Discussion in '6mm, 6.5mm, and .25 Cal (Not 6BR)' started by crustyrusty, Aug 29, 2019.
257 Robert's necked down.
Amplifying on my previous post on neck wall thickening:
The neck wall of nearly any factory case is tapered - thinnest at the case mouth, thickest approaching the shoulder junction. When you neck turn, you are largely mitigating this by rendering the neck wall nearly uniform in thickness along its length. If you start with a 7x57 case (neck not turned) and form it in a 6mm Rem FL die, you are creating a case with a significantly enhanced constriction at the base of the neck (near the shoulder junction.)
I reformed 7x57 first in a 257 Roberts FL die, then in a 6mm Rem FL die. Then I used pin gages to probe the neck ID. My notes say:
Translation: A 0.231 gage was the largest that entered the neck past the neck/shoulder junction. A 0.235 gage only entered ~halfway into the neck. One may extrapolate that the ID at the case mouth is ~ 0.239 (assuming a uniform wall taper.)
The OD of the neck after sizing in 6mm Rem FL die was 0.269. So (extrapolating some more) the neck wall at the case mouth was likely ~0.015 thick, but near the shoulder junction 0.019 thick.
I leave it as an exercise for the reader to deduce the implication of this these neck wall dimensions on subsequent bullet seating and neck sizing. But I reiterate you should strongly consider turning the necks of the 7x57 cases before forming into 6mm Rem. This will reduce the stress associated with sizing the necks down that far, and avoid carrying along and enhancing the original doughn... er, thicker region near the shoulder junction.
Right, right, and right.
I turned my necks to .0125".
I neck turn everything I own if just to make sure the case neck is uniform from the shoulder to end of the neck,,, then i check for wall thickness!!
I've got a 6mmAI and I just neck down the 7x57 brass. Works perfectly.
Fair enough. It would be informative, however, to know your chamber neck dimension, bullet used, and depth it is seated to.
I would put it in a long action, if I did another one. No problem with magazine length that way. I shot probably somewhere over 150 deer with a 6 mm and 100-grain Interlocks. Great round. I smoked the barrel and made it into a .260.
I second building it on a long action. I built my 6 Ackley on a savage short action and am now limited by magazine length and have to single feed the heavies.
I plan on building my 6mm on the long action any ways because if you need extra length for shallow seating the bullets you have it in bunches,, with the detachable magazine... i like how they work. as for the 6mm AI not so much interested never been a speed nut... a 100gr pill @ 3100fps or 3200 fps is good by me.
Q. what powder / brass combo is your pet load and did you run this through a chrony for ES / SD information?...what bbl length U have ?
Reloader 23/Norma brass
Averaging 3,047 fps
22" barrel length.
Using RL23 with 90gr bullet....what amount of powder might be a good starting point
Alliant's site doesnt show data for R23 with a 90 gr. , butbtheybdo shownforna 100 gr. With a max of 46.6 gr for a 100 BTSP, thisbwas the max load. They suggest reducing by 10% for starting loads. I'm thinking one would be able to take the max charge for the 100 gr. And use it as a starting load for the 90 gr. As if done this wothnother powders in the past. Maybe someone else can chime in.
Found this- it should help
+1 You can't go wrong with RWS brass in the 6mm Rem!!
See Plumsask's post. That should be the best way for you to approach it for your particular rifle.
I save my RWS which is 7x57 for benchrest. I have 2 6 Rem. Imp. and also turn before necking down.
For hunting I have stash of Remington brass. I have a old #1, and am going to build a new 6 Remington on a 700 long action. I have a new JGS 6 Remington SAAMI spec. reamer.
I have always used H4831sc with 105's in br guns, and also with 90 Scirocco's, and 95 SST's for hunting.
PERFECT...thank-you! My RL23 is on order and arriving next week. Looking forward to those low ES and SD results.
If your have H4831sc you should give it a shot for low es&sd. I use it in my 6mm rem Ackley eith a 90 gr tipped game king and it's great velocity (3500 FPS) with an ES of 7 FPS on well prepped win brass. It was better than N-160 quite a bit Es&sd wise.
+1 on the H4831SC
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