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JJD
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Location: Right Side WA state
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Cartridge Length

Here’s a co-workers reloading question. He’s new to reloading and trying to figure it all out. Just wondered how you’d answer his question?

Question;
Reloading for a 30-06
New model 70 win
He’s trying to find a proper seating depth.

He says, I have measured where my bullet contacts the lands of the barrel and seated the bullet another .010 deeper. My reloading manual says max C.O.L. (cartridge overall length) is 3.340 and when I measure the round after seating the bullet with the .010 deeper and I’m nearly .175 longer than the max C.O.L. listed in the manual. What’s with that?

Don Fischer's picture
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Cartridge Length

I would tell him he's making more of it than he needs. If he's like most of us, he's measuring from the rim to the bullet tip, that's what I do. The right measurement is from the rim to the bullet ogive, need new tools and don't gain enough in my opinion.

What he needs is the bullet seated just off the lands, how much, how would I know. Not only that but without the proper tools it would be impossible to say precisely how much you are off the lands. The overall length is a figure that will allow the cartridge to be loaded into all chambers, probably the same as factory specs.

Each chamber may be just a bit different and each bullet just a hair different to the nose of the bullet. Because of that, it's best to ignore the overall length in the book and develop your own length for each bullet you use. How far, haven't got a clue. Play with it till it shoots well. It will be the last adjustment in the search for an accurate load. That's where we tweek the load.

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Location: Montana
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Cartridge Length

Chamber casting.. And its something anyone can do

JJD
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Location: Right Side WA state
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Cartridge Length

I appologize for being absent after posting my question. Wx conditions have had our power go out at least once a day for over a week. I have been reluctant to run my computer while this is going on.

I am not familiar with chamber casting. Could you explain how this is dome?

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Location: Pipestone, MN
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Cartridge Length
JJD wrote:
I appologize for being absent after posting my question. Wx conditions have had our power go out at least once a day for over a week. I have been reluctant to run my computer while this is going on.

I am not familiar with chamber casting. Could you explain how this is dome?

This is a post regarding chamber casting I did on another board.
It may not answer all your ?'s as sometimes I take things for granted.
If you think of something I didn't answer or overlooked, don't be afraid to speak up.>>>>>>>>>

Anyhow, to me casting the chamber tells me exactly what I have!!!!
First for me it's a necesssity, with custom chambers as being tight, I need to know how much trimming and neck turning is needed. Some of my barrels are tight enough, that brass or bullet runout of over .0004" creates problems in chambering smoothly. I'm guessing some if not most factory rifles have 3-5 times that tolerence. So why would one need to chamber cast a factory rifle?,,,,same reason, so you know what you have.
Most don't do it however, until the find they can't get it to shoot with any load satisfactorily. Then they take it to the gunshop or gunsmith, saying "I can't get this &*(%^#$*(_* thing to shoot. He says" leave it and come back tomorrow" when your gone, he goes in the back and chamber cast it in 5-10 minutes. If you didnt buy it from them/ him he'll like charge you 25 bucks, more than the cost of the cerrosafe which can be used over and over.
The most common problem found is a crooked chamber, which means back to the factory with it for a rebarrel. But if you cast your self from the start, you know what you have and possibily save frustration and ammo in the process.
So the first thing I do with a new barrel is clean it, than cast it before it's ever shot (usually). I have let it slide on ocassion, only to end up doing it later anyhow. I get in a rush sometimes, and it usually ends up a frustrating situation!
I usually just cast into the lands/grooves on my barrels to see as stated above. But on factory barrels I would cast an 1" deeper just so I could measure if the chamber is straight to the bore.
You need to be pretty good at measuring this, and your avgerage .001" caliper just don't cut it. You need a mic with .0001" capability. Or if not, then take it to a good gunsmith and have him measure it, but you need to be watchful of the time, as the info I'm going to paste here will show.
I have heard of chambers being far enough off center you can see it with the naked eye. Those you won't get to shoot no matter what. Personally, any barrel I have gotten, goes back if it's more the .0002" canted off of center, or ovaled out. But then, I'm likely pickier than some.

I was asked to do pic tutorial, and will in the future, but the process is quite simple. Cerrosafe melts at a low temps,(158-190 degress), and I use a Rowell 2# ladel, and heat it on my little camp stove, while I'm runnig a very lightly oiled patch in the chamber and first 1" of the bore. Then that patch or TP and wad it up into a ball and plug the bore to my desired depth, mentioned above.
By this time the cerrosafe solid be liquid state or close. The just pour it in and wait a few mins. After it has shrunk, push it out from the muzzle end carefully. I will wait for the maximum shrink period of 30 min.s in most situations,,,mores o if I'm casting deeper into the bore. It just comes out easier. After 60 minutes it expands back to the chamber dimension. So it is something you do need to have some time to deal with it (hour + mins), other wise you will be subracting by time after the 60 min.. You'll see what I mean with the pasted info.
Now bolt guns aren't as easy to a point as my single shots. It's just more difficult to see what you are doing , plus you need a funnel and short tube to get in there past the locking recesses. That the problem area, you don't want this stuff in those recesses for obvious reasons. So I'll do some cheacking to see what the bolt guys do to ensure they don't over fill the chamber and get back with a post.
I have my ideas, but that don't mean there aren't better ideas out there, which I'm sure there are in this case

here s the paste info

Cerrosafe is the best known material from which to make a casting of the chamber and throat of a firearm - to determine caliber or check the dimensions. It melts at a temperature just above M&M's, so all you need is a propane torch and a bullet casting ladle. It can also be used to make a cast of a dovetail slot or any other hard to measure area. Also, it is great for removing the front half of a case from the chamber, in the event of case head separation; and lots of folks cast a small portion of the barrel to determine bore diameter. For best results, measure the casting one hour after casting.

Technical Information

Material:

Proprietary Alloy (exact mixture unavailable)

Basic Instructions:

Plug the bore immediately ahead of the throat of the chamber using a small cleaning patch.

Pour the alloy directly into the chamber until full and allow it to cool, it will turn a shiny silver color. As soon as it has cooled enough that it is no longer a liquid (and doesn't present a burn hazard), remove it from the chamber. Take care not to overfill the chamber as the alloy will then run into the locking lug area, making removal extremely difficult.

During the first 45 + minutes of cooling cerrosafe shrinks. At the end of one hour it should be "exactly" chamber size.

Notes

Melts between 158 and 190 degrees Fahrenheit

Should be melted in a clean iron ladle without direct flame on the product.

The chamber being cast should be cleaned thoroughly and a thin coat of oil or graphite applied.

Reusable

Contraction - expansion factor versus time, measured in inches per square inch:

2 minutes -.0004"

6 minutes -.0007"

30 minutes -.0009"

1 hour +-.0000"

2 hours +.0016"

5 hours +.0018"

7 hours +.0019"

10 hours +.0019"

24 hours +.0022"

96 hours +.0025"

200 hours +.0025"

500 hours +.0025"

http://www.midwayusa.com/eproductpage.e ... mid=462291

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Location: Montana
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Cartridge Length

Simple as that Thumbs up

JJD
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Location: Right Side WA state
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Cartridge Length

Very interesting, thanks for the info.

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Cartridge Length

Spend the $40. and buy an Overall Length Gage and a modified case. Stoney Point makes a good one. It's cheap insurance. I run .005 off the lands for match rifle and .040 to .050 off the lands for hunting rifle. Then make sure that it will fit in the magazine and feed properly and your good to go. And if you shoot the same caliber you can share it with him and split the cost. And if you change bullet weights you can find the right depth for those too. JMHO. Yes

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Location: Montana
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Cartridge Length

If OAL is all desired, taking a EMPTY fire formed case from that rifle, loading a bullet that youll be shooing with it loose and chambering it after smoking it with a candle will give a much more accurate length with the olgaves then a OAL measuer will, it will be in essence custom to your rifle.
It still doesnt give all the exstra measurments chamber casting will.

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Location: Pipestone, MN
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Cartridge Length
BuffaloWYO wrote:
Spend the $40. and buy an Overall Length Gage and a modified case. Stoney Point makes a good one. It's cheap insurance. I run .005 off the lands for match rifle and .040 to .050 off the lands for hunting rifle. Then make sure that it will fit in the magazine and feed properly and your good to go. And if you shoot the same caliber you can share it with him and split the cost. And if you change bullet weights you can find the right depth for those too. JMHO. Yes

These are a quick and easy tool without doubt. I do question them are far as usefulness however, even though I haven't tried one.
Here's my thoughts.
#1- you can do the same thing with a fired case at less expense.
#2- bullet ogives vary enough between the same lot of bullets, that your seating depth may vary by as much as .002" or more.
( i can eyeball that difference with a bullet next to the cast)
The only way to maintain accurate ogive to land tolerances, is to start long and use a micro seat on each and every round.

It depends on how particular you want to be I guess.

Dave

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Location: Buffalo,Wyoming
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Cartridge Length

plus or minus .002 for a hunting rifle I would qualify as nothing to worry about and if you micro analyze bullets then none are equal except maybe in weight and then only if you are talking about match grade. And I have segregated match bullets because they were 1/10 grain off. The only shooters that I know of that seat against the rifling are bench rest shooters, and not all of them do it. Seating close to the rifling boosts pressures. If I went from seating .005 away from the rifling to seating against the rifling, I would change pressures.

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