NECK REAMING

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  • Last Post 01 August 2009
cityboy posted this 31 January 2008

A lot has been written about NECK TURNING,  but very little about NECK REAMING. IT seems to me reaming makes more sense. Variation in case wall thickness cause the case to stretch unevenly resulting in a bowing of the case body. This results in the axis of the neck being unaligned with the body. So when the round is chambered the bullet will not be “looking" straight down the bore.  This cannot add anything to accuracy. At least that is my take on the subject.

I took 50 once fired 30-06 GI cases and preped them in the usual manner. THen I used my Wilson case trimmer to neck ream 25 of them. Jacketed bullets were then seated in all the cases and the bullet runout measured using a NECO concentricity gage and got the following results. Runnout (RO) was measured on the bullet just in front of the neck.

Necks Reamed

0 =<  RO <= 0.002: 20 cases

0=< R) ,= 0.004:  5 cases

Necks not Reamed

0 =< RO =< 0.002: 10 cases

0.002 < RO <= 0.004: 14 cases

0.004 < RO <= 0.005: 1 case

NOTE: “<” means less than

           “>” means greater than

          “=” means equal to

THese results show than reaming produces necks concentric with the axis of the case. I don't know if this will result in better accuracy. Only time will tell. What do you gents have to say about this?

Jim/cityboy 

 

 

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RicinYakima posted this 31 January 2008

Jim,

I ran this same experiment about 20 years ago. However, I got to do it with L.E. (Sam) Wilson in his shop in Cashmere, WA. With his tools, bolted down to a good bench, his reamers work very well, as you noted. But it is better if you full length resize the cases in one of his old style dies. It will have the neck in line with the case.

Then we did cases that were neck sized from firing and used his new (at the time) outside case turner. These would turn the necks so that they were in line with the chamber, if you orient the cases to the chamber.

Needless to say, I bought one of his new outside neck turners.

Hand held neck turners will uniform the thickness of the neck, even out neck tension and all the rest. But, the hole in the neck doesn't necessarily point down the center of the bore.

Since I shoot production and military rifles, not bench rest chambered guns, this doesn't make that much difference, as there are other ways to increase accuracy, but it does make some difference! I wrote an article for “The Fouling Shot” and the new Cast Bullets  book about cartridge concentricity that you may find interesting.

Ric

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CB posted this 01 February 2008

Jim,

Sounds like a kitty chasing its tail.  ;)   I think if you shoot those reamed cartridges, then process them (size and load) again you'd probably have the same RO as the un-reamed cartridges. You only 'fixed' those cases at that particular moment. A good BR quality sizing die will keep the neck square to the bore and sometimes(if you get a good one) a Lee or RCBS will do it (but not all of them will).....................Dan

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RicinYakima posted this 01 February 2008

EUREKA Dan!:dude:

Once I got a concentricity gauge, I tested twenty (20) sizing dies in 30/06. I wrote that up in an article also that is in CAST BULLETS . Once you have a die that is “good” and you uniform case neck thickness, all the cases are good. But if you don't have some way to measure that, or don't have a good die, you will have varying run out. Then if you use an “M” or expanding die, you have to measure them also. Then seating dies have to be measured for performance.

What I found was that military chambers in Model 1903 Springfield's can't tell the difference between ammo with 0 to .003” bullet run out. Chambers are so loose and aren't accurately alined with the bore enough for me to tell on the target. But those with .004 run out or greater do make larger ten shot groups over a long series of targets.

Ric

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CB posted this 01 February 2008

HEY! Same to ya  :dude:

Yup, them concentricity gauges can sure get ya spinnin' in circles. A true sizing die is a blessing. You're right Ric, that possibly up to .003"- .004” Run Out won't show a probable difference in accuracy. Divide that Run Out by 1/2 and that's Off-Center (OC not RO) from bore.

I finally got my ducks fairly straight in a row (I think)?  I put the concentricity gauge to good use like my championship jacketed <uh> Varmint Match competitor buddy does and segregate loaded ammo by run out and shoot accordingly. Remember readers, this about Bench Rest accuracy. This won't bring a 2” load to sub-MOA, unless maybe you do have a severe RO problem, really severe! :shock: ................Dan

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RicinYakima posted this 01 February 2008

Dan,

Oh yeah, your right! The difference is small. Ammo with RO between .004” to .006” was about 1.30” for a series of 10 ten shot groups with a NRA Sporter and 14X Unertl scope. With a RO of 0.0 to .003", groups were only about a tenth of an inch tighter for a series of 10 targets. Small but of significance to me shooting for smalls groups over the long haul!

Ric

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cityboy posted this 01 February 2008

Rick, Dan

I would like to thank you gents for your input; it gives me a lot to think about. The cases were FL sized in a RCBS die that had been midified by Neil Jones to take bushings similar to those offered by Redding. Thew neck was not sized during FL sizing.

The necks were sized using a Lee collet die with the decapping pin removed to preclude the chance of bending the neck if the flash hole in off center. I want to make some other concentricity measurements on the cases and perhaps these will shed some additional information.  The bullets were seated in the cases using a RCBS competion seater.

Jim

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cityboy posted this 06 February 2008

After reading the comments of Rick and Dan, I decided to check my dies to see if the are bending the brass.

Using the Sinclair gage with the indicator placed st the end of the neck, the following values were obtained.

0.000 <= RO <= 0.002    33 cases

0.002 < RO <= 0.004       16 cases

RO = 0.005   1 case

Usung the NECO gage with the indicator placed of the case body just before the shoulder the following values were obtained.

0.000 <= RO <= 0.002   41 cases

0.002 < RO =< 0.004       9 cases

This shows that the dies are not bending the cases. That suits me fine; saves me the expense of buying new ones.

 

Cityboy

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billwnr posted this 07 February 2008

I don't do anything to my .30/06 cases.   I shoot them “as-is".

'Course I bought some Lapua cases. :dude:

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CB posted this 07 February 2008

Jim,

That's about what I get for average when sizing.

My RCBS 30-06 FL sizing die is perfect. :dance   My RCBS 308 FL sizing die is a disappointment.:X    My Hornady 243 FL sizing die is a pure disaster!:taz:

 

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cityboy posted this 07 February 2008

You are quite correct, Lapua brass is very good. I bought 100 a few years ago and they are my best brass. I decided to dig out the 1961 FA Match brass because I have a LOT of it and brass has become rather expensive.

cityboy

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billwnr posted this 08 February 2008

i am a bit biased towards Lapua brass because of it's uniformity, but good scores and groups can be shot with other brands of brass.

Ric had an article in the Fouling Shot about 2 issues ago on how he prepares ammo he shoots in the military matches.  It was a very educational article.

I'm not sure if Dan shoots Lapua or what.

I've switched to Lapua as the uniformity of it inspires confidence and it's one less thing to worry about.   If price is a consideration, commercial brass sells for about $28 per 100.  Lapua was either $56 or $74.   That $50 difference gets 100 good cases.    Only thing really cheaper is picking up range brass after hunter sight in.  There's lots of good 06 stuff on the ground.

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TRKakaCatWhisperer posted this 13 February 2008

Outside neck turning using a pilot results in the neck wall thickness being uniform.  Assuming the neck area of the chamber is coaxial (same axis) as the bore,  on the next firing the neck expands and assumes the location of the containing chamber.

Neck reaming using Wilson neck trimming/reaming tool aligns the cartridge in a holder to be coaxial with the cutter - and neck reaming will produce an ID of the neck appropriately aligned (assuming the correct alignment of the body of the chamber with the axis of the bore).  The neck reaming doesn't affect the regularity of thickness of the neck - which after the next firing would affect the position of the ID with respect to the chamber.

 

 

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Chic posted this 05 December 2008

I'm trying to learn how all this is done.  It seems to me that if a case was reamed while it was in a sizing die, it would have uniform thickness and concentricity.  Obviously, it would have to be reamed undersized the amount you want for tension and the reamer would have to be guided by the die.  Any thoughts?  Does anyone make such a setup?

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Lillard posted this 05 December 2008

I outside turn 22 /250 and 7mm stw brass juct enough to give me a uniform neck thickness I size and seat with wilson inline dies and a arbor press both guns have hart barrels with benchrest grade chambers I don't shoot competion but the time spent neck turning is worth the effort.

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JetMech posted this 05 December 2008

Chic, At that point, you would have a uniform neck concentric with the die, not neccessarily with the bore. But given that it is concentric to both, your chamber would have to be tight or you'll end up with shortened case life due to excessive neck expansion on firing. I've found that the best method, for me at least, is as Lilliard states. Outside neck turn just enough to uniform the thickness. You'll usually only be removing material from part of the neck. Then, as TRK states, on firing, the neck is aligned with the bore. Using component indexing and neck sizing (I allow the die to float a little) you should get good results.

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CB posted this 01 August 2009

I read all the feelings here on neck concentricity and aligning the case neck to the bore. OK.

Here is my spoof. I prepare cases for BR barrels.

1st step

I usually work with Lapua cases. I set my mandrel die into my Rockchucker press. You have to make an assumption here once the die sets in the press that the mandrel is a parallel path with the axis of your chamber, big assumption here.

2nd step

Very important step. I feel you need to clean and lube the inside of the case neck before running the neck over the mandrel. Forrester and several others use a platform with brush sizes attached not bad. I use a RCBS handle with a nylon brush screwed in. Just using the brush alone inside the case neck does a good job of getting the case ready to push over the mandrel. I roll my brush over my case lube pad before I start.

3rd step

I pre-set my mandrel so the case stops before it hits the collar on the mandrel. All my cases are trimmed to length after the mandrel sizing as now the cases have stretched.

4th step

I fire form twice using max loads before I call them range good. To me and others the fireforming determines the alignment of the case and neck to the axis of the bore. I use the Wilson neck sizing die, FL die, and case trimmer along with Harrel FL sizing dies and JLC Seater. I use several types of neck rurning tools- Miller, Marquart, Nielson, JACO. I also use Sinlair, LACO, Nielson, Wagner mandrels. For lube I use Imperial Sizing Wax and RCBS Case lube. Others work fine too.

If there is a conclusion here it is. Some of these steps will not not show up on the target for factory chambers but establishing a routine for case preparation allows you to remove a varaible in your shooting game. It also adds to your knowledge of the relationship of ammunition to barrel specs. What you learn and know aboUt the shooting game is yours alone, add to it.

Stephen Perry

Angeles BR:fire

 

 

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