How much accuracy degradation from excessive TIR

[RTodd]

So I have a 700, Douglas bbl 300 whisper I bought here. Can't tell you much about the smithing, etc. but I have some excellent groups mixed in with some strange but poor groups. Here is what I mean (all groups are 5 shots at 100 yds, mild to flat conditions). The rifle has turned in 1/3 of all groups under 1/2 minute, with some in the .2s and .3s, but also generates groups up to 1-1/8" with the same load. The large groups often have 3 - 4 shots in one hole, with the remaining shots opening things up significantly. The scope is a used/unknown VX-III which I will change before the next outing. Absent that, the only obvious problem is excessive TIR. I checked the last 12 rounds loaded from my newly formed-from-223 Whisper brass and have runout .002" to .022" (not a typo), with the mean around .010". I have not had a chance to sort for effect, and with this fireforming brass I'm not sure I can get enough good rounds to shoot a group. FYI a carbide metal cutting saw is a super fast way to shorten 223 brass, but pulls the soon to be neck out of round at the cut, and even trimming .030" after FL sizing leaves some deformity. Good news is the fired brass measures .000 - .002" TIR fresh from the chamber.

So my question, do you think the fliers will go away when I get to the fire formed, and hence straight brass????

Thanks for the help.

Randy

 

[Tripwire]

Re: How much accuracy degradation from excessive TIR

Thanks, didn't have a headache before reading that.

Oh yeah, .022" is a tad too much runout.....may as well throw rocks instead.

 

[shoepop]

Re: How much accuracy degradation from excessive TIR

My guess, yep fliers will go away once fired formed if you reload correctly and don't induce run out.

 

[RTodd]

Re: How much accuracy degradation from excessive TIR

Sorry, next time I'll try to include more detail, but in a less organized fashion. It reads a lot better in my mind than on paper.

I could/should have narrowed it to the last line with TIR readings.. . .

I have sorted to less than .005" TIR ammo for the 600 yd line in highpower, but never tested to see where the effect of runout became noticable. The lots of LC match ammo I ran across the gauge years ago ran as high as .015" TIR, with mean around .007" from memory only.

Has anyone actually sorted and fired "crooked bullets" to test the effect? I have a prime opportunity to do so here, but may have to shoot one shot groups for runout below .005"!!! I only have 40 pieces of non fireformed brass left to measure and sort, and I'm not sure there I will find 5 pieces of "straight" brass in the lot!

 

[RTodd]

Re: How much accuracy degradation from excessive TIR

I guess I should be tickled with the groups I'm getting after checking runout. I may scare myself when I start feeding this rifle "straight bullets"???? If the fliers go away, this may well become my most accurate rifle, and it sure is fun to shoot!

Randy

 

[Fuzzball]

Re: How much accuracy degradation from excessive TIR

"How much accuracy degradation from excessive TIR"

Bottom line, it ain't all that calibrated and the chamber itself will limit the runout at a certain point.

'Once fired' works no magic on runout if your loading methods, case necks and tools aren't up to par. It takes good cases loaded the right way with proper dies to obtain straight ammo and that's not easily explained in a hundred words or less.

 

[RTodd]

Re: How much accuracy degradation from excessive TIR

Fuzzball,

Your point about the chamber limiting gross runout is well made. I don't recall having seen that in print, but there is no question that you are correct.

With regards to making straight ammo, I've been loading since 1984 and I've read a few hundreds of pages (maybe thousands?) on precision loading, but am smart enough to know that I have more to learn.

I actually haven't pulled out the concentricity gauge in 8 or 10 years, but thought I might have some problems based on my groups, and based on my "trimming" method which involved a low speed metal cutting mitre saw used to cut the brass at the body/neck junction prior to FL sizing/forming and finish trimming. The saw pulled the case slightly out of round, presumably to the detriment of my finished brass.

Following up on your comments re: many factors being involved I have done some additional meausing. Here is what I've found:

My not-fire-formed brass TIR is running comparable to my loaded ammo TIR, say .008" - .010" mean. My fired cases are running much lower, say 0 to .002" max. The interesting part, and in line with your comment that TIR is a result of many factors, my sizing operation is INCREASING runout to as much as .004". I am using a Redding std full length die, with the carbide expander ball conversion. I have raised the ball so that the ball contacts the neck after a minimal amount of downward movement as the case is withdrawn from the die, and this seems to have slightly improve TIR, but it is still not as good as I would like to see. No reason to expect any improvement on bullet seating!! I will see what happens when I begin to load this brass, and in case anyone thinks this at all interesting, I will report on my results.

Thanks for the comments, and though you didn't type a dissertation or even a few hundred words, your comments did prompt me to do a little more looking to my benefit.

By the way, this is Fed GM brass fired through Army Marksmanship Unit match chambers at Ft Benning high power matches. Definitely not the best quality brass, but it is soft and easy to form, and cheaper to screw up than Lapua. . . Hopefully we'll see wider availability of factory Blackout brass soon, and eliminate some of the chore of making acceptable brass.

Thanks and Best Regards,

Randy

 

[Tripwire]

Re: How much accuracy degradation from excessive TIR

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RTodd</div><div class="ubbcode-body">I am using a Redding std full length die, with the carbide expander ball conversion. I have raised the ball so that the ball contacts the neck after a minimal amount of downward movement as the case is withdrawn from the die, and this seems to have slightly improve TIR, but it is still not as good as I would like to see. No reason to expect any improvement on bullet seating!! </div></div>

Take the floating carbide expander stem completely out of your FL Redding die and size the case down that way, without the expander. 'Course this method is much easier if you've already decapped your brass in a decapper die. They're cheap enough, buy one. I have two of them, both from Redding, one large case and one small case....standard gear on my bench.

Then in a second step put the expander stem back in the die, screwed all the way down as far as it will go (IOW so it would be very hard for the neck or case body to recieve any more sizing)....and then expand your necks by pushing the lubed/cleaned neck UP over the floating ball instead of pulling it down over it.

That's exactly how I do it with the exception of having a second FL die with the stem installed as I described to save me the time of taking the stem out and putting it back in all the time.

My actual sizing die, the stemless one, is set up to bump the shoulders back only .001"; that, and expanding the necks as I said, and turning the necks true, will really knock the shit out of runout.

My die set up and use produces between .000" and .003" total runout, with most between .000" and .002". My runnout gauge easily tweaks the "bent" ones straight with minimal effort and no adverse impact on accuracy. I shoot .001" or less, as standard practice.........

Per bullet seating....use a comp die. Seat the bullet in four short gentle "strokes" turning the case 90 degrees for each one. That helps reduce runout also.........

 

[RTodd]

Re: How much accuracy degradation from excessive TIR

Tripwire,
Those are impressive numbers, and sounds like you've worked hard to get there.

I pulled my decapping assembly and ran a few through. You're on the money, the needle barely wiggles absent the expanding operation. I still have the standard expander ball assembly from these dies that could easily be polished under size with a drill and emery cloth to handle decapping and expanding as you describe.

For the expanding, I have a Lyman M die with interchangeable expander plugs. Do you think it would generate the same results as pushing the case over the expander ball? I don't have an appropriate sized plug for .308 jacketed bullets (I use it for cast loads with light neck tension) but for the purpose of testing, I'm going to give it a try. If it doesn't work, I'll find a donor die body somewhere and set it up as you describe.

I follow you on neck turning, and have a Wilson style tool, but it sure is a time consuming pain in the neck. I'd be tickled with consistent groups under 1/2moa for this rifle, and I'm hoping I can get there without the effort of neck turning. OTOH, neck turning is a cry once operation, and I doubt the Whisper is going to be hard on brass. . .

Thanks again for all the help. Like I said, more to learn for sure!

Randy

 

[turbo54]

Re: How much accuracy degradation from excessive TIR

I am getting between 0.000 and 0.002 loading 308 on my dillon 650 using Forster bushing/bump and their sliding sleeve type micrometer seater. Both dies are "floating" via the oring trick.

 

[Tripwire]

Re: How much accuracy degradation from excessive TIR

Can't ever recall owning a Lyman die, so you're speaking greek to me.......

The Redding system I'm using is something I've done for a LOT of years, and I wouldn't do anything at my bench unless it had a very useful result. I like FL sizing with a .001" bump and that's why I never went to neck/bushing dies, though I have tinkered a time or two with it, a long time ago.

Redding nailed it for me with the floating carbide expander, it's just a matter of using it with the proper physics applied to the brass.

Pushing up over has WAY less impact than pulling down. I believe it has something to do with the shell holder being designed to be most accurate when pushing up. When pulling down there's a certain amount of slop incorporated and the action on the brass is gauged by the extractor groove and not the case head. The case head is one of the governing factors per headspace and fit in the chamber...it's my belief that it's where all things should begin per consistancy and concentricity.

The reason most common use of sizer dies employs the decap/expander on the pull out motion is simply a matter of convenience for the user. Doesn't mean it's the best treatment for the brass.

I hear you on neck turning, but as you said it's a one time deal for the life of the case. When you are looking for a .001" or less runout it's awful hard to ignore necks that are even slightly thick/thin......

 

[Fuzzball]

Re: How much accuracy degradation from excessive TIR

"I have a Lyman M die with interchangeable expander plugs."

IF you're going to use an expander - and I do find it a good idea much of the time - the M expander is THE way to go. Not only does it leave necks pretty straight it helps bullet seating to be consistant at the start. A bullet that starts canted usually stays canted.

I used the M dies for years, until I tried my first Lee Collet neck die. Now the Lee's are all I use when neck sizing; the difference isn't huge but it's real. Many people think it doesn't provide enough 'bullet tension' but they are wrong; in fact, too much 'tension' is a contributor to bullets starting canted.

No sizer or seater can make straight ammo in a neck that's not concentric inside and out. Turning - lightly - helps improve that but don't turn more than maybe 60-80% of the circumfernce or you're just make a sloppy neck fit even worse.

 

[Tripwire]

Re: How much accuracy degradation from excessive TIR

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">
No sizer of seater can make straight ammo in a neck that's not concentric inside and out. Turning - lightly - helps improve that but don't turn more than maybe 60-80% of the circumfernce or you're just make a sloppy neck fit even worse. </div></div>

One of the few times I'll agree with Furrball.........

 

[Fuzzball]

Re: How much accuracy degradation from excessive TIR

Even a blind hog finds the occasional acorn, right?

 

[RTodd]

Re: How much accuracy degradation from excessive TIR

Well, it looks like you're both right. I pulled another 10 fire formed cases, and FL sized with no expander. Straight as before. I then expanded with the M die - crooked. So I expanded with the floating ball on a push stroke - crooked. Dang.

So, I chose the worst offending case from this batch (.009" TIR) set up my old Marquart for 60% cleanup, FL sized again, and now the needle barely wiggles.

I don't have a ball mic to give you a precise variance on neck thickness, but using a fixed pin and dial indicator, it is on the order of .002" - .003" variation around any given neck.

Looks like I'll have something to do with my (no) spare time over the next week or so.

Really appreciate the help guys. Stumbling through this on my own would have taken months instead of hours. . .

Hope I can return the favor some time.

Randy

 

[RTodd]

Re: How much accuracy degradation from excessive TIR

Turbo,
What sort of brass are you using? I've shot some awfully good groups from a Dillon 550, but can't say I ever turned in TIR like that! Sure do like your sig line. I've rarely felt like my match performance suffered due to anything forward of the trigger finger. . .

I used to do the O-ring thing, but truth is I ran out of O-rings and haven't used them as I've added additional calibers over the last several years. Maybe time to restock. I also like my Forester sliding seater, but I have never tried their bushing sizer. Does it share Redding bushings, or proprietary?