Neck clearance

[BenPerfected]

At 400+ yards, do you see any difference on the target between neck clearances of .0025, .002, .0015, .001 and .0005?
Ben

 

[expiper]

there are too many things to try that do work to waste time trying what doesnt work,,,,stay around .003" total clearance,it is proven to work over and over,,,,time is much better spent trying to find seating depth/jump/jam and neck tension that works,,,,Roger

 

[dkhunt14]

At 400+ yards, do you see any difference on the target between neck clearances of .0025, .002, .0015, .001 and .0005?
Ben

I like .003 plus. I tested from .001 to .004 in A Dasher and couldn't see a difference. I believe it needs to be able to let the bullet go. I hear some like a .284 like .005 or more. I prefer to stay on the safe side and run .003 minimum. It you get a little carbon or a neck not turned right, brass flow or anything that can hold a bullet it will ppose accuracy and drive pressure up. Matt

 

[mikecr]

At 400+ yards, do you see any difference on the target between neck clearances of .0025, .002, .0015, .001 and .0005?

The answer would depend on more than just the clearances.
What cartridge? Sizing plan?
How many reload cycles do you expect from the cases?
What rate do you intend to anneal?
How straight will the ammo be maintained?

If one clearance was always best, we'd all be at it by now.

 

[kvd]

At 400+ yards, do you see any difference on the target between neck clearances of .0025, .002, .0015, .001 and .0005?
Ben

Ben,

Things seemed a little tight when I was only allowing 0.001 inch per side between case neck and chamber neck. Only after opening up to 0.0025 inch per side did I see noticeably better results at 400 yds and better. This was with a 7 SAUM and 0.315 inch chamber neck.

Ken

 

[Alex Wheeler]

I have tested it at 1k. No difference from .001-.005". Clearance is clearance. The neck does NOT align the bullet. A tight neck does NOT align the bullet. There is less than .00025" clearance on each side of a bullet in the freebore, so unless your neck fit is tighter than that, the freebore is doing the aligning. Its best to not fight it with a tight case.

 

[ireload2]

One of the problems with extremely small neck clearances is the lack of measuring capability to be able to tell the difference between .001 and .0005. You really need an instrument that will resolve 1/10 of the smallest measurement. For .0005 you would need to be able to accurately measure to the nearest .000050 which is 50 millionths. There is no one here able to do that with the equipment they have at home. When you can't reliably measure that well you tend to reach the conclusion that it makes no difference because you cannot tell any difference. Throw in the affect of conditions when shooting at 400 yards you don't have the means easily discriminate such tiny variations.

 

[T-shooter]

One of the problems with extremely small neck clearances is the lack of measuring capability to be able to tell the difference between .001 and .0005. You really need an instrument that will resolve 1/10 of the smallest measurement. For .0005 you would need to be able to accurately measure to the nearest .000050 which is 50 millionths. There is no one here able to do that with the equipment they have at home. When you can't reliably measure that well you tend to reach the conclusion that it makes no difference because you cannot tell any difference. Throw in the affect of conditions when shooting at 400 yards you don't have the means easily discriminate such tiny variations.

For neck clearances, I just measure the case neck on the outside before and after seating the bullet and see how much it expands.

 

[Capt. Oblivious]

I like to have enough clearance not to worrie about carbon messing with me with long days of shooting. Other than that i just leave it alone

 

[dkhunt14]

One of the problems with extremely small neck clearances is the lack of measuring capability to be able to tell the difference between .001 and .0005. You really need an instrument that will resolve 1/10 of the smallest measurement. For .0005 you would need to be able to accurately measure to the nearest .000050 which is 50 millionths. There is no one here able to do that with the equipment they have at home. When you can't reliably measure that well you tend to reach the conclusion that it makes no difference because you cannot tell any difference. Throw in the affect of conditions when shooting at 400 yards you don't have the means easily discriminate such tiny variations.

I don't understand why you think you have to go two decimal points past. 0001. I can easily measure to .0001 reliably. Even if i am off plus or minus .0001 it is still well within 25% .001. The scale on the backside of the Micrometer tells you what .0001 your at. A good friction or ratchet thimble micrometer will read the same number 99 percent of the time. Matt

 

[Jet]

My results are similar to those posted above. I have tested .001-.003 clearance on the dasher and found it didn't make a difference on the target. If you choose to shoot with very tight clearance make sure you are paying attention to the diameter of your bullets when changing lots or brands.

Good Shooting

Rich

 

[mikecr]

For neck clearances, I just measure the case neck on the outside before and after seating the bullet and see how much it expands.

That's a neck thickness measure, not a chamber clearance measure.

I suppose we could measure chamber neck with long pin gages.
Fired neck OD (-) assumed spring back(1thou conservative) gives useful enough ballpark of chamber neck.
That minus loaded neck OD is clearance.

Grouping in an often short term of brass life may seem less affected by clearance, but this does not mean we should concede to big clearances. There can still be advantages to lower neck clearances, where understood and planned.
For one, bigger clearances contribute or cause carbon buildup in the chamber neck(opposite of a cure).
Way back shade-tree mechanics thought mitigating broken rods/cranks meant going bigger in bearing clearances. The truth was that their already ridiculous clearances were causing loss of hydraulic support(oil) between surfaces, with eventual impact events. They actually needed to get back to the basics, and then do all needed for tighter assembly(like any of today's engines). The back edge of the sword, for tighter build, is runout, and chambered tension caused by it. Just like in a racing engine, you make it tight, then make it right.
Also, the tighter your neck clearances, both to chamber end and chamber neck, the faster necks seal, the less rearward gas migration, and lower to no carbon buildup.
Neck clearance and your sizing plan affect your ability to manage tension as well. This matters where you intend to use the same cases for a long time.
The less you size necks, the lower your runout from that operation.

As implied already there is no immediate gain in lower neck clearance, and therefore, no immediate detriment either.
I've run with fitted, tight, SAAMI min, SAAMI max. In only a few reload cycles it won't matter unless your ammo is crooked as hell.
If SAAMI max, then it won't be long for crooked ammo..
Fitted is under 1thou, neck sizing no longer required
Tight requires turning for 1thou at least
SAAMI depends on the cartridge, I would think minimum would be ~2thou

IMO, 2thou over unturned necks, FL sized cases, is reasonable. 1thou over turned necks. Fitted requires improved cartridges and better reloading engagement to manage.