High spots on brass found on second neck turn

[AI Perfector]

Hi all, I'm F Class Open shooter using necked up Lapua 6.5 x 284 brass to get to straight 284 Win. I turned the virgin brass necks down to 311 (chamber reamer 312). Then fired the brass after which I neck sized with Redding Competition die with 309 bushing. On then turning the necks for the second time, I came into 4 equi-distant high spots (and intervening low spots) from about half way back to the neck/shoulder junction to as far as that junction. The feature is pretty consistent in all this once fired Lapua brass. The barrel is a Lilja with, you guessed it, four lands. Is there a connection and is it going to affect accuracy.

Thanks in advance for any thoughts. Cheers

[dannyt]

Hi all, I'm F Class Open shooter using necked up Lapua 6.5 x 284 brass to get to straight 284 Win. I turned the virgin brass necks down to 311 (chamber reamer 312). Then fired the brass after which I neck sized with Redding Competition die with 309 bushing. On then turning the necks for the second time, I came into 4 equi-distant high spots (and intervening low spots) from about half way back to the neck/shoulder junction to as far as that junction. The feature is pretty consistent in all this once fired Lapua brass. The barrel is a Lilja with, you guessed it, four lands. Is there a connection and is it going to affect accuracy.

Thanks in advance for any thoughts. Cheers

 

 

Very common with necked up brass / The brass will always flow from the shoulder into the neck shoulder base(forwards).

 

2nd pass with the neck turner is always a good idea, after all your after uniform neck wall thickness, you probably wont need to do it again .

[Ronin]

Are you getting dohnut forming at the base of the neck (inside)?

 

Suggest you take a cut into the neck shoulder junction of about .025" - .030" which may alleviate the problem youre having.

 

I also form brass for my 284 imp the same as you, but n ot had the issue youre describing..

 

Image shows a 6.5x284 Lapua case before resizing - in this case it was remaining a 6.5x284.

 

But the priciples the same.

 

[AI Perfector]

Thanks, Donut. I don't think that a doughnut is the problem yet; I turned back and into the neck shoulder junction on first neck turn. That said, I am scheduled to get the bit needed to remove them next week.

 

 

Danny, Here's a better photo of the result of the second neck turn. You'll see the quite distinct straight sided square depression (uncut/turned) which is one of four 'equally' spaced depressions on each case, some being more distinctive than others. These must, I suggest, be associated with four high spots in the chamber. I don't know the mechanics of chambering/rifling too well but these look like mechanically formed depressions.

 

Any further comments?

 

 

[dannyt]

Thanks, Donut. I don't think that a doughnut is the problem yet; I turned back and into the neck shoulder junction on first neck turn. That said, I am scheduled to get the bit needed to remove them next week.

 

 

Danny, Here's a better photo of the result of the second neck turn. You'll see the quite distinct straight sided square depression (uncut/turned) which is one of four 'equally' spaced depressions on each case, some being more distinctive than others. These must, I suggest, be associated with four high spots in the chamber. I don't know the mechanics of chambering/rifling too well but these look like mechanically formed depressions.

 

Any further comments?

 

 

That can only be as you have stated a rough area in the chamber , you need to get hold of a bore scope and have a look also talk to the rifle builder .

 

As long as you are turning your necks down in stages ie if you need to remove 2 thou from the neck take two cuts per case to achive in 1 thou steps so to speek. You should not put any cases under any undue stress when turning .

 

Personaly i expand my 6.5-284 brass =first with a 6.5 expander then turn the necks to within .5 of a thou of were i whant to finish , i also take the turning cut into the shoulder as Ronin has shown .

 

I then expand to 284 and take the remainder of the neck material of , the use of two cutters for one job may be over the top for some people but iam trying to avoid any Dohnuts and stressing the necks.

 

I leave the 284 cutter set without any changes in cutting depth so after one or two fireings of the brass i just pass the cutter back over the case necks .

 

some cases show more brass movement than others some have none at all but this is rare.

 

Iam Talking about taking brass from the lower part of the neck and have never found any change in neck wall thickness higher up the necks .

 

Hope this helps, its just my way of turning necks .

[AI Perfector]

Thanks, Danny, for advising your method.

I've contacted the riflesmith and will post the outcome.

Cheers,

 

 

 

[AI Perfector]

Thanks, Danny, for advising your method.

I've contacted the riflesmith and will post the outcome.

Cheers,

 

 

 

 

I spoke to the rifle-smith, who advised that it was a faulty reamer, which he had had replaced shortly after delivery of my rifle at which time he had had other rifles with the same problem.He offered to remedy by cutting 30 thou further into the chamber (not sure of terminology) but thought accuracy would not be affected, just the case appearance. So, given that wind is my major challenge, I've left it be.

Cheers

[Ronin]

Im struggling to understand how the reamer, if it is faulty would leave "4 equi-distant high spots (and intervening low spots) from about half way back to the neck/shoulder junction to as far as that junction"

 

 

I say this because when chambering, the reamer does not turn, as it is held in a fixture held by ones fingers and "pushed" into the barrel by the tailstock.

 

The barrel rotates and the reamer cuts the chamber, so any imperfections in the reamer would show as a radial (360 degree) mark, not 4 equidistant marks....

 

An example of a damaged reamer or poor chambering job would show as a radial witness mark on the fired case due to the scratched chamber surface.

 

Personally, I would do as suggested and have the chamber cut deeper, the riflesmith would also have to ajust the barrel tenon length accordingly untill the damaged area of barrel is removed.

 

 

just my own opinion, be interested to hear what the other chaps think who put sticks together..

[AI Perfector]

just my own opinion, be interested to hear what the other chaps think who put sticks together..

 

I hear what you say Ronin and thank you for your contribution. Any other offers from others?

 

That all said and done, my only concern would be accuracy and if that is not going to be affected, I'm pretty relaxed about it ..... or should I not be?. After all, I'm not (yet) in the top ten!

Cheers

[Elwood]

Sorry but I can't help with the technical side of things, but I would want the work done otherwise you (i) would always be wondering.

[dannyt]

Well iam with the re chamber side of things i have never herd of a reamer being ground with this fault but you never know , the most likely reason for this type of problem is when a chip or swath attaches to the reamer (welds) hence un even cuting .

 

you realy need to recut the neck .

 

Dont forget any uneven necks will play hell with the(EXTREAM SPEADS)from shot to shot,at longer range you will suffer vertical , at least thats what i would of expected from uneven neck tentions which is what you must be getting if all is as you have said.

 

Take the barrel of recut the chamber . I would not think 30 thou would not of taken the problem area out .

 

Danny

[AI Perfector]

Well iam with the re chamber side of things i have never herd of a reamer being ground with this fault but you never know , the most likely reason for this type of problem is when a chip or swath attaches to the reamer (welds) hence un even cuting .

 

you realy need to recut the neck .

 

Dont forget any uneven necks will play hell with the(EXTREAM SPEADS)from shot to shot,at longer range you will suffer vertical , at least thats what i would of expected from uneven neck tentions which is what you must be getting if all is as you have said.

 

Take the barrel of recut the chamber . I would not think 30 thou would not of taken the problem area out .

 

Danny

pm sent

[Ronin]

Looks closer to .120" to remove the issue....

[AI Perfector]

Looks closer to .120" to remove the issue....

I'd tend to agree Ronin.

 

 

My chrono results from y'day (at 40m) don't seem too bad to me but I defer to my peers' better judgement. Having got to what I thought was a good load (53.8 H4831SC with the head 5 thou' back from the sample bullet passed to the riflesmith), I'm just a little reluctant to go through the process again but, hey ho, if that is the consensus, so be it. A man's gotta do what a man's gotta do! I'm thinking barrel life here.

Cheers, again

 

 

[dannyt]

I'd tend to agree Ronin.

 

 

My chrono results from y'day (at 40m) don't seem too bad to me but I defer to my peers' better judgement. Having got to what I thought was a good load (53.8 H4831SC with the head 5 thou' back from the sample bullet passed to the riflesmith), I'm just a little reluctant to go through the process again but, hey ho, if that is the consensus, so be it. A man's gotta do what a man's gotta do! I'm thinking barrel life here.

Cheers, again

 

 

I would look at 56 grns ish for your loading , the real acid test for grooping is at 300 yrds this will tell you all you need for longer range , most people can get single figure es and sd or at worst early teen spreads.

 

I think any thing grouping under 1.5 inches at 300 will get you were you need to be .

 

Regards Danny

[Ronin]

Well looking at the groups and Chrono download, the rifle certainly shoots and ES is single digit,

 

If your happy with the way it shoots then you could leave as is, Danny has a point though about neck tension, which may go to rat xxit with reloads - be interesting to see if that does happen with reloaded cases.

[Ronin]

Danny, its a straight 284 not improved - 56g may be a little harsh....

[dannyt]

Danny, its a straight 284 not improved - 56g may be a little harsh....

 

 

yep your spot on sorry over sight

[dannyt]

Right ive had bit of a think , if the chamber has been cut with a bad reamer AND ; the chamber necks have a proud spot internaly , happy days just run a true reamer into the chamber again this will or should buy the laws of the great gunsmith in the sky take any rough or proud spots out of your chamber necks.

 

 

Also i have re read your first post .

 

It may be that you also may have under turned your necks ,i may of mis read your intent on neck turning so measure a loaded round you should have 3 to 4 thou under the chamber dimentions/ so if you have a 312 neck (CHAMBER) you realy should have a loaded round of 308/309 in OD.

 

The better reloaders have stated that a very close neck to chamber contact can and will regrip a bullet before it has left the case neck and chamber once it has been fired.

 

Almost like a bounce back from the chamber wall by the case neck.

[Ronin]

You could be on to something there Danny,

 

.312" neck

 

Loaded round should be circa .309" - allowing .0015" clearance around the circumfirance of the neck.

 

Therefore what you want is:

 

Loaded round neck diameter = .309" minus bullet diameter of .284 = total case wall thickness of .025" (halve this) gives you a neck wall thickness of .0125".

 

 

Whats the neck wall thickness at the moment AI?

[AI Perfector]

Whats the neck wall thickness at the moment AI?

 

Loaded round is uniformly 0.311"

.^.. neck wall thickness is 0.135" being {311-284}/2

Using a 0.309" Redding neck size bushing, Should I not get 2 thou' of neck tension from 0.311"?

[AI Perfector]

Right ive had bit of a think , if the chamber has been cut with a bad reamer AND ; the chamber necks have a proud spot internaly , happy days just run a true reamer into the chamber again this will or should buy the laws of the great gunsmith in the sky take any rough or proud spots out of your chamber necks.

 

 

Also i have re read your first post .

 

It may be that you also may have under turned your necks ,i may of mis read your intent on neck turning so measure a loaded round you should have 3 to 4 thou under the chamber dimentions/ so if you have a 312 neck (CHAMBER) you realy should have a loaded round of 308/309 in OD.

 

The better reloaders have stated that a very close neck to chamber contact can and will regrip a bullet before it has left the case neck and chamber once it has been fired.

 

Almost like a bounce back from the chamber wall by the case neck.

Thanks, Danny

Re-ream solution sounds good and not disruptive of established loads

Good that I've under turned and not over turned!

Noted re 'bounce back'

Clearly I've work to have done on chamber and for me to do on brass but that may have to wait til after Blair Atholl.

 

 

 

 

[dannyt]

Loaded round is uniformly 0.311"

.^.. neck wall thickness is 0.135" being {311-284}/2

Using a 0.309" Redding neck size bushing, Should I not get 2 thou' of neck tension from 0.311"?

 

 

Paul i think your loaded rounds are to tight to the chamber you need to turn your necks down so a loaded round measures 309 at the most(in a 312chamber), that will give you 3 thou clearance , idealy you need about 4 thou you realy will not help your self if you have only.5 thou clearance all around your loaded round inside the chamber .

 

The greater shooters in the world who have put much more time into 284 loading and shooting than many of the rest of us have all found best results giving more clearance in the chamber neck.

 

Neck tention can be distracting when first loading for a 284 or improved version.

 

First and formost what i look for is the right neck to chamber clearance (3/4 thou) then i will play with neck bushings 307/308/309 in this area i only look at the paper down range and the chrony and pic the best results with what ever neck bushing gives me this.

[AI Perfector]

Paul i think your loaded rounds are to tight to the chamber you need to turn your necks down so a loaded round measures 309 at the most(in a 312chamber), that will give you 3 thou clearance , idealy you need about 4 thou you realy will not help your self if you have only.5 thou clearance all around your loaded round inside the chamber .

Okedoke, Danny. I can manage that before next w/e, though may be light on neck tension as only have 309 bushing at the moment. Will get 308, 307 bushings on the way up to Blair.

[baldie]

I cannot see how that has been caused by the reamer personally.

 

Be aware that ANY more reaming in the chamber automatically means the gun MUST be reproofed.