308 Bolt action, obtaining bullet seating depth without specific tools

[EROCO]

I wanted to determine the proper seating depth for my hand loaded 308 round using this method:

1. Using a new and unfired empty case, I did a full size resize.
2. I seated a bullet just enough to square the bullet into the case I will be using.
3. I chambered this dummy round into the rifle slowly and closed the action.
4. I then slowly ejected the round into my hand and took a measurement of the COAL.
5. I did this procedure twice and got the same result using two different bullets/cases.

The loading manual says max COAL for a 308 WIN is 2.810. My measurement is 2.868.

Question, should I seat this bullet to a COAL of 2.848 using my caliper?

I also did this for my 223 bolt action and the disparity between factory spec and actual measurement was even greater.

Factory spec for 223 is COAL = 2.260, my measurement from my rifle = 2.406.
Should I seat this 223 to 2.386?

Is this method safe?

Thanks.

Please see pics below.

308 Factory vs. 308 Chambered from my rifle

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223 Factory vs. 223 Chambered from my rifle

[HKROB]

I did the same thing on my 300wm except I seated the bullet an extra .010 from the lands. Not sure if this is the right or wrong but it worked for me.

[G-forceJunkie]

Are you going to single load, or do they have to fit in a magazine? Whats the max length for you magazines?

[EROCO]

Are you going to single load, or do they have to fit in a magazine? Whats the max length for you magazines?

There appears to be plenty of room in the magazine for both rifles.

[killshot44]

As long as your sure of your measurement.....I used that method in the past but found the weak "link" there is the extraction of the round without disturbing the bullet's location. (just because you got the same measurement twice, doesn't mean it's the right measurement) I finally got a Hornday OAL guage and did it right.

That said, no problem seating to the lands (some load into them) or reducing the jump. You should reduce your load at first if you're truly into the lands to avoid pressure problems, otherwise just watch for pressure signs.

You'll need to experiment with various depths, I used .010" increments, and with different projectiles. Some like a little jump, others won't tolerate jump at all.

[EROCO]

As long as your sure of your measurement.....I used that method in the past but found the weak "link" there is the extraction of the round without disturbing the bullet's location. (just because you got the same measurement twice, doesn't mean it's the right measurement) I finally got a Hornday OAL guage and did it right.

That said, no problem seating to the lands (some load into them) or reducing the jump. You should reduce your load at first if you're truly into the lands to avoid pressure problems, otherwise just watch for pressure signs.

You'll need to experiment with various depths, I used .010" increments, and with different projectiles. Some like a little jump, others won't tolerate jump at all.

Good point. To elaborate a bit more on how careful I was, not only was I very slow in the extraction I also seated the bullet into the case using the seating die after it was fully resized so there was quite a bit of neck tension holding the bullet in the neck.

[RobG]

Your method is fine generally. A gauge, I like and use the Sinclair, will give better results. The oal of your rounds will be determined by trying different oal's to see what works best for your particular combo. The coal is not going to be exactly the same as the chamber of a given rifle. There is usually excess freebore to accomodate a variety of rounds that are available. Some bullets like to "jump" and some like to be touching or even "jammed" into the lands. Its all about experimenting with your rifle and load combos.

[problemchild]

If your going for accuracy there is a whole lot more to it. Some rifles like jump and some dont. Some rifles like light and some like heavy bullets. Some like slow bullets and some like fast. There are about 100 different variations. Ask someone who has your gun and that reloads what shoots best.

[EROCO]

If your going for accuracy there is a whole lot more to it. Some rifles like jump and some dont. Some rifles like light and some like heavy bullets. Some like slow bullets and some like fast. There are about 100 different variations. Ask someone who has your gun and that reloads what shoots best.

I thought I heard somewhere that it is conventional wisdom to have the bullet as close to the rifling as possible to minimize the time/distance that the bullet is unsupported after leaving the case neck..

But yes, I am going for accuracy. If I were to find someone running the same rifle, bullet, brass, etc. would it really help since their tolerances might be a little different since mine might have been assembled on a Thursday and his on a Monday? lol

[RobG]

I thought I heard somewhere that it is conventional wisdom to have the bullet as close to the rifling as possible to minimize the time/distance that the bullet is unsupported after leaving the case neck..

But yes, I am going for accuracy. If I were to find someone running the same rifle, bullet, brass, etc. would it really help since their tolerances might be a little different since mine might have been assembled on a Thursday and his on a Monday? lol

Again you are working with generalities. Some like a jump and some don't. Load say 5 rounds at the factory oal then 5 rounds .010 longer and so on until you are just touching the lands and see what works for your rifle. There are a ton of good load combos on Snipershide to pour through for some reference...

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=323517&nt=9&page=1

[bjl333]

Do this test. Using the cartridge you showed in the picture. Use a permanent marker to mark the the bullet (perfer a dummy round), put this cartridge slowly into the chamber. Close the bolt very slowly. You will see how much for the marker has been removed. Using your seating die, seat the bullet .001" deeper and repeat. Ideally you should only see very light rub mark on the marked bullet. This way you won't have the bullet jammed up against the rifling, yet you've just eliminated the jump to the rifling.

Make sense?

[EROCO]

Again you are working with generalities. Some like a jump and some don't. Load say 5 rounds at the factory oal then 5 rounds .010 longer and so on until you are just touching the lands and see what works for your rifle. There are a ton of good load combos on Snipershide to pour through for some reference...

http://www.snipershide.com/forum/ubb...17&nt=9&page=1

Okay. Thanks, I'll try a couple of different measurements and which ever one gets the better grouping is the setup Im gonna go with.

From what I hear though it seems I can get it to within .010 and still be safe..

I think I'll bring some with factory COAL, some at .020, and call it a day..

[huckberry668]

I'd say your method isn't a very good or safe one. When you chamber the dummy the rifling is pushing the bullet into the case but they're also cutting into the bullet due to neck tension. You are effectively 'jamming' the bullet into the lands and not 'touching' as you would want. Also, every bullet has a slightly different datum line. This is a cause for higher pressure of unknown amount and it isn't safe.

When it comes to safety, it's not worth saving a few bucks. At least get a set of bullet comparators. http://www.midwayusa.com/viewProduct...tNumber=231904

Make yourself a modified case by cutting a vertical slot from the mouth of the case to the shoulder of a resized case. this way the bullet will just 'touch' the rifling for more precised measurement of the zero jump seating depth. You find different measurements compared to yours and yours should be a few thousands longer.