Bullet sitting depth?

[traumatizer]

Hello folks! Here I have a brand new RPR in .338 Lapua and I'm loading for this rifle and caliber for the first time, trying to do my best for long range accuracy.

To maximize the accuracy, I assumed I was supposed to sit the bullet as shallow as the bolt can close, at this moment the whole cartridge length is somewhere 3.9"+ I don't remember exactly. But at this length the whole cartridge can't come out through the ejection port, unless I pull out the bolt, and the cartridge is too long to fit inside a magazine.

To let the cartridge fit inside the magazine and able to be ejected out as a whole cartridge, I need to sit the bullet further down, resulting the whole length to be 3.7625".

I got my reloading recipe from a person who has the same rifle and I'm certain he did put tons of work into developing the load. So with the same bullet, brass, powder and primer, his cartridge overall length was set at 3.7250". Unfortunately there's no way for me to contact this person any more.

So assume the recipe I'm using is the best for this gun(I will develop more loads to compare in future but let's set it aside for now), should I sit the bullet to 3.7625" or 3.7250"? Or toss the magazine and sit for the maximum length 3.9+"?

 

[straightshooter1]

Just because his recipe works in his gun doesn't mean it's going to work in yours. Every chamber, barrel and combination thereof tend to be unique even though the intent was to manufacture them to be the same. But, that load recipe can very well be a good starting point and you can refine it to work well in your gun.

If you want to know more about how seating the bullet long (like close close to or into the lands), you might take some time to understand what's going on by reading the series of articles on bullet jump here:

Reviews & Field Tests - PrecisionRifleBlog.com

These are the independent reviews and in-depth, data-driven field tests conducted by PrecisionRifleBlog.com.

precisionrifleblog.com

 

[traumatizer]

Just because his recipe works in his gun doesn't mean it's going to work in yours. Every chamber, barrel and combination thereof tend to be unique even though the intent was to manufacture them to be the same. But, that load recipe can very well be a good starting point and you can refine it to work well in your gun.

If you want to know more about how seating the bullet long (like close close to or into the lands), you might take some time to understand what's going on by reading the series of articles on bullet jump here:

Reviews & Field Tests - PrecisionRifleBlog.com

These are the independent reviews and in-depth, data-driven field tests conducted by PrecisionRifleBlog.com.

precisionrifleblog.com

Thanks. Yes I'm using the said recipe as a starting point.

These articles are great. I never thought sitting depth is a variable I need to develop for.

 

[Carlos Danger]

Is this the first rifle you're reloading for?

 

[never_summer]

How much reloading experience do you have? A .338 is a big cartridge to make a bad mistake on. Also don’t assume all lots of powder are going to behave the same, might want to work up to said load

 

[traumatizer]

Is this the first rifle you're reloading for?

I did reload some .270 win back 8 years ago. So basically yes.

 

[Carlos Danger]

I did reload some .270 win back 8 years ago. So basically yes.

Ah. Seating depth is not always about touching / jamming the lands. Proper bolt closure, magazine use come into consideration. Some jumps are quite large.

 

[nikonNUT]

I would read this post. TresMon's article is very informative and got my loads on point very quickly!

Hand Loading for Long Range 3: finding start OAL

Chapter 3: "Where’s my rilflings and where should I put them?" So having prepped and primed our brass & sorted our bullets into identical lots now we need to know at what overall length we need to seat the bullet into the case. How do we figure that out? Well there are a few ways to establish a...

www.snipershide.com

P.S As has been said they aren't all the same. I can manage .025" jam and still fit the round in the magazine but my case length measures like .030" longer than SAMMI spec. Point being they are all different and using others data can lead to disaster!

 

[Snuby642]

Are you yanking our chain?

Look here there are over 100 loads that are published.
See if your recipe fits in.

Hodgdon Reloading Data Center – The Brand Thats True

www.hodgdonreloading.com

Get a book, revisit the basics.
That is a lot of power to learn on.

 

[Snuby642]

Fyi your measurement is about .100 longer than anything out of the 100 loads I saw.

But that was just one quick resource my books are accross town.

Please be careful.

 

[traumatizer]

Fyi your measurement is about .100 longer than anything out of the 100 loads I saw.

But that was just one quick resource my books are accross town.

Please be careful.

Right amount of R33 powder takes lots of space, with 300 gr A-tip it's over 3.71" with no more space inside the brass.
And my old book doesn't even have R33 in it.

 

[Snuby642]

I don't do magnums, old and beat up.

Like 80g or more of powder?

A new book? 25$

Also sounds like you have more experience than o p let on. Lol

 

[Snuby642]

Will look and see if Hornady 10th edition lists it.

 

[traumatizer]

I don't do magnums, old and beat up.

Like 80g or more of powder?

A new book? 25$

Also sounds like you have more experience than o p let on. Lol

Alliant's official guide on the R33 with 300 gr bullet is 97.5 gr but listed no powder range. R33 seems to offer higher velocity at higher amount of powder without higher pressure, sounds like it burns slower maybe? Hornady 300gr A-tip bullets have quite thin tip and it's quite long overall, that's why it makes the overall length longer, and if I load it with magazine length the bullet jump to land would be long because the tip is thin. I(and the person who gave me his recipe) chose this bullet for it very high BC at .863 and interesting weight balance design.

I did spend hours and hours adapting from other people's experience across multiple websites, but my own hand-on experience is low. I feel my knowledge is imbalanced, I'm gonna look for a newer book.

It gets really frustrating using newer stuff sometimes, it's harder to find good information about them. Like this scope I bought for my .338 rifle, it has a reticle newly designed for optimistic long range shooting, but even their own ballistic calculator doesn't have this reticle in the choices, it has been at least 5 months ffs.

 

[straightshooter1]

Alliant's official guide on the R33 with 300 gr bullet is 97.5 gr but listed no powder range. R33 seems to offer higher velocity at higher amount of powder without higher pressure, sounds like it burns slower maybe?

R33 is a pretty slow burning powder. See the chart below (#157 on the list):

 

[traumatizer]

R33 is a pretty slow burning powder. See the chart below (#157 on the list):

View attachment 7336732

hahaha my physics checks out.

 

[Josh1978]

I want to make sure I understand the “rules” on seating bullets to different depths. It’s ok to exceed SAAMI specs on C.O.L.? My Lyman load book for 338 Lapua states that maximum C.O.L. is 3.681. If I need to make the C.O.L. 3.700 for accuracy purposes, that’s ok?

 

[spife7980]

I want to make sure I understand the “rules” on seating bullets to different depths. It’s ok to exceed SAAMI specs on C.O.L.? My Lyman load book for 338 Lapua states that maximum C.O.L. is 3.681. If I need to make the C.O.L. 3.700 for accuracy purposes, that’s ok?

Your book doesnt actually know what your chamber or bullet is. Do what the chamber and bullet let you.

 

[Josh1978]

Thank you!

 

[Snuby642]

I want to make sure I understand the “rules” on seating bullets to different depths. It’s ok to exceed SAAMI specs on C.O.L.? My Lyman load book for 338 Lapua states that maximum C.O.L. is 3.681. If I need to make the C.O.L. 3.700 for accuracy purposes, that’s ok?

I think you will find that most cases that is mag lenght agreed apon as a standard.

The throat / freebore I think is a minumum.

A lot of barrels are getting longer throats for the secant ogive longer bullets. I think so they can set the bullets out and get more powder in.

Not sure about the throats.