Bullet TIR

[justjeff]

Hi Guys,

Just started measuring TIR in projectiles, wondering if any of you have any experience in this. What is 'good', and 'not so good' I have 200grSMK here measuring about 1.5 - 2 ten thousandths, Hornady 208 grAmax going 4-5 ten thousandths and Berger 210 going 4 - 9. Just wondering if anyone has done the tests, and fired the different tolerances to see the difference.

Thanks

Jeff

 

[Wilbur]

Pretty sure somebody has done that - Pete Wass comes to mind.

I have a question that maybe you would know. Which of those bullets mentioned shoots better in your rifle without measuring?

 

[John Kielly]

What's TIR?

 

[Charles E]

Wilbur is too gentle. Before you worry about the dimensional consistency of ANY component (includes bullets), first figure out which "brands" shoot best in your barrel -- includes bullets, powder, & primer. Next the get the powder charge, then the seating depth & perhaps neck tension.

Now start sorting stuff. I got to the IBS bronze level without much sorting -- well, at first I sorted bullets, then got BIBs, and had to stop. Too much boredom. Danger of narcolepsy. I'm sure there are other custom bullets about as good.

On the other hand, Charles Bailey (IBS shooter of the year around 2000) found Berger 210s shot best in his rifle. Here's the important part: This was in the days after Mr. Berger had sold the company, and before he bought it back. Quality suffered during that period. But those bullets shot best, so he used them. All that meant was he was in for a lot of sorting.

As a side note, I'd add that a bit after Walt Berger bought the company back & Eric Stecker took over day-to-day management, most of the consistency issues seem to have disappeared. I now use Bergers in my .338, and they are extremely consistent.

BTW, John asked a good question -- what do those numbers you gave refer to? And just what do you think is important in bullets?

 

[alinwa]

What's TIR?

Total Indicated Runout

As defined by the User

Contrast with TIRABSITAWSHPASDATH which is Total Indicated Runout After Being Smacked In The A$$ With Six Hunnerd Pounds And Shoved Down A Tiny Hole and draw your own conclusions.

al

 

[mikecr]

justjeff, have you polished an offending bullet & remeasured to see if it's really runout, or surface profile?
Are you measuring this with a Juenke?
Just curious

 

[Charles E]

Contrast with TIRABSITAWSHPASDATH which is Total Indicated Runout After Being Smacked In The A$$ With Six Hunnerd Pounds And Shoved Down A Tiny Hole and draw your own conclusions.

How tiny a hole? About .270?

(Sorry Jeff, I couldn't resist...)

 

[justjeff]

Hi Guys,

Thanks for the replies, I think. The bullets in question are all 30 cal, suspended at a uniforn dimension on the ogive (0.1 in), and also suspended at a uniform point on the base of the boat tail. Measurement is taken on the shank, immediately before the beginning of the ocive with a 0.0001 mit dial test indicator. I haven't tried sandpapering the bullets, as in all cases the out or round is a gradual thing, so seems more like either the point or the boat tail are not concentric with the shank.
Charles, I know we don't shoot as small a groups over here in Aus as you blokes, but I have finished second to JR the last 2 years, which bites. I am waiting on some BIBs at the moment, but in the meantime, I need to make lemons into lemonade so to speak. The Sierra's, in front of 66.3 gr AR2209, with 210M primers seated 25 thou out have certainly proved the best so far.( I use the same case as JR, but Norma or RWS brass). Currently using an 11.25 twist Kreiger barrel, and have an 11 twist Hart in the cupboard.

Anyway, back to the lemonade. Is one of the reasons I get the odd open group with the other bullets due to this TIR difference? I am already measuring hell out of the bullets, 6 differnet dimensions and also Juenke.

Regards

Jeff

 

[Dan Conzo]

justjeff--tir .0002" or less is very good if you are spinning the base of the bullet IMHO.

 

[Busdriver]

I've never considered spinning a bullet to determine runout until recently.

I was making up a dummy round and checking neck diameter. I got an unexpected number from the first dummy so I made a second. It measured exactly as I expected, so I went back to make certain I wasn't seeing things, and the first dummey measured significantly bigger than the first time.

After pulling the bullets with a kinetic puller, I started measuring. The first bullet was .3069 at the pressure ring one way and .3086 after turning it 90 degrees. The other bullet was .3081 all the way around. I have literally measured hundreds of bullets since then and never found diameter differences of more than .0001" on any of them.

I have a friend with a juenke. I'm going to take this funny one to him and see if the juenke detects the out of round condition.

Does anyone else have a good tool for checking this without going blind in the process?

 

[alinwa]

Please tell us what the Juenke finds

al

 

[Charles E]

Jeff,

As I look at your setup, I think what you're actually measuring is boattails that are not concentric to the shank. You're setting up on them, assuming they're true. But what if they're the biggest problem? In the '90s, I found off-center boattails fairly often with Sierra bullets, using a different testing technique.

Things I check for, borrowed mainly from Charles Bailey, are:

1. Is the boattail concentric with the shank? (not an issue with the 187 BIBs, which are FB). Using the Juenke, set the bullet on the balls so the boattail is over the head. Use both "deviation" and the absolute number readings. (Actually, for most sorting, I use the "what's the number range" more often than "deviation." Bullets with the same number reading on the various tests are grouped together.)

This is probably the most important measurement, because if the boattail is not concentric, it acts like an offset mass -- the old CG offset problem, which can cause significant dispersion.

Of less importance until you get down into the sub 5-inch region (10 shots):

2. How long is the boattail.

3. Measuring from the end of the bullet (now that the boattail lengths have been sorted), where does the ogive begin, relative to it's mates? I do this with the Juenke, but there are many ways.

I think this is less important if you jump bullets +.020 or more, or use a deep .015 or more jam. Others, who believe bore friction is a factor, would disagree.

Since I currently repoint, trim, then repoint meplats again, I use a visual check on the meplats. Not sure any of this matter -- most likely trimming the meplats matters. And of course, with the A-Max, it's already been taken care of.

* * *

My general feeling is consistency in bullet manufacture is as critical as all the BC numbers tossed around. Why the BIBs do so well, & hold so many records.


Hope this helps

Edit:

I know we don't shoot as small a groups over here in Aus as you blokes

???


I've shot against both Stuart Elliot & the late Alan Peake (miss him) when they were over for a SS & shot at Hawks Ridge. Everything about them was fun, except having to try & beat them. Those guys could flat out shoot!

And Jeff Rogers would be competitive at the International level. I'm sure there are others I just haven't had the pleasure of meeting...