Seating depth question

[DTF370]

I am in load development for my 338LM RPR.

Measuring to the Ogive I measure base to Ogive at 3.023. My magazine will allow OAL lengths up to 3.760 or so. Recommended COL in my manuals call for around 3.650 or so. If I load at standard length, I am jumping approximately 0.220 depending on the bullet. At max mag length I can jump from 0.080-0.030 depending on the bullet but I am seated pretty far out.

Here is my question. If you were in load development, would you load as close to the lands as you could get to reduce the length of jump? Or would you load at standard length, conduct load development to find a good load with low SD then start working your way closer to the lands?

Thanks in advance guys.

 

[Aftermath]

I start out load development by seating the bullets to just barely touch the lands. I then adjust powder charge seeking the accuracy node, 5 round groups. Once I have the powder charge "good", I check velocity and then start backing the bullet away from the lands 1/1000" at a time in 10 round groups and when I find that accuracy spot, I again check the velocity. I often adjust the powder charge again but about 95% of the time, the original charge proves to be the best.

Also, I have found that 200 or so rounds down the barrel often makes a huge difference so I just shoot and clean, shoot and clean for about 200 rounds using factory spec ammo before I start finding the most accurate load for THAT rifle.

 

[Supersubes]

I can’t remember a single instance where I loaded to book length. I always measure for a “touching” dimension, then adjust as necessary for mag fit or desired jump. I usually start at .020 jump or as close as possible if I have a magazine constraint.

 

[DTF370]

In my rifle, I don’t see myself being able to touch the lands and till have significant contact between the the bullet and the neck. So maybe load at max magazine length and forget it ?

 

[MikeMcCasland]

I can’t remember a single instance where I loaded to book length. I always measure for a “touching” dimension, then adjust as necessary for mag fit or desired jump. I usually start at .020 jump or as close as possible if I have a magazine constraint.

This.

 

[MtnCreek]

In my rifle, I don’t see myself being able to touch the lands and till have significant contact between the the bullet and the neck. So maybe load at max magazine length and forget it ?

Make sure all 5 rds fit the mag and leave a little room for bullet variations.

 

[Howland]

I just crossed this bridge with the same rifle and cartridge.

Loaded to max mag length left me with .080 jump. If I were willing to single feed I'd have run seating depth testing all the way to the lands but because I choose to feed from the magazine exclusively, I took that as my limit.

Forget book OAL. SAAMI chamber and cartridge specifications are so rifle and ammo manufacturers are on the same page and all SAAMI ammo will chamber and safely fire in any SAAMI chamber. If your mag, chamber and throat has room it is safe to load longer. It will increase case volume and might take a bit more powder to get the same velocity.

In another rifle I have started at the lands and tested out to longer jump, finding .010 best. In the RPR I found .080, .090 & .100 jump had very similar group sizes but those opened up as I went further out. I chose the middle road of .090. I am using the 285 gr. ELD-M which has a reputation for being forgiving of jump. Not all bullets and rifles are so.

Bottom line is I don't know what less jump with single feeding would get me because I want to feed from the magazine and .5 - .7 MOA is acceptable. For all I know, less jump could be bugholes.

 

[918v]

I start out load development by seating the bullets to just barely touch the lands. I then adjust powder charge seeking the accuracy node, 5 round groups. Once I have the powder charge "good", I check velocity and then start backing the bullet away from the lands 1/1000" at a time in 10 round groups and when I find that accuracy spot, I again check the velocity. I often adjust the powder charge again but about 95% of the time, the original charge proves to be the best.

Also, I have found that 200 or so rounds down the barrel often makes a huge difference so I just shoot and clean, shoot and clean for about 200 rounds using factory spec ammo before I start finding the most accurate load for THAT rifle.

That’s a great way to wear out a barrel.

 

[918v]

In my rifle, I don’t see myself being able to touch the lands and till have significant contact between the the bullet and the neck. So maybe load at max magazine length and forget it ?

Yes.

There are multiple sweet spots available.

 

[Alabusa]

Start load development with the bullet touching. Find the node. Adjust seating depth to fine tune. That's how I do it anyway.

 

[DTF370]

I just crossed this bridge with the same rifle and cartridge.

Loaded to max mag length left me with .080 jump. If I were willing to single feed I'd have run seating depth testing all the way to the lands but because I choose to feed from the magazine exclusively, I took that as my limit.

Forget book OAL. SAAMI chamber and cartridge specifications are so rifle and ammo manufacturers are on the same page and all SAAMI ammo will chamber and safely fire in any SAAMI chamber. If your mag, chamber and throat has room it is safe to load longer. It will increase case volume and might take a bit more powder to get the same velocity.

In another rifle I have started at the lands and tested out to longer jump, finding .010 best. In the RPR I found .080, .090 & .100 jump had very similar group sizes but those opened up as I went further out. I chose the middle road of .090. I am using the 285 gr. ELD-M which has a reputation for being forgiving of jump. Not all bullets and rifles are so.

Bottom line is I don't know what less jump with single feeding would get me because I want to feed from the magazine and .5 - .7 MOA is acceptable. For all I know, less jump could be bugholes.

Thank you sir. I think I’ll do the same. I was really hoping to get a bit under .5 moa but your right, with a factory rifle I should probably be happy with .5 or a hair over. I have some 285 BTHP already, I may try them. I like the ELD-m and I’ve read good reports on hunting performance over the ELD-x.

I defiantly need to confirm that my rifle will like H1000 before it come available again. I have a stinking suspicion it won’t be available for very long.

 

[Aftermath]

That’s a great way to wear out a barrel.

I like to wear out the factory barrels so I can justify buying a Kreiger or Brux or...I've learned that those custom barrels usually don't need any sort of breaking in, just find that sweet spot combo of powder charge/seating depth and commence to wearing out that new Kreiger.