This morning's brain twister

[sako2]

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?

[stagpanther]

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

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.

[stagpanther]

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?

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.

[tangolima]

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

[44 AMP]

What is a "hard stop" with a No-go gauge?

[tangolima]

Originally Posted by 44 AMP

What is a "hard stop" with a No-go gauge?

Perhaps unable to turn down the handle however hard he tried. For me "no-go" happens when any additional resistance is felt.

-TL

Sent from my SM-N960U using Tapatalk

[stagpanther]

Yeah--I call a "hard stop" that point where any progressive resistance hits the wall.

[44 AMP]

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.

[georgehwbush]

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....

[tangolima]

Originally Posted by georgehwbush

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....

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 "spe[color=#FF0000]█[/color][color=#FF0000]█[/color][color=#FF0000]█[/color][color=#FF0000]█[/color][color=#FF0000]█[/color][color=#FF0000]█[/color]t".

-TL

Sent from my SM-N960U using Tapatalk

[stagpanther]

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.

[tangolima]

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

[stagpanther]

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?

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...

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.

[sako2]

My loaded 6.5 round the neck od is .294 a fired unsized neck is .300 od

[stagpanther]

My loaded 6.5 round the neck od is .294 a fired unsized neck is .300 od

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?

[44 AMP]

By all means please enlighten me!

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.

[stagpanther]

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.

[sako2]

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.

[stagpanther]

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.

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.

[44 AMP]

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

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.

[stagpanther]

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.

[stagpanther]

@ 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.

[sako2]

Nothing wrong with a 25-06. It's a flat shooter start with Retumbo for powder.

[stagpanther]

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).

[georgehwbush]

now that's using your boom-stop for something besides shooting glasses holder.