Why is the neck tension so high on my 6mm-284 using norma brass?

[RossL]

I just built a 6mm-284 two weeks ago. I didn't think much about it when I ordered my brass and purchased 6.5-284 norma brass. Now after reading many threads here it might have been better to get Lapua.

Here is the story of the tight necks: After necking down I discovered the brass had unbelieveably high neck tension when seating a 115 DTAC which was further confirmed when pulling test loads I didn't want to fire. Neck wall thickness of unturned brass is .0155". The RCBS collet bullet puller would slip off the bullet and required some very hard crushing on the bullet to remove them. At that point I knew that tension was way too high. FYI the hornady FL die would reduce the neck diameter .003" smaller than a loaded round. In my 25 yrs of reloading I have found that .003" is a common size difference when using RCBS or Hornady standard die sets.

The chamber has a .003" neck release, so decided to turn off .001" from necks. Tension was better but still quite hard. The difference between the hornady FL die's sizing and a loaded round became .002". Pulling bullets was a bit easier but still hard IMO.

I decided to try using the K and M sizing mandrel after sizing in the hornady FL die. Careful measurement has the sized dimension vs the loaded dimension difference of .0005" or 1/2 a thousandth. The seating feels much better, pulling bullets is easier. I thought with this little tension I could soft seat as part of my shooting tests. I set the bullet out .020" into the rifling and the bullet won't relocate in the case!!!

I have never worked with this small a diameter case. Up to now all my wildcat adventures were with 7mms or larger. The smaller diameter neck has to be a factor in the higher neck tension. The long bearing surface of the 115 DTAC has to add to this.

I suppose I could trim off another .001 from neck diameter and it wouldn't affect the loads. While the bench rest crowd might cringe a .005 neck release wouldn't be that bad.

Can anyone tell me what a 6.5-284 lapua's neck wall thickness is after it is necked down to it 6mm-284?

Has anyone noticed excessive neck tension with their 6-284s?

I will be getting a S bushing die eventually. I thought I could get away with a Hornady FL/seating die set to get started. Once I finalize the neck wall thickness I will go that route.

I have not tried the K and M neck tension yet, that test takes place this morning.

It would seem every time you think you have the reloading game figured out a new twist shows up.

I would appreciate any comments.

Thanks

Ross

 

[jonbearman]

Did you create a tight spot when necking down.What about reaming the case neck to smooth the highs and lows.If you turned the outside then a light ream on the inside would probably cure your ills.Just try this on one case,dont do the whole lot.You will need a reamer at the size or .0005 tenths different to clean the neck up.One other thing ,have you verified that your measuring equipment is accurate? If the mic or vernier is off then you will have to upgrade.

 

[treeman]

you might try annealing a few casses and see if that helps lessen neck tension

 

[mikecr]

It would seem every time you think you have the reloading game figured out a new twist shows up

It doesn't seem to me that you've 'figured out' the basics in working with brass, or sizing in general.

I didn't think much about it when I ordered my brass and purchased 6.5-284 norma brass. Now after reading many threads here it might have been better to get Lapua

Not sure about your basis here. Neither Norma nor Lapua, offer preformed 6-284 cases, and Your problems so far seem unrelated to brass brand.

After necking down I discovered the brass had unbelieveably high neck tension

You realize that sizing down brass thickens it right?.
You said it measured .0155". Assuming that's after necking down, what did it measure beforehand?
Maybe you could measure other 'normal tension' cartridge brass thickness and figure something out right there.

the hornady FL die would reduce the neck diameter .003" smaller than a loaded round. In my 25 yrs of reloading I have found that .003" is a common size difference when using RCBS or Hornady standard die sets

The chamber has a .003" neck release

It is common,, and completely rediculous. FL Dies are made for the smallest ammo, while chambers are typically made for the largest. Worse still, FL dies size the entire neck, which is ALWAYS more than needed. Only the bullet bearing sizes the necks back up, leaving any neck below that unexpanded(full of energy).
You have 6 to 8thou cycling of your necks here. That's a lot of working of the brass, and now your bullets have to add more energy by resizing up those very thick necks by 3thou. Your chamber, dies, and method, are combining horribly.

You should learn here given that you've mentioned observing it, that it takes little differential to hold a bullet with plenty of grip. There is just no need for you to go beyond that, and creating this problem.

 

[RossL]

Thanks for the comments Jonbearman and Treeman.

I went to the range twice today. The new minimal neck tension tightened up the groups almost to 1/2 of what they were. I am now shooting 10 round 1/4" groups. Time to move out to longer distances and verify further.

Mikecr,

I don't think much of your comments. What is your problem? I had an interesting question and you treat me as some dolt that knows little of what I do. I do have the reloading game figured out despite what you say.

If you read around the net and this site you will find most of the guys loading for the 6mm-284 prefer lapua brass.

I KNOW that sizing down brass can cause the necks to get thicker but I never noticed much of a size difference with the 25-284, the 7 rem mag brass necked down to 257 weatherby, 308 necked down to 7-08 or the 7-08 brass necked down to 243. Even if there was a thousandth increase I never noticed an issue with neck tension like this one.

I have loaded and owned for the following rifle chamberings over the last 1/4 century and have loaded even more rifles for many others:

22-250-4
6mm-284 -1
6mm rem-4
243-3
25-284-1
25-06 –2
257 Weatherby-2
6.5-284-1
264 win mag-2
270 win-2
270 weatherby mag-1
7-08-1
7 x 57-1
284-5
280-1
7 rem mag-6
7 STW-2
7 RUM-3
30 BR-2
308-2
7.62 x 39-2
30-06-4
30-06 AI-1
30-338-2
300 win mag-3
300 RUM-1
338-06-1
338 RCM-1
338 win mag-2
357 mag-1
358 win-1
375 taylor-2
44 mag-3

I have NEVER encountered anything like the neck tension that I found with this 6mm-284

I am certain the DTAC bullet with its long bearing surface is part of the story.

As for the dimensions I'll put them all together so you and others can see that it IS unusual to have such a small difference in sized brass and loaded ODs.

Chamber neck .276"
Original loaded ammo .274"
Original neck wall thickness .0155" very high neck tension


Current data
Turned neck wall thickness .0145"
Loaded ammo OD .273"
Sized brass .2725" moderate neck tension
Fired round after springback .275"

Yea sure lots of working of the brass on this one Mike!

A person who knows the dimensions he is working with can do all sorts of things with a variety of dies. While a S bushing die is useful, a FL die used as a partial FL sizing does a fine job. If you read enough threads you will hear of plenty of BR guys that are not fond of just neck sizing. Many prefer to bump the shoulder back .001". As for the issue of sizing the entire neck give me a break...the DTAC is so long it touches the entire neck and below the neck shoulder junction.

Your math is wrong, read above data: your quote: "You have 6 to 8thou cycling of your necks here. That's a lot of working of the brass, and now your bullets have to add more energy by resizing up those very thick necks by 3thou. Your chamber, dies, and method, are combining horribly."

The "cycling" as you put it is .0025" not 6-8 thousandths.

I thought I'd get reasonable answers here didn't figure I'd get someone like you who looks down on a guy and suggests I am a tyro. If you had something to add you did a poor job expressing yourself. I cannot understand why you are so condescending. Perhaps you should reflect on your abilities....

 

[johnmyers]

Ross I'm with you on mikecr. You asked a question and deserved a respectable answer instead of being told how little you know. I have seen this attitude from him before and it should be stopped on this site because it won't be good for anyone.
John

 

[RossL]

Thanks John.

 

[TonyR]

Ross. I doubt that there is anything basicly wrong with necked down Norma brass. I have necked a bunch of 300RSAUM brass to 7mm and neck tension with the 180 Berger VLD, a long shank bullet seated well into the neck, is just like what I experience with my 284 which is made by necking up 6.5X284 Lapua brass. Both the 284 and RSAUM use an 0.310 inch loaded round neck in an 0.313 inch chamber neck, so 0.003 clearance. I turn the necks to 0.0127 on a side to get this loaded neck diameter with the Berger bullets. I F/L resize with an 0.309 inch bushing with these cases. I use an inside neck reamer that was ground to the diameter of my neck turner mandrel before I turn the necks. I lube the inside of the case necks with Imperial Dry neck lube after I have cleaned the cases before I seat the bullets. seating force feels about the same to me with either the Lapua or Norma brass. I have tried seating bullets in either brand new cases or cases just out of the ultrasonic cleaner without the dry neck lube and some of them have been sticky going in but I never saw anything on the target that indicated a problem. +1 on the inside neck reamer as jonbearman has suggested. I like the inside neck reamer because it gets rid of anything in the donut area but also cleans up some irregularities in the inside of the case neck. I just miced the diameter of my neck turner mandrel and ordered that diameter Wilson inside neck reamer from Sinclair. Different neck turners use different diameter mandrels and some of them might work with the standard Wilson reamer for that caliber. Mine is a Hart and it needs an 0.2825 reamer. As I recall, the K&Ms are a little bigger.

 

[jo191145]

Ross

If you have a bushing die for your 6.5 X 284 could'nt you use that with the appropriate bushing? At least for now?

Personally I buy a Redding S series FL die for every new cartridge. FL everytime and be done with it. No more necksizing for me.
They don't work too well for that initial neck down operation though do they?

Possibly Hornady could hone out your die if you prefer.
Anyhow looking at your new numbers they look pretty good.
The Imperial dry graphite Tony mentioned is a good idea

 

[Ironworker]

I have the type C Redding FL sizing die in 6x284. Is that the only suitable Redding die for sizing from 6.5 to 6mm ?

 

[TonyR]

I find that necks can be sized down with bushing dies except for the final step with a full length sizing die. It doesn't even have to be a bushing die for the cartidge you are forming for as long as the neck is the right size and the case will fit into the die. I have a 7mmRSAUM die that I have used for a couple of cases that are smaller than the SAUM at the shoulder. I have necked 8mm and 30 cal brass to 7mm that way. A bushing die can also be the best choice if you need a false-shoulder for fire-forming. It really depends on the diameter of the small part of the die body that supports the bushing above the shoulder.

 

[RossL]

Hi everyone,

I sure appreciate all the ideas. I agree I should have a S bushing die. I rummaged through my stuff and found a 6-284 redding form die! I forgot I had it. It was in with another die, of all things a 6.5-284 shoulder bump die. These came in a 6.5-284 package I bought from a friend 8 years ago.

I now have a better handle on what might have happened. By chance I called Redding to talk and got Robin Sharpless IIRC the VP of Redding or other administrative position. He had a guy out and was answering the phone which he usually doesn't do.

We had a long conversation. His former job was with Chey-tec. He said I should never have used a FL die to reduce the neck diameter. He went on to say a FL sizer was made for a variety of brass/chamber variables and not best for a specifically created package like mine. He suggested I work hardened the brass using that die. After the conversation I did some measurements. The FL die reduces the OD of the neck BEFORE the sizer ball resizes it to an OD of .264"!!! Then the sizer ball opens up the brass .009". It was also explained to me that some of my loaded vs unloaded measurements would be inaccurate because of the springback effect of the thick overworked brass.

One eye opener for me was his comments on neck turning. He said there is no reason for anyone other than a benchrester to have to neck turn. He said case neck walls that require turning to get them concentric still have case bodies that also have irregular wall thicknesses. The brass flows as the case is fired and sized so the case gets warped over time and the necks also have brass flow that again makes them non concentric. It made sense. He said it is best to not use the cases that are much more than .0015" out and use the good brass as is.

His comments on benchresters continued. He said the reason they go with minimal neck release of approx .002 is to prevent brass flowing into the necks. That way the cases can be fired many more times without any extra work.

I am going to buy some new Lapua brass, measure them for anomolies and work with them full size with bushingd dies when my current lot of Normas wear out.

Update: I suppose a few of you will think I am nuts with my tempory fix. If you remember I necked down the norma brass to .014" neck wall thickness. The group size shrinked slightly compared to the .0155" original size. I decided to turn a few to a smaller dimension to see if tension would decrease and groups would tighten up. I ended up going all the way down to .011" wall thickness. Tension was much much better. The necks were thin enough that I was able to run the brass up into the FL die and not use the sizer ball. Difference between loaded round and sized round was .002". I realize in doing this my neck release is huge at .009". I went to the range and the group size got even smaller and the tendency to be slightly vertical disappeared with a slight horizontal spreading. Part of this is due to not using the sizer ball. Runout was zero something I just couldn't do before.

So... once the necks begin to split, I'll order Lapua brass, get my measurements and order a S bushing die. To be honest I am not totally convinced that a super thick neck wall won't have some tension issues even with proper necking down techniques but I am willing to try it first and not do any neck turning.


Anyway I now know the rifle will shoot. I am very happy with how easily the Bartlein 5r cleans up. RL-17 is giving me very consistent velocities of 3265 with the 115 DTACs. I am not a competitive shooter but a hunter. This rifle will be used for long range varminting with only occasional shots fired. The targets are jackrabbits and coyotes. The idea is to simulate our coues wt hunting. I will set up just as I do for the deer hunts with 15 x56 swarofskis on a tripod, glass up the jacks, range, consult comeup chart, go prone and shoot. I want to extend my current abilities of 600 yds out to at least 750 yds.

The rifle is a SA rem in a Stock's Bobby Hart Long range target. It is a clone of a A-5 Mcmillan. Has a Leupold VX-3 8.5-25 x 50 LR with target turrets. Also has a picatinny rail and Burris extreme rings. The stock was hollowed out in the rear with two 7/8" x 5" holes which currently have 1 1/2 lbs of lead shot. Weight is 20 lbs and a joy to shoot.



I discovered this site and read every thread in the forum on the large 6mm wildcats. Gleaned a bunch of good information.

I appreciate all the positive feedback. I know I didn't do some things correctly in the beginning. I needed a FL die to size the necks down and thought maybe I could also use it to make my finalized loads. Turns out to have been a poor decision.
Thanks again for all the advice.

Ross

 

[Bnhpr]

Ross,

I've found the Norma brass in 6,5x284 more sticky and softer than the Lapua.

I think your on the right way with S bushings and an expandiron. I would get a variety of bushings so you can tune your neck tension how you want. Lube and run the expandiron to uniform the inside dia of the case before reloading.

I agree with other comments about neck turning, and I do not like it. You'll find that many benchrest shooters are evolving to thicker necks anyway. Skimming the necks to achieve uniform thickness is where most of the "low hanging fruit" is In my opinion.

Don't let the internet snipers get you down, they are plentiful on these sights, just ignore them and don't dignify them with a response.

Ben

 

[bozo699]

Ross,
after all our pming each other I didn't realize you had a thread going on the subject. You already know all my thoughts on the subject so I won't take up bandwidth typing I will say you handled the one upsetting post very well,..much better than I would have done (GOOD JOB) I spent a couple of hours and and sorted 100 pieces new blue box 6.5*284 I only got about 5 pieces of fairly close to perfect pieces hopefully when I get through the other 400 pieces I have 20 pieces of match quality brass to get me through the season.
Wayne.

 

[RossL]

Wow that is alot of brass to get some perfect ones!

I went out yesterday and verified my comeups out to 500 M. We have a silhouette range, the first one built in the US, west of Tucson. They have several permanent 4" thick rifle proof silhouettes. We drive through the range and spray all surfaces black. Best way to get things sorted out. The clang is a perk.

Now ready to go out and do some long range varmint shooting!

 

[Ironworker]

I have had extraction problems in both Norma brass and Lapua brass. Mostly in Lapua brass. As brass work hardened in Norma brass ,extraction problems developed. Is it because I've been using wrong dies all along for sizing down 6.5 x284 to 6x284 ? I've been using Redding type C full length die ? So should I order type S bushing full length Redding dies ?

 

[RossL]

I did some more investigating on the best way to size down the 6.5-284 lapua brass so I don't make the same mistake that I did with the norma brass.

A redding 6mm-284 form die will reduce neck OD to .295". This is really for reducing the size of 284 win brass. It will do minimal reduction to a 6.5 case may do nothing. Redding suggested I buy their standard FL and seater die set. The seater can be used as an intermediatary step down sizer. Then finish with their FL die. It took some effort but the tech finally told me the reduced neck dimension BEFORE it is pulled over the sizer ball. It is .268".

Hornady's FL die reduced the neck OD to .264" according to them. My readings are .2625" but some brass springback could be why my measurement is different. Then the sizer ball makes the OD go back up to approx. .270"!!!

I decided NOT to use the Redding idea just not interested in oversizing/working the brass. I machined a piece of a worn out .264 win SS takeoff barrel into my own sizing die using the 6mm-284 PTG reamer! After some polishing of the neck, brass neck diameter is reduced to .277". I tried sizing down some FIRED 284 win brass using the 6mm-284 redding form die then my form die. The win brass even though fired a few times sized down easily.

Once the lapua brass is reduced to .277" I think I can use the S bushing die to size down to finalized neck diameter. Rifle neck chamber dimension is .276". Loaded ammo should be .273". Bought .272", .271" and .270" bushings. I wouldn't be surprised with the thick unturned neck walls that I may not need ANY neck sizing to soft seat a bullet after first firing due to springback.

Will report back once this process is done.

 

[RossL]

Went to the range yesterday with the new lapua brass. All loads shot much tighter groups than with the norma brass. I am impressed with this brass.

Details:Used the brass with unturned necks. Used my form die to reduce neck OD to .277". Then used a .272 bushing for finalized neck diameter. Measurement difference of loaded round vs final sized neck is .0015". Even with full bearing surface of the 115 DTAC in contact with the necks, the neck tension is just right. Cannot soft seat but bullets do pull or seat easily.

Finally can move on to finalized loads and use the rifle for its intended purpose, long range jackrabbits and coyotes.

I appreciate all who contributed.

Ross