6ppc neck clearance ??

T

Tim Singleton

Member
Still learning with my 6 ppc. I have to say its a little confounding for me. I have had enough really good days at the range to hook me. But I also have a lot of not so good days. I have learned just how close to perfect each round has to be to the rest in every way.
All that said my rifle has a .262 neck chamber. I am currently turning necks for a loaded round measuring .259

Should I be turning for a little more clearance ? For a more consistent release
 
If you have a true .003" over the pressure ring, you have more than enough clearance. I would recommend a minimum of .002" measuring a seated bullet over the pressure ring. You could have as much as .0035" to .004" clearance with your current setup. I consider this too much clearance because you are working your brass more than you need to. Just because the reamer has a .262" neck, the reamers often cut .0005" over their actual diameter. The reamers also measure closer to .2625" in many cases. The reamer tolerance is usually -.0000" and +.0004". I recommend getting an accurate measurement on the neck diameter of your chamber.

Michael
 
Sort of a religious topic. Use to be that some of the greats used .0005 to .00075 total clearance -- like Tony Boyer in the late 1990s. Well, Mr. Boyer is still great, but rumor has it he uses a little more clearance now.

There's a sort of holy writ that in long range benchrest, you need at least .002 total clearance, and .003 or .004 is better. I've always used .002. For short range, I still use .001 to .002 total.

Having said that, there are some .30BR shooters using .004 total, and some using .002 and a couple as little as .00075.

You're using .003.

Unless you want to do a lot of work testing (probably the best way, certainly the best way to wear out a barrel), you'll have to take things on limited experience.

BTW, neck clearance interacts some with bullet pull (tension) and bullet jam/jump and powder choice. Also, likely with the throat & throat angle. Nor is there a clear best here -- more like IF you use a lot or a little jam, and a powder that does/does not like a lot of neck tension, then...

Most of us, over the years, find something we can make work & don't do exhaustive testing with each barrel & bullet & powder. If using .003 works best with a jam of X & bullet Y for you, while I use .001 with a jam of A and bullet B, so what? We make the necessary compromises given our selection of components. You didn't think all this was some magical property of just the barrel, did you?

Edit:

Michael posted while I was writing. Good points. When I say I use .001 or .002, it *is* that. BTW, the usual matter of faith the "use a lotta clearance" people make is "it cuts down on vertical." I've always found other ways to eliminate vertical, including 1,000 yard rifles, where it can be a big problem.
 
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One short range world record holder told me between .002 and .003 for a better release. Another, more recently, told me that he shoots for around .00275. Lately, I (no where near a world record holder) have been somewhere between .0025 and .003 depending on the bullet pressure ring diameter. You should be fine. If I were ordering a new reamer, it would be a .263. I miss a little of the neck tension that I used to get with slightly thicker necks.
 
Tsingleton said:
Still learning with my 6 ppc. I have to say its a little confounding for me. I have had enough really good days at the range to hook me. But I also have a lot of not so good days. I have learned just how close to perfect each round has to be to the rest in every way. All that said my rifle has a .262 neck chamber. I am currently turning necks for a loaded round measuring .259. Should I be turning for a little more clearance? For a more consistent release
Click to expand...

Turn for LESS clearance.

A 6PPC with a .262" neck chamber, has in the past, had its brass turned so that with a bullet seated in the case and measured at the bullet's pressure ring, have had an Outside Diameter of .261", .2605", and .260".

.260" seems to be the new norm. Jack Neary probably had a lot to do with that. Here are some videos that I recommend to those willing to learn from a BR Hall of Fame inductee: http://www.youtube.com/view_play_list?p=7D85822FD9E41FF2

If you want the definitive guide to the 6PPC, I highly recommend Tony Boyer's book: The Book of Rifle Accuracy, available here: http://www.brunoshooters.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=BSS&Product_Code=TBSC . :)
 
Jack talks about .0081 to .0082 (for a .262 neck), and if he is shooting Hottenstein BTs I think that he is closer to .003 than .002. Anyone have one handy to mic.?
 
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It sounds like I should be good with loaded round clearance. But after watching the video link. Although i check and trim if needed at each reloading? My trim length is a little long.
Im going to give that a try next

thanks
Tim
 
I think that trimming often is a good idea for your application, as well as paying some attention to the end of your chamber neck when cleaning. What you don't want is to have a longer neck extending over fouling left behind by a shorter neck, in a tight neck chamber. That could make for an inconsistent bullet release. By keeping necks shorter, they end in a part of the neck that is more likely to be reached and kept clean using normal cleaning methods. As you get closer to the end of the chamber neck, that gets harder to do.
 
& pray in whatever direction you choose...

In general, short range benchrest success is all about being able to read conditions -- wind and mirage. It is rumored that someone of the skill of Tony Boyer can shoot through a reverse (complete change of wind direction) and still turn in a group that will make him competitive in the aggregate. Pretty much trumps anything you can achieve with trimming your necks.

You do have to have good equipment. That means equipment hat doesn't throw shots, like issues with the bolt (ignition system), or a barrel that's wonky. How can you tell when you're new to it all?

There is an element of luck, how good is your barrel. You can either trust you luck, or you can buy & fit a whole bunch of barrels.

On the other hand, long range benchrest is all about preparing ammunition. Unless it is really windy. No one can read subtle changes over 1,000 yards. But gravity still gives a drop of 32 feet per second^2, and that 1.2 to 1.5 second bullet travel time brings things into play that just don't matter in the .1 second travel time for point-blank BR. Some you can tune for -- vertical due to velocity variations -- some you can't, so your bullet testing and reloading have to be top-drawer.

OK. I shoot 1,000 yard BR. And I keep seeing things posted by the point-blank guys that just don't matter at 1K. How could they matter at 100?
 
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Tim,
I believe you are good to go. There are other things that I believe are more important than a couple thou. of neck clearance. Your consistence from load to load is most important and watch your windflags.
 
Butch
I'm liking your rest. I'm trying to learn my flags it's taking time for me to learn how much has what event. It's easier to blame it on my loading than my lack of experience. It maybe the last one where my problems are

I seem to be having a hard time with my Sinclair neck turning tool to get consistent results. Some at .0085 some at .008. I try to re cut the .0085 ones again and it won't cut anything off.
Maybe I need a different tool
 
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Mandrel

What type tool are you using to neck up the brass to 6mm? I use a 90 degree gear motor to turn brass. I have two neck turners. One for initial cut to close to .010" thickness and another cutter set @ .0085". I always let my mandrel cool after 10 pcs of brass. (use a good lubricate). After I'm done, I go back again w/the .0085" cutter. Not all but about 1/2 the brass , the cutter will remove just a little more. I find that I'll end w/a pretty consitant .0085" wall thickness and .260" loaded rd. (using Bart's Ultras) I get just slightly larger measurement w/Wilbur's fat boys and others. (I use the .0085" cutter twice on every pc of brass)
Tsingleton said:
Butch
I'm liking your rest. I'm trying to learn my flags it's taking time for me to learn how much has what event. It's easier to blame it on my loading than my lack of experience. It maybe the last one where my problems are

I seem to be having a hard time with my Sinclair neck turning tool to get consistent results. Some at .0085 some at .008. I try to re cut the .0085 ones again and it won't cut anything off.
Maybe I need a different tool
Click to expand...
 
I have a sinclair expanding die and mandrel. I'm using 2 Sinclair tools one set to make the first cut then another to make the final cut to .0085

They do not have the carbide cutters. I do notice it getting hot and probably am not letting it cool properly. I use imperial dry wax to lube.
It may just be that I haven't been re turning necks as I've went along I've paid attention to trimming to consistent lengths but haven't been re turning. They have 8 firings on them now. I'm using a Ken Light annealing machine to anneal
 
If you are not using carbide turning mandrels, and your turners are getting hot, it is likely that you are getting some brass buildup on the mandrel right under the cutter, which will cause necks to be thinner after it happens. I have tried various turning lubes, and find that there are better ones than what you are using (IMO, fully braced for disagreement). What are you driving your cases with, and how fast are they spinning? I have never known of a short range benchrest competitor that annealed his 6 PPC case necks. Given the typical neck thickness, getting a high enough bullet pull is an issue, and annealing necks would seem to possibly be counterproductive, since it might reduce bullet pull, by softening the brass. Back in the day, when my only turner was the cheapest Sinclair, I was running into friction related brass on turning mandrel problems, until I reduced the diameter of my turning mandrel slightly. If you hold your tools the right way, and operate them as I do, you really don't have to have a wring on fit of the case neck on the turning mandrel to produce excellent results. As far as I am concerned, the idea that a tight fit is required is a widely repeated myth.
 
the brass flows with firing. so we trim to length on each re loading. Should I also be re turning?
When the brass flow happens will it cause neck thickness to become inconsistent?
 
Tsingleton said:
the brass flows with firing. so we trim to length on each re loading. Should I also be re turning?
When the brass flow happens will it cause neck thickness to become inconsistent?
Click to expand...


Sorry to change the topic but the statement"brass flows with firing" is simply wrong....... Brass DOES NOT "flow with firing."

It is entirely possible to fire a single piece of brass 50 times at 60,000+++ psi and not trim it at all.

I do this, consistently, with cartridges/chamberings from BR/PPC up to and including blown out 338 Lapua cases.

Brass "flows" from improper die fit and setup, in simple terms you push it up through the resizer too far, and yes, when you do this you're running shoulder brass up into the neck which makes a mess but more importantly you WILL suffer case failure, casehead separation is inevitable if you're constantly trimming your necks since that brass you trim off has to come from somewhere and where it comes from is the junction of the casehead to case body.

I state this only because this is a public forum and IMO info need be vetted for accuracy, people spend real money based on info found here on BRC.

al
 
I apologize if I have miss stated something or phrased it wrong.
If this is so, and the brass does not grow when fired. Why do people say That a round with a 40 degree shoulder doesn't grow as much as a 30 degree thus requiring less trimming?

I have just began to loose some ppc brass, it is separating at the head. Probably 25x loaded. I bump the shoulder back .001 with my Harrel die. I don't think I am running it up into it to much or using it improperly. But I do have to trim regularly maybe not every firing but probably every other to keep it the same.

help me understand this
 
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Tell us how much FL sizing reduces the diameter of the body of your cases, at the shoulder, and a little above the extractor groove. Also, how have you established the dimension that you bump back to? How many neck sized warm load firings did you do to come up with a reference dimension, to subtract .001 from? The reason that I ask is that if you set up your bump in reference to the measuring of a case that did not represent the maximum shoulder to head dimension for that barrel in that rifle, you may be bumping more than you think that you are.
 
I started out by firing 3x several pieces of brass by slip fitting the bullet back in the case. It had a slight amount of grip. I sent 3 pieces to Harrels. They sent me a die and their brass shoulder comparator.
I use it to measure the shoulder of a fired round and after sizing to measure the amount shoulder is set back.

Fired case at shoulder measures .4315 sized case .4305
Just above extractor groove fired .440 sized .4395
 
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