nub question about seating depth

[saidtheblindman]

Hello,

I am completely new to reloading. Relatively new to shooting, too.

I was recently gifted a .303 rifle which has some feeding issues. I only have handheld reloading kit for now, I cannot currently afford a press. I have Campro .311 180 grain for projectiles.

When reloading, I note that the maximum overall length of a .303 cartridge is to be 3.075 inches.

Obviously making them longer than this won't work, but what about slightly shorter? For instance, if I made a cartridge with an overall length of 3.035 or even possibly 3.00 inches would that be a major issue? Or will it blow up?

I did measure factory-produced ammunition from both Winchester and Federal with digital calipers. Winchester actually fluctuated around 3.050 - 3.060, while the Federal ammunition was even shorter. I have not fired the latter from the gun.

How much of an issue would it be if one made a .303 cartridge that fed properly through the rifle but was, say, 3.030 inches rather than 3.075? Is there some sort of acceptable range here?

I am not so concerned about pinpoint accuracy. I'm talking more about the risk of the rifle exploding in my hands. Sorry, I am a total noob.

thx

 

[threecentsolution]

Well it probably won't blow up. However you should start your load work up at the low end because seating deeper will increase pressures.

 

[gyates93]

Buy and read a reputable reloading manual. Follow the recipe exactly. Each will have a minimum overall length. "It probably won't blow up" is not an acceptable answer. This is your life we're talking about and we must speak in absolute terms.

One example from Hodgdon's online reloading data:

 

[coleman1495]

What’s your magazine length?
How long can you load your rounds and have them fit?

Yes too short will cause increased pressure, so will jamming the bullets into the lands.

I’d start by loading shorter than the magazine, then checking if you are jamming the bullet in the lands. I think folks generally want to be.020-.050” from the lands.

 

[stubblejumper]

Well it probably won't blow up. However you should start your load work up at the low end because seating deeper will increase pressures.

In some cases yes, in some cases no. If you are seating on or near the lands, seating slightly deeper will actually result in less pressure.

https://www.shootingsoftware.com/pressure.htm

Scroll half way down the page to the 6PPC data, and see for yourself.

 

[84fuegoturbo]

Lee enfield magazine can be adjusted for feeding issues, bending the lips might help without playing with seating depth.

 

[Dogleg]

Beginners should start with starting loads, and likely stay there for awhile. The great thing about starting loads its hard to do anything so wrong that you’ll hurt anything. Thats sort of the point.

 

[Ganderite]

In a rifle, the seating depth has very little to do with pressure. In my experience, the only time I have seen a change of pressure related to seating depth is when I increased the length and the bullet touched the rifling.

Assuming you have started with the START load (this is important). Pressures vary dramatically between rifles. I have seen a START load (in a 6.5x55) that was way over Max for a particular rifle.

You have to find the correct OAL for your rifle. I ignore the value in the book. It does not relate to MY rifle. The first thing to note is that the round has to fit the mag. Make 3 dummy rounds, (no primer or powder) and seat the bullet about 25 thou shorter than mag length. Chamber the round. If the bullet does not touch the rifling, note this OAL in you log book as the MAX OAL for that bullet in that rifle.

Load all 3 rounds in the mag and see if they feed well.

If they don't, seat the bullets 50 thou deeper and try again.

Repeat until you find the OAL that feeds smoothly and note that in the log book.

In the case of a Lee Enfield, the stamped steel mag lips might need tweaking. That is, the feed issue could be a mag issue, not an OAL issue.

Now you can go shooting and develop a load.

 

[Joe Amorosi]

I have loaded the same 180gr Campro bullet behind 40gr of IMR 4895 or 38gr of IMR 3031 with an OAL of 2.955. This load functions/cycles flawlessly in both my No.1 and No.4. This gets the neck into the cannelure of the bullet. Don't forget to give 'er a nice crimp.

 

[Lead hammer]

In a rifle, the seating depth has very little to do with pressure. In my experience, the only time I have seen a change of pressure related to seating depth is when I increased the length and the bullet touched the rifling.

Assuming you have started with the START load (this is important). Pressures vary dramatically between rifles. I have seen a START load (in a 6.5x55) that was way over Max for a particular rifle.

You have to find the correct OAL for your rifle. I ignore the value in the book. It does not relate to MY rifle. The first thing to note is that the round has to fit the mag. Make 3 dummy rounds, (no primer or powder) and seat the bullet about 25 thou shorter than mag length. Chamber the round. If the bullet does not touch the rifling, note this OAL in you log book as the MAX OAL for that bullet in that rifle.

Load all 3 rounds in the mag and see if they feed well.

If they don't, seat the bullets 50 thou deeper and try again.

Repeat until you find the OAL that feeds smoothly and note that in the log book.

In the case of a Lee Enfield, the stamped steel mag lips might need tweaking. That is, the feed issue could be a mag issue, not an OAL issue.

Now you can go shooting and develop a load.

You know way, way more than I, however in my 6.5 Creedmoor, I have had a load near the top shoot ok, then during a seating depth test, 0.003" deeper per test load. Once I got 5 tests in, found pressure, so its possible to get pressure from change in depth.

 

[John Y Cannuck]

Seating depth affects pressure, however, for most applications, or at least the ones I've used personally, it's really hard to see it.
Take for example the 30-30. It's common for the bullets in that round to be pushed right back into the case by the spring pressure of the tube magazine, coupled with recoil. Yet I've never seen even one instance where this resulted in anything happening other than a regular discharge when fired.
IMO the seating depth changes you are mentioning in you OP will result in differences too small to measure.
That said it's always best to back off a bit and work back up when making any change.
One more thing, please post the rifle you are using. Folks here are assuming it's a Lee Enfield of some description. But the 303Br is chambered and has been chambered in a hell of a lot of rifles.