Wouldn’t it be .0015 clearance on the Peterson? Thou and a half? My loaded rounds measured .274 on Peterson and I have a.275 neck as well. So to me I have half a thou-ish. Which makes me wonder, but so far so good?
6XC ground truth as of Jan 2020?
- Thread starter Boatschool02
- Start date
Maybe but my loaded peterson only measures .272, not .274 like yours.
.275-.272=.003 total
.003/2=.0015 per side
So different brass lots I suppose is the reason for the discrepancy. I bought mine from brownells in July of 19.
I too wouldnt feel comfortable with only .0015 total clearance on .274 brass. I also find it curious that your brass is that thick, it isnt a good match for any chamber other than tubbs reamer. All the others are .275-.276.
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Heck if I know. It hasn’t caused any problems yet. Probably got 3-4 reloads on it. I guess if there’s a problem I’ll be turning necks. When I rebarrel I probably will get a 278 neck. But until then I guess I’ll not look for a solution to the problem that doesn’t exist.
seems kinda tight though
Hoot
Silver $$ Contributor
I've been out of the loop with some god awful lung rot. Finally feel like I turned the corner tonight. Not back to full capacity but well enough to go to work and take an easier track there for a few days.
$47 bucks later and the PTG Go gauge is still a perfect fit. Bolt drops down with it but a .002 piece of scotch tape and it only drops half way and refuses to go any further. So much for that concern.
The idea about the necks holds water however. A new piece of brass with a bullet seated in it measures .2715-.272 using a Brown and Sharpe mic. That having been said and as I spoke of some time back in another thread, seating bullets offers so much resistance as to leave a force ring around several different lots of bullets. Neck walls mic between .0145 and .015 as I rotate them. Pulling a seated pullet with an inertial puller takes an incredible 20-25 hard whacks on a concrete floor. No other caliber I reload for is like that. Fired brass measure .274 OD and regardless of whether I chamfer or lightly flair the mouths or not, several different 243 bullets will not drop down into them. Heck, you cant even push them in with firm finger force.
As suggested, this could be the source of my excess pressure. I have a neck turner but had hoped to not need to turn them. It seems like my two choices are turn the necks or get the chamber neck re-cut a little more open than it appears to be. I really like my shorter freebore as it allows me to still play with lighter bullets, so having the chamber re-finished to most of the reamers made to accommodate 115 DTACS doesn't appeal to me. While I hate turning necks, there is plenty of winter left up here, before comfortable shooting weather returns. As previously stated, it is also my intention to shot plate some bullets with HBN. That should help a little as well.
Hoot
$47 bucks later and the PTG Go gauge is still a perfect fit. Bolt drops down with it but a .002 piece of scotch tape and it only drops half way and refuses to go any further. So much for that concern.
The idea about the necks holds water however. A new piece of brass with a bullet seated in it measures .2715-.272 using a Brown and Sharpe mic. That having been said and as I spoke of some time back in another thread, seating bullets offers so much resistance as to leave a force ring around several different lots of bullets. Neck walls mic between .0145 and .015 as I rotate them. Pulling a seated pullet with an inertial puller takes an incredible 20-25 hard whacks on a concrete floor. No other caliber I reload for is like that. Fired brass measure .274 OD and regardless of whether I chamfer or lightly flair the mouths or not, several different 243 bullets will not drop down into them. Heck, you cant even push them in with firm finger force.
As suggested, this could be the source of my excess pressure. I have a neck turner but had hoped to not need to turn them. It seems like my two choices are turn the necks or get the chamber neck re-cut a little more open than it appears to be. I really like my shorter freebore as it allows me to still play with lighter bullets, so having the chamber re-finished to most of the reamers made to accommodate 115 DTACS doesn't appeal to me. While I hate turning necks, there is plenty of winter left up here, before comfortable shooting weather returns. As previously stated, it is also my intention to shot plate some bullets with HBN. That should help a little as well.
Hoot
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I'm not gonna go back & read all the previous posts (to see if this has been covered) so I have to ask: Hoot, have you considered having a chamber cast made of your chamber?
Be an easy way to determine just what your chamber's neck ID happens to be.
To my mind it certainly appears you need more neck clearance to be on the safe side. Since taking up reloading I've used a Rule of Thumb that if I can't drop a bullet of the diameter being loaded into a fired case's neck, the neck of the chamber it was fired in is too small. Solution is to A) turn necks to gain back a reasonable amount of neck clearance or B) have a gunsmith open the chamber's neck with a proper neck-only reamer.
Turning necks just isn't a Big Deal. You may not even have to turn your case necks to the point you're taking brass off 100% of the neck surface, but even that's not a chore with the right frame of mind and equipment.
You stop to think a moment about the pressures generated in a rifle case and how it behaves when it's pushing the bullet out past the neck it's easy to understand why there has to be enough clearance between the bullet leaving the neck and the case neck ID to let that pressure out fast enough or high pressure's going to have an adverse affect on the rest of the case because it's acting over a time frame longer than the case may have been expected to withstand it.
Be an easy way to determine just what your chamber's neck ID happens to be.
To my mind it certainly appears you need more neck clearance to be on the safe side. Since taking up reloading I've used a Rule of Thumb that if I can't drop a bullet of the diameter being loaded into a fired case's neck, the neck of the chamber it was fired in is too small. Solution is to A) turn necks to gain back a reasonable amount of neck clearance or B) have a gunsmith open the chamber's neck with a proper neck-only reamer.
Turning necks just isn't a Big Deal. You may not even have to turn your case necks to the point you're taking brass off 100% of the neck surface, but even that's not a chore with the right frame of mind and equipment.
You stop to think a moment about the pressures generated in a rifle case and how it behaves when it's pushing the bullet out past the neck it's easy to understand why there has to be enough clearance between the bullet leaving the neck and the case neck ID to let that pressure out fast enough or high pressure's going to have an adverse affect on the rest of the case because it's acting over a time frame longer than the case may have been expected to withstand it.
Hoot
Silver $$ Contributor
Yes, I have considered it. I have the Cerrosafe and the time. Based upon the Criterion reamer print, I'm banking on it being .275 but making a cast this weekend is on my agenda. I didn't realize that a neck only reamer was available.
Hoot
It sounds to me you have a sizing problem not a chamber or brass problem. What is the neck diameter before you seat a bullet? If loaded is 0.272, unloaded should be no less than 0.269. I would shoot for 0.2705 to 0.271. Are you using an expander in your sizing die? If a bushing die what diameter bushing?
They are but likely by special order rather than off-the-shelf.
Given the added expense for the reamer and a competent ‘smith’s time to employ it were I you I’d opt for ‘neck-skimming’ if your chamber cast tells you anything definitive.
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Hoot
Silver $$ Contributor
That was new Peterson brass I got from SSS. Unloaded necks mic at .269. I have bought a plethora of sizing die bushings from .267 through .272, searching for the right tension. On FL sized, fired brass, using the .270 seems to leave the necks with what feels like the right amount of tension. Here's a big however: I have not annealed my 1, 2 and 3-fried brass yet. Before comfortable shooting weather vanished, I was mainly using new brass. Annealing is another project I was ready to finish last weekend when the creeping crud invaded me. Hope to get back to it this weekend as well. I mention that because I suspect that once properly annealed, the best choice in neck bushing, based upon feel, will change.
Hoot
6MMsteve
Gold $$ Contributor
how do you get the 105 rdf to shoot big jump or jammed..my 6xc 30in 8t criterion will not shoot them 1.5 inch is the best..but bergers and hornies smks all shoot great..berg shoots .2 or better
I’m not the person you asked but I’m shooting the 105 RDF at .030 jump. I have .140 freebore reamer I used and I always use a .242 expander mandrel for .001-.0015 neck tension.
Anywhere from .020-.030 off of touch via the wheeler method should be fine in the couple 6xc criterion barrels Ive tried them in.
First 7.5 twist 26" barrel with norma brass was 39.4 gr h4350.
This new 7.5 twist 18" barrel is 40.2 in peterson brass with 4350 (but my limited testing with norma brass shows likes it too).
I read a post that David made a point to recommend Peterson brass for high volume shooters...I love it and buy in bulk on sales
Hoot
Silver $$ Contributor
Finally looking at the lung rot that set upon me, in my rear view mirror. Not a fun way to spend 11 days and nights, especially when you have to work, not to mention whoring other coworker's On Call duty to support this habit.
I did the cast and the neck is spot on .275 as per the Criterion chamber reamer. I will be out of town this coming weekend through the 11th. Plenty of pondering time to embrace either having the chamber neck opened up or start turning brass. Neither of which I wanted to do when I chose this caliber over all the other 6mm choices out there, back when I was weighing re-barreling this action in mid-2018. Ya' pays your money, Ya' takes your chances and learn what questions to get answered before finding your wallet the next time around.
Hoot
What does Norma brass measure on a loaded round?Finally looking at the lung rot that set upon me, in my rear view mirror. Not a fun way to spend 11 days and nights, especially when you have to work, not to mention whoring other coworker's On Call duty to support this habit.
I did the cast and the neck is spot on .275 as per the Criterion chamber reamer. I will be out of town this coming weekend through the 11th. Plenty of pondering time to embrace either having the chamber neck opened up or start turning brass. Neither of which I wanted to do when I chose this caliber over all the other 6mm choices out there, back when I was weighing re-barreling this action in mid-2018. Ya' pays your money, Ya' takes your chances and learn what questions to get answered before finding your wallet the next time around.
Hoot
Hoot
Silver $$ Contributor
I don't have any Norma but from what I've read, that is indeed a 3rd option. I'm just a Peterson fanboy. Love their 260 Rem brass.
Hoot
I have the same neck dimensions as you. Same brass. If you are dead set on it being a neck clearance issue I’d turn necks before paying someone to ream the neck. Or try Norma.
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