rock that bad boy all day long. Both in ar and bolt action.

Bullet length too me means nothing when it comes too group size. Group size comes from seating depth, powder charge and type (burn rate), primer, twist rate and barrel length for velocity it can make.

[Sinclair]

[QUOTE=Lemonaid;231916]

Berger had a good explanation about the problems of optimal bullet design and how difficult it was to design when they announced their AR hybrid bullet.

I would very much be interested in reading that, and may answer some of my questions. Where can I read that?

I did not find the original article, but there is a summary if you go to: Berger Bullets/ Home/ Announcements/ AR hybrid. Sorry I could not copy the link, but that will get you there.

Click on the announcement and it will redirect to the summary. I have tried it and it works.

I have no luck searching for anything, but you might be able to find the original article that was in a shooting magazine, it had more info on the design constraints.

[Lemonaid]

Thanks Sinclair, appreciate it!