Difference between book COL and distance to lands

V

VARidgerunnr

New member
This is my first post on the board, but I've been gleaning info for some time as I'm starting to reload. I must say thanks because I've learned alot just hanging around.

Currently, I'm looking to reload my Savage 270 with 130 grain Nosler Accubonds. I don't have a Nosler manual, so wasn't exactly sure of the recommended COL for the loaded round. I know in my Speer and Hornady manuals all rounds are listed at less than 3.34, the maximum COL.

I thought it would be interesting to measure the length to the lands using a cleaning rod and some stop collars. I measured it at approximately 3.475 and was surprised at the difference between recommended maximum COL and my measurement. I seated a bullet at slightly less than that length and the bolt closes easily with no notable marks on the bullet.

I have three questions. (1) Is it normal for the distance to lands to be that much further that book maximums? (2) Would this suggest that the headspace on the rifle isn't set properly? (3) How deep would you seat the bullet?

I appreciate any insight you might have for a guy getting started.
 
First off, welcome to PM. This is a GREAT place to hang out and ask questions as you have done.
I don't know the exact answer to your first question as someone more versed with COL's and distance to the lands from a SAAMI point of view should respond to that one. I see no relationship between the two.
Second,the headspace of the rifle is not related to COL or distance to the lands.
I seat bullets based on the magazine length dictating seating depth, and if the magazine will allow, I set bullets .010 off the lands. I want my loaded ammo to feed thru the magazine, so that dictatetes how deep I can seat bullets. The .010 distance is based on my own personal experience in getting the best accuracy for rifles.
 
Thanks for the kind works and your help.

I did speak with Mike at Nosler and he was very helpful and understanding. He suggested that many 270 rifles have a long throat and that the seemingly large variance between the manual's max OAL and the OAL I measured was no surprise.

As you had suggested, I was planning to drop 0.010 to 0.015 from the lands - with that long Savage magazine I have room to grow and can fit the longer load. However, I was concerned with such a large discrepancy from a safety standpoint. My wife and kids would probably frown on blowing up the rifle and getting injured!
 
VARR:

Welcome to the Forum. You've gotten some good advice and you're headed in the right direction. Generally speaking you won't get yourself in trouble with COL. The one exception I might mention is that seating a bullet at the lands or into the lands may result in higher pressure than you would see if the bullet has a little jump or "freebore" so...be careful if you load to maximum then start experimenting with longer COL. You could see a spike in pressure once you begin contacting the lands. Unless you're really pushing the envelope, you probably won't "blow up" your rifle but be careful. I haven't experimented extensively but in general I've also found my best accuracy at .01 to .02 off the lands. Your fortunate to have a rifle/cartridge that will allow you to do that. But each rifle has its individual likes/dislikes. YMMV

Good luck.
 
I shoot that bullet in a Ruger and a Rem 700, they both love 58-58.5g of R 22 with a Fed 210 in a Win case, seated to touch the lands.

Groups with both rifles are 1/2-5/8 inch at 100 and 1 1/2 at 200 yards.

All 270's that I have worked with, shot exceptional groups with the bullets just touching the lands with the 130g Noslers, Sierra's, and Hornady flat base.
 
The answer to number 1 is yes. It is quite common for a chamber to have extra free bore on modern guns, and free bore is the area of the barrel that has been reamed out up to the rifling that creates bullet jump. Modern rifle makers add in extra free bore because it helps to reduce pressures and lawyers like anything that reduces pressures. Sammi specs are voluntary guidelines for ammo makers and gun makers. It helps all of us by standardizing ammo so it will work in everyone’s mag well and fit the chambers on our rifles.

#2. Like Martin4208 said overall length has noting to do with headspace. Headspace is measured from a datum point on the shoulder to the bolt face. Here is a fairly good description on wikipedia:
http://en.wikipedia.org/wiki/Headspace_(firearms) As you can see, head space has nothing to do with OAL.

#3. If the mag well permits, I would start off with the bullet .020 off the lands which is 3.455 on you gun. Once I found an accurate powder charge, I would make some more loads from zero to .050 off the lands say in .10 increments. However, I wouldn't go below .010 on an autoloader. I like to allow plenty of room for the round to chamber on autos. As long as one makes accurate measurements, it would not be unsafe to start at .010 off the lands.

COL is something I really don't have an exact definition of. To me it can have two meanings: cartridge overall length and comparator overall length. I use OAL in my notes when I'm using overall length and I use COL when I'm using my comparator.

Here is a link to hornandy's comparator: http://www.cabelas.com/p-0044517.shtml

I take a bullet and use the same method as you to obtain the maximum OAL for a given bullet in a given barrel/gun. This is my zero jump OAL dimension. I then seat that bullet in an unprimed case with no powder too. I then measure the OAL of this dummy round, and I then add or subtract to find the difference between these two OAL differences. I then measure the COL of the dummy with the comparator. I then add or subtract the OAL difference to the COL to obtain my zero jump dimension for using the comparator. This becomes my zero COL. The reason for this is you get better consistency because bullet orgives vary a little. By measuring near the bullet's bearing surface you take some of that error out. Thus, my loading notes have both OAL and COL written in them. With that said, I simply used the same exact method as you for many years.

I hope this helps and doesn't confuse you.
 
Get the Hornady's tool as the AZnative gave you the link to, and you wont be sorry.
When I start on a new box of bullets I will check the new rounds with the Comparator and adjust the seating die accordingly. I just opened a new box of Nozler 150 Gr Ballistic tip bullets and had to seat the bullets from the new box about .004" deeper to maintain the correct distance from the rifling of .010 of an inch. Goes to show you there can be a difference from one box of bullets to another for where the Ogive is.
DAB
 
I'm certainly grateful for everyone's help, both in this thread and in the others I've read. I held off posting until I was able to shoot today.

I loaded the 270 to 3.34 OAL to find a powder load from which to vary seating depth. I ran from 47 grains to 54 grains of RL17 behind a 130 Accubond in 0.5 gr increments, but stopped shooting around 53 grains because I felt that I was seeing some flat primers. My best accuracy was around 49-50 gr anyway as I had groups there of 0.73 and 0.68 for 5 shots at 100 yards. Thats good enough, but I cant help but tinker from there (I suspect that anyone who reloads can appreciate that thought). I'll certainly start moving toward the lands and as you've already recommended and I suspect I'll find even better accuracy there.

I also loaded a series of 69 gr Matchkings for my Rock River Predator Pursuit. I loaded from 24.0 grains to 25.6 grains of RL15 in 0.2 increments and my rifle seems to like 24.7 grains as I shot 0.89 inches for 5 shots at 24.6 grains and 0.54 for 5 shots at 24.8 grains. That matches some results I've read for that bullet and powder.

Now there were certainly some groups with each rifle outside of of these ranges where the 5 shot groups were 1-2 inches. The best groups I've mentioned were honest-to-goodness 5 shot groups and are probably the best I could have shot today. I'm often amazed by some folks internet accuracy and wonder if they shoot for money to profit from their shooting prowess!

I have to say that I feel like I've been climbing a mountain in my shooting of factory ammo and my starting to reload. I also feel like I'm on top of the crest and see a great, sun covered valley below. I can't wait to see where this adventure will take me. It's definitely time to split some fur with these chunks of lead!!







 
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VAR....purchase some RL22 and 4831...(i prefer Hodgdon's 4831 but thats just my experience)...for those heavier bullets...and we all know you will try'em...it's part of the handload'n addiction.
 
VAridgerunner,
I don't use flattened primers as a pressure guide. You can get flattened primers with just a little head space and average pressure. Headspace is basically linear end play of the case in the chamber. Accoding to the info published in my RCBS precision mic guide, the 270 min dimension from the back of the bolt face to a datum point on the sholder will measure 2.0487 and the max dimension is 2.0587. That is .010 of laterial end play. Cartridge dimensions will max out at the min chamber dimensions so they will still fit, but sammi still has a minumum on cartridge case size too. A reasonable guess would be .006. If you had max chamber and a min cartridge size, you would end up with .016 of linear end play. What happens is when the primer fires the pressure is in the primer pocket and the case moves forward at the instant of primer ignition. The powder ignites creating pressure equally against everything in the case including the primer pocket and the walls of the case against the chamber. Before the case can move backwards against the bolt face the thin brass of the primer pocket will swell outwards. When the case finally pushes back against the bolt face it will flatten the primer. On a bolt gun, I simple look at how hard the bolt is to turn and watch for other signs like primer rupture and loose primer pockets after just a few reloadings of the brass. I've had instances where I've had flattened primer with min loads. The rcbs precision mic is a great tool IMHO. If you get one, get the 30/06 because it will also work on 280 rem, 270, 25/06. Here is the link:

Cabellas
http://www.cabelas.com/cabelas/en/templates/links/link.jsp;jsessionid=
ALLTLNNUGFB2JLAQBBKCCO3MCAEFKIWE?id=0012726210537a&type=product&cmCat=
froogle&cm_ven=data_feed&cm_cat=
froogle&cm_pla=1230101&cm_ite=0012726210537a&_requestid=111401

midway
http://www.midwayusa.com/viewproduct/?pr...m_campaign=9315

It also has a CAL gauge, but I don't trust in on autoloaders. I'm too worried that I won't get accurate readings on autos because you gotta let the bolt slam shut. I use your system coupled with the hornandy comparator.
 
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