Proper Neck Clearance question.

[Pa.Mike]

My question is quite simple, should an unfired bullet slide into a fired round case? I have a 6 creed. and realize this cartridge was designed to a close cartridge / chamber relationship to promote optimum accuracy. I have two 6 creed firearms both chambered with different reamers that were not match reamers and two different brands of brass and an unfired bullet will not slide into the fired case. My H-S Precision firearm in 7saum lets fired cases easily accept an unfired bullet. Are the two 6 creeds susceptible to pressure issues due to this? Thanks for any opinions you may have!

 

[pdog2225]

My question is quite simple, should an unfired bullet slide into a fired round case? I have a 6 creed. and realize this cartridge was designed to a close cartridge / chamber relationship to promote optimum accuracy. I have two 6 creed firearms both chambered with different reamers that were not match reamers and two different brands of brass and an unfired bullet will not slide into the fired case. My H-S Precision firearm in 7saum lets fired cases easily accept an unfired bullet. Are the two 6 creeds susceptible to pressure issues due to this? Thanks for any opinions you may have!

Keep in mind that the neck of a fired case upon cooling will shrink back normally .002th of an inch.You may or may not be able to seat an unfired bullet into that case. Lots of necks on hunting rifles may be as large as .008ths over loaded case diameter. Keep investigating.....pdog2225

 

[ShtrRdy]

I don't know where the "easily slip a bullet into a fired case" recommendation came from but I think it's a little extreme.

If you measure the case neck diameter on a loaded cartridge and the case neck diameter on a fired case. As long as the fired case neck diameter is at least 0.001" or greater than the loaded cartridge neck diameter you are good to go.

 

[joshb]

I like at least 4 thousandths clearance. You should cast your chamber.

 

[Fast14riot]

Don't forget the slightest bit out of round will stop a bullet from slipping through the neck.

 

[LVLAaron]

I like 4-5 thou total clearance. Some BR guys like less. Why does it matter if a bullet can fit in a fired case?

 

[AlNyhus]

My question is quite simple, should an unfired bullet slide into a fired round case?

It may or may not. If it won't, that doesn't always mean the clearance is too tight. If it's a magazine fed gun, the case neck can be slightly tweaked and cause a bullet not to fit. Sometimes the case mouth will pull in a bit more than the rest of the neck. It can also be from the case mouth being too close to end of the chamber.

There's really just two things to check. With a micrometer, measure the O.D. of the neck when a bullet is seated. Then repeat this with a fired case and compare the two. The other thing to check is the chamber length using a Sinclair chamber plug. Compare that dimension to the O.A.L. of your case to know if the case length is ok.

Hope this helps. -Al

 

[Laurie]

Why does it matter if a bullet can fit in a fired case?

This is one of these historical things. Go back 30 or more years, and many reloading manuals said bullets should slip freely through fired case necks, otherwise there was something wrong, usually the case having been allowed to become over-long thanks to inadequate trimming. They don't say that nowadays, but this is one of these 'facts' that are passed from generation to generation of handloaders.

As an example of neck to chamber clearances of that time, I have the remnants of what was originally 600 Norma 308 Win cases that I bought (really!) cheap as 150gn PSP factory ammo back in the 80s. This came from a large ammo lot with light (<160gn), thin-walled cases that wouldn't sell as the brass was 'unreloadable'. What that meant was that with the chamber-neck dimensions of 308 Win deer rifles of the era, even many 'match' rifles, necks expanded too much and quickly split after sizing and refiring. With once-fired Boxer-primed 308 brass highly sought after in the 1980s and expensive in the UK (ex-military was all Berdan here), this removed the financial benefits of buying expensive factory ammo for many if you couldn't reuse the brass. So they ended up being heavily discounted. My 308s at the time were an ex-club 7.62 'Target Rifle' rebuilt by G E Fulton & Sons from a former Lee-Enfield No.4 0.303 'Service Rifle' with an RSAF Enfield Lock manufactured and chambered heavy barrel, and a Ruger 77V heavy-barrel sporter, both of which shot well by contemporary standards, Chambers were slack by today's standards on both, so I kept that Norma brass back. Bullets dropped freely straight down through fired Lapua case necks from both rifles, no friction at all with the available clearance. That brass had relatively (compared to Winchester) thick necks in the 14 to 15 thou' range.

I pulled the bullets and reused them and the powder in heavier cases. Eventually, as chambers became tighter and neck clearances reduced, those Norma cases became usable and gave good life especially with quality match and/or bushing dies that didn't massively over-size necks. Neck-wall thickness was mostly around 12 thou' in these cases, but could be as low as 11. They work very well in minimum-SAAMI 308 Win chambers, and I also resized many to 7mm-08 when I had an F-Class rifle in this chambering.

 

[Will Henry]

When I first started shooting benchrest, it was not uncommon for guys to shoot "fitted necks". In my case, I was shooting a 6x47 (222Rem Mag, necked up) with a chamber neck diameter of .266. I turned my case necks so they measured .2655 over the seated bullet. The neck would spring back enough that sizing was unnecessary. Later on, having proven to myself that there was no advantage, I quit the practice. WH

 

[butchlambert]

I have some of Red Cornelison's brass from days long passed. He machined a step in the neck and set the bullet in the neck with a slip fit. The step controlled the seating depth. He used the old original Remington 6BR brass shortened .125 and rebated the rims to 222 dimension.

 

[RGRobinett]

Considering all of the above, for neck-turned cases, I turn for a minimum over-all (total) clearance of 0.0015" under the chamber and a maximum of 0.002" total clearance. Of course, this is determined using a micrometer and measuring across the heel of a seated bullet (total clearance/loaded neck diameter may/will vary with different bullets).

PSYCO-logically - can he say THAT? - I like it when after firing, and before de-capping, a bullet is such a perfect fit that the compressed air will not only prevent the bullet from falling into the case body, but also,
as long as the bullet base does not pass below the neck/shoulder junction, pressing the bullet deeper into the neck, then removing the pressure, the air pushes the bullet back out! When, on occasion, this fit is achieved, yours truly is pretty pleased . . . but cannot shoot the difference.

It pays to KNOW the actual chamber dimensions, not what a drawing - SAAMI Spec., or, otherwise - displays. That said, some of the newer SAAMI spec cartridge/chamber dimensions call for only 0.002" clearance between the maximum loaded round and minimum chamber neck diameters. RG

 

[butchlambert]

Yes Sir! You hit the nail square on the head!

 

[ISS]

In the eighties and early nineties, the TNT* concept was in vogue. Loaded rounds had a .001" clearance per side on the chamber. I had a factory 22-250 with about .008" total clearance on a loaded round. I experimented with FL sizing 250 Savage brass in my 22-250 die. Clearance dropped to about half that. Group size went down about 2/10ths at 100 yards. These days, they just cut the chambering reamers to achieve that goal. It also cuts down on the need to trim cases as often.

ISS
* Tight Neck Turkeys

 

[Kiwishooter]

My personal preference is to be able to slide a bullet into the neck of a fired case, this way I know I have enough clearance.
The bullet should slide nicely into the neck and not wiggle around
If you can't slide a bullet into the neck of a fired case you need to start measuring things to determine how much clearance you have got on a loaded round.

This is not as easy as it seems for some, getting consistent correct readings with a micrometer to a 0.0001" isn't easy and how do you measure what your chamber neck diameter is to a 0.0001"

I simply would rather have too much clearance than not enough and the above is my personal opinion, is it right or wrong? I find it works.

 

[AlNyhus]

I simply would rather have too much clearance than not enough and the above is my personal opinion, is it right or wrong? I find it works.

Amen. I use a similar analogy with the race engines we dyno.

With a little extra bearing clearance, nobody will know. With not enough....everbody will know.

 

[JFrank]

My question is quite simple, should an unfired bullet slide into a fired round case?

Never really gave a hoot about it, the bullets gone by then so if the group is small and a spent round cycles freely~ I think I’m ok