Seating Depth Question

[lakesidefoxfarm]

I'm new to reloading and I just started prepping my first lot of .22-250 rounds. I purchased the Lee Anniversery Kit along with the Lee Deluxe Die Set. I will be using Varget powder with Nosler 40g and 55g bullets along with Winchester casings. I'm using fireformed cases that have been only neck sized. The gun I'm shooting is a Savage Model 12 BTVS .22-250. My question is how do I determine the proper bullet seating depth to use? Should I just use a factory round to determine this? I would also like to know the distance to the lands but don't know how to do this. Any other advice would be greatly appreciated. Thanks Gary

 

[Guest]

You can check any good load manual, as well as the powder manufacturer's various websites online, where they post nearly all of their data. Or you can use a factory round of the same basic bullet shape and type. Be aware that polymer tipped bullets are going to be longer than lead tipped bullets of the same weight, so COAL (Cartridge Over All Length, also known as COL) will be longer for these than lead tips, to give the same residual case volume under the bullet.

In all honesty, if you start handloading these, just start at the 'spec' seating depth, and then once you find your powder charge, seat out and in a bit to determine what the best depth is. Be careful with this, as you can create abnormally high pressures by seating excessively short, or deep, as case volume shrinks when you do this.

 

[Greg Nolan]

You can check the point where the bullet starts touching the lands by using a fired case and the type of bullet you plan to load. Lubricate the heel end of the bullet so it slides easily in and our of the case mouth gently lube the front part of the bullet that will touch the lands. Place the bullet so it's long sticking out of the case mouth and gently chamber the cartrige in your rifle. Pull back the bolt and hopefully you will see how far in the bullet was pushed. If it looks like the bullet was pulled back out it didn't work. You should try this 4 or 5 times to make sure your getting an accurate reading. Most manuals say you should be 25 or 30 thousanths from the lands. This may be a mute point because the magazine of your rifle may not work with that length bullet. As dubyam stated it's usually best to go with the manual OAL and try a little bit shorter or longer but this way you know your max length. The changes you make in seating depth will be in hundreths of an inch, As in 3.25 vrs. 3.23. That small a change can make a noticable difference in your group size once you start fine tunning. Also if you go longer watch for pressure signs. As said different bullets will be very different so either check every single type or stay real close to SAMMI specs in your manual.
Some rifles and loads are sensitive to OAL and a lot aren't very. Unless your getting unsatisfactory groups for your purpose it may not be worth the effort and you won't be able to safely lend bullets on a hunt if you loaded them long.
Most reloading manuals, like Nosler's, go into pretty good detail on these points.
Good Hunting
elkhunt :grin:

 

[Guest]

Actually, you should watch for pressure signs if you go shorter, due to decreased case volume, and longer, due to higher start pressures due to the bullet being in close proximity or in contact with the lands. I have four rifles, and only one of them has magazine length that will allow me to seat out touching the lands - a Remington 700 in 8x57 (because it is a long action, which accepts up to 63mm case length, I believe). With this rifle, I don't yet have a load that cares so much if the bullet is close to the lands or not. With my other rifles, the magazine length dictates the bullets be seated nowhere near touching the lands.

 

[roysclockgun]

I have a Savage Model 12 in 22-250. Here is how I handload all my bullets. First, take a new or sized case with no primer or propellent and very carefully seat a bullet into the case, just so it holds in the mouth. Meaure the OAL. Coat the part of the bullet that you know will touch the lands, with a fiber tipped pen and load that the cartridge into your chamber. Closing the bolt will cause the bullet to push against the lands and seat it deeper than your starting point. Carefully extract the cartridge and measure the OAL. Make a note that at that OAL the bolt will close, but the bullet is to tight against the lands. You will see clear marks in the ink made from contact with the lands. Again coat the bullet with ink. If the bullet gets distorted by chambering, start with a new bullet. Turn your seating die down a bit and continue to try the cartridge in your chamber until no marks of contact with the lands shows up on the inked bullet. I like to begin by being off the lands about .005". Load five rounds and back off another .005". Try a number of test loads, being at various distances from the lands, until you find your rifles sweet spot.
Even if the rounds are too long to fit the mag, I will use them on varmints if they are grouping best. I just single load them.
You will have to experiment with every bullet change in your rifle. These cartridges will be custom loaded to that rifle only and the box should be so marked. Of course record all the data so that you will not have to go through that process each time you load the same bullet. Occasionally put the ink on a bullet to check to see if you are still not touching the lands.
Many rifles will fit into the mag at the sweet spot length.

 

[Val]

For hunting loads, often the magazine sets the upper limit on how long the bullet OAL (OverAll Length) can be. Unless you are OK with a single shot mode you need to check and see if the magazine will cycle the rounds. I start at the reloading manual called out OAL and find the powder and powder charge that gives me the tightest group. I then reload with the selected powder and the best powder charge and load up some rounds with increasing OAL in .010" increments. I then go with the best grouping OAL after I insure they cycle properly through the magazine.

 

[rbwhotrod]

I am also new to reloading. I Just got my press set up and reloaded my first 10 rounds. The way I got my COL on my 7 mag was to use a fired case and and place a 150grain BT just in the neck. I then gently closed the bolt and then removed the cartrage. I did this about 10 times. I consistently got a COL to the lands of 3.387. I seated the bullet in to a COL of 3.36 so I should be .027 off the lands. If this is an incorrect way to do this any advice would be great as I am new to this.

 

[tjen]

You have two things to determine first what is the max COL your magazine will allow and the best COL for that any only that rifle.
Invest in a comparitor gage that measures form the top of the bullets full bore diameter not the tip its more consistent. Check hornadys web site for these gages and their discriptions on seating depts and pressure (latest manual page 25).

If your max COL is shorter than the magazine than you can find the best COL for that rifle with out being restricted to the max length the magazine will allow.

Find the distance to the lands and reduce that COL by 0.010" . You said you were new to reloading so to be safe .010" gives room for tolerances and error. Benchrest shooters I know are as close as possible to the lands but they are experts and have been reloading for years. Now work up to your max pressure load. Once establihed you can now reload a batch at that COL. Now at the range shoot five of these rounds. Then seat five more 0.005" deeper and shoot them, by the time your reach 0.025 to 0.030 from the lands you should have found the rifles sweet spot.

Use a chronagragh to measure the velocity of all these loads you can see if there is any change in velocity if it is less ok if it goes higher it would been due to higher pressure and stop. I say this because some will argue setting deeper will cause higher pressure. I have only seen lower velocities in any of my setting deeper changes and Hornady states the further from he lands the lesser the pressure and that is my personal experance as well as every benchrest shooter I know. Seting changes will be suttle changes unless you touch the lands and that will be a large pressure spike and can be dangerous so start high and work down is safer.

Sinclair also has comparator gages their simple and work with you caliper.

 

[Guest]

Use a chronagragh to measure the velocity of all these loads you can see if there is any change in velocity if it is less ok if it goes higher it would been due to higher pressure and stop. I say this because some will argue setting deeper will cause higher pressure. I have only seen lower velocities in any of my setting deeper changes and Hornady states the further from he lands the lesser the pressure and that is my personal experance as well as every benchrest shooter I know. Seting changes will be suttle changes unless you touch the lands and that will be a large pressure spike and can be dangerous so start high and work down is safer.

Pressure can spike due to deep seating in small volume cases, but in most large volume cases, it is not a problem. Mostly you see this in pistol cases, where the percent of volume reduction is greater tahn in bottleneck rifle cases. As this forum is generally read by many shooters and handloaders, I always state that both directions can cause pressure spikes. In fact, it is my belief that poor handloading technique leading to deep seating, coupled with insufficient case head support, caused the numerous 40S&W ruptures in Glocks over the years. I handload for a Glock 23 in 40S&W, and am very careful, and have had no problems. But then, my chamber is well supported, as I checked that when I first bought the gun.

As I said, probably not an issue deep-seating a rifle bullet, as the case volume is reduced by only a small, nearly immeasurable amount (generally speaking) but it is good to keep in mind that pressure changes can occur at any time when changing seating depth or other aspects of handloading.

 

[lakesidefoxfarm]

Thanks for all the information. Here's what I end up with for a load.

Fireformed Winchester Casings
CCI BR-2 Primers
Nosler 40g BT Bullet
Varget Powder 34g
OAL of 2.350"
Distance to Lands .159"

Here are two 5 shot groups with this load. These were shot off a bi-pod at 100 yards.

 

[Guest]

By my best guesstimate, that's about a 1.1" group, if I am reading that correctly. Nice work. You might be able to tighten the groups a tad working with charge weight and seating depth, but for a first run, that's good stuff. I bet you can get it under an inch with some work.

 

[SOTN]

I recommend you make sure you are at least .030 off the lands. That should take care of any variables.

Using the OAL shown in a loading manual may not be safe in your rifle.

The Hodgdon Annual Manual shows loads for Nosler 160 grain Partitions in the 7mm RM at 3.290 which was too long for the throat in my Rem. 700 rifle. Had I used that OAL without checking, the bullet would have been pushed back into the case on chambering, which could be a bad thing.

Smitty of the North