Cannelure on 6.5cm v COL per load data?

KIBarrister · Oct 16, 2019

Started reloading for my 6.5 RPR and AR10. 140 grain Hornady SST has a cannelure, but when loading to COL spec’d in load data the cannelure is about .3” forward of case mouth. My understanding is that with Lee FCD I can crimp without the cannelure, but aside from looking a bit odd is there an issue with the cannelure not matching up with case mouth? Am I correct in thinking that COL is more important for pressure/safety considerations?

Speed3 · Oct 16, 2019

You are correct, COL is more important than matching the cannelure.

Doco Overboard · Oct 16, 2019

I load a full patch 270 round for years without the cannelure at the case mouth but its for a bolt gun. I'm not an expert re-loader but I wouldn't crimp anything outside of the cannelure on purpose. And then even up to the forward part and close as possible to the cannelure when I want to crimp. Adjusting seating depth can raise and lower pressure dependent upon the rifle,propellant, bullet case combination. For instance, a partially filled case that does not exhibit pressure signs with a specific type of powder when it's cold could give pressure indications when its hot out. Bullet seating depth for a specific combination could affect internal ballistics significantly with such a load as conditions change in a negative manner or if the cartridge is used in a different rifle.
I always start with published loads and work up for a particular rifle so I'm pretty conservative. Some one here will know more or have more insight.

Pinecone · Oct 16, 2019

Seating depth/COAL is another way to tune your load.

In my Rem 700, the longer I get, the tighter the groups. So I load as long as will fit in the mags (Manner's mini chassis stock).

Park ranger · Oct 16, 2019

Why crimp at all? Use enough neck tension and you won't need to.

Speed3 · Oct 16, 2019

Park ranger said:
Why crimp at all? Use enough neck tension and you won't need to.

I don't pretend to know loading for semis, but agree that is the route I'd go. Although I'm not sure many people outside match/serious shooters have bushing dies, or send out dies to be custom ground from the manufacturer.

Doco Overboard · Oct 16, 2019

Park ranger said:
Why crimp at all? Use enough neck tension and you won't need to.

How do you do that without reducing the neck diameter smaller than the shank of the bullet by more than .001 while keeping even neck tension at the same time?
I have a couple rifles and one pistol I always crimp for.

Thanks.

Pinecone · Oct 17, 2019

Doco Overboard said:
How do you do that without reducing the neck diameter smaller than the shank of the bullet by more than .001 while keeping even neck tension at the same time?
I have a couple rifles and one pistol I always crimp for.

Thanks.

That is what you do.

Adjust neck diameter to get the desired neck tension.

The bullets will seat. Even "flat" based, as there is a radius at the back.

Boat tails are EASY.

Speed3 · Oct 17, 2019

Pinecone said:
That is what you do.

Adjust neck diameter to get the desired neck tension.

The bullets will seat. Even "flat" based, as there is a radius at the back.

Boat tails are EASY.

Easiest way to measure neck tension(its what most do including myself but not reliable), take outside diameter measurement of a loaded round. Lets say it measures at .261. A .260 bushing will give your unloaded case neck .001" neck tension. In the example, for semi auto you will need more neck tension say .004" or a .257" bushing to give you the .004" neck tension(I don't know what is needed for a semi, but its more than needed for a bolt gun).

Although there are many factors that effect the bullet grip (neck thickness, springback, neck length, coating on bullet, lubing the neck, etc). In order to get a consistent neck tension, all brass you load will have to have the same neck thickness. There are 2 ways to accomplish this. You can turn necks to desired thickness or you can shoot them and after 3 or 4 firings, the necks thin out. Example, I necked down some 6.5x47 to 6x47 which caused thick necks and after 3 firings they thinned out and I had to change the neck bushing to be tighter to adjust.

Doco Overboard · Oct 17, 2019

Pinecone said:
That is what you do.

Adjust neck diameter to get the desired neck tension.

The bullets will seat. Even "flat" based, as there is a radius at the back.

Boat tails are EASY.

Even when you reduce the neck diameter smaller than the diameter of the bullet and then the bullet is seated, wouldn't the bullet then be sizing the neck to the detriment of the bullet and case?

I think sizing the neck as little as possible, just enough to hold the bullet would be a better bet because the more you move it, the more out of alignment the entire case becomes with the bore and chamber. In fact I know it does.
Not to mention, a bullet is a very poor expander. Most dies have enough clearance in the bullet seating guide alone to allow.003 room for oversize bullets so they are easy to get started crooked.

The why behind it is that a neck that is off by being sized more on side of it than the other for whatever reason allows the concentrically to be off half as much as the neck was sized to begin with.

Wouldn't this be like almost shooting a new cartridge case every time because you have the lost the benefit of the case being formed to the chamber and then the neck misaligned with the bore?

One last question, how can you tell when you have enough neck tension and what is the generally accepted number in pounds for neck pull?

I'm not trying to be argumentative, just trying to learn more about handloading.

E.Shell · Oct 17, 2019

Doco Overboard said:
Even when you reduce the neck diameter smaller than the diameter of the bullet and then the bullet is seated, wouldn't the bullet then be sizing the neck to the detriment of the bullet and case?

Elasticity.
The tighter neck grips the bullet harder and the small (customarily 0.001 to 0.003") difference isn't enough to permanently expand the case neck.

This might be helpful:
http://www.shell-central.com/Brass_Prep1.html

Doco Overboard · Oct 17, 2019

E.Shell said:
Elasticity.
The tighter neck grips the bullet harder and the small (customarily 0.001 to 0.003") difference isn't enough to permanently expand the case neck.

This might be helpful:
http://www.shell-central.com/Brass_Prep1.html

I see! Theirs an additional step that should always be done. Thank you for taking the time to share your knowledge and insight. I admittedly read through quickly but have learned in more than one discipline that you outlined a couple things that were a constant. I can return and study further.
I have already fell into the trap of work hardening with ammo that had been loaded and then stored for a period of time. Thats a pain in the backside when that happens. What went well initially didn't, after a period of time especially in a finicky platform.

On another note;
The picture of the old man in the store was great. A way of life that has all but nearly disappeared. I was fortunate enough to spend some time with some of the last of the legends the other night at a picnic, soon they will all sadly be gone. Some well into their 80's and still mentoring sharing wisdom with the young-ins. Great web page, thank you.

Pinecone · Oct 17, 2019

Doco Overboard said:
Even when you reduce the neck diameter smaller than the diameter of the bullet and then the bullet is seated, wouldn't the bullet then be sizing the neck to the detriment of the bullet and case?

I think sizing the neck as little as possible, just enough to hold the bullet would be a better bet because the more you move it, the more out of alignment the entire case becomes with the bore and chamber. In fact I know it does.
Not to mention, a bullet is a very poor expander. Most dies have enough clearance in the bullet seating guide alone to allow.003 room for oversize bullets so they are easy to get started crooked.

The why behind it is that a neck that is off by being sized more on side of it than the other for whatever reason allows the concentrically to be off half as much as the neck was sized to begin with.

Wouldn't this be like almost shooting a new cartridge case every time because you have the lost the benefit of the case being formed to the chamber and then the neck misaligned with the bore?

One last question, how can you tell when you have enough neck tension and what is the generally accepted number in pounds for neck pull?

I'm not trying to be argumentative, just trying to learn more about handloading.

Springback

Just like when you size the case, the die squeezes it down smaller, and then when it comes out of the die, it gets a bit bigger. Die is designed so that after is springs back, it if the correct size.

So for neck tension, you use the springback to hold the bullet. The bullet pushes the neck larger, but it is not enough to cause permanent change in size.

And therefore the bullet is held properly.

Rifle dies do not have any clearance for bullet start. You see that on pistol dies. And mainly for cast bullets.

Most long range shooters full length resize after every firing. More consistent. Neck sizing does not consider that your chamber may not be perfectly straight (slight bend) or may not be exactly round.

As for the right about, it is another factor to test what works for you.

I forget the neck tension I am using. The second article recommends starting with 0.003" Which sounds like what I remember.

https://bisonballistics.com/articles/case-neck-tension-a-stress-analysis

http://bulletin.accurateshooter.com/2019/04/reloading-tip-how-to-set-optimal-case-neck-tension/

Park ranger · Oct 17, 2019

I'm not going to give a long lesson here, but .003-.005 is enough to hold a semi.

Doco Overboard · Oct 17, 2019

Pinecone said:
Springback

Just like when you size the case, the die squeezes it down smaller, and then when it comes out of the die, it gets a bit bigger. Die is designed so that after is springs back, it if the correct size.

So for neck tension, you use the springback to hold the bullet. The bullet pushes the neck larger, but it is not enough to cause permanent change in size.

And therefore the bullet is held properly.

Rifle dies do not have any clearance for bullet start. You see that on pistol dies. And mainly for cast bullets.

Most long range shooters full length resize after every firing. More consistent. Neck sizing does not consider that your chamber may not be perfectly straight (slight bend) or may not be exactly round.

As for the right about, it is another factor to test what works for you.

I forget the neck tension I am using. The second article recommends starting with 0.003" Which sounds like what I remember.

https://bisonballistics.com/articles/case-neck-tension-a-stress-analysis

http://bulletin.accurateshooter.com/2019/04/reloading-tip-how-to-set-optimal-case-neck-tension/

Thanks for the tips!

Cannelure on 6.5cm v COL per load data?

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