This morning's brain twister

It's not unheard of for newer cartridge designs to result in some initial reamer dimensioning discrepancies between reamer suppliers.
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Thanks unclenick. Of course I wouldn't actually see if I could cam lock an oversized caliber cartridge--even if I do do stupid stuff every now and then!

This was just a straight-up 6.5 PRC cartridge--but if I understand you correctly--the risk still remains with the smaller diameter 25 PRC that it could cam lock the bullet (which makes sense, since that "stop line" would be further out towards the outer edge of the case mouth)?

The reamer situation is probably even worse than you mention--this being a "flash in the pan" wildcat that as far as I know never really caught on.
 
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I just measured my resized to 25 PRC cartridge and the case length is 2.028, and then I marked it in the same way as I did the 6.5 cartridge; there is no sign of contact at either the mouth or neck when I close the bolt--even when I put a couple of layers of tape on the rim face to put extra pressure forward and the bolt would close with resistance--but still no scuff mark anywhere--so I assume the case shoulder is stopping on headspace datum as it should. But I am kicking myself for not casting the chamber when I had the barrel off--it's such a pain torching the scope base screws loose and then re locktiting them.:)
 
Does the scuff mark go all the way around the mouth? What's does the outside diameter of a fired case measure? A new case fits without a bullet but with a bullet doesn't. Can you turn the neck a case so the outside diameter would be the same diameter with a bullet seated as it is without a bullet. Seems the neck area in the chamber is to big but not big enough to fit a bullet. Maybe .002 difference.
 
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Yes, the scuff mark does go all the way around the case mouth for the 6.5 cartridge.

I'm probably confusing the issue at this point--My principal concern was/is the readiness of being able to chamber the 6.5 PRC case into the 25 PRC chamber. After resetting the headspace I'm no longer getting pierced primers or signs of flow at the top of the case head for my 25 PRC cartridges. I am, though, still getting about .005 diameter difference in the neck between the sized and fired--though this was in part because I went down .001 in the bushing size in the die. I'm not sure turning the brass is going to get me anything since there already is "barely enough there" in diameter.

What I suspect is the issue is that the chamber was simply cut and polished pushing out to the maximum spec and created an "overlap" with the sizing die and factory ammo for the 6.5 at minimum spec for the cartridge. Max spec chamber and min spec case sizing is not all that unusual--but it isn't really acceptable for a match-grade barrel. Like Unclenick says, I'm going to have to take the barrel off and do a cast for a better idea of what the issue really is. To be honest, my "friggin wit da riggin" patience with this one is nearing the limit and I may just toss the barrel in the lost cause pile and start anew with a new project.
 
Panther. What's the brass neck wall thickness? What is the difference in neck diameter between a sized brass with and without seated bullet?

-TL

Sent from my SM-N960U using Tapatalk
 
My thought is the neck area in the chamber is around .290 and when you seat a bullet your neck is around .294 and that made the scuff mark. What the od on a fire case?
 
Panther. What's the brass neck wall thickness? What is the difference in neck diameter between a sized brass with and without seated bullet?

-TL
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The brass seems to have "memory" of the 6.5 case, so I think I'll need to do a few cycles to get a definitive answer.
 
My thought is the neck area in the chamber is around .290 and when you seat a bullet your neck is around .294 and that made the scuff mark. What the od on a fire case?
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I agree--that scuff mark though is from the mouth of the 6.5 PRC cartridge. A fired resized to 25 PRC OD of the neck is about .291; so I agree with your assessment and that does seem in the bounds of what you would expect for a .257 cartridge. I'm going to take the barrel off and do a cast when I can, hopefully this weekend, to get a better idea of what really is going on.
 
There are a few .25 cal chamber specs I could quickly look up. The neck diameter min. spec range from 0.286" to 0.291".

Bullet diameter is 0.257". 0.012" normal neck wall thickness. The neck diameter with seated bullet

0.257+2*0.012=0.281"

Before seating bullet, the diameter is probably 0.279".

0.05" increase in neck diameter doesn't seem too sloppy. I guess your chamber is probably 0.285".

-TL

Sent from my SM-N960U using Tapatalk
 
The gun should not lock shut (at all) on a NO GO gauge. That's why its called NO GO.

From what has been posted, the OP is using a custom chambered barrel, adjusting the headspace in his Savage rifle, doesn't have dies for the cartridge, is using the "parent case" sizing die, and a collet set to squeeze the neck from 6.5mm to .25 caliber and is puzzled why he's having issues.

If a 6.5 case chambers in a .25 cal barrel SOMETHING is off. Might be a brain twister figuring out exactly what, but it seems obvious to me WHY...

Time for a good chamber cast and careful measurements so he can make ammo that properly fits what he's built.
 
i have resized 308 to 243 and the difference is quite obvious

but i still don't like the head stamp not matching the actual round, i really wouldn't like having 6.5 head
stamp on .25 cal ammo... i've just seen too many things repackaged and then forgotten....
 
georgehwbush said:
i have resized 308 to 243 and the difference is quite obvious

but i still don't like the head stamp not matching the actual round, i really wouldn't like having 6.5 head
stamp on .25 cal ammo... i've just seen too many things repackaged and then forgotten....
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Electric pencil is my friend. I just tattoo the new identity on the head stamp. I love doing brass conversions. It really enables me to go on journeys impossible. It is a specialty of handloading. It takes a bit more to become a proficient "specialist".

-TL

Sent from my SM-N960U using Tapatalk
 
I don't have any other PRC rifles--so I'm not worried about the caliber designation on the headstamp. I do keep the brass in boxes/jars that are specifically marked for the 25 PRC.

Took the barrel off today--only to discover that my chamber lead casting kit got moved to parts unknown in my home during the last makeover/renovation so I'll have to do some digging to find it.
 
If you only want to know the neck diameter, pin gauges or even numbered drill bits will work.

How about slugging it with lead ball?

-TL

Sent from my SM-N960U using Tapatalk
 
If you only want to know the neck diameter, pin gauges or even numbered drill bits will work.

How about slugging it with lead ball?
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You'll just have to buy some extra beer and popcorn and wait in suspense :)--I've done quite a few chamber casts and have it down to a system--I just have to find it--I keep everything in a sealed box since it is lead after all.
Might be a brain twister figuring out exactly what, but it seems obvious to me WHY...
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By all means please enlighten me! ;) The technique of using an existing cartridge die as a basis for forming a necked up/down wildcat by using a parent case bushing die is fairly common and i've done that for others that commercial dies were not available for including the Tac 30 (sort of an AR version of the 30 Herret) and 6mm Predator (which eventually became the 6 ARC) and the 25 PRC is formed in the same manner by most people who adapted it when introduced.
 
My loaded 6.5 round the neck od is .294 a fired unsized neck is .300 od
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Appreciate that--I'll dig up that casting kit in the next day or two hopefully and get the measurements done this weekend.

Presumably you have .002 of residual "not snapped back all the way" for .298--resulting in about .002 between the OD and chamber wall--yes?
 
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