Possible runout caused by chamber?

[dellet]

What you might want to try, is with new or full length sized cases, including setting the shoulder, is to index the rounds before firing.

If it is a chamber problem, the the “bent” part of the case will be in the same place every time.

If the bolt face or breech block is not square with the chamber, case head to base of shoulder length will not be square making it near impossible to have a neck perpendicular and centered over the base.

You mentioned, twice fired and the bolt is not sticky. A low pressure load that has not expanded to fill the chamber, can not be expected to be true to form.

One thing I have learned from sub sonic shooting is that low pressure loads cause more problems on the target and loading bench than you would think possible. It is impossible to set a die up to reform varying sizes of brass to the same size and shape, unless you set the die up to size/correct the smallest piece.

Your problem may just go away once the brass has been fully formed, because only then can it be consistently re-formed.

 

[dgeesaman]

BTW, I've always wondered if the typical reference (especially in this forum) to "runout" is the TIR or the "actual runout"???

I think it’s usually the total indicator reading.

I mostly use radial runouts in calculations. They have little value in measuring and inspecting.

to the original poster, have you sorted your ammo by runout and confirmed that runout is affecting your results on target?

If so, I would start by confirming the issue comes from the process as opposed to the piece of brass itself.

David

 

[Uncle Ed]

Until the OP checks runout on the case body of a fired case he will not know if he is rotating a egg shaped case on his runout gauge. Meaning his cases may not have a uniform case body wall thickness or his chamber is out of round. When fired the thin side of the case body will expand more. And the case will bulge outward and stretch more on the thin side also causing the base of the case to be tilted.

Below I'm using my RCBS case mastering gauge to measure case wall thickness. This gauge can tell me if the case body has variations in wall thickness and stretching and thinning in the base web area. So again the OP needs to put the gauge on the case body and see if it is out of round and if that is causing his neck runout indication.

Bottom line, if you rotate an egg shaped case body on your runout gauge it will show up as neck runout. So if you do see excessive neck runout after sizing then move the gauge to the case body and see if it is egg shaped.

This is why my first check of the case is using my Redding neck thickness gauge. And if the case neck looks like the image on the right below its a good bet the case body has the same thickness variations. And the thin side will bulge when fired and become egg shaped. And this same case will stretch on the thin side and become banana shaped or curved. So does the OP have a out of round chamber or have poorly made cases.

Tech Line & Tips (FAQs)
https://www.redding-reloading.com/tech-line-a-tips-faqs/142-concentricity-a-bushing-dies

To create precision reloads, you must start with cases of good quality. They should all be from the same manufacturer and lot number. A good measure of case quality is how uniform the neck wall thickness is. Cases with uniform neck wall thickness, will be of uniform thickness all the way to the base. This is important for accuracy, as the cases will expand uniformly upon firing, and contract uniformly when sized. Neck turning helps, but it's only a partial cure, as you can't turn the case wall all the way to the base. The Redding Case Neck Gauge is the preferred instrument for checking neck wall thickness and uniformity. Also note that the concentricity of a fired case only indicates how concentric your firearm's chamber is. It provides you with little or no information on the quality of the cases you're using.

 

[Richard Coody]

I checked a lot of brass years ago with one and came to this conclusion

That is why i buy lapua and at least skim turn necks.

 

[PopCharlie]

That is what I have done. I have not full length or body sized the brass at all. I don’t have any fired brass that haven’t been ran through my collet die but I will check that too after my next trip to the range.

Is there a way to set up a Lee collet die so badly that it could induce that much runout? I have followed the at length instructions for setting the die up that are floating around this forum somewhere and I am getting exactly the neck tension I’m aiming for.

I recently went thru my loading process and equipment to minimize runout. I found runout being induced every step of the way. Here are 3 things I did that made the biggest positive improvement in reducing runout.
1. Found the dies were not straight when screwed in to the press. This was caused by slop in the press threads. Fixed by using a flat stainless steel machined washer placed on top of the shell holder. With lock ring loose, run the ram up until the washer contacts the bottom of the die. Put a little upward pressure on the ram, watch what the die does. It will straighten itself out. Then hold the die body so it doesn't move and tighten the lock ring. This works for seating dies, sizing dies, or any die you are screwing into the press.
2. Stopped using bushing type sizing dies, and collet dies. Switched to full length non bushing sizing dies. When set up straight like above, they produce the straightest cases. Less than .0005 runout on the neck, shoulder and body.
3. Had custom seating stems for my seating dies made for each bullet I shoot in each cartridge.
A couple of notes: I polished the washer on a hard arkansas stone to make sure it was flat. Don't use a thin washer, it will bend.
Turning case necks will not fix runout. It will fix thickness variance. I don't have tight neck chambers so I only turn necks to fix excessive neck wall thickness variance. Variations in neck wall thickness will induce runout.
Start with good brass. Lapua and Peterson are both high quality and consistent.

I hope this helps.

 

[1811shooter]

I recently went thru my loading process and equipment to minimize runout. I found runout being induced every step of the way. Here are 3 things I did that made the biggest positive improvement in reducing runout.
1. Found the dies were not straight when screwed in to the press. This was caused by slop in the press threads. Fixed by using a flat stainless steel machined washer placed on top of the shell holder. With lock ring loose, run the ram up until the washer contacts the bottom of the die. Put a little upward pressure on the ram, watch what the die does. It will straighten itself out. Then hold the die body so it doesn't move and tighten the lock ring. This works for seating dies, sizing dies, or any die you are screwing into the press.
2. Stopped using bushing type sizing dies, and collet dies. Switched to full length non bushing sizing dies. When set up straight like above, they produce the straightest cases. Less than .0005 runout on the neck, shoulder and body.
3. Had custom seating stems for my seating dies made for each bullet I shoot in each cartridge.
A couple of notes: I polished the washer on a hard arkansas stone to make sure it was flat. Don't use a thin washer, it will bend.
Turning case necks will not fix runout. It will fix thickness variance. I don't have tight neck chambers so I only turn necks to fix excessive neck wall thickness variance. Variations in neck wall thickness will induce runout.
Start with good brass. Lapua and Peterson are both high quality and consistent.

I hope this helps.

That's an interesting take. I'll give the washer trick a shot. Not sure I'm ready to give up my collet die. By using a standard full length die I wouldn't be able to control neck tension anymore, which I can only imagine would likely outweigh the benefit of having less overall runout. I do have a Lee and Redding standard full length dies, but I don't remember how much neck tension each one left me with. With a necking die that doesn't have a mandrel, that would probably be a product of neck thickness.

 

[Uncle Ed]

A set of Redding competition shell holders will do the same thing as the washer trick. You set the die up to make hard contact with a standard shell holder with press cam over. Then test and select the proper Redding competition that gives the correct amount of shoulder bump. These shell holders are always making hard contact and pushing up on the die and centers the die in the press threads. I use Lee die lock rings with a rubber o-ring recessed in the base of the lock ring, this allows the die to float and self center in the press.

The Redding competition shell holder kit contains five shell holders that push the case from .002 to .010 "LESS" into the die than a standard shell holder. And by changing these shell holders you control the amount of shoulder bump.

Competition Shellholder Sets
https://www.redding-reloading.com/online-catalog/35-competition-shellholder-sets

Now you can control headspace. The new Redding Competition Shellholders are packaged in five piece sets in .002” increments (+.002”, +.004”. +.006”, +.008” and +.010”). Each shellholder has a distinct black oxide finish and is clearly marked to indicate the amount it will decrease case-to-chamber headspace. You can now easily adjust the shoulder bump to customize cases to your specific chamber.

 

[Ledd Slinger]

I'd bet your factory chamber is off a little. But there are other possible issues.

Making straight ammo has everything to do with the brass, dies and the bullets you are using.
- Neck sizing is NEVER a good idea if you want straight ammo with minimal runout. Always FL size.
- Get good brass from Lapua or ADG. All other brass is junk in my opinion.
- Forster makes good seaters, but the stems dont mate well with VLD style bullets. Your bullet tips are most likely hitting the top of the stem. The Forster stems also make contact way too high on the ogive where a bullet is the least consistent dimensionally.
- Hornady bullets are usually pretty inconsistent dimensionally. I'm sure you have some ogives that vary a bit. Couple poor dimensions with a poor mating surface on a seating stem and it can mess stuff up in a hurry.
- Your press is probably fine as long as the ram has some slop in it. Tight press rams dont allow for proper die alignment with the shell holder.

So my advice is to:
* Check a fired case to see what the chamber is doing. If the chamber is good...
1) Throw the Lee collet die in the trash and get a Whidden FL sizing die with bushings and expander ball set.
2) Pick up a Whidden seating die with a VLD seating stem or a Wilson inline micrometer seating die with the VLD seating stem. (Will need an arbor press if you go with the Wilson inline die).
3) Get some Lapua or ADG brass
4) Pick up some Berger bullets
5) Make up some ammo and test again.

Even if the runout is still present, the Lapua brass and Berger bullets will probably shoot better

 

[PopCharlie]

That's an interesting take. I'll give the washer trick a shot. Not sure I'm ready to give up my collet die. By using a standard full length die I wouldn't be able to control neck tension anymore, which I can only imagine would likely outweigh the benefit of having less overall runout. I do have a Lee and Redding standard full length dies, but I don't remember how much neck tension each one left me with. With a necking die that doesn't have a mandrel, that would probably be a product of neck thickness.

You can control neck tension using different sized expander balls. For example, using a .264 ball in my 6.5x47L, I get a neck sized to .288. Which is the bushing sized I used in my bushing die. Whidden gun works make expander ball kits for their dies.

 

[PopCharlie]

I'd bet your factory chamber is off a little. But there are other possible issues.

Making straight ammo has everything to do with the brass, dies and the bullets you are using.
- Neck sizing is NEVER a good idea if you want straight ammo with minimal runout. Always FL size.
- Get good brass from Lapua or ADG. All other brass is junk in my opinion.
- Forster makes good seaters, but the stems dont mate well with VLD style bullets. Your bullet tips are most likely hitting the top of the stem. The Forster stems also make contact way too high on the ogive where a bullet is the least consistent dimensionally.
- Hornady bullets are usually pretty inconsistent dimensionally. I'm sure you have some ogives that vary a bit. Couple poor dimensions with a poor mating surface on a seating stem and it can mess stuff up in a hurry.
- Your press is probably fine as long as the ram has some slop in it. Tight press rams dont allow for proper die alignment with the shell holder.

So my advice is to:
* Check a fired case to see what the chamber is doing. If the chamber is good...
1) Throw the Lee collet die in the trash and get a Whidden FL sizing die with bushings and expander ball set.
2) Pick up a Whidden seating die with a VLD seating stem or a Wilson inline micrometer seating die with the VLD seating stem. (Will need an arbor press if you go with the Wilson inline die).
3) Get some Lapua or ADG brass
4) Pick up some Berger bullets
5) Make up some ammo and test again.

Even if the runout is still present, the Lapua brass and Berger bullets will probably shoot better

Yup...this is it...also take off the steel shell holder clip and install a rubber o-ring on the ram. This allows the shell holder to move around a bit more.

 

[JFrank]

Hey guys. I’ve been lurking here for a couple years and taken in a lot of great knowledge since then. I finally have a dilemma I can’t cure with the search function so here it goes.

I recently got a Sinclair concentricity gauge and have been messing around with bullet and case runout on my .308. I’m having a hell of a time trying to get my bullet runout within an acceptable range. So far i seem to be averaging between .003 a .005. I’m using Nosler brass that how now been twice fired in my rifle and neck sized only with a Lee Collet die. I haven’t needed to bump the shoulders yet though I’m sure I will in the next firing or two. The bullet is a 178 grain ELD-X. I am seating with a Forster seating die and loading on a Hornady LNL AP progressive. I realize the progressive isn’t ideal for precision loading but I can’t imagine this being the culprit as the press has been surprisingly precise in all other measures.

I have tried partial seating and rotating and seating the rest of the way, which did not seem to improve anything. I know I am using the gauge correctly. I took some factory hornady match ammo and was able to measure less than .001 of runout.

I have also tried turning my necks which does not seem to offer any improvement to bullet runout.

Next I took a sharpie and marked the high point on the bullet on a handful of loaded rounds. After that I took the same rounds and measured the high point of the necks. I found that the high points of the necks and bullets were always 180 degrees apart, never 90, 45, etc.... given that this brass is twice fired from my rifle I concluded that perhaps there is something wrong with my chamber since each round must be coming out slightly banana shaped, though I have no idea how I would measure this, or how a chamber reamer could even make a banana shaped cut.

The rifle is an off the shelf Bergara Premier series HMR, which is supposed to be on par with their custom line as far as quality goes.

How did it shoot prior to gaining the consentricity tool and all this knowledge?
Was there an accuracy problem?
J

 

[sqrlgtr]

What are you trying to say j...

 

[dgeesaman]

How did it shoot prior to gaining the consentricity tool and all this knowledge?
J

Now, let's not confuse data with knowledge just yet...

 

[1811shooter]

How did it shoot prior to gaining the consentricity tool and all this knowledge?
Was there an accuracy problem?
J

It shoots just ok but not to the degree of accuracy I’m hoping for. I can still get consistently tighter groups with factory Hornady match ammo.

Once I figure out where the runout is being introduced I’ll start switching things out. There’s a lot of great advice here but if I were to take it all at once I’d be throwing away a lot of expensive gear and replacing it with a lot more expensive gear, which I’m just not in a position to do right now.

I have however ordered some Lapua brass and found a Rock Chucker $for 120 so I’ll be giving that a try. In response to the comment about using the press’ camover, there are only three single stage presses available that I found that actually use a cam over and two of them are Hornadys. What press are you using Uncle Ed?

 

[JFrank]

Humm
Well so far I haven’t seen consentricity effect accuracy anywhere close to what powder , seating and bullet choice do.
I would also prefer a die that minimal sizes smoothly versus forcing a press beyond hard contact therefore stressing the linkage.
Just a thought
J