Question on .338 LM bullet seating depth

J

jamesf553

New member
Hey guys. Quick question on bullet seating depth. I'm sure from all my posts you've seen I've begun reloading. I'm trying to take the cautious route on everything I'm doing so I wanted to ask just in case.

I have been shooting 300 grain scenars out of my lapua brass with great success. I purchased a variety of other bullets as well to try and see which I liked best. One of the ones I purchased are the Barnes Tac-TX bullets (265 gn). They are a blue tipped bullet which makes them a little longer then the scenars.

They have what looks like 4 canelures (if they're not canelures i guess just rings around the bullet). I seated the bullets down to the top of the first canelure. Measuring it with my caliper, this puts about .84'' of the bullet into the cartridge.

Using Hodgen's online reloading data center, I loaded them with 80 gn of Retumbo. The only thing I thought was weird was that they indicated a COL of 3.685 on the reloading data which is over what the lyman's guide indicates as the max allowed col (3.681).

Anyways, I seated it to the first canelure so it will fit in my box magazine for my savage. I just want to know if seating the bullet that deep in presents any safety issues for my rifle or body. I read up on the pressure increase when you lower the volume inside the cartridge, but I can hear the powder shaking around still inside so it's not compressed much, and I chose the lower side of the load suggestion. I may just be making a mountain out of a mole hill, but I'd rather just ask first then be sorry later

Any thoughts? I only made 10 and made sure they weren't any longer than the max COL. They are all about overall length 3.675''.

Thanks! Below is a pic of the bullet and a loaded cartridge for reference. Also included is a screenshot of the hodgen website load I looked at.

https://drive.google.com/file/d/1J6KqFTpaO0ZSf8NXTiBIcHe6K0f0tT1t/view?usp=sharing

https://drive.google.com/file/d/17QgTu_6w-uPbUO5Mspeuz1SDjdjjzJVI/view?usp=sharing
 
In short , no .004" isn't going to make any measurable difference as far as pressure in a .338 LM because the internal case volume is so large. Even a .01" won't make any difference.

In something like a .40 S&w or other short pistol cartridges, it will make much more difference because of the lost volume relative to total volume.

The only time in a cartridge that large, where you will get a pressure spike from such a small adjust is if you INCREASE the OAL and it puts you into the lands.

FYI, 80 gr Retumbo is a pretty light. In mine I use the 300 gr smk to around 2880 fps which is about 92 gr Retumbo in my M98B.
 
Mississippi said:
In short , no .004" isn't going to make any measurable difference as far as pressure in a .338 LM because the internal case volume is so large. Even a .01" won't make any difference.

In something like a .40 S&w or other short pistol cartridges, it will make much more difference because of the lost volume relative to total volume.

The only time in a cartridge that large, where you will get a pressure spike from such a small adjust is if you INCREASE the OAL and it puts you into the lands.

FYI, 80 gr Retumbo is a pretty light. In mine I use the 300 gr smk to around 2880 fps which is about 92 gr Retumbo in my M98B.
Click to expand...
Gotcha. Yeah I just picked middle of the road between what hodgens site said. I'll work upwards now that I know it's safe
 
so small update on this. I shot the barnes tac-tx loads today and i gotta be honest I didn't care for them. They grouped ok but the placement was kind of weird.

I zeroed in my scope when shooting 300grain scenars and they are always a bullseye at 100 yds. The barnes grouped about 6'' to the right of the bullseye. Is that common? That different bullets may have a different trajectory? As soon as I went back to the scenars it went back to a bullseye again. I understand that the bullet weight is different but I didn't think it'd make a big difference in horizontal trajectory, just mostly vertical.

Below is a 3shot group of scenars at 200 yds with my 2nd batch of homemade ammo :).

https://drive.google.com/file/d/14x_kd4HyfHkPn7fXabl2Ko0XMzzqPjL5/view?usp=sharing
 
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Some very good reading on seating depth!

Hi all.

I am sharing this article because it helped me so much in developing a very accurate bullet for my Savage 30-06. I was getting large (3"-6") groups with factory ammo and it never really seemed to matter what I tried. I checked my stock for barrel clearance and then tried working up several loads but could not get to MOA. My friend, Richard, told me to play around with seating depth. Being new to reloading, I knew little of it and began combing the web for some good information on where to start.

After finding the article (see link below) I started at .010" off the lands and tried seating the bullet deeper into the case in groups of 3. It turned out that .010" off the lands was my best group. The old guy who was shooting next to me saw all my bullets neatly lined up in groups of three and my note pad and asked if I was working up a load. I told him I was working on seating depth. I fired the first three and all three holes were touching at 100 yds. He says, "looks like you're done". I shot the rest of them and the group got larger as the bullets were seated deeper. I kept my barrel cool and was very consistent in everything I did.

I eventually worked up my charge to a good bit over max load in my old speer manual. It turns out my Savage has a long jump. I can't do this with 165 grain bullets because they are barely in the brass but with the 180 grain SST I can shoot 1/2" groups all day with a cool barrel. My COAL is 3.374". That is .34" longer than SAAMI spec! I will keep my hot load to myself but I did back it off 1 grain and am still at 2750 fps, which is just fine by me! .010" off the lands and a 180 grain SST. The bullet stopped short of exit at the hide after going through a rib on each side my elk. The irony is that it was a 40 yard shot! Could have been 500!

Anyhow, enjoy the read! Here is the link to the article by Bryan Litz from the bergerbullets website:
http://www.bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf
 
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