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Discussion in 'Reloading' started by Iron Worker, Nov 6, 2012.
Why do you neck turn ?
* example #1; chamber is .222 Remington N.M. with a .246" neck. Gotta turn the necks? Not everytime as of late. I have one batch of brass that when loaded comes out to .2445" unturned. But if I use regular brass and shave the necks I can get my loads to come out around .00075" TIR rather consistently. But the proof of the pudding is group size, isn't it? Not too much difference here, and maybe .10" at the most. What I seem to have picked up on is velocity spreads. They seem to be a little tighter with the shaved necks (I already know there's no way to prove this to be true, but it's what I see on the chronograph. Not important anyway as the round goes thru a hand gun
* example #2; .223 Remington with a very tight N.M. chamber that has an actual .247" neck size. Pretty much the same results as in chamber #1. I do have some Blackhills brass that will easilly chamber after being loaded. Difference in group size is about .120" when compaired to a case that has a .242" neck and .2455" after being loaded. Both these two rounds are sized and loaded with Wilson inline dies. Cannot quite get the loaded rounds as strait as the .222, but usually see well under .001" TIR. Still not enough to stay awake at not for. Plus the barrel is junk!
* example #3; a 6mm/250AI chamber cut on the tight side, but with a minimum spec neck (about .272"/.273"). I usually shave the necks to
.2665 +/-.0025", with a loaded round comming at a tick under .270". The chamber would probably handle a .272" neck, but I think there might be some pressure problems. The rifle is a solid .275" five shot group gun. I do not load this round with Wilson dies as I've just never bothered to build a set. I get about .0015" TIR using a set of Redding .243 dies that have been reworked. On the otherhand I don't think there's much room for improvement in the chamber / die combo till I do some work on the action and stock itself
* example four; a 6mm Remington (actually two guns). Both were Ruger 77's (old style). One wouldn't shoot well (about 3.5" groups), and was rebuilt by Woods from the ground up. A new factory chamber was cut on a .38" barrel setback to factory spec'd Remington. In that mode it was a 3/4" grouping gun. I tried shaving the necks as the brass wasn't anything to write home about. and picked up almost a quarter inch in groups with the same bullets and loadings. I later got it down to .400" groups with some powder changes and very hot loads. The other rifle responded even more, and was a 5/8th's gun (had the sporter barrel) . I used three different sets of dies with these two rifles if it matters much. An RCBS standard die set, a Forster Ultra set, and a Wilson set. The Wilson die set always gave me the best groups. A further note: I really saw the greatest gains in these two rifle at 350 yards and further out as the groups seemed to be a little more consistent. My longest kill was at 670 yards with the 77V using a Berger 88 grain bullet
It's an accuracy thing. The idea is to make the neck wall thickness consistant so the bullet will be more concentric in the chamber and enter the lands square thereby enhancing accuracy. Or something like that.
outside neck turning works best the tighter the chamber. I don't see it doing a whole lot in a factory rifle with a SAAMI spec chamber. I do not own or shoot a factory rifle. Sometimes I neck turn, other times I do not. If I'm finding a rifle to be overly picky, I start turning necks and most of the time it helps.
Well I'm shooting a 6/284 . Neck of loaded round is .275 neck of fired case is .275 plus I'm getting tough extraction and pressure signs so it must be things are too tight.
Sounds more like the load is too hot. Reduce your load buy a couple of grains, and try again.
Actually to know what is going on with your chamber, you need to cast it with Cerrosafe. That will tell you what the neck diameter of your loaded round should be. I usually am .002 to .003 under my chamber neck dia.
I turn em just to make the neck consistent thickness, sounds like you need you need to reduce the diameter.
if loaded and fired are the SAME, you have a really tight chamber and your cases need necks turned.
It's usually safe to assume about .001 springback after firing. Meaning a .276 chamber neck will give .275 fired case necks. If loaded rounds are .275 then you've maybe only got .001 clearance or .0005" all the way around the loaded neck/bullet before it's fired.
In a stricly competition gun that is kept squeaky clean, that would maybe work if you didn't want to resize cases......fitted neck gun is the term I've heard........I bet you need a press to seat bullets (without sizing first)...... they probably wont seat with your fingers??
If that's the case, and it's a hunting gun that might get a little dirty between cleanings, I'd clean up (or turn down) the necks a little. Shouldn't take much, maybe .0005 to .0008 off the current neck thickness. Whatever you take off will be double by time you go full circle. After you turn necks, the tension on a loaded round will decrease unless you change bushing size in the resize die. You may have a tight enough bushing or die neck already, so this might not apply in your case.
If you dont want to turn the necks, a gunsmith can sometimes ream out the chamber neck just a touch. Or, you could try a different brand of brass that has thinner necks to begin with. If you've never turned necks, you can be in for quite a little expense with expander mandrels, turning mandrels, power case drivers, case holders, neck turner and cutters, tubing or neck thickness micrometers, ect. They are all necessary to turn a high volume of cases to within tight tolerances.
Sinclair International is a great place to get neck turning equipment IMO. Most of the customer service people know what they are talking about and are very helpful.
Just my opinion, but most rifles that are capable, don't need neck turning for 1/2 MOA groups, 1/2 minute and even better should come easy with good rifles and decent handloads/load development. But.........If we are after sub 1/4 MOA and better all the time, that's when we take off the high spots, or get tight neck chambers and turn down brass.
I have a gun with a fitted chamber(not just necks).
26wssm imp, chamber nk: .291, I turn necks to 13thou thick: .290 loaded.
My fired necks spring back to .289, and I lightly partial NS using a Wilson & .288 bushing for tension that worked out from load development.
I'd say it's fitted necks in that I don't have to resize them(didn't for ~5-6 reloads).
Also, this is a 16.5lb BR gun that is kept in pristine condition.
No way to say what my dimensions contribute to precision, but it's even easier to reload than a 223 or 6br, and easily shoots 1/4moa grouping to 300yds w/139Laps at 3025fps.
I didn't go tightneck for accuracy in the short term, but for accuracy in the long term.
I use a Sinclair neck turner (have two actually), and if I were to buy another neck turner; it'd be a K&M! The Sinclair is pretty accurate, but a real bugger to make adjustments on (even with a .0001" dial indicator attached to it. Both of mine will freeze up if not in semi constant useage. Aluminum and steel are not compatable working together and steel will cause aluminum to corrode around the male threads of the adjustment screw and cutter. For some reason the K&M's don't do this. I did fix one of my Sinclairs a few years back, and it works great.
Ron Pence used to have a 6BR (or 6PPC) that the neck and chamber were fitted very tight. He never resized a case, and literally seated the next bullet in a once fired case untouched except for priming. Was the gun accurate? Good enough to win 80% of the benchrest shoots in this country
Thanks every one I have a K&M and I have Neck turned before . I'll be doing that in this caliber from now on ?
I could do this. If I had an enclosure for my RCBS CM, I could go to the range with a single case, shoot all day, & it wouldn't slow me a bit.
As part of reloading ease in this, I do not need predictable precision in turner adjustments(K&M), because I rarely replace any brass once prepped. I also don't need to trim, or anneal beyond initial.
I can use use Sinclair's cheapest turner(although I have their best), with a feeler gauge and a couple cases culled due to thickness variance. And IMO getting the exact thickness is trial & error anyway.
Not a big deal.
I started with K&M, but switched to Sinclair for their expander system, which is the best overall whether turning or not.
For my preps, I picked ~120cases from 1,000 that were closest matching in thickness variance. Prepped them, Lead dipped to mid body, fireformed, measured H20 capacity & picked ~70 that matched. These have outlasted 1.5 barrels now, and I can see they will just keep going.
Most competitors can wear out their brass with all kinds of clearances and shortcuts in reloading. But it doesn't have to be that way, and they're not really shortcuts.
I suspect that Ron Pence's approach would work as well and easier while planned for up front.