Variations in max c.o.a.l.

[nf1e]

Just goofing around this morning and realized we don't discuss max c.o.a.l. and it's relationships for handloaders often enough.
Doing my annual chamber measurements I thought perhaps someone else might be interested in getting a conversation going on the forum.
I think this is important to keep an eye on because throat erosion will cause this measurement to change over time.
This shows the max o.a.l. measurements on a few of my rifles from base of cartridge to bullet tip with ogive contacting lands and how they vary with different bullet shapes.



Semper Fi
Art

[Litt'le Lee]

you know that a lot of us use magazines in our pistols and rifles--which limits this

[nf1e]

you know that a lot of us use magazines in our pistols and rifles--which limits this

Max c.o.a.l. does not care what you are feeding from. It is a measurement that is fixed to the weapon and only changes as throat erosion occurs. This is exactly why I thought a discussion might prove of use to others. We try to find something between min and max coal that works for our individual situation. For instance for the 110 gr Sierra the recommended min coal is 2.500" and the max for my XM21 87 is 2.641. In order for the bullet not to fall out of the case, you would load somewhere between the two measurements. Either of which would not present a problem for the magazine.

[Sunray]

"...to ogive..." Ogives do not apply to OAL. OAL is measured from the pointy bit to the flat bit.
Ogives apply to the off-the-lands length. That's different for every rifle chamber. Even two identical, consecutively numbered, rifles will have chambers that are slightly different and each will prefer a different distance from the lands.
The whole off-the-lands stuff is a load tweaking technique that doesn't make much difference in a hunting rifle, anyway. It's mostly a benchrest technique that's gotten out of hand on the assorted internet forums. Isn't really necessary.
Throat erosion takes a very long time and thousands of rounds. Doesn't apply to hunting rifles either. Does somewhat to target rifles.

[PWC]

"The whole off-the-lands stuff is a load tweaking technique that doesn't make much difference in a hunting rifle, anyway. It's mostly a benchrest technique that's gotten out of hand on the assorted internet forums. Isn't really necessary."

Yessssss! Finally, another's opinion that makes me feel vindicated.

[nf1e]

"...to ogive..." Ogives do not apply to OAL. OAL is measured from the pointy bit to the flat bit.
Ogives apply to the off-the-lands length. That's different for every rifle chamber. Even two identical, consecutively numbered, rifles will have chambers that are slightly different and each will prefer a different distance from the lands.
The whole off-the-lands stuff is a load tweaking technique that doesn't make much difference in a hunting rifle, anyway. It's mostly a benchrest technique that's gotten out of hand on the assorted internet forums. Isn't really necessary.
Throat erosion takes a very long time and thousands of rounds. Doesn't apply to hunting rifles either. Does somewhat to target rifles.

My point in this thread exactly. Listed on the left side of the card are 3 of my XM21 rifles with their serial numbers #2 and #3 being consecutive receivers and builds. The variations are evident.
The max oal posted in my little card is set by a measurement from the base of the cartridge to the ogive and then measured while in the oal guage to the tip of the bullet from the base and will vary with different bullets and rifles. Listed in loading manuals you will see col listed which would be the min col for that particular bullet. Therefore loading would be generally somewhere between the listed col " min" and measured col max for your rifles. Starting in the .020- .040 under max is a relatively safe area.
For anyone really interested in safe and accurate handloading this type of discussion can be invaluable.
Throat erosion is an important factor which indeed , depending on type of bullet used , flat base or boat tail does not take thousands of rounds to change col.
Not many prairie dog hunters using a 22-250 or 22-243 for instance get much more if even 1000 rnds before needing a new barrel.

Art

[nf1e]

Perhaps a better example of what I am trying to get across is that we have handloaders of varying expertise frequenting all sorts of information.
One of the most easily misinterpreted has been the mention of Mexican match and how they were done. " Simple, you just pull out one bullet and stick another in the case". Whoa! That can create a very dangerous situation if not spelled out. Just imagine someone new to the operation that has been loading 110gr plinker ammo and decides he wants to be a mall ninja and substitute a 30 cal. AP in it's place. Pulls the 110 and seats the 30 AP to the same col. leaving the same powder charge. That would shove the bullet .577 inches deeper into the case and raise the pressure curve into " dangerous " territory. Pictured are a 110 gr FB and a 30 cal AP.
Caution is the name of the game.



Semper Fi
Art

[p246]

Yeah I keep track of my long range rifle because I want to keep my jump at one thousands. Being a magnum it erodes fairly quickly to my other non magnums. There are some new hybrid ogives that are supposed to not be as sensitive to seating depth. My next barrel blank'stwist rate was set for Berger 215 Hybrids. I'm running 210 VLD Targets now. I'll be interested to see how the Hybrids work out. How often do you measure. I measure ever 100 rds in this gun.

[nf1e]

Yeah I keep track of my long range rifle because I want to keep my jump at one thousands. Being a magnum it erodes fairly quickly to my other non magnums. There are some new hybrid ogives that are supposed to not be as sensitive to seating depth. My next barrel blank'stwist rate was set for Berger 215 Hybrids. I'm running 210 VLD Targets now. I'll be interested to see how the Hybrids work out. How often do you measure. I measure ever 100 rds in this gun.

What I call my precision rifles, Rem 700 and FN SPR I check annually unless I get ambitious they I might check a bit more ofter. I like the Berger 150 FB since they stopped making my favorite 135 FB. I noticed recently that folks are having good luck with the darn things as much as .150 off the lands so you are right, they are not as sensitive to seating depth as that we were used to. No more real benchrest for me, but I like to squeeze what I can out of my bolt guns. My thing is first rnd accuracy out to only 300.
Berger changes stuff often, it's hard to keep up.
The majority of my shooting these days is with M-14 type rifles in sub min competitions at 100yds. It's all fun. After 50+ years of shooting these guys, this is my favorite current rig.



Semper Fi
Art

[p246]

Very nice set up. I only own one modern bolt gun, blue printed 700 long action in 300 win mag. It's been in a HS precision stock and a Bartlein 24 inch M24 profile Barrel. All me and a couple friends do it shoot at a 24 inch gong at long range. One property we can shoot to 1350 and another but further drive 1800 yards. Once this barrel is burned up I'm going a different route. I have a Manners T4A stock and am going to rebarreled with a Bartlein 30 inch in Whitney Palma profile. The only reason I only own 1 rig like this is they are expensive to run and maintain but I enjoy it.

Berger does jump around a bit I agree. This current gun shot the Hornady ELD Ms good but the VLD Ts a little better. I shoot a lot of SMKs in my milsurps but OAL is a different game in them as we all know.

What spotting scope is that pixels out when I blew it up. I'm running a Bushnell Elite which has been fine. Speaking of changing times one of my shooting buddies has an expensive drone. Last time he hovered 75 feet high and upwind and videoed the hits/misses.