This morning's brain twister

By all means please enlighten me!
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The part that seems obvious to me is that you've got "too many irons in the fire".

There are a number of things you didn't mention, that I don't know about, along with what you did say. First one is, do you have complete spec drawings of the .25 and 6.5mm cases? Are they exactly identical, or not??

Particularly the shoulders. Generally speaking, when you neck down the parent case to something smaller, it often changes the shoulder angle or length or both. is this what is happening here? The shoulders on the cases in your first pic, (fired .25 and new 6.5) look different to me. This could be the result of the camera angles and lighting, or are they actually measurably different??

You are sizing in the parent case die, (6.5) and then using a "work around" a collet to size the neck, which obviously works, but isn't the same as a properly cut die for the .25 round.

Next point is that, while that method is producing functioning ammo, what is the relationship between the ammo made that way and how your chamber is actually cut.

You've set the headspace twice (so far) and still have issues. It may be that your problems are the result of "stacking tolerances" because you have stacked so many things upon each other.

This is not meant as any kind of criticism, but as a possible explanation of what is going on, based on what you posted.

I think you've got so much going on you can't really tell for sure which thing is causing what.

From what I can see there is a likely solution, but its not even remotely cheap. There's no such thing as "can't get a die for..." there's only "can't get a die for .... at a price I'm willing to pay".

A custom cut die, made to match your rifle's chamber isn't cheap, but does offer the best chance for bughole accuracy and long case life. It is not impossible you could tinker with everything and not get the results that make you happy, without it. I hope you can, but do consider that when you've tried everything that should work, but doesn't, it might be time to consider a different approach.
 
Actually there really is no issue with firing the 25 PRC, although even though my initial setting of headspace passed the no-guage test (ejector and extractor removed)--like Jim Watson said that doesn't mean it's the "ideal" setting because typically a no-go guage will allow tolerance stacking of around .005 to .006 before you can close the bolt. I've had a couple of instances (like the original 350 legend) where it was more than that. How often do you check the tolerances of your gauges and compare them to specs? My "issue" if it even is one, is that the 6.5 PRC case goes into the chamber just as easily as the sized 25. And I'm not so much concerned about the safety aspect (although it is conceivable that a too long case could result in the case mouth cam-locking on the bullet). My original quest was to inquire to what extent a possibly oversized neck/freebore ("oversized" meaning max spec--maybe a bit over with polishing) could affect the accuracy of the 257 projectile when fired. I'm guessing it could possibly result in some erratic bullet stability and gas/pressure consistency in the transition from chamber to bore.

It's not unusual when an "unofficial" wildcat is released that there are different variations of the chamber reamer and freebore specs "floating around in the wild" before the final "winner" becomes an agreed-upon standard--probably a big reason there's a lag in availability of factory dies. You could have someone make one for you--but then you are committing to a particular chamber and reamer spec. That's why I think early "bleeding edge adaptors" go the bushing die route. I've already decided in the last year or two from now on I will no longer be an early adaptor of any cartridge regardless of whether or not it has been standardized upon release.
 
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The od on a new 6.5 case is .290 the od on a fired 25-06 case is .290 thats why the unloaded 6.5 case chambers but the loaded 1 does not.
 
The od on a new 6.5 case is .290 the od on a fired 25-06 case is .290 thats why the unloaded 6.5 case chambers but the loaded 1 does not.
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Yup--that explains it. :) Another thing I've been giving some thought to--Savage commonly uses a floating bolt head backed by a compressible friction washer to achieve better concentricity of the bolt to receiver. I can see how that might introduce some extra headspace when setting it if you don't purposefully compress the bolt to take up the slack that could be introduced by that washer.
 
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It's not unusual when an "unofficial" wildcat is released that there are different variations of the chamber reamer and freebore specs "floating around in the wild" before the final "winner" becomes an agreed-upon standard
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One of the classic examples of this is the .22-250. Spent around 3 decades as a wildcat with several slightly different case variations, before Remington finally adopted one of them as the standard.

The first .22-250 I got was a converted Mauser made up by our local smith. I was lucky that the chambering he chose just happened to be the same one Remington chose, and the gun was great with Rem factory ammo.
 
Two recent examples of "official release" (SAAMI spec published) cartridges that had different spec reamers out among barrel makers "jumping on the bandwagon" upon initial rollout were the 350 legend and the 224 valk.
 
@ sako2:

With my rifle apart I realized that I have no bolt action quarterbore at my disposal--so I decided to assemble a 25-06 frankengun out of spare parts I have lying around, a mix of savage 110 and Axis stuff I've accumulated over the years. The barrel is a short 22" well used savage sporter barrel I found in a consignment shop years ago.

I'm giving second thoughts to just building a new, modern configuration 25-06 AI rather than goofing any more with this 25 PRC.
 
In the meantime, I've decided on a "back-up barrel" to the 25 PRC--I was just about to pull the trigger on a 25-06 AI when the thought occurred to me--how about a modern take on a 257 weatherby? So I'm having a fast-twist one made anticipating being able to use berger's 133 and 135 gr modern high BC bullets (just so happens I have 1,000 of them).
 
now that's using your boom-stop for something besides shooting glasses holder.
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:D:D It will actually be the smallest of the Weatherby's I've ever owned or shot--and I love Weatherbys--for some odd reason I never have considered it.
 
After removing and examining the barrel as best I could--I couldn't find anything wrong with it (within the limits of my powers of observation) other than the throat is showing signs of wear, which is to be expected with hot 25's. So I put it back together but took it out of the Boyd's stock and put it in an MDT chassis instead. I'm impatient to try out Hornady's 134 gr ELDMs, thinking 7828 or N565 as my first attempts.

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After removing and examining the barrel as best I could--I couldn't find anything wrong with it (within the limits of my powers of observation) other than the throat is showing signs of wear, which is to be expected with hot 25's. So I put it back together but took it out of the Boyd's stock and put it in an MDT chassis instead. I'm impatient to try out Hornady's 134 gr ELDMs, thinking 7828 or N565 as my first attempts.

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Nice looking rig.
 
Thanks--I'm hoping that it shoots better than I had it in the Boyd's stock. I also saw a bit of wear in the receiver's face and lugs and did a bit of truing on them; it's an old one and been used for several different builds, I need to invest in some new ones--but they are very expensive these days. I keep wanting to commit to a true custom receiver but there always seems to be a hitch which means committing to some kind of major re-investment in over-all "equipment topology" which I just can't seem to get over.
 
My first batch of 134 ELDMs. Formerly I've had my bullets very close to the lands, with these I'm backing them off to see if that makes any difference. I've seen instances of where the ELDs and VLDs occasionally do better with a healthy jump to lands.

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stagpanther said:
My first batch of 134 ELDMs. Formerly I've had my bullets very close to the lands, with these I'm backing them off to see if that makes any difference. I've seen instances of where the ELDs and VLDs occasionally do better with a healthy jump to lands.



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You can tune the jump for best group. Make sure use small step size(<0.005") though.

-TL

Sent from my SM-N960U using Tapatalk
 
Overbore cartridges--especially new ones with little prior load development history--can be an expensive proposition to develop loads for. Barrels may not make it to 1000 shot count before being shot-out (and perhaps far short of that if shot hot frequently); and custom made barrels have surpassed the $500 mark which makes it a bit harder to digest as a regular "consumable." Take your average ladder-development bullet/powder testing total round count for just one combination (which might be 100 or more) and you can see how it's much more expensive now than it was even just 4 or 5 years ago. As a rule I never shoot more than a dozen shots at a time when testing new loads these days with cartridges that tend to run hot.
 
I use a simplified version of ladder test. For each load I need 35 rounds; 10 for powder charge, 20 for COAL, and 5 for "qualification". You have fixed the powder charge, so 25 rounds will do.

I bring to the range a lee hand press with seating die, and a caliper. Starting with max COAL, fire 2 rounds. Look at the distance between the holes. If it has potential, fire one more round. Still good fire another. 4 rounds max for each COAL. Move to next COAL 2 - 3 thous shorter and repeat process. With 20 rounds I cover 5 to 8 COAL settings. Pick the best and fire 5 more to "qualify". The final "qualification" group will have 7-9 shots.

Not the best method, but it works out for a miserable cheapskate like your truly :) .

-TL

Sent from my SM-N960U using Tapatalk
 
To each their own. :) Generally speaking, nowadays I try to do most of my testing at 200 yds with a labradar. Optimum stabilization at distance beyond 100 yds "is a real thing" based on my experience for modern high SD bullets. I can't always get out that far and will settle on 100 only if I have to. It's a distinct possibility that by the time you find your unicorn node for your particular barrel--it may be close to shot out. That's a factor I'm much more mindful of when trying out new hot burning cartridges--and high SD .257's are a good example. My 7mm STW is another.
 
I am doing the same for the same reason. 150yd is the max at our club, so I test fire there. I have access to 300yd at other place, but it is windier there. I have also noticed long and pointy bullets indeed more time to settle down. Many a time I shoot better moa groups at 150yd than 100yd.

-TL

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