Is this normal?

[dkhunt14]

The Sinclair plug is sized to contact somewhere in the middle of the 45-deg transition between the chamber neck and the leade. You'd have to have an awfully tight neck for the Sinclair not to fit easily.

If a pin gage has a sharp edge I use a fine diamond hone to soften it with the gage chucked in a drill press.
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A .286 is a fairly tight neck. I would be betting git would be turned down. I would also bet that the neck is want is stamped on the barrel. If you know the gunsmith he probably has a Reamer print and could get you close on trim length. Matt

 

[ireload2]

You can easily measure a chamber neck without a lot of monkey business.
Take a tapered punch and expand a case neck into a trumpet shape about .020 to .030 larger than the suspected size of the neck.
Then chamber the expanded neck case and it will crush back to the diameter of the neck. Carefully remove the case and measure the diameter of the case mouth.
Have any doubts? Measure it 4 or 5 times with different cases. Once you see that the numbers are easily repeatable you will have confidence in your dimension.

 

[Brians356]

You can easily measure a chamber neck without a lot of monkey business.
Take a tapered punch and expand a case neck into a trumpet shape about .020 to .030 larger than the suspected size of the neck.
Then chamber the expanded neck case and it will crush back to the diameter of the neck. Carefully remove the case and measure the diameter of the case mouth.
Have any doubts? Measure it 4 or 5 times with different cases. Once you see that the numbers are easily repeatable you will have confidence in your dimension.

You don't expect any (repeatable) brass spring-back?
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[Pigdog]

Hey guys all solved I got in touch with the gunsmith and he gave me the reamer print outs the measurement is 1.860. I have some brass that is 1.853 I'm thinking 1.855 will be the max I will allow before trimming thought? Iam going to get a customer lee trimmer made the one that goes in the drill I'm thinking getting it made to 1.853 which will give me 7 thou clearance and allow to grow 2 though giving 5 thou clearance before trimming? Thoughts

 

[Brians356]

Unfortunately I don't have any Sinclair plugs in 6.5 6mm (really!) but here's how much larger than bullet diameter are the ones I have:

22: +.025"
6mm: +.022"
25: +.022"
270: +.025

So even if the 6.5 plug is only .022" larger than bullet, it's .286" and probably too tight in your chamber.
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[ireload2]

Try it for the only answer you can trust.
That is why I recommended that you measure your chamber 4 or 5 times. Most people cannot believe the process is accurate.
If your brass is annealed it will not have much spring back. If there is any it might only be a few tenths of a thousandth. That is closer than you can usually get with a .001 increment gage pin.

You don't expect any (repeatable) brass spring-back?
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[Brians356]

Try it for the only answer you can trust.
That is why I recommended that you measure your chamber 4 or 5 times. Most people cannot believe the process is accurate.
If your brass is annealed it will not have much spring back. If there is any it might only be a few tenths of a thousandth. That is closer than you can usually get with a .001 increment gage pin.

Wouldn't just measuring fired case neck ODs, and assuming .001" or less spring-back, be just as repeatable? The fired cases are already in hand in this instance.
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[Pigdog]

hi guys just to follow up on this like i said i would. Got some lapua scenars today and did some neck tension tests.

I seated 2 bullets. First case neck diameter before seating was .281 after seating the bullet it was .282 and measured 2.751 overall

second case neck measured .2805 before seating after seating measured .282 and measured 2.747 overall

So according to my gauge that is between 1-1.5 thou of neck tension which would seem good. Im planning to soft seat and i had to use pliers to pull the bullets out!! I was under the impression that 1-1.5 thou of neck tension is finger type tension (ie you could almost seat and unseat the bullet with your fingers??) this certainly seemed like more than finger tension and i could visibly see marks on the bullet where it was seated.

thoughts?

 

[spclark]

0.0010"-0.0015" difference between neck dia. before & after seating's a bit more than what I'd find compatible with 'soft seating.' 0.0010 is what I usually aim for with my Palma loads & as you suggest, bullets won't move under finger pressure alone.

And using a bushing die I only size the forward 0.1" of the case neck too. My fired brass chambers fine before re-sizing, the neck reduction's just to add enough grip to hold bullets during transport.