7-08 shooting faster than it should?

[Crazymonkey]

I was out this weekend and finally got to Cronograph my 7-08 and its shooting above barnes velocity .Here are the gun and load specs.

Custom 7-08 brux #5 26inch barrel work by Phoenix custom rifles.

Lapua brass trimmed to spec

140 gr ttsx barnes

45.6 gr r17 middle of the recommended charge weight per barnes

Federal mag primer

Coal is 2.755

2.165 to the olgive

Bullet seated .05 from the lands as checked with a Hornady gauge.

Labradar has me at 3026 low and 3042 high .

I'm not getting any pressure signs but barnes has 47.8 gr r17 as a high and 2910 for velocity.I'm no where near max but above the speed .The gun groups outstanding if I do my part but that seems way fast given the charge weight.Anything to worry about or run it up the ladder and see what it gives me for max?Accuracy always trumps speed but this seems fast .

[452b264]

How many rounds does the barrel have through it? 

It has a 26 inch barrel and I will guess Barnes used a 24 inch barrel. The Brux barrel has cut rifling so it will speed up after it breaks in, so you may gain 65 to 100 fps over whats in the book plus 20 to 40 fps per/inch of barrel.

[PRDATR]

Why are you using Magnum Primers?

[lancetkenyon]

1.  Brux.  I have found Brux are usually fast.  But Barnes did use a Bartlein, so this is a variable.  

2.  26".  Test barrel per Barnes is a 24".  That is anywhere from 50-60fps+ alone.

3.  Fed 215.  Mag primers are hotter.  Barnes used Fed 210 LR primers.  This could be 10-20fps more with the mags.

4.  Brass.  Barnes used Rem brass.  You are using Lapua.  Without knowing the actual case capacity, I bet the Lapua have less than Rem, meaning you are creating more pressure.

5.  Powder lot.  You could easily have a hotter lot.

You have too many differences in components and rifle build to compare and think you would get the same results.

 

 

[Crazymonkey]

6 hours ago, PRDATR said:

Why are you using Magnum Primers?

Before the primer shortage I was only loading pistol and 223 and magnum stuff and would pickup a sleeve or two of large rifle primers for my muzzleloader and didn't have any to run .Now I try and keep a brick of each around .My dad being a old school metallic shooter said they were safe to run if you start slow and work up slowly.Not having a chronograph to use for load development I started slowly and found this groups .I'm assuming its the first accuracy node and I stopped there .The accuracy is good the speed is outstanding I've got a hunt in a few weeks but will test more and see what the gun likes.

[L Cazador]

Before you do anymore testing measure head diameter and check for expansion. Anymore than .0008" over new brass is too hot. If you're under that measurement then you should be able to go up in .5 grain increments till you see that head expansion over .0008". What you think is .005" off the lands may be well into the lands. I wouldn't trust that measurement. If you're into the lands, that could drive pressure significantly. By the way did Phoenix Rifles make a barrel stub for you for measuring headspace and seating depth. Also did they give you a blueprint of the reamer specs they used on your rifle. It may not be too late to ask for this. 

[Crazymonkey]

2 hours ago, L Cazador said:

Before you do anymore testing measure head diameter and check for expansion. Anymore than .0008" over new brass is too hot. If you're under that measurement then you should be able to go up in .5 grain increments till you see that head expansion over .0008". What you think is .005" off the lands may be well into the lands. I wouldn't trust that measurement. If you're into the lands, that could drive pressure significantly. By the way did Phoenix Rifles make a barrel stub for you for measuring headspace and seating depth. Also did they give you a blueprint of the reamer specs they used on your rifle. It may not be too late to ask for this. 

Outa ten cases I got a avarage of .0003 expansion.I'm set .05 from the lands .I didn't get a stub but I can call Keith and get reamer specs.I'm probably worried about nothing.It was definitely a surprise at how fast it was running.I didn't have a Cronograph to start loads and went old school and just started low and worked for good groups.The first time I Cronographed was Saturday when I was checking out stocks and scopes with Lance .I figured I'd be 2800 to 2900 with a mid range powder charge and was surprised.I've got a hunt in a few weeks but when I'm back ill probably do some more testing with a chronograph this time.

[lancetkenyon]

1 hour ago, Crazymonkey said:

Outa ten cases I got a avarage of .0003 expansion.I'm set .05 from the lands .I didn't get a stub but I can call Keith and get reamer specs.I'm probably worried about nothing.It was definitely a surprise at how fast it was running.I didn't have a Cronograph to start loads and went old school and just started low and worked for good groups.The first time I Cronographed was Saturday when I was checking out stocks and scopes with Lance .I figured I'd be 2800 to 2900 with a mid range powder charge and was surprised.I've got a hunt in a few weeks but when I'm back ill probably do some more testing with a chronograph this time.

The first shot was 3030, and I thought, "dang, the old 7-08 just gained a bit of respect from me."

Then I saw 3034, 3030, 3028 (I think) and was impressed.

[Crazymonkey]

Yep it ran from 3026 to 3042 and was a big surprise.Me being new to most of this it had me thinking I was pushing it to hard .But everything checks out ok .The primers are good and the brass is not stretched at the head .I do need a front rest like yours and a rear bag for sure .So I can take out as much human error out of my group size while I'm testing. Thanks again for letting me check out your stock and scope its definitely the direction I want to go with my 280 ai build.

[lancetkenyon]

3 hours ago, Crazymonkey said:

Yep it ran from 3026 to 3042 and was a big surprise.Me being new to most of this it had me thinking I was pushing it to hard .But everything checks out ok .The primers are good and the brass is not stretched at the head .I do need a front rest like yours and a rear bag for sure .So I can take out as much human error out of my group size while I'm testing. Thanks again for letting me check out your stock and scope its definitely the direction I want to go with my 280 ai build.

Anytime.  I have plenty of other scopes and stocks if you want to check them out.

[cjl2010]

1 hour ago, lancetkenyon said:

Anytime.  I have plenty of other scopes and stocks if you want to check them out.

My parents warned me about people like you!!!

[L Cazador]

Why build a 280AI when you have a 7/08 shooting like that. 👍!

[trphyhntr]

Thought this was a .270 call out thread 

[Crazymonkey]

2 hours ago, L Cazador said:

Why build a 280AI when you have a 7/08 shooting like that. 👍!

I had the perfect 280ai build in my head till that moment where I went Damm that's fast with the 7/08 .It might still have more in it also .Will need more testing to tell.The 280 was to be a light weight in between caliber not a magnum but not a slouch.I don't have the twist to push a heavier bullet with the 7-08 and its heavy probably pushing 14 lbs .I'm now in a spot do I build the 280 or something else?I already have a rem 700 long action waiting to go.

[PRDATR]

10 hours ago, Crazymonkey said:

I had the perfect 280ai build in my head till that moment where I went Damm that's fast with the 7/08 .It might still have more in it also .Will need more testing to tell.The 280 was to be a light weight in between caliber not a magnum but not a slouch.I don't have the twist to push a heavier bullet with the 7-08 and its heavy probably pushing 14 lbs .I'm now in a spot do I build the 280 or something else?I already have a rem 700 long action waiting to go.

What twist is it now? I used to run 168's in a 7-08 with the factory 1:9 1/4 and never had any problems out to 500 Meters. Anymore I tend to keep my hunting rifles at 8 pounds.