Neck clearence

T

Tod Soeby

New member
My new 300 wby bbls are both .334 necks. I have 200 brass which have been turned, fired once, trimmed to length, and some have been fired again. Everything, including accuracy is very good. Considering my Dasher nightmare, all is right with the world!!!!! SILLY ME. :D I was doing some measuring the other day and grabed a hand full of loaded rounds left over from the Iowa shoot. I grabed my calipers and measure the necks.....3315!!!!!!!!! I measured 10 and they all read the same. This didn't compute..... I grabbed my micrometer. .332, which is more like it. This is what I checked my first loaded rounds with during my origonal set up. Both of my measuring tools are Top of the line Mitutoyo. Now confusion sets in...I grabed my Ball micrometer and measured some brass that I have ready to load. .01175. X 2 + .308 = .3315. :eek: :eek: :eek:.

My guess is (since I didn't keep ALL of my paperwork when I was doing my figuring) is that I forgot to carry a number about 3 digits right of the decmel point when I was doing the math.

My question is...is there anyone out there who runs things this close? I would like to have another .001 clearance. I have never tried to take .0005 off of a neck before.

Very important lesson here. As that little Texas hand grenade with a bad hair cut ( H. Ross Perot) once said...."measure twice and cut once"!!!

A truer statment has never been spoken.

Thanks for you time, and, come the November elections, Please remember me!!:D

Tod
 
Tight!!!!!!!

Tod---- Let's see that's a bit tight but not out of reason. Most shooters like at least two thousand per side and many like three. And well anyone that can turn necks precisely to .1175 can take .0075 off can't they?
 
Tod

Clean your necks real good and go back over them again without changing your neck turner. 1. It will shave off a little bit and may give you the clearence you want and 2.It's the only way to get absolutely uniform necks

Dave
 
Dave Tooley said:
Tod

Clean your necks real good and go back over them again without changing your neck turner. 1. It will shave off a little bit and may give you the clearence you want and 2.It's the only way to get absolutely uniform necks

Dave
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The necks are clean, but I have tured 6.5 and 6mm brass since turning these.
 
oneflyer said:
Tod---- Let's see that's a bit tight but not out of reason. Most shooters like at least two thousand per side and many like three. And well anyone that can turn necks precisely to .1175 can take .0075 off can't they?
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I never exactly said I was AIMING for .01175......that is just where they ended up while I was doing the set up. I measured them after test turning some culled brass, and when I did the math, I , um ,well, I did the math wrong!!!!!! I thought total was .3215....which I was fine with. Had I actualy learned to add properly and saw the actual number, I would have done a little more "tweaking" before I actualy started turning my match brass.
 
Dave Tooley said:
Oops
Good luck

BTW neck turners are pretty cheap. I leave one set up for each chambering.

Dave
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Four sinclair 3000 neck turners.....327.60


Four .001 dial indicators...............104.00


Freight and taxes........................27.50



Cost of NOT learning how to add to the right of the decimal point in 3rd grade.....................................................................................................................................................................................










Wait for it..........................................................................................................................................................................................













PRICELESS!!!!:D:D
 
Don't beleive the word "Sinclair" was in Dave's post. Last time I looked (a while ago) a K&M with a carbide mandrel *with* inside uniforming (most expensive way to go) was around $60 for just the neck-turning part. You don't need 4 separate drivers.

If you haven't used carbide mandrels, you've been missing out.

If you have a ball mike, why in the world would you need a dial indicator? Doubly so on the dial indicator if you set 'em up & leave 'em alone.
 
Tod,
My 7mm SAUM LG has a .318 neck, loaded rounds measure .316.
It shoots pretty good, worn out barrel and all. My 6-6.5 Creedmoor LG has a .272 neck, loaded round measures between .2695 and .270.
I am getting an occasional flyer with the Creedmoor but don't believe it is due to clearence issues.

The way you are shooting I wouldn't worry about it.

James
 
I run .002" total clearance (.001" per side) on all my 1000 yard BR chamberings. I make sure it does not get less than this because it can cause issues with the larger cases, necks & etc. we work with. I commonly take a skim cut after the brass is fully fire formed to make sure all are uniform.
 
Charles E said:
If you have a ball mike, why in the world would you need a dial indicator? Doubly so on the dial indicator if you set 'em up & leave 'em alone.
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I baught the neck turner in 1999 when I got my first tight neck chamber. I didn't have any decent measuring tools at the time, so I got it with the dial indicator.
 
For what it's worth, the smallest 600, 800 and 1000 yard groups with at least 20 shots I know of have all been done with chambers having standard SAAMI dimensions for body, headspace and neck. Same thing for most 10-shot groups at these ranges. All have been done with full-length sized cases.

30 caliber cartridges with typical .336- to .338-in. loaded round neck diameters do great in chambers with .344- to .345-in. diameter necks.

Note that a rimless bottle neck case neck's positioned in the chamber neck when the case shoulder's slammed into and centers on the chamber shoulder as the firing pin drives the case forward setting the shoulder back a few thousandths of an inch. If the case neck's not centered on the shoulder, it won't be centered in the chamber neck when the round fires. So the case neck's gonna be pretty well centered in the chamber neck when fired regardless of the clearance around it.

Besides, as there's no such thing as a perfectly round case or chamber, axial alignment of both when the round goes off is typically very close, but never perfect. The case's back end is pressed off center by the extractor so it's never centered in the chamber except when pressure's at its peak and the bullet's about half way down the barrel.
 
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Tod Soeby said:
My new 300 wby bbls are both .334 necks.

Tod
Click to expand...

Stop right there. Why do you think they have .334 necks? Have you measured the chamber? I have had two chambers done with match reamers that were NOT what they stated. My latest, a 260 done by one of the $400 chambering guys who will remain nameless, is stamped .294 but is closer to .292.

I just mention this so that you might check and find that you have plenty of clearance after all. Generally, if you can still a bullet back in a fired case with only slight finger pressure, you have enough clearance.
 
slugger said:
Stop right there. Why do you think they have .334 necks? Have you measured the chamber? I have had two chambers done with match reamers that were NOT what they stated. My latest, a 260 done by one of the $400 chambering guys who will remain nameless, is stamped .294 but is closer to .292.

I just mention this so that you might check and find that you have plenty of clearance after all. Generally, if you can still a bullet back in a fired case with only slight finger pressure, you have enough clearance.
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I have never tried to do that with a fired case (yet), but I tried to load some with a .332 bushing this weekend, and when I set the loaded rounds in my shell case bullet up, about a third of the bullets had worked there way deaper (via gravity) by the time I had got the shell case to it's home on the shelf. I am guessing I can pull all of the bullets loaded with the .332 bushing by hand. All of my loads have been with the .330 and .328 bushings, and, since I had a .332 bushing on hand, I figured I would try a few groups. I am going to pull those bullets and run the brass through a .331 bushing and see how they group compared to the .330's.

Thanks again,
Tod
 
Sounds like you are OK then. I ran into trouble with Nosler brass in a 260. It was so thin that a standard die would not size it enough. My regular bushings weren't enough. I had to buy an additional bushing, just for that brass.
 
Bart B. said:
For what it's worth, the smallest 600, 800 and 1000 yard groups with at least 20 shots I know of have all been done with chambers having standard SAAMI dimensions for body, headspace and neck. Same thing for most 10-shot groups at these ranges. All have been done with full-length sized cases.

.
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what 600yd or 1000 yd BENCHREST competition is done with 20 shot groups ??


mike in co
 
Mike in CO asks:
what 600yd or 1000 yd BENCHREST competition is done with 20 shot groups ??
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None that I know of. But a 20 shot group tells more about the accuracy one can count on than a 5 or 10 shot one. Any rifle will shoot a tiny 5 shot group once in a (great) while; few if any folks holding 5-shot group records equal or better it. Almost the same odds with tiny 10 shot ones. I'm more impressed by a tiny 20 or 30 shot one. Such as these examples.....

One made in 1991 with twenty new, virgin .308 Win. cases with metered powder charges (.3-gr. spread) shot at 600 yards measuring 2.7 inches.

And the 40 shot one made in the late '60's at 600 yards measuring 1.92 inches, to me, is more impressive than the recent 5 shot ones at that range at about an inch. The same rifle shot a series of back to back 10-shot groups at 600 ranging from 1.5 down to .7 inches. Not too shabby for a Hart barreled pre-'64 Win. 70 action in a wood stock shooting full-length sized WCC58 .308 cases.

In the late 1990's, a .30-.338 Win. Mag put 30 consecutive shots into a bit under 7 inches at 1000 yards. 15 with Sierra HPMK 200's from full-length sized cases and 15 with 190's from new, virgin cases.

These groups were shot testing NRA "match," "any" or Palma rifles and their ammo for accuracy.

As far as I know, none of the 10-shot 3-group (or more) averages/aggregates at 1000 yards has all of them under 7 inches. Same for 5 or 10 shot 600 yard avg./agg.; none of them have all the individual groups under 2 inches. If one does, I'll be glad to see a link to it then I'll retract my claim.
 
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