False Shoulder - 6mmBR to 6mm Dasher
- Thread starter BCBRAD
- Start date
Did a bunch this past weekend.
Full length sized.
6.5mm expander to open up the neck
6mm with neck bushing at .265 (necks are turned) to create a false shoulder.
False shoulder should only be about a third of the way down the neck.
CCI 450
31.5 gr varget
various bullets from my .243 stock some 100 gr some 95 gr.
I was using Lupua 6mm brass (5 loadings) for form 6 dasher brass.
Full length sized.
6.5mm expander to open up the neck
6mm with neck bushing at .265 (necks are turned) to create a false shoulder.
False shoulder should only be about a third of the way down the neck.
CCI 450
31.5 gr varget
various bullets from my .243 stock some 100 gr some 95 gr.
I was using Lupua 6mm brass (5 loadings) for form 6 dasher brass.
I shoot a 6BRX but the method used is the same.
FL size 6BR brass
Use an expander mandrel and die to open necks to 6.5
Now the trial and error starts.
Use a bushing sizing die with a 6mm bushing (your choice what size, .265, .268 etc)
Only size 1/3 of the neck down to 6mm and try to chamber the brass.
If it doesn't chamber size the neck dozen a little more and try again.
Repeat above until the case chambers with the slightest resistance.
I fireform at mid range matches. 107 SMK's pushed 30 grs of Varget and lit off by CCI-450 primers in Lapua brass. Extremely accurate even at 600yds.
FL size 6BR brass
Use an expander mandrel and die to open necks to 6.5
Now the trial and error starts.
Use a bushing sizing die with a 6mm bushing (your choice what size, .265, .268 etc)
Only size 1/3 of the neck down to 6mm and try to chamber the brass.
If it doesn't chamber size the neck dozen a little more and try again.
Repeat above until the case chambers with the slightest resistance.
I fireform at mid range matches. 107 SMK's pushed 30 grs of Varget and lit off by CCI-450 primers in Lapua brass. Extremely accurate even at 600yds.
skiutah02
Silver $$ Contributor
I do what jr600 has indicated, except I used a 0.257 mandrel and 105 Hornady HPBT to fireform (inexpensive and accurate) While around 30 gr of varget for fireforming is very common, I elected to use a hard jam (0.020") and explore for a node starting from 28.5 and working up. I took a picture of the process if that helps. Knew someday it might come in handy. Drew
Longtrain
Gold $$ Contributor
I have FF'ed many, many Dasher cases using the false shoulder model, as recommended by my gunsmith. I've never had a case head separate at any time after FFing.
My gunsmith explained that a possible problem with jam and shoot is that if the case moves forward a bit on the firing pin falling, then there may be a void which will allow the case to stretch back to the bolt face, thus creating a possible head separation problem a few firings down the road. This is more likely if round doesn't fire on the first attempt and then the bolt is cocked again on that round at which time it does fire.
A fellow shooting forming cases had this happen on several cases on which he re-cocked and then fired. On the third firing there was case head separation.
I don't want to debate the jam and shoot, this is what I do and I feel the reasons are sound. My results speak for themselves.
My gunsmith explained that a possible problem with jam and shoot is that if the case moves forward a bit on the firing pin falling, then there may be a void which will allow the case to stretch back to the bolt face, thus creating a possible head separation problem a few firings down the road. This is more likely if round doesn't fire on the first attempt and then the bolt is cocked again on that round at which time it does fire.
A fellow shooting forming cases had this happen on several cases on which he re-cocked and then fired. On the third firing there was case head separation.
I don't want to debate the jam and shoot, this is what I do and I feel the reasons are sound. My results speak for themselves.
Long train makes a good point. Another reason I don't jam and shoot is the ejector. If you have a spring-plunger ejector, like a Remmy 700, the ejector is pushing on the case head when in battery. There is a good amount of force applied to the base of the case. It takes a lot of neck tension to overcome this force and have the case head stay in contact with the bolt face. This could, like Longtrain stated, make for a head space problem.
If you don't have this type of ejector jamming works but you may loose a few cases.
If you don't have this type of ejector jamming works but you may loose a few cases.
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