I am wanting to order a reamer for a 243AI. I would like to have some neck neck turn on it. My question is how do I figure out the reamer neck diminsion without a loaded round. I'm assuming the neck thickness will change when it's pushed to a AI.
Gunsmithing how to find neck turn diminsions for reamer
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Re: how to find neck turn diminsions for reamer
Normally you do not determine the chamber neck by the ctg. neck. Have a reamer ground and tailor the brass to fit that. Do you want to just clean the neck up to a more uniform thickness or do you want a true tight nackedf chamber. You decide what you want and someone will be able to help you.
Normally you do not determine the chamber neck by the ctg. neck. Have a reamer ground and tailor the brass to fit that. Do you want to just clean the neck up to a more uniform thickness or do you want a true tight nackedf chamber. You decide what you want and someone will be able to help you.
Re: how to find neck turn diminsions for reamer
When using Lapua 243 brass, the loaded round/neck will be approx .273" to .275". A fairly standard tight neck 6mm neck is .269". The .272", while not a standard tight neck diameter, is and at times, too tight for a true no turn neck chamber.
For a true no turn neck using Lapua brass, order your .243AI reamer with a .275" neck and just skim cut the necks to .272" / .273" for 100% cleanup. I wouldn't run a tight neck chamber on a field/comp rifle.
When using Lapua 243 brass, the loaded round/neck will be approx .273" to .275". A fairly standard tight neck 6mm neck is .269". The .272", while not a standard tight neck diameter, is and at times, too tight for a true no turn neck chamber.
For a true no turn neck using Lapua brass, order your .243AI reamer with a .275" neck and just skim cut the necks to .272" / .273" for 100% cleanup. I wouldn't run a tight neck chamber on a field/comp rifle.
Re: how to find neck turn diminsions for reamer
Thanks Roscoe. Am I wrong in thinking that the neck thickness will be more on the brass one it is fireforms.
Thanks Roscoe. Am I wrong in thinking that the neck thickness will be more on the brass one it is fireforms.
Re: how to find neck turn diminsions for reamer
What are the drawbacks to a true tight neck application?
What are the drawbacks to a true tight neck application?
Re: how to find neck turn diminsions for reamer
One of the concepts of the tight neck chamber being used was to jam the bullet in the lands while maintaining minimum clearance in the neck of the chamber to help maintain a "slip fit" of the loaded round in the chamber in an effort to help keep the loaded round lined up dead center with the receiver, chamber and bore center lines. Usually, there's only .001" clearance between the loaded round neck and chamber neck wall, .0005" per side although some like a slightly looser fit of .001" per side.
My 6BR uses a .269" Nk and the necks are turned so loaded rounds measure .268". My Dasher uses a .272" Nk and I turn the brass to just give me 100% cleanup. The Dasher is considered a no turn Nk chamber. The Dasher rounds measure .270" loaded. Both the BR and Dasher are drills. Either way that’s too tight for a field type rifle.
I've found that as long as I maintain no more than .005" clearance total between the loaded rounds neck and chamber neck walls, .0025" per side, my accuracy is stellar and loaded round run out is at an absolute minimum, if any at all.
No more than .005" clearance between the loaded neck and chamber neck wall is one of the criteria my reamers must have when I have a new one ground. The other dimensions starting at the base of the neck to the case head are all at minimum SAAMI spec. Free bore varies from reamer to reamer depending on the desired COAL, bullet type/style and weight but, the lead is always at 1 degree 30.
Call Dave Kiff at PTG, chances are, he already has a drawing that’d work great for what you want to do but, for a no turn .243AI using Lapua Brass I'd run the following:
#1 .275" Nk with .103" Free bore, 1 degree 30 for 105/107/108's
#2 .275" Nk. with .148" Free bore, 1 degree 30 for DTAC 115's
One of the concepts of the tight neck chamber being used was to jam the bullet in the lands while maintaining minimum clearance in the neck of the chamber to help maintain a "slip fit" of the loaded round in the chamber in an effort to help keep the loaded round lined up dead center with the receiver, chamber and bore center lines. Usually, there's only .001" clearance between the loaded round neck and chamber neck wall, .0005" per side although some like a slightly looser fit of .001" per side.
My 6BR uses a .269" Nk and the necks are turned so loaded rounds measure .268". My Dasher uses a .272" Nk and I turn the brass to just give me 100% cleanup. The Dasher is considered a no turn Nk chamber. The Dasher rounds measure .270" loaded. Both the BR and Dasher are drills. Either way that’s too tight for a field type rifle.
I've found that as long as I maintain no more than .005" clearance total between the loaded rounds neck and chamber neck walls, .0025" per side, my accuracy is stellar and loaded round run out is at an absolute minimum, if any at all.
No more than .005" clearance between the loaded neck and chamber neck wall is one of the criteria my reamers must have when I have a new one ground. The other dimensions starting at the base of the neck to the case head are all at minimum SAAMI spec. Free bore varies from reamer to reamer depending on the desired COAL, bullet type/style and weight but, the lead is always at 1 degree 30.
Call Dave Kiff at PTG, chances are, he already has a drawing that’d work great for what you want to do but, for a no turn .243AI using Lapua Brass I'd run the following:
#1 .275" Nk with .103" Free bore, 1 degree 30 for 105/107/108's
#2 .275" Nk. with .148" Free bore, 1 degree 30 for DTAC 115's
Re: how to find neck turn diminsions for reamer
Thanks again
Thanks again
Re: how to find neck turn diminsions for reamer
For some reason known only to the guy that first did it the standard chamber neck is .262. Maybe not standard but by far the most popular. As far as B.R. shooting is concerned anyway. I am not familiar with tac. shooting at all but in the accuracy aspect of it the big drawback in a tight neck is having to turn the necks to a very precise thickness. As rosco says the idea of a one thou. total clearence between chamber and a loaded ctg. is a nice set up, at least for me. This has been taken to the extreem of having the neck turned to a thickness that will allow the case to be loaded with no sizing at all, and has been quite sucessful for some guys. I have never tried it and cannot speak from experience.
As far as freebore, the last few reamers I have had ground have had no freebore at all and have worked very well as far as accuracy is concerned.
For some reason known only to the guy that first did it the standard chamber neck is .262. Maybe not standard but by far the most popular. As far as B.R. shooting is concerned anyway. I am not familiar with tac. shooting at all but in the accuracy aspect of it the big drawback in a tight neck is having to turn the necks to a very precise thickness. As rosco says the idea of a one thou. total clearence between chamber and a loaded ctg. is a nice set up, at least for me. This has been taken to the extreem of having the neck turned to a thickness that will allow the case to be loaded with no sizing at all, and has been quite sucessful for some guys. I have never tried it and cannot speak from experience.
As far as freebore, the last few reamers I have had ground have had no freebore at all and have worked very well as far as accuracy is concerned.
Re: how to find neck turn diminsions for reamer
I shoot tight necks in my 22 PPC and 6 PPC barrels. It is stupid accurate. I have not resized a PPC case in years. I do have to turn the necks to 0.0085 thickness though. I punch out the primer and reprime, charge with powder, and seat bullet. Very quick an easy. The brass is not excessively worked so it lasts a lot longer. The drawback to tight necks is you can't shoot factory ammo.
If I was having a reamer made, I would get a bunch of brass and find out what the neck thickness is. Or fine out what the thickness is after at least 80% cleanup, add bullet diameter, and .003" for firing and that would be my neck diameter.
If I were building a target gun or varmint gun, it would indeed have tight neck. A big game hunting or tactical gun would not require neck turning. It might be a tad tighter than SAAMI though, like Mr Roscoe mentioned, is a great way to go.
I shoot tight necks in my 22 PPC and 6 PPC barrels. It is stupid accurate. I have not resized a PPC case in years. I do have to turn the necks to 0.0085 thickness though. I punch out the primer and reprime, charge with powder, and seat bullet. Very quick an easy. The brass is not excessively worked so it lasts a lot longer. The drawback to tight necks is you can't shoot factory ammo.
If I was having a reamer made, I would get a bunch of brass and find out what the neck thickness is. Or fine out what the thickness is after at least 80% cleanup, add bullet diameter, and .003" for firing and that would be my neck diameter.
If I were building a target gun or varmint gun, it would indeed have tight neck. A big game hunting or tactical gun would not require neck turning. It might be a tad tighter than SAAMI though, like Mr Roscoe mentioned, is a great way to go.
Re: how to find neck turn diminsions for reamer
For my 6x47L I had my reamer ground for a .270 neck.Virgin brass is .269 which allows me to just clean the necks all the way in one pass on the turner and have .0015 neck expansion.Seems like it's a good compromise for a tactical rifle as far as being a precision neck fit but also being able to function reliably in dusty conditions.Never a problem in about 5000 rounds off the bipod in the dirt.
Later on after after 8 or so firings I inside neck ream.I bought some different sized Forsters,.0005 difference and use the one that takes off the least amount of brass.
The interesting thing that happens is by the time all this brass prep is done most of the brass ends up being real close together in weight.I have 800 brass that are less than 2 grains from heaviest to lightest.
For my 6x47L I had my reamer ground for a .270 neck.Virgin brass is .269 which allows me to just clean the necks all the way in one pass on the turner and have .0015 neck expansion.Seems like it's a good compromise for a tactical rifle as far as being a precision neck fit but also being able to function reliably in dusty conditions.Never a problem in about 5000 rounds off the bipod in the dirt.
Later on after after 8 or so firings I inside neck ream.I bought some different sized Forsters,.0005 difference and use the one that takes off the least amount of brass.
The interesting thing that happens is by the time all this brass prep is done most of the brass ends up being real close together in weight.I have 800 brass that are less than 2 grains from heaviest to lightest.
