Bullet Profiles

[Ernest T]

Where, or how do you find bullet profiles measurements?

The case head to rifling measurement, with a 140 grain Hornady ELD match bullet, is too long to make a cartridge that will fit my magazine and come close to the lands. It looks like I have three options for addressing the situation; 1.) Try to find a load and COAL for the ELDs that is accurate and will fit in my magazine. I'm working on that option right now. 2.) Change bullets. And 3.) Skip the magazine and hand feed the cartridges. I guess there is a fourth option, removing the magazine binder plate and notching the feed ramp of my rifle, but that would be a last resort for me.

I don't know how to go about number two? What should I look for in a bullet profile that will close that gap between the lands and ogive while making a bullet that will fit the mag and where do I find that information? I know the ELDs have a lot of length in front of the ogive, but I have not seen the actual measurements anywhere, even on the Hornady site.

 

[mikecr]

IMO You don't need anything close to lands and you don't need a magazine.
But I vote option #1 to begin, find optimum seating that fits in your magazine, and then powder develop with that.
If your sure there is better, test longer CBTO, and possibly ditch the magazine.

Accuracy is more important than capacity, so 'where' good seating ends up should be accommodated.

Land contact datum -vs- nose length is likely impossible info to 'find', as it varies with leade(land) angles.
A bullet maker would have to declare land angle at something common (like 1.5deg) as a qualifier.

 

[mgunderson]

Shoot the bullet you want. I would suggest finding a seating depth that the only is shorter than mag length. As a learning exercise find a longer seating node that is closer to the lands. You will learn a lot doing this and have fun!

 

[CharlieNC]

Try using just using the bullet length, which should get you in the ballpark.

 

[Ernest T]

IMO You don't need anything close to lands and you don't need a magazine.
But I vote option #1 to begin, find optimum seating that fits in your magazine, and then powder develop with that.
If your sure there is better, test longer CBTO, and possibly ditch the magazine.

Accuracy is more important than capacity, so 'where' good seating ends up should be accommodated.

Land contact datum -vs- nose length is likely impossible info to 'find', as it varies with leade(land) angles.
A bullet maker would have to declare land angle at something common (like 1.5deg) as a qualifier.

I'm trying to see if I can find a configuration that that fits the magazine and provides sub MOA accuracy at 100 yards. That's my first goal. I've worked up loads starting at the minimum weight and maximum magazine length and will work back in length and up in weight to see if something clicks.

The next option is to try different bullet profiles. I think I identified the type of profile I need, but identifying a bullet that matches the profile could be problematic. I think I need the tangent ogive on the right below.

The last option would be to modify the magazine and rifle to accommodate a 2.920" cartridge.

 

[Ernest T]

Shoot the bullet you want. I would suggest finding a seating depth that the only is shorter than mag length. As a learning exercise find a longer seating node that is closer to the lands. You will learn a lot doing this and have fun!

Thanks! I've learned a whole lot more than I wanted! It has been fun though.

 

[Twdmar]

If this is a factory barrel, expect a lot of freebore and so hitting the lands from mag length may be quite difficult. Many bullets shoot very well with a pretty long jump. My palma load is a sierra 155 jumped something like 75 thou. Try some ammo at mag length and tune from there. There are multiple tuning methods, some that should work at 100 yds. Finding a 1moa load that is mag length should be easy. Service Rifle shooters do it all day long.

 

[HSMITHTX]

For a hunting rifle don't hesitate to start at mag length and starting charge, load 3-5 and then set the bullet back .020" for the next 3-5 and repeat until you are .100-.120" shorter than mag length. Find the length that shoots best in the first test and then load 3-5 rounds at that length and 3-5 more plus and minus .005" from that length and then work up pressure on the best of those 3. Once you find pressure back of .3-.5 assuming a 6.5 manbun and likely you will have a load that shoots well. If not I would switch powder next and still if not after that switch bullets and test. With a rifle capable of good accuracy this has worked great. I used to run single shot in a repeater to get close to the lands and things like that, for me I have found that all of the rifles I have done the above to will shoot very very close to if not just as good with a much longer jump. The other benefit is my window of distance to the lands before accuracy falls off is much wider. I find the shortest long jump that shoots well and load there, throat erosion only moves me closer to the middle of the window that shoots well.

 

[Rob01]

140 ELD-M, like other ELDs, do not mind a jump. They don't have to be near the lands.

What chambering are you loading them in and what rifle and magazine exactly?

 

[Ned Ludd]

Trying to make the gun (or the magazine) fit the bullet is likely to be an exercise in frustration. I'm not saying it can't be done with a little luck and perseverance, but it's not the typical approach. The bottom line is that you have a lot of jump when loading your bullet of choice to mag length, which means the rifle is throated long for mag length with that particular bullet. You're likely to be much better off just tuning the load using your bullet of choice with the realization that you may have to jump it a long way. If a seating depth optimum consistent with a long jump cannot be identified, then you need to be testing some different bullets that are more easily tuned with relatively long jumps. Trying to find a bullet of just the correct dimensions such that it can not only be loaded to mag length, but will also maintain a close relationship between ogive and the lands might be a relatively tall order to fill.

Nonetheless, Bryan Litz' "Ballistic Performance of Rifle Bullets" is a very good reference for bullet dimensional measurements, and other bullet-specific info. For obvious reasons, it doesn't have info on every single bullet known to man, but it has quite a few and it's a very useful resource. I wouldn't be without mine, and maybe it will help you to find just the right bullet.

Ballistic Performance of Rifle Bullets 3rd Edition

store.appliedballisticsllc.com

 

[Ernest T]

For a hunting rifle don't hesitate to start at mag length and starting charge, load 3-5 and then set the bullet back .020" for the next 3-5 and repeat until you are .100-.120" shorter than mag length. Find the length that shoots best in the first test and then load 3-5 rounds at that length and 3-5 more plus and minus .005" from that length and then work up pressure on the best of those 3. Once you find pressure back of .3-.5 assuming a 6.5 manbun and likely you will have a load that shoots well. If not I would switch powder next and still if not after that switch bullets and test. With a rifle capable of good accuracy this has worked great. I used to run single shot in a repeater to get close to the lands and things like that, for me I have found that all of the rifles I have done the above to will shoot very very close to if not just as good with a much longer jump. The other benefit is my window of distance to the lands before accuracy falls off is much wider. I find the shortest long jump that shoots well and load there, throat erosion only moves me closer to the middle of the window that shoots well.

I've started doing exactly that. except I've started at mag length and moved back .015 at a time with the starting load. I planned to work my way up with heavier loads and got through 38.7 and 39.5 grains (it didn't seem to like either one) and started on 40.4 grains when I noticed the screws holding the picatinny rail to the rifle had started backing out. I didn't have the right tools to fix it so I had to call it a day. That's too bad because the groups had started to tighten up some.

 

[Ernest T]

140 ELD-M, like other ELDs, do not mind a jump. They don't have to be near the lands.

What chambering are you loading them in and what rifle and magazine exactly?

It's a 6.5 CM in a Savage Axis II Precision with a 22" barrel. The polymer magazine says .308 and savage on it. I measured the opening at 2.870".

 

[Ernest T]

Trying to make the gun (or the magazine) fit the bullet is likely to be an exercise in frustration. I'm not saying it can't be done with a little luck and perseverance, but it's not the typical approach. The bottom line is that you have a lot of jump when loading your bullet of choice to mag length, which means the rifle is throated long for mag length with that particular bullet. You're likely to be much better off just tuning the load using your bullet of choice with the realization that you may have to jump it a long way. If a seating depth optimum consistent with a long jump cannot be identified, then you need to be testing some different bullets that are more easily tuned with relatively long jumps. Trying to find a bullet of just the correct dimensions such that it can not only be loaded to mag length, but will also maintain a close relationship between ogive and the lands might be a relatively tall order to fill.

Nonetheless, Bryan Litz' "Ballistic Performance of Rifle Bullets" is a very good reference for bullet dimensional measurements, and other bullet-specific info. For obvious reasons, it doesn't have info on every single bullet known to man, but it has quite a few and it's a very useful resource. I wouldn't be without mine, and maybe it will help you to find just the right bullet.

Ballistic Performance of Rifle Bullets 3rd Edition

store.appliedballisticsllc.com

Thanks for the link.

 

[Ernest T]

This was 40.4 grains at 2.192 CBTO which gives me a bullet. just short of magazine length. I wish I’d been able test this load a little more today.

This is a 1 1/4” group which is by far the best I’ve shot with 5 rounds in this gun.

On edit: This is a .072 jump.

 

[Beiruty]

The VLD bullets love to jump 0.040" or more. Some would like to be jumped 0.080"
All you need to know about Bullet jump to the land

Bullet Jump Research: Executive Summary & Load Development Tips

This is the last post in a series of articles focused on bullet jump research that has been conduct...

precisionrifleblog.com

 

[Rob01]

It's a 6.5 CM in a Savage Axis II Precision with a 22" barrel. The polymer magazine says .308 and savage on it. I measured the opening at 2.870".

With the 140 ELD and a SAAMI chamber you are touching the lands at 2.870" OAL. Not saying your Savage will be that as factory chambers can vary. That being said if you load to 2.820" factory ammo length there should be no problem with the jump and being able to be accurate with the right load.

 

[Ernest T]

With the 140 ELD and a SAAMI chamber you are touching the lands at 2.870" OAL. Not saying your Savage will be that as factory chambers can vary. That being said if you load to 2.820" factory ammo length there should be no problem with the jump and being able to be accurate with the right load.

Not on my rifle. With the Hornady 140 ELD Match, the COAL has to be longer than 2.920 to reach the lands.

 

[Ernest T]

The VLD bullets love to jump 0.040" or more. Some would like to be jumped 0.080"
All you need to know about Bullet jump to the land

Bullet Jump Research: Executive Summary & Load Development Tips

This is the last post in a series of articles focused on bullet jump research that has been conduct...

precisionrifleblog.com

Man, there's a lot of info in that series of articles that I have to read now!

 

[Dusty Stevens]

Seat them as long as you can feed in the mag then start testing. You can only go one way

 

[dgeesaman]

Sometimes an aftermarket mag exists that allows a longer coal. Tikka for example.