Am I too worried about neck Diameter..?

M

Marine sniper

Guest
I shoot a little benchrest, but most of my long range shooting is sniper style / hunting. I try to learn as much as I can from the bench rest guys and apply it to the disciplines I shoot.

My primary long range rifle is a 300 WBY. I shoot 210 Berger's at 3000 fps. I could not be happier with the combination, it will shoot 1" (3 shot) groups at 300 yards if I can do my job. The rifle is a custom rig on a Mark V, .332 neck (.3315 loaded round) I go through all most as much brass prep as the bench rest guys, neck turn, trim, anneal, primer pockets inside and out, clean the inside of the neck before powder, etc. My ES is usually around 15 fps.

I recently built a 30-378 Wby that I would like to start playing with. I originally had it done for a friend but he decided he did not want the rifle and gave it to me.

Hall E action
34 in 3/3 Pac-Nor 1.25 straight taper
Factory Wby Chamber .344 neck "I think" I know it is a factory chamber, not sure what the neck is.

I had Bruce Bear bed the rifle and as I was getting it reading to go to the range discovered there is a problem in the chambering, it will not feed a factory round, or even a factory brass....it needs re-chambered anyway.

I have been looking for someone with a benchrest chamber for this thing, .332-.333 neck. The loaded round (non NK) goes .333. I can not find anyone. I was put in contact with Howard Wolfe. I talked to him, seems like a nice guy. He has a .339 reamer, so here is the question....am I making too much out of this? Should I go with the .339 reamer or keep looking for a tight neck deal? I do not mind the extra work that comes with a tight neck, I want maximum accuracy.

Thanks,
John
 
Marine sniper said:
I shoot a little benchrest, but most of my long range shooting is sniper style / hunting. I try to learn as much as I can from the bench rest guys and apply it to the disciplines I shoot.

My primary long range rifle is a 300 WBY. I shoot 210 Berger's at 3000 fps. I could not be happier with the combination, it will shoot 1" (3 shot) groups at 300 yards if I can do my job. The rifle is a custom rig on a Mark V, .332 neck (.3315 loaded round) I go through all most as much brass prep as the bench rest guys, neck turn, trim, anneal, primer pockets inside and out, clean the inside of the neck before powder, etc. My ES is usually around 15 fps.

I recently built a 30-378 Wby that I would like to start playing with. I originally had it done for a friend but he decided he did not want the rifle and gave it to me.

Hall E action
34 in 3/3 Pac-Nor 1.25 straight taper
Factory Wby Chamber .344 neck "I think" I know it is a factory chamber, not sure what the neck is.

I had Bruce Bear bed the rifle and as I was getting it reading to go to the range discovered there is a problem in the chambering, it will not feed a factory round, or even a factory brass....it needs re-chambered anyway.

I have been looking for someone with a benchrest chamber for this thing, .332-.333 neck. The loaded round (non NK) goes .333. I can not find anyone. I was put in contact with Howard Wolfe. I talked to him, seems like a nice guy. He has a .339 reamer, so here is the question....am I making too much out of this? Should I go with the .339 reamer or keep looking for a tight neck deal? I do not mind the extra work that comes with a tight neck, I want maximum accuracy.

Thanks,
John
Click to expand...

John something is wicked confused here..........one of us isn't making sense.

Some questions...

#1-When you say "I shoot a little benchrest." What does this mean? You actually have a PPC? Or you sometimes shoot off a bench?

#2-Also you say "I had Bruce Bear bed the rifle and as I was getting it reading to go to the range discovered there is a problem in the chambering, it will not feed a factory round, or even a factory brass....it needs re-chambered anyway." What does this mean? Did Bruce Baer BUILD the rifle? CHAMBER the rifle??? or just BED it??? How can the bedding be in any way relevant???? Let me be clear in stating that if Bruce Baer did the chambering work it's HIGHLY doubtful that it "needs rechambered"..........

#3- You say "it won't feed a factory round"....... what do you mean? "feeding" is taking a shell from the mag to the chamber. "Chambering" is closing on a loaded round. What exactly are the symptoms? Does the bolt stop 1/4" short? Does it go clear to the belt? Does the handle try to rotate? Does the round stick or jam? Where is the round marked?

All that aside..... NO you're not making too big a deal of the neck. The neck is absolutely crucial to accuracy and having neck clearance over .002 is an abomination. Remember, the bullet WILL be canted in the bore by at least as much as the neck clearance allows. If it's decided that your chamber does in fact have a huge factory neck, then yes, I agree that it needs to be rechambered to be satisfactory. But if it won't accept rounds you must find out WHY, it might be because it already has a tight neck......doubtful but maybe.

Please advise.


al
 
Sorry for the confusion.....

I have shot benchrest competition in the past, but only 50 cal benchrest stuff when I was in the Marine Corps.

Bruce only bedded the rifle, I was trying to show that I take accuracy serious with the components I used and the guy who bedded it.

The bolt will not close, or even start to with a round in the chamber. It will not close with a factory 30-378 brass, or a neck turned one.

Pac-Nor chambered the rifle, they told me the only 30-378 Reamer they had is a factory spec.

The bolt will close on a loaded 300 WBY and a factory 300 WBY brass.

John
 
Methinks

Sounds like a chamber cast is in order.
 
Just a few questions.

Has this rifle ever been fired? Is the barrel marked with the cartridge info? Is the chamber and bore free of obstructions?

longshooter
 
Yes, marked with 30-378. no obstructions, never fired.
 
longshooter said:
One more question.

Is everything operating properly, without binding, at the breach face of the bolt?

longshooter
Click to expand...

Yes, everything works fine, just won't close the bolt on a 30-378 brass.
 
I recently had a pre chambered barrel come with no throat, rifling was square to the end of the chamber. If you seated a bullet so the ogive was below the end of the case you could chamber the round.
Stuff happens and I know all the people I have dealt with are more than willing to fix a problem, IF THEY KNOW ABOUT IT.
 
I talked to Pac-nor, they said they would re-ream it with the factory spec reamer, I have no interest in that. I want a benchrest spec chameber.
 
As I understand your original question, yes, you may be worrying too much about neck size.

There is nothing magical about thin necks. There is something magical about close tolerances, specifically, that the chamber is as true to the actual bore as it can be. "Tight" (really, thin) necks per se came about in the era of the .222, where the neck wall thickness of factory brass could be so far off that a chambered round would have the lands engraving on one side of the bullet, but not the other. By turning the neck, the wall thickness was made even, but also by turning the neck, it was thinner, so the chamber neck had to be correspondingly smaller. That was and remains the basis for determining the correct chamber neck diameter.

Alinwa indicated his belief that any chamber clearance greater than .002 over loaded-round neck diameter was anathema. There are a number of us who compete in long range benchrest who would disagree. Some use .0025, some .003, some as much as .004. That is total clearance, not "per side."

The right way to do all this when getting a custom chamber is to get your brass first. Mike the necks, to see how much you will have to turn off them to get even wall thickness. If you don't have confidence in a particular *lot* of brass, assume you might have to turn off another .001 or .002 on subsequent lots.

Now you are almost ready to spec the neck diameter on the chambering reamer. Let's say that the original neck wall thickness was from .014 to .016. You figure that using .013 will clean up all variance in the brass.

Now you have to make decisions. If you are confident with the .013 number (per side) for a .308 caliber, your loaded round will be .334. Add whatever clearance you want -- say it is .002 total. That gives you a neck diameter of .336.

But there are other considerations. If you plan to try custom-made, flat-base bullets, there will likely be a pressure ring, so the bullet at the pressure ring will mike about .3085 instead of .308. Or, you may feel you'd be more comfortable with a .012 neck, to allow for lots of brass that aren't as consistent. Or you may want to try only .001 total clearance.

At some point, you cannot have it all. If you spec a .331 neck, and it turns out, as is likely, that you have fewer fliers running .003 total clearance, you are going to have to turn your necks to .010. That's about as thin a neck as I'd like to go with a .30. With that same number, if you really want .001 total clearance, you have a neck of .011 -- unless you run into a favorite bullet that mikes .308+

Somewhere around .332 is a pretty good compromise. Personally, I won't shoot the long-range rounds without at least .002, and prefer .003. I also like .012 wall thickness for necks, and BIB bullets which mike .3085. That gives a chamber neck of .3345, so I go with .334.

It is a matter of fitting; not particular numbers. The *right* numbers are the ones needed to make things fit.

As for the not chambering rounds: DON'T FIRE IT UNTIL YOU KNOW WHY, AND FIX THE PROBLEM.
 
Last edited:
John, Charles E, explained in great detail what I attempted to do on the other site. The pressure ring really comes into play with that tight of clearances, tho I am unsure if those bullets have such a pressure ring.
good luck! Ron Tilley
 
OK, so if the bolt is closing on a 300Wby then the belt is headspaced for clearance. The next logical stop seems to be the shoulder. Do you have a die that you can run down slowly on the brass until you begin bumping the shoulder? Then you will proceed to bump the shoulder back in smallest possible increments, a thou or less/bump, and see if the bolt doesn't close.....

I have all of my chambers cut to NOT accept un-bumped brass so that I can set the shoulders for a nice tight fireforming crush fit. Maybe this was planned, not a problem at all.

I still think the 11 thou of clearance is too much but if you can find the bind I'd certainly try it out while the barrel's still long, if nothing else just to establish some loading and velocity baselines before you shorten it an inch and a half.


hth


al
 
tillroot1 said:
John, Charles E, explained in great detail what I attempted to do on the other site. The pressure ring really comes into play with that tight of clearances, tho I am unsure if those bullets have such a pressure ring.
good luck! Ron Tilley
Click to expand...

Hey Ron, this is a different rifle ! I am talking about my 300 WBY on LRH. I am trying to decide what to do with my 30-378 here.
 
Marine Sniper

John
Even though the 300 Weatherby is way smaller than the 30-378 the fact that you can get it to chamber up means the neck is not your problem as they both have the same diameter necks.
I would sacrifice one case to find were the problem is.Cut the entire neck off that one case and see if it now fits.If it doesn't cut the shoulder off next.This is the fastest way to solving were the problem is.
Let us know what you find out.
Lynn
 
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