7mm-08 muzzle velocities

Kelly Timoffee

Kelly Timoffee

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Just wondering if others think this sounds right.

completed my load testing.

here is the specifics on the rifle:
7-08, 26" barrel 1 in 9 twist 5R rifling
the load:
150 grain scirooco II, 42.8 grains of 760 , CCI 200 primer
chrono average on 5 shot group was 2790 Ft/sec

I understand that barrel length has an effect on speed. BUT the re-loading manuals have speeds WAY lower approx @ 2500 ft sec, maybe a touch higher.

Just wondering if this sounded right to others.

FYI - the chrony did seem to register the variations in powder loads consistently also. So doubt it is the unit.
 
"...re-loading manuals have speeds WAY lower..." That's because they reflect data from their test barrels with the components they list on the day of the testing. A different barrel length and/or twist and components will give slightly different numbers. Powder charges in manuals change over time too.
What manual are you using?
"...42.8 grains of 760..." Something is wrong. According to Hodgdon's site, 42.8 is below minimum for a 150. 44.0, at 2640 fps, is the starting load. 46.5, at 2776 fps, is the max Win 760 load. They don't give the barrel length or the twist. Mind you, the 1.2 grains isn't going to cause you any grief.
You shouldn't be getting above current max velocities with a below current minimum load. You may want to pull one or two and check the powder weight though. Or check the calibration on your chronograph. Distance from the muzzle, maybe? Either way, your rifle isn't going to be damaged.
Typical 7mm-08 twist is 1 in 9.25. That .25" isn't a big deal though. The rifle manufacturers all use different twists. For example, Remington uses 1 in 9.25. Savage uses 1 in 11.5. Browning, 1 in 9.5.
 
I had the chronograph at about 16-17 ft , the barrel is a Kriegger , the twist was suggested so that i could use heavier bullets if I want to, maybe have to get a different chronograph to compare, I don't want to have to slow of a bullet either as this will be my hunting load for medium and large game.
 
I use a 154g hornady interlock with reloader 19 in a remington788 with a 18.5" barrel and get 2650fps with it, so your speed seems about right.
 
Hi. I'd be more concerned about accuracy than velocity for any load. Especially with a hunting load. Game doesn't care how fast the bullet that killed it went. Being able to place the shot exactly where you want it is far more important. A 150 at 2640 will kill just as fast as one at 2776.
I'd still pull a few to check the powder charge. Something ain't right. You just shouldn't be getting those velocities with that load. Not unsafe though.
"...the barrel is a Krieger..." Geez, you don't fool around when you build a rifle. You get the #5 or #0 contour? Just curious.
Always wanted to build a rifle in .243/6mmBR/WSM. Life keeps getting in the way. Poverty sucks.
 
I believe I have seen on here that many guys suggest shooting a .22 rimfire over your chrony to check it as the .22 ammo velocity is apparently pretty close to the published data on the box.
 
Kelly Timoffee said:
Just wondering if others think this sounds right.

completed my load testing.

here is the specifics on the rifle:
7-08, 26" barrel 1 in 9 twist 5R rifling
the load:
150 grain scirooco II, 42.8 grains of 760 , CCI 200 primer
chrono average on 5 shot group was 2790 Ft/sec
I understand that barrel length has an effect on speed. BUT the re-loading manuals have speeds WAY lower approx @ 2500 ft sec, maybe a touch higher.

Just wondering if this sounded right to others.

FYI - the chrony did seem to register the variations in powder loads consistently also. So doubt it is the unit.
Click to expand...

How is this possible?:confused:
 
How is this possible
Click to expand...

A 26" barrel will add approx 20-30fps per inch of barrel for say 150fps over a 20" barrel.It may also have a tighter than factory chamber which will result in higher pressure,and therefore higher velocity.I have also found higher end barrels like those by Kreiger to have a smoother finish,and produce more velocity for equal pressure,compared to a factory barrel.
 
Well the above mentioned load , .488" 5 shot group. Accuracy is not my concern.The barrel is a Rem varmint contour.

But like you all said, how is this possible this is my concern., Well, more of a , WTF to me.
I just wanna figure it our for my own peace of mind.

But on the other hand, when i tried my reloads from my previous barrel which was 22" it increased 160ft/sec when I tried the same load in my new barrel.

I'll give you a bargain on it Sunray!!


Maybe there is enough variables that changed to make this possible??
 
Load three new cases with your load,then fire the three cases.Then reload each case and fire them until each case has been fired five times with your load.If after five firings,the primer pockets are still tight,the load is good to go in your rifle.If after five firings,the primers go into the case much more easily than with new cases,back off the powder charge.
 
Ok i am gonna try that , although my test loads were as high as 44.9 grains of powder and a reported average vel of
2855 ft/sec with that charge and no signs of any excess pressure.If you like I can send you the excel spread sheet with all my data for this load development if it interests you. My test charges went from 41.3 to 44.9 grains at .3 grain increments
 
stubblejumper said:
A 26" barrel will add approx 20-30fps per inch of barrel for say 150fps over a 20" barrel.It may also have a tighter than factory chamber which will result in higher pressure,and therefore higher velocity.I have also found higher end barrels like those by Kreiger to have a smoother finish,and produce more velocity for equal pressure,compared to a factory barrel.
Click to expand...

I still don't get how this well below "minimum" starting charge results in a higher velocity than the what is stated for the "maximum" charge for the load...

That's more than just barrel length difference,...that is some serious difference...
 
I still don't get how this well below "minimum" starting charge results in a higher velocity than the what is stated for the "maximum" charge for the load...

That's more than just barrel length difference,...that is some serious difference...
Click to expand...

As posted,barrel length explains part of the difference,and a Kreiger barrel and a tight chamber could easily add another 100fps.All of the rifles of mine that exceeded the loading manual listed velocities,wore high quality aftermarket barrels,and the chambers were cut with minimum spec reamers.I have also seen differences of up to 120fps when changing lot#s of powder.One factor on it's own does not explain the difference in velocities,but a combination of factors could realistically add up to that much difference.I owned an 8mmRemmag that exceeded the maximum velocity listed in the manual with a starting load,and adding any more powder resulted in pressure signs.
 
The more I think about it and research, things aren't as out of whack as I first figured. just from my reloading manuals powders charges start as low as 38 and go as high as 46. And published velocities from 2300 to 2700+ roughly. This is from 3 different manuals. So like stubblejumper stated , a combination of many different factors AND variances in what is published in manuals it all seems a very reasonable possibility.

So I guess these firearms are like finger prints , never gonna get the same thing twice.

But I definitely feel better now hearing some of the responses here.
 
stubblejumper said:
As posted,barrel length explains part of the difference,and a Kreiger barrel and a tight chamber could easily add another 100fps.All of the rifles of mine that exceeded the loading manual listed velocities,wore high quality aftermarket barrels,and the chambers were cut with minimum spec reamers.I have also seen differences of up to 120fps when changing lot#s of powder.One factor on it's own does not explain the difference in velocities,but a combination of factors could realistically add up to that much difference.I owned an 8mmRemmag that exceeded the maximum velocity listed in the manual with a starting load,and adding any more powder resulted in pressure signs.
Click to expand...

Amazing to me being a new reloader...

You are getting velocities that are greater than bokk states you should, with 4 grains less powder, none the less!
You are using below minimum charge and getting above maximum charge velocity...

I wish I could do that and save all tha powder !!!!!:D

I would be afraid of the velocities you would get if you went with the minimum cahrge, or imagine "MAX CHARGE" !!!!

You gonna keep working higher??:)
 
NO NO,lol nuthing higher, I am workin on accuracy. I have the load doing under .5 MOA @ 100 yards with a top quality hunting bullet. maybe all the clink I have been blowing on this rifle is paying off for me a little!!

Will just be interesting when I start doing my target load.

AND FYI , I am pretty new at loading also, only second season for me
 
Amazing to me being a new reloader...

You are getting velocities that are greater than bokk states you should, with 4 grains less powder, none the less!
You are using below minimum charge and getting above maximum charge velocity...
Click to expand...

Something that can't be stressed enough is that all loads listed in a loading manual may not be safe in all guns.Loading manuals are guides,but even they contain warnings to start with reduced loads and work up from there.
 
5r

A 20 inch rifle barrell with 5R rifleing will equall the speed atainable in a 26 inch barrell with standard land and groove rifleing. This is why so many 308 sniper rifles are built with short tubes. It's free speed.
 
A 20 inch rifle barrell with 5R rifleing will equall the speed atainable in a 26 inch barrell with standard land and groove rifleing. This is why so many 308 sniper rifles are built with short tubes. It's free speed.
Click to expand...

That wasn't the case with my 700-5R,the velocity was almost identical to other 308win rifles with the same barrel length.The barrel did however foul less,and was easier to clean.
 
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