Last week the big brown truck left a nice new Pacnor barrel at my house, I thought it was nice of them. I figured I would get some OAL's figured out this morning before I put the barrel on. I use a FL sized piece of brass to start with. I put the brass in the chamber and measure the case head protrusion. It was .129". I then seat a bullet of my choice (seated long), in this case it is a 105gr VLD (target). I put the case back in the chamber untill the bullet just touches the lands and I measure the case head protrusion again. We are now at .199". Subtract one from the other and you get .070" Now take the .070" and subtract that from the current OAL of the test round that was 2.310" to begin with and I get an OAL of 2.24". The question is, does this sound right? I am not questioning my method or math just wondering if this OAL sounds correct. I didn't have any special throat cut, just a standard .272" 6BR.
Just checked my oAL
- Thread starter Samdweezel05
- Start date
What exactly do you think I did? I didn't use a fancy tool or gauge, I used the barrel they will be shot in. Unless you plan to use a gauge and measure each bullet individually and then load each bullet differently based on that measurement, I have done the same thing.
May I suggest while everything is new and fresh, ask the barrel maker to fashion a chamber gauge with the same reamer as was used in making your barrel. This is the handiest tool and takes all the guess work out of bullet seating. No more fumbling with rods, dummy cases etc. in hard to reach places. With such a tool you will know exactly when the ogive touches the lands with each loaded round and from there how much into/off the lands you want your load to be.
jefats: Chamber gauge will only work until throat erosion becomes a factor, then you've gotta use the "real" chamber to get the proper lengths. With some ctgs. like the 6.5 x 284 it's useful life will be very short. I used to have them made with each new chambering until I realized their limited value.
fdshuster,
I've been loading for half a centry and only recently "found" this most useful tool. It has simplefied a frustrating step, for me at least, with a way to be more precise in determining cartridge length. Most shooters I show it to are like me, they never heard of it before and want one.
When I rebarrel or build a new rifle this item will difinently be part of the package.
I've been loading for half a centry and only recently "found" this most useful tool. It has simplefied a frustrating step, for me at least, with a way to be more precise in determining cartridge length. Most shooters I show it to are like me, they never heard of it before and want one.
When I rebarrel or build a new rifle this item will difinently be part of the package.
jefats: Yes, I understand your enthusiasm about this gauge, but you have not addressed the issue of throat erosion. In fact, when starting with a newly cut chamber I've seen seating depths change (grow longer) by as much as .015" with the first 100 rounds fired, so of what value is the gauge when the actual chamber/throat dimension is not the same as the dimension shown by the gauge? You are now comparing apples to oranges, and if continueing to use the gauge, you will be seating your bullets to a progressively shorter length, as the throat "grows" longer, giving you false seating depth information. I've been loading since 1960, so also have a bit of "background".
jefats said:May I suggest while everything is new and fresh, ask the barrel maker to fashion a chamber gauge with the same reamer as was used in making your barrel. This is the handiest tool and takes all the guess work out of bullet seating. No more fumbling with rods, dummy cases etc. in hard to reach places. With such a tool you will know exactly when the ogive touches the lands with each loaded round and from there how much into/off the lands you want your load to be.
This is why I am doing it before the barrel is on the rifle. There are no rods or hard to reach places at the moment. I have done 6 different bullets I plan to use so I have a starting point for each of them. After a few hundred rounds go through this barrel I will take it back off and check them all again. I figure nothing is better than the actual chamber I will be loading for.
Ackman
Gold $$ Contributor
Your method is kind of backasswards but I guess it's one way. What works really well to find the lands is just use a split neck case. The cost of a case and about one minute to make it, that's all. Then to be really high tech use a Davidson ogive checker or whatever it's called - from Sinclair - and don't be even be worrying about cartridge OAL.
One of these gauges should be included with every new chamber. Best when it's from a cutoff piece of the actual barrel. And also best with a pie shaped lengthwise cut so you can see whats' going on in there......then it becomes a "window" gauge. Finding depth to lands is a lot quicker with a split neck case and one of these things than to be chambering it in the gun. Do it initially with every bullet you'll ever use. That's just for the new chamber. After the gun has been shot and the throat has grown, the gauge is still very useful. Very handy for checking how much the throat has grown, also case length growth. And the need for trimming?.......with the window cut you can see exactly the relationship between caseneck length and chamber length. You'd be surprised how much use these things will get.
jefats said:
One of these gauges should be included with every new chamber. Best when it's from a cutoff piece of the actual barrel. And also best with a pie shaped lengthwise cut so you can see whats' going on in there......then it becomes a "window" gauge. Finding depth to lands is a lot quicker with a split neck case and one of these things than to be chambering it in the gun. Do it initially with every bullet you'll ever use. That's just for the new chamber. After the gun has been shot and the throat has grown, the gauge is still very useful. Very handy for checking how much the throat has grown, also case length growth. And the need for trimming?.......with the window cut you can see exactly the relationship between caseneck length and chamber length. You'd be surprised how much use these things will get.
Ackman said:
I am using a fired case that has had the neck expanded, same as splitting the neck with a dremel tool but I don't ruin a case for the job. Mine has a bit more tension on the bullet than a split case but I can feel when it touches the lands instead of hoping it pushes the bullet into the case and not go into the lands at all.
Ackman
Gold $$ Contributor
Samdweezel05 said:
A fired/neck expanded case isn't the same as a split neck. Doesn't work near as well, I've tried it and know. But you seem to have all the answers, so whatever turns your crank. True.....split the neck of a .75 case - to make a tool - and it does "ruin" the case for shooting. Sometimes you just gotta suck it up and accept the expense.
Ackman said:
I never said they were the same. The split neck allows you to push the pullet into the case with out pushing it into the lands as well, or so we hope. My method requires a little math, and I know that can be scary to some people, but the end result is the same with the exception of not messing up a case. I have no issue excepting expense, if I did, I would find another hobby.
As my father would say, "this ain't my first rodeo". I have split necks in the past with mixed results. Do it 20 times and 10 of those times the bullet barely sticks in the lands and you pull out a case with no more bullet in it. Can you say for sure that using a split case is giving you 100% perfect results? Maybe the bullet pulls out .010" wile you are taking out the case. Who knows. Last time I checked, there were about 1000 ways to perform any given task and exactly 0 ways to tell what method was better.
Ackman said:
The same end result, or so we would hope. I never intended to make it sound like they were the same process and for my poor choice of wording, I apologize. There is more then one way to remove the hide from a feline.
ttfreestyle
Silver $$ Contributor
WOW!!
NorCalMikie
Gold $$ Contributor
Phil:
The thing that has me wondering is, you spend $300.00 + for a barrel, not counting the inital cost of the stock and action, and no telling how much you spend for bra$$, powder and bullets and you don't get the tools to get the correct and "repeatable" measurements for seating your bullets.
You buy the tool and get a modified case for each caliber you're shooting, you get accurate measurements, keep notes that you can refer back to as the seating depth gets longer. (and it will!!)
How do you plan to measure the seating depth once the barrel is installed? What happens when you decide to use a longer/shorter or different brand of bullet?
The thing that has me wondering is, you spend $300.00 + for a barrel, not counting the inital cost of the stock and action, and no telling how much you spend for bra$$, powder and bullets and you don't get the tools to get the correct and "repeatable" measurements for seating your bullets.
You buy the tool and get a modified case for each caliber you're shooting, you get accurate measurements, keep notes that you can refer back to as the seating depth gets longer. (and it will!!)
How do you plan to measure the seating depth once the barrel is installed? What happens when you decide to use a longer/shorter or different brand of bullet?
SamD,
"I am not questioning my method or math just wondering if this OAL sounds correct. I didn't have any special throat cut, just a standard .272" 6BR."
Measuring the conventional way i.e., overall length of a loaded round, a 105 Berger VLD just kissing the lands goes 2.733" in my Cooper 6BR. All bullets are checked for the same ogive before loading and seated with a known measurement to the lands using a Sinclair comparator (and chamber gauge
).
Hope this helps.
Your 2.720" OAL is in the ballpark seems to me.
"I am not questioning my method or math just wondering if this OAL sounds correct. I didn't have any special throat cut, just a standard .272" 6BR."
Measuring the conventional way i.e., overall length of a loaded round, a 105 Berger VLD just kissing the lands goes 2.733" in my Cooper 6BR. All bullets are checked for the same ogive before loading and seated with a known measurement to the lands using a Sinclair comparator (and chamber gauge
). Hope this helps.
Your 2.720" OAL is in the ballpark seems to me.
fdshuster
Thanks for info, never new erosion was so great after just 100 rounds, that explains allot of things , such as how a barrel may shoot at one lengh for awhile then all of a sudden it doesnt i recently went through this saw a big difference and correct my seating depth to a longer oal problem solved it just didnt dawn on me til reading your post
Thanks for info, never new erosion was so great after just 100 rounds, that explains allot of things , such as how a barrel may shoot at one lengh for awhile then all of a sudden it doesnt i recently went through this saw a big difference and correct my seating depth to a longer oal problem solved it just didnt dawn on me til reading your post
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