Concentricity Vs Headspace

[MKnarr]

Intro first. New to the forum but started reloading in 1964. High Power National Match competition from 1964 to 1972, Small bore position and prone competition from 1968 to 1978. Rimfire Benchrest competition from 2004 to 2015.

I have a Remington 700 with a Lilja Heavy Varmint 24" SS barrel, Timney Trigger, pillar bedded with Devcon and receiver and bolt face trued. Stock is a Richards Microfit Varmint in Fancy Walnut. Caliber 221 Fireball.

Problem, with best handloads the groups will have three shots .25 to .37 and two more shots will open the group to 3/4 or a bit more. Cases are either Lapua or Norma, 15.5 gr H4198, bullet 50 gr Sierra Blitzking. Primers CCI magnum small rifle. Bullets seated .010 off the lands using a stub gauge. This has been an ongoing problem since I started developing loads.

Cases have been neck turned to.247 as the reamer was .250 and I need to go that low to get the cases to feed in the chamber. I try to blow the cases out to fireform to the chamber but using a stub gauge, the "headspace" will run 2.115 to 2.120. Most cases will be from 2.117 to 2.119. BTW, I use a full length sizing die but with a .008 shell holder so I don't bump the shoulder.

I suspected the concentricity and kludged together a set up and found a wide variation in concentricity. So I bought a Sinclar Concentricity gauge and found most run out from a bit under .002 to .004 or .005. The case neck run out is less than .001, closer to .0005 after sizing and loading the bullet.

Today I did a test on rounds than had less than .002 run out and headspace from 2.117 to 2.120 and got a group of .234 with one round out at .630. I think I'm on the right track and have a Forester Benchrest die on order which I hope will solve the run out problem.

The real question is, in your experience much run out is acceptable and according to my test, headspace from 2.115 to 2.120 didn't seem to have much effect or am I kidding myself. My load is a bit light but I use a heavier load to try to blow the cases out. I also tried to straighten out some of the run out to less than .002 run out but that didn't see to do much.

 

[CMB]

Following

 

[AJC1]

Based on your history I was curious if you considered soft seating with low neck tension. It sounds to be a target only rifle.

 

[troy fairweather]

Sounds like it's the barrel.

 

[jmorris]

Welcome to the forum.

When I come across a problem, I find it helpful to measure everything along the way. So, I would start with a fired case (from that chamber) and see what the runout is. If the load had enough pressure to fully form the case to the chamber, it should be about perfect, if the chamber is.

Then I would remove the expander from the size die and just size a case and measure.

Then add the expander and measure. Bullet seat, measure. At this point you can see the cause/effect of every step.

As far as setting a size die up for a particular bolt action, this method often produces great results for me.



And I have seen seating bullets out to the lands or even have them seated deeper upon bolt closure cure runout upon chambering, so that’s another option or at least something to try, reduce load accordingly. Also remember they may or may not eject if you decide you don’t want to fire and unload. Not much of a problem with paper punchers but can be with hunting rifles.

 

[JFrank]

Welcome

 

[Walkalong]

.005 run-out/concentricity is unacceptable at the level you want to be. .002 is not bad, but I would want to be at .001 or less.

First you have to have straight cases, which means your sizer die could need checking. With a bushing die if you are sizing the necks too much in one pass you might need to use two bushing and break it up into two passes, I've had to do that. Try different bushing. Die might need replacing.

Seaters, assuming straight cases, you just need to check them. Might need a different one.

Neck tension, light neck tension is easier to make repeatably consistent than heavy. Soft seat into lands to help start pressures.

I'm not a believer in a "crush fit" of the case to the chamber, I want a smidgen of head clearance. YMMV.

 

[MKnarr]

For those who are not familiar with a stub gauge and it's use, it's made from the cutoff from your barrel and mine is about 1 1/4inch long. It is not made from the very end because in a lapped barrel, the very end does not match the rest of the barrel. Then the chambering reamer is used and run in far enough so the shoulder is about 1/4 inch in. Then a groove is cut in the barrel so you can see the leade into the lands. Now it matches your chamber. You can measure headspace or the relationship with fired cases. Of course it measures the gauge and case but after fire forming you can tell if all cases have the same relative headspace or if it is changing over time. It is most useful in bullet seating. You measure the headspace on a sized casend, insert a bullet long and measure again with the bullet up against the lands. Measure with your collet tool, subtract the first measurement from the second and add .010 and you know the new collet measurement to seat the bullet .010 from the lands. Now on to my issue.

I'll try not to bore you with the details. I took two fired cases and measured the neck diameter at .250 just what the smith told me the reamer was and run out was .0002 or less. I ran one through the sizing die without the expander ball and a .008 shell holder so as to not touch the shoulder. Neck diameter was now .0425 and run out was the same. I seated a bullet and neck run out increases and bullet run out increases a lot. The other I sized with the expander ball and and neck size was .247, just what it is supposed to be but run out increased. After seating a bullet, neck run out increases and so did the bullet run out. I repeated with 2 more cases and results were about the same.

Here is what I think I have learned. Looking at the end of the sizing die, you can see the decaping pin wobble as the adjustment screw is turned and doesn't necessary center when the nut is tightened. If that isn't exactly centered, that starts the run out. I've seen some sizing dies with an O ring between the nut and die. That might help or I can do as I do with another caliber and not use the expander ball at all. Even if there is only .0002 neck run out when seating a bullet, bullet run out can get greater. I have an old Herters bullet seating die for my .308 target rifle which has a sliding collar to hold the bullet in place and run out is not a problem with that die. I'm hoping the Forrester Benchrest die wlll do a better job at seating the bullet. I will try soft seating when I can get more Sierra bullets, as well as no expander ball and an O ring on the sizing die.

To answer some questions. This is a pic of the group of 5 rounds all HS 2.117 or less, and bullet run out .002 or less. At this point i can't really fault the barrel and run out seems to be more important than head space.


No the rifle is not a target rifle, it is only used for Prairie Dogs
Thanks for the help folks. I really do appreciate it. Unfortunately in the current climate bullets and primers may be a hard to come by. The Forrester seating die won't be here until Jun sometime. I made a little tool to straighten the run out and I may fool around with that a bit until I get more supplies.
I forgot, this is not a bushing die. They aren't available for the .221 fireball. So far the problem with the sizing die appears to be with th centering of the expander ball not the sizing of the neck.

Jim B.

 

[edwardware]

. . . you can see the decaping pin wobble as the adjustment screw is turned and doesn't necessary center when the nut is tightened. . . I've seen some sizing dies with an O ring between the nut and die.

I've used the oring, but I observe that in most dies (except RCBS Comp) the ball is positioned such that the case comes out of contact with the die before the base of the neck hits the ball. It's all floating at that point.

 

[Walkalong]

For those who are not familiar with a stub gauge and it's use, it's made from the cutoff from your barrel

I have one from my Benchrest days.

 

[Walkalong]

I'm hoping the Forrester Benchrest die wlll do a better job at seating the bullet. I

The Whidden seater is very similar, but with a floating seater stem, mo better IMHO.

 

[AJC1]

I would abandon the expander ball and use a mandrel insted to see if that induces run out. If that part is fixed the use a chamber seating die like an le wilson.

 

[Walkalong]

forgot, this is not a bushing die. They aren't available for the .221 fireball

Forster will hone out the necks on their sizer dies if they make the .221 Fireball sizer.

 

[Walkalong]

So far the problem with the sizing die appears to be with th centering of the expander ball not the sizing of the neck.

They often have a detrimental affect, which is why we try to stay away from them and use expanders by 21st Century, Sinclair, Wilson, etc

 

[Thomasss]

Looking at cause and effect, I would back off to a standard or match primer and bump your velocity by .1 or .2 grains and check the results. From your description this has been an on going issue, your concentricity gauge should have improved or even corrected the problem right away and apparently has not.

 

[jmorris]

Here is what I think I have learned. Looking at the end of the sizing die, you can see the decaping pin wobble as the adjustment screw is turned and doesn't necessary center when the nut is tightened.

This is exactly why I wrote,

When I come across a problem, I find it helpful to measure everything along the way. So, I would start with a fired case (from that chamber) and see what the runout is. If the load had enough pressure to fully form the case to the chamber, it should be about perfect, if the chamber is.

Then I would remove the expander from the size die and just size a case and measure.

Then add the expander and measure. Bullet seat, measure. At this point you can see the cause/effect of every step.

No need to guess, a step will make things better, worse or have no measurable effect.

 

[NMexJim]

I’m with Walk on the shoulder - a smidgeon of clearance. Personally, I hold bullet runout to .002 and under, but there are some recent interesting articles on higher runout not changing poi. Sounds like a good set of dies is called for to me.

Out of curiosity, how many times have the cases been fired?

 

[forrest r]

Forster will hone out the necks on their sizer dies if they make the .221 Fireball sizer.

+1 this ^^^^^^^^

Typically I hone my own

 

[Slamfire]

Intro first. New to the forum but started reloading in 1964. High Power National Match competition from 1964 to 1972, Small bore position and prone competition from 1968 to 1978. Rimfire Benchrest competition from 2004 to 2015.

The real question is, in your experience much run out is acceptable and according to my test, headspace from 2.115 to 2.120 didn't seem to have much effect or am I kidding myself. My load is a bit light but I use a heavier load to try to blow the cases out. I also tried to straighten out some of the run out to less than .002 run out but that didn't see to do much.

Let me offer this old saw : the appearance of precision is the illusion of control.

You have conducted a huge amount of work controlling the things you can measure, but what can't you measure?

Are you measuring your bullet concentrically and center of gravity? I will bet not. I don't know how to measure center of gravity. Tthere are Vern Juenke bullet concentricity machines, and copies on the market for measuring concentricity. Vern died in 2018.

http://www.bulletinspector.com/
http://www.bulletdoctor.com/

I am quite sure your entire shooting career you have been buying good bullets, loading them up, and assuming that none of them vary in weight, center of gravity, or jacket concentricity. And yet, these things happen



And, we shooters don't have a good means to inspect for these bullet faults. Unlike the other guy, when my space ship arrived on earth. I lost my X Ray vision super powers.. Its a real bummer, can't see short or long cores in bullets, can't see voids in the cores, can't see what fell behind the dresser. And I am sure, you don't have X Ray vision either.

At the group sizes you are firing, unless you are weighing bullets, and have a means of ensuring the center of gravity is within the axis or rotation, all those other variables you are controlling, are pretty meaningless for shooting one hole groups. You are going to get flyers, and not know why. Perfect bullets are incredibly important for accuracy, and yet, who has the ability to inspect all the important physical characteristics of bullets?

Which gets back to: the appearance of precision is the illusion of control.

(as an aside, how do you know that truing actions really does anything, or at what level does truing make no further difference on paper. Most of what shooters do and believe about precision are untested assumptions: ideas based on philosophical ideas and the Texas Sharpshooter fallacy. Unless you have the ability to model the deflection of the bolt face under pressure, you don't know if truing makes any difference on action and bolt flex at all)

 

[forrest r]

[QUOTEUnlike the other guy, when my space ship arrived on earth. I lost my X Ray vision super powers.. Its a real bummer, can't see short or long cores in bullets, can't see voids in the cores, can't see what fell behind the dresser.
[/QUOTE]

Sora sounds like you missed the 1st step when you got off the ship
You ought to know x-ray and lead don't mix

 

[JFrank]

Good bullets make a huge difference in a target rifle.
Too light of neck tension/bullet hold will also cause erratic or inconsistency in groups I can see on paper.

 

[AJC1]

[QUOTEUnlike the other guy, when my space ship arrived on earth. I lost my X Ray vision super powers.. Its a real bummer, can't see short or long cores in bullets, can't see voids in the cores, can't see what fell behind the dresser.

Sora sounds like you missed the 1st step when you got off the ship
You ought to know x-ray and lead don't mix[/QUOTE]


Xray vision doesn't work through lead..... just saying.

 

[JFrank]

Sounds like it's the barrel.

Lilja makes excellent barrels, this is probably not the reason for fliers nor is Consentricity or Headspace.

 

[forrest r]

Sora sounds like you missed the 1st step when you got off the ship
You ought to know x-ray and lead don't mix

Xray vision doesn't work through lead..... just saying. [/QUOTE]


Aaahhhh, I think that's what I was alluding to.

 

[MKnarr]

I think for the time being I may have solved my concentricity issue with the Redding sizing die by using an O ring under the jam nut. Measuring run out after firing and after neck sizing the run out is still .0002 or less. I'm still looking into the Forester die but I'll have to talk with them because my necks have been turned to .047. and are that after loading the bullet.

Even though I have been handloading for a little over 30 years, this is the first time I've been into precision handloading. My .308 loads for my target rifle will still hold 10 shots in an inch at 100 yards with metallic sights and for position, which I no longer do, that is good enough. Although all my target shooting days are over, I'm now 82, I still like to impress the guys at the range with sub .2 inch groups at 50 yards with my custom Anschutz but that's with a carefully selected lots of Lapua Midas at about $15.00 a box of 50.

But I have a neighbor who is into precision handloading and get's honest 1/4 inch groups with a .219 Hornet at 100 yards in a Ruger #1. He has been helping me and what he does to his seating die, is he takes a round with zero run out, puts a bit of epoxy in the end of the seating stem and lets it cure, I'm thinking of trying that to see if that helps in the Redding die.

For the record, I've tried Sierra 50gr BlitzKing, the 50 gr Spitzer, 53 Gr match and their 40 grain bullets and Hornaday 50 gr V max. I've also tried about 3 or four different powders and several brands of primers. Consistently, the best groups have always been the 50 Gr Sierra, H4198 powder and a bit of improvement with the CCI small rifle magnum primers. I've tried a couple of different seating depths and not much change. I Haven't tried soft seating but that will also be tried when supplies become available.

One more thing. "unless you are weighing bullets". I don't want to start an argument but weighing bullets in not in my vocabulary. I've gone through this issue in Rimfire and have proved beyond any doubt that bullet weight has so little affect on velocity spread it is a non starter. Tests on a .270 Remington in a tunnel have shown no measurable impact difference. The theory behind that is a, yes, everything else being equal, a heavier bullet will have a bit lower velocity than a lighter bullet but it also has a bit more BC than a lighter bullet so retains velocity a bit longer and virtually ends up at the same point of impact. This is not a target rifle. If and when I get the concentricity issue solved, I will be willing to bet groups will consistently be .375 or less and that's all I need for pest control.