reloading for accuracy questions

[Steve Sheasly]

I am new at precision reloading and have been reading a bit before I start to purchase a lot of tools. I was an engineer in the paper industry and understand the importance of concentricity's of bearing fits and can apply this to a bullet spinning down a rifled tube we call a barrel. In order to be consistently accurate all of the concentricity's would have to be perfect from the centerline of the cartridge when chambered to the bottom of the barrel grooves. Pretty hard to measure.

I have read a lot of articles and have a question:
The distance to the ogive of the bullet and bottom of the case (end of the neck) is one measurement.
The distance from the datum line of the case to the bolt face is headspace.
The COAL is the distance from the base of the bullet to the tip of the projectile.

Seems to me that the case should fit exactly into the camber with the neck of the case touching its seat (not sure what this is called yet) and the datum line snug in the chamber. Basically zero clearance for the cartridge to move at all. The ogive of the projectile should be snug and touching the leading edge of the lands of the barrel grooves.

Once this is done I understand that the case should be bumped back .002 or .003 so the fluctuations in ambient temperature will allow the chambering of the cartridge and the projectile should be seated about .005 to .015 (which ever is more accurate for my rifle with load development).

Is this correct?

Also how do I know the neck will extrude to its limit with a fired round -- I assume the pressure formed case will be an accurate image of my chamber but will the neck hit its limit. Maybe the answer is apparent -- would the cartridge separate if the neck does not seat?

Steve Sheasly

 

[Canhunter35]

What cartridge are you loading for?
Seating off the lands doesn't work for cartridges with freebore.
Sometimes a jump of .05 will out shoot a shorter jump, no two rifles, bullet/powder combinations r the same.

To me it seems you're over thinking it. Just follow your load manual and see what kind of accuracy you get then experiment from there.

 

[Howland]

Glad to see you here, Steve! Good to have you aboard.

I want to add a couple disclaimers to my reply in our conversation.

If you use Lee Collet dies, you are resizing the outside of the neck. Variation in neck wall thickness leads to variation in case neck tension, which leads to variation in muzzle velocity. Suboptimal. (I added that for the engineer that will always be within you.)

Variation in neck wall thickness at different points of the same case leads to poor concentricity, which can be measured as run-out.

I strongly suspect that true long range precision shooters (hopefully a few will weigh in shortly) will size the neck from the inside, not the outside.

Also, I trim to a uniform case length below maximum in an attempt to maintain uniform neck tension for the bullet. The importance of keeping case length below maximum is that if you exceed maximum, chambering a round can put a severe crimp at the case mouth with a potentially dangerous pressure spike to say nothing of what it can do to muzzle velocity and accuracy.

Using the Lee Collet dies I've been able to keep sub 3/4 MOA in my Remington 700 .30-06, which is fine for hunting but won't win even club matches against the benchrest crowd, let alone any competitions.

BTW, where are you located?

 

[coop2564]

You might try just normal reloading first. Use a manual FL sizing and stay in manual specs. This alone by working up a load will give you much better accuracy than just grabbing factory loads. Many match shooters will tell you that all the other stuff like shoulder bumping and seating depth are .250" gains on groups at best. The most important thing to me is working up a load and finding that Node your gun like best. Thats often plenty good enough for a hunting load. If your planning on match shooting then as you develop skills you can start trying to squeeze those .250" out of reloading. Just my 2 cents.

 

[Steve Sheasly]

What cartridge are you loading for?
Seating off the lands doesn't work for cartridges with freebore.
Sometimes a jump of .05 will out shoot a shorter jump, no two rifles, bullet/powder combinations r the same.

To me it seems you're over thinking it. Just follow your load manual and see what kind of accuracy you get then experiment from there.

You are right I tend to overthink. The load is .338 LM. I am trying to understand how a reloaded cartridge will best fit in to the chamber. I would like the round to fit as perfectly in the chamber as possible without getting it stuck. I understand some jump is needed and load development will determine the best jump by trial and error. I want this brass to last as long as possible. It is close to $5 when I pull the trigger on factory

Glad to see you here, Steve! Good to have you aboard.

I want to add a couple disclaimers to my reply in our conversation.

If you use Lee Collet dies, you are resizing the outside of the neck. Variation in neck wall thickness leads to variation in case neck tension, which leads to variation in muzzle velocity. Suboptimal. (I added that for the engineer that will always be within you.)

Variation in neck wall thickness at different points of the same case leads to poor concentricity, which can be measured as run-out.

I strongly suspect that true long range precision shooters (hopefully a few will weigh in shortly) will size the neck from the inside, not the outside.

Also, I trim to a uniform case length below maximum in an attempt to maintain uniform neck tension for the bullet. The importance of keeping case length below maximum is that if you exceed maximum, chambering a round can put a severe crimp at the case mouth with a potentially dangerous pressure spike to say nothing of what it can do to muzzle velocity and accuracy.

Using the Lee Collet dies I've been able to keep sub 3/4 MOA in my Remington 700 .30-06, which is fine for hunting but won't win even club matches against the benchrest crowd, let alone any competitions.

BTW, where are you located?

Thank you for the reply. It seems that the neck is crucial to accuracy for the reasons you have outlined and you have confirmed my thoughts. Seems like bullet jump and COAL are fairly easy to determine with the gauges on the market. I have not found much on the neck or the amount of free chamber needed for accuracy. I am just starting to research however and I am sure there are articles out there. Our ranch and home is in Pendleton Oregon.

 

[Steve Sheasly]

You might try just normal reloading first. Use a manual FL sizing and stay in manual specs. This alone by working up a load will give you much better accuracy than just grabbing factory loads. Many match shooters will tell you that all the other stuff like shoulder bumping and seating depth are .250" gains on groups at best. The most important thing to me is working up a load and finding that Node your gun like best. Thats often plenty good enough for a hunting load. If your planning on match shooting then as you develop skills you can start trying to squeeze those .250" out of reloading. Just my 2 cents.

A good 2 cents worth. I have reloaded quite a bit and made a lot of mistakes in the process. This is a new caliber for me. .250 at 100 yards is a lot different at 1200 yards. I have killed elk at 700 yards and shot my last deer at 550 yards on the trot up hill (three shots) with a 270 WSM Winchester 150 gr. factory ammo. Where we hunt these distances are fairly standard. And ..... we miss a lot.

 

[Canhunter35]

annealing the case necks is a great way to prolong brass life and I've found it help with consistent neck tension.

I have no experience with the 338lm, but found in my 308 no accuracy difference between neck sizes and fl sized cases, but I do notice a major accuracy gain and velocity spread decrease with lapua brass over my federal brass. I've had good luck neck sizing my 300wby brass everything else I full length size.

 

[Rich Coyle]

tag

 

[Barrelnut]

If I read your question correctly, your wanting to know best way to reload for best case life and accuracy.

First you need to understand what happens to the case in the chamber when the rifle is fired. There is an excellent detailed and diagrammed explanation for this in the Hornady Reloaders Guide. It will teach you about headspace and how and why brass wears out at the web body junction. It is worthy reading for an engineer like yourself

Once understand how a case grows and shrinks in the chamber, you will be informed enough to understand why reloaders adjust dies to only "bump the shoulder" back only .002 each time they resize. It is to stop the continual stretching that happens at the web junction that can eventually cause the case to split there during fire! This is called case head separation. I'm sure someone will come along here and write you a whole dissertation on this, but you will be better served by reading the chapters in the Hornady Reloading manual yourself.

Another advanced dies adjustment you can do is only resize the first 2/3 of your case necks after firing. This leaves the remaining 1/3 closer to the actual size of your chamber, in the neck area, after resizing the case. This allows the bottom 1/3 of the neck to align the bullet for better concentricity with the bore during subsequent firings. (You really need a set of bushing dies to take advantage of this.)

Do the above and don't run loads hot enough to blow out the primer pockets and your brass should last a looong time. Remember you can even destroy Lapua brass if to try hard enough.

 

[Capt RB]

FL resize move the shoulder back .002. Consistent seating pressure will do more for on target and deviation than alot of other things.
I turn my necks on once fired cases(fired in the rifle using them). I turn enough to make sure they are round and true and that is it. Very little material is removed as I do not own a tight necked rifle anymore. Most custom rifles will set up with .004 clearance for the neck. Not all agree on this number however. Alot of people set the bushing die up for .002 neck tension. Some will use .003 with coated bullets. A regular die honed to the preferred neck tension will in most cases make straighter ammo if the person doing the work does it correctly(big if so caution)
Less benchrest shooters shooters neck size only today than ever before. They might be on to something
Broz has a good video on how to resize the brass here

 

[Steve Sheasly]

great video

FL resize move the shoulder back .002. Consistent seating pressure will do more for on target and deviation than alot of other things.
I turn my necks on once fired cases(fired in the rifle using them). I turn enough to make sure they are round and true and that is it. Very little material is removed as I do not own a tight necked rifle anymore. Most custom rifles will set up with .004 clearance for the neck. Not all agree on this number however. Alot of people set the bushing die up for .002 neck tension. Some will use .003 with coated bullets. A regular die honed to the preferred neck tension will in most cases make straighter ammo if the person doing the work does it correctly(big if so caution)
Less benchrest shooters shooters neck size only today than ever before. They might be on to something
Broz has a good video on how to resize the brass here

vi

 

[bigngreen]

Reloading is a very simple and methodical process, the worst thing to do is over think it! Best thing you can do is find someone who loads the 338 Lapua and get advice, a LOT of horrible generic advice can be found on the internet!!

 

[Rich Coyle]

Most folks are not going to take the bolt apart. Once the cocking piece is cocked the cocking cam does not have to cock again. Therefore you will not have the resistance if you don't dry fire it.

At the end he finally mentioned trying different cases to verify. I would use a different case every time. Once the die is set I would then go back and do the long ones.

For people who don't have a set of various height shell holders they can set the die a little away from the shell holder. Size a case and check it. If it's not right turn the die down 1/20th or less of a turn. That moves the headspace about .003". This is quite tedious but works.

 

[bigngreen]

Most folks are not going to take the bolt apart. Once the cocking piece is cocked the cocking cam does not have to cock again. Therefore you will not have the resistance if you don't dry fire it.

At the end he finally mentioned trying different cases to verify. I would use a different case every time. Once the die is set I would then go back and do the long ones.

For people who don't have a set of various height shell holders they can set the die a little away from the shell holder. Size a case and check it. If it's not right turn the die down 1/20th or less of a turn. That moves the headspace about .003". This is quite tedious but works.

This is of subject but most rifles except a couple customs have some amount of cock on close, you really need to pill the firing pin assembly and ejector to get solid numbers and not over size.