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.

[Taco280AI]

I haven't followed up with my testing, the birth of twin boys takes a lot of free time away.... or all of it   

[Taco280AI]

With twins it's hard to find the time to do some testing. Finally got out yesterday to verify the AI, and tried BG with the 139 LRX out of the 7-08. Going off a velocity flat spot, 49.1 was easily sub MOA but 49.0 went .495. I might try two more, going down .1gr each time, but happy with what I'm seeing.

[addicted]

Lots of new thinking is that the velocity flat spots will disappear if you run the test enough times.


How fast was it?

[Taco280AI]

Lots of new thinking is that the velocity flat spots will disappear if you run the test enough times.


How fast was it?

It wasn't... apparently Tikka barrels are pretty slow, 2816

[addicted]

Its a relatively stiff bullet. Are you going to shoot far enough to need more speed?

[jrebel]

2816 fps isn't that slow out of a 7-08.  I would think you could squeeze another 100 fps out of it with the right powder.....but wouldn't hesitate to hunt with 2816 if it is accurate.  Barnes says minimum velocity is 1600 fps (Lower than I would trust a Mono), which should make it a 500 ish yard gun. 

Accuracy trumps speed in my books.  Anxiously watching to see how these end up shooting for you.   

[Taco280AI]

Certainly don't need more speed, and I'll try a little less to see how it does accuracy wise. For all I know it might do one ragged hole, but using a fixed 6x I think a half inch @100 is pretty good. And have the 280AI for longer reach.

[addicted]

Barnes says minimum velocity is 1600 fps (Lower than I would trust a Mono),

Ditto, want to see a test of that one.

[jamesjett]

The mono’s like to be seated deep.  Start at .100 off lands and out to .175 off the lands.  I have reloaded Barnes for about 10 years now and had some good conversations with their tech guys.  The suggested I start at .075 off the lands and run them hot.

In my 7MM the 150 TTSX shoots .3 groups @ .090 off the lands and the 145 LRX likes .150…

[yakimanoob]

@7mmfan any update? Can't believe I missed this thread - I'm working on a 139gr CX load for my Savage 16 LWH 7mm-08 and have been closely eyeing the 139gr LRX bullets as potential options.

Just FYI for everyone - Barnes told me very clearly that the 1600 fps for 2x diameter expansion is specific to the 139gr 7mm LRX and does not apply to the LRX line in general or even the rest of the 7mm LRX bullets. Personally, I really appreciated their pointing out that each bullet is different due to the (vast) complexities of terminal ballistics.

[7mmfan]

I have not had time to delve into this yet. Taco's load is very similar to what I was planning on trying, so that gives me a lot of hope. What I know is my gun is very temperamental, so regardless of other's successes, it just might not work. I sure would love to have a confidence building load for that rifle though.