7mm-08, Barnes 139 LRX Load Development

[7mmfan]

Ok, I'm coming to the group to open a can of worms and get 100 different opinions.

I've been doing some thinking of late on my problem child 7mm-08. I was ready to re-barrel it, and I still might end up doing that, but I'm going to give it one more shot based on some hypothesizing that I've done recently.

My rifle has a 22" 1:9.25 twist barrel. I tried for the longest time shooting 120 gr bullets with subpar success. My best load yielded a 1.5" average group. A couple years ago I tested some 140 gr Accubonds and had better success, hovering around 1 MOA. I still felt I could do better.

In the last couple of years I've learned more about ideal twist rates for various bullet weights, and learned that in reality the twist rate applies more to bullet LENGTH than weight. Weight and length are synonymous in most reloading data because its all based on lead core bullets. However, I'm developing loads with monolithics so it took me awhile to make the connection between length and twist rate. From what I understand, many stock 7mm-08's have a factory barrel with a 1:10 twist, ideal for bullets in the 120-140 gr weight range. Mine being at 1:9.25, is closer to a twist rate better suited for 150gr and higher. All of my light bullets fell well under that threshold. The Barnes 139 LRX however has an almost identical length to the 160 gr Accubond. My HOPE is that this longer bullet will perform better based on the twist rate of the barrel.

So, the bullets are on the way, and I'm beginning to sniff out which load I'm going to start with. Per Barnes load data for that bullet, they do not have the powders listed that I have shot in the past (H4895 and H4350). They do have Varget, which I have a small amount of on hand. Big Game seems to have a pretty devout following for this cartridge and bullet size, posts significantly higher velocity than Varget, and luckily is available at Powder Valley right now. Many recipes I've seen online say they use magnum primers with this powder. 

Has anyone on here loaded this particular bullet in 7mm-08, or played with the Big Game/magnum primer loads in this chambering?

[jrebel]

I can't help you that specific bullet, but I do load for 2 7mm-08's and it is a fantastic round.  I also load monolithic bullets and can give you my two cents....you can take it for exactly what it's worth..... !!  Another thing.....I would love a 1:9 or 1:8.5 twist barrel on my 7-08....especially for mono's. 

My current load is a 101grain HH with 44.4grains of varget and that little bugger is going 3150 ish feet per second.  This is in a savage 1-10 twist 20" barrel. 

Point being....I don't think you can over spin most mono's.  I would think your barrel twist would work great with 139grain mono's (lrx bullets) and I would push them hard.  Varget or Big Game Hunter powders should work nicely, though there are a variety of powders with similar burn rates that would also work.  I would also not rule out a lighter weight mono....something int he 100-120 grain weight.   

I may have some 120 grain Hammer Hunters laying around if you want to give them a shot (depending on how the LRX performs).  As for the primers...I would personally stay with LR and not magnum for this cartridge.   Good luck and keep us posted. 

What rifle are you working with??

One last thing....anytime you go from a cup and core to a mono...it is critically important that you start with a super clean barrel that is clear of all copper fowling.  This will guarantee optimal performance.  When I made the switch to mono's in some of my rifles.....some very knowledgeable folks told me the same thing and it has made all the difference in the world.  My first experience with mono's sucked as I didn't know what I was doing....Now I love them.

[7mmfan]

Thanks Jrebel. I'm all over the clean barrel. I learned that lesson as well when I made the switch over in my 7mm Rem Mag. I've been shooting the 145 LRX in that one for a few years now with exceptional performance.

I've tried the 120 gr Barnes TTSX in the 7mm-08, with subpar performance. Maybe with more tinkering I could get it dialed in better, but I shot a lot of variations with basically the same performance across the board.

The rifle is a Remington 700 Mountain Rifle, LSS. They have a good following, but man it's finicky little sucker.

[addicted]

I'll follow this before it gets moved to another section in the forums. I've had success w/ my 7-08 but I don't do monos

[7mmfan]

Whoops, didn't realize I was in classifieds. Please move mods!

[7mmfan]

@jackelope please move to appropriate board. Thanks.

[Taco280AI]

Never tried the 139, but love the 145 in my 1:9 280AI

[Stein]

A shortcut I found is to search for premium commercial loads with the same bullet.  I have a sample size of one caliber, but they all seemed to be box rated at nearly the same velocity.  I bumped my old load up so I was getting an actual chrono velocity that matched the stated box velocities and bingo, group size shrunk as did velocity variations.  I don't know if I missed that in my original workup, didn't have a large enough sample size or what, but a half dozen range trips has confirmed it.

I think a lot of the manufacturers have found velocities that nearly universally shoot well for most hunting bullets.  If you can find some it might be a good place to start.  Of course you likely don't know what powder they are using but the internet is good at showing what powders reloaders favor as known to work well.

[addicted]

A shortcut I found is to search for premium commercial loads with the same bullet.  I have a sample size of one caliber, but they all seemed to be box rated at nearly the same velocity.  I bumped my old load up so I was getting an actual chrono velocity that matched the stated box velocities and bingo, group size shrunk as did velocity variations.  I don't know if I missed that in my original workup, didn't have a large enough sample size or what, but a half dozen range trips has confirmed it.

I think a lot of the manufacturers have found velocities that nearly universally shoot well for most hunting bullets.  If you can find some it might be a good place to start.  Of course you likely don't know what powder they are using but the internet is good at showing what powders reloaders favor as known to work well.

Where is the best location for factory loads?

[Stein]

I just google them up and read what's on the box.  I shoot 168 TSX and all kinds of factory loads are available.  The vast majority are loaded at 2,800 fps and I figure they may know more than I do.

[7mmfan]

That's a good tip Stein. I just looked up a couple. There aren't any factory options that I could find but a couple custom options were on there. They posted lower velocities than I expected.

[addicted]

Any Success?

If you give up you can have benchmark rebarrel it to 7SAW. They are working on one for me going on a Mack Bros Titanium action.

18" Spiral flute #3 contour with a titanium two port brake. The bead blast finish should match the titanium finish pretty good. Gonna be stupid lite.

[Platensek-po]

Thanks Jrebel. I'm all over the clean barrel. I learned that lesson as well when I made the switch over in my 7mm Rem Mag. I've been shooting the 145 LRX in that one for a few years now with exceptional performance.

I've tried the 120 gr Barnes TTSX in the 7mm-08, with subpar performance. Maybe with more tinkering I could get it dialed in better, but I shot a lot of variations with basically the same performance across the board.

The rifle is a Remington 700 Mountain Rifle, LSS. They have a good following, but man it's finicky little sucker.

My sons 7mm-08 does not like the 120gr Barnes much either but shoots the 120 and 130hh really well. I absolutely love the HH and find they shoot well out of all my rifles and the performance on game has been great. Both deer my son has shot dropped right there. Love the low recoil but hard hitting bullets in the lowere weight monos. I would try a lighter bullet, push it fast and give it a jump.

[huntnphool]

 My kids guns both shoot 140 partitions very well. PM if interested in the specific load.

[7mmfan]

I haven't had an opportunity to dig into it yet. I have a good idea of where to start with it, just need some time.