I think I was happier not using a chronograph

Last year I got a Mod 70 featherweight 308.
Loaded up 44 grns Varget with 150 grn interlock below max for deer load for niece. She shot a nice doe at 125 yds.

Shoulda left it at that, maybe I still will but I am curious

Last week I chronographed the load
4 shots 2565, 2590,2572

Little slower than I thought, but a 300 savage sounds good

But thought I would try Mule Deer's 308 load of 46 grns Varget

So first 45 grns
2 shots 2682, 2687

then 46 grns
2 shots 2676,2680

Now I am REALLY courious. I know some barrels are slow, chamber dimensions and other things, thats not the issue for me.
But 46 grains shooting slower than 45 is odd to me.

Obviously I need to reshoot the test and with more shots to get a better data sample if I want a more accurate picture.

My question is:
Can this be a sign of erratic pressures, and if it is, is it safe to reshoot 45 and 46 grains before looking for a cause?

Your velocities are not quite at a maximum load for the 20� barrel 307 Winchester. Not bad performance. I have had more one shot, dropped in its tracks kills on white tail deer with the 307 Winchester than with any other cartridge, and my wife and I have tried a few.
There is a bit of magic in a conventional 150-grain .30 caliber bullet driven to 2,550 fps or so. I prefer heavier bullets but it is simply a preference.

There are many circumstances which can cause a load to chronograph slower with an increase in powder charge, particularily when you are not at a mximum load level.
Your velocites look pretty good to me but you might consider these thoughts.
For uniformity I often tie a string between the chronograph stand and the front sling swivel to ensure a uniform distance from the start screen between shots. I generally find this of most use with 22 lr cartridges but you might consider doing something to ensure you have your muzzle the same distance from the start screen for each shot and each group fired. This will help to uniform some of your day to day differences when choreographing the same load from the same rifle.
If it helps, all of my barrels appear to be slow barrels.

EDIT] I should have said hat 44.0 grains of Hodgdon Varget will drie the 150-grain bulk remington JRN bullets between 2,525 and 2,550 fps in the 20" 307 Winchester, depends on the day. Reloder 15 gives higher velocities with not quite as good accuracy.

That does seem odd, and unusually slow. I'd try to shoot something of known velocity through it to confirm it's accurate. My 308 shoots 165 ABs at 2820 with 46gn of Varget> It's always been on the fast side though (26" barrel). ...or, can you shoot at long range and measure drops to get an idea if it's accurate?

Just a guess PRM but if you cut your 26" tube to 22" like the OP's what do you guess your 2820 loads would be running?

I'd guess you'd drop 80-100 fps or so?

Dober

He's shooting 150s, not 165s though. It would be in the ballpark if they were 165s.

True that he is

Thx
Dober

Re-shoot them. Two shots with each load is not statistically significant and the velocities may reverse.

For all intents and purposes those two loads are identical. That the one with more powder is reading a blink slower means nothing.

Were it me, I would split the difference (45.5 grains) and bet money on an accurate load that had low SD.

You're shooting a .308 Win by definition you can't be worried about getting max speed out of it or you'd be shooting something else that would give you that speed. It looks to me like you are shooting a load and rifle with a lot of potential for accuracy and probably are getting it.

Chronographs spoil lots of loads especially when we move from Internet or loading manual expectations to shorter hunting length barrels,and different components which vary from that used in the tests.

I don't see anything unusual going on here.

My rifles tend to be a bit slower than Mule Deer's.

I figure as long as I stay behind his position on the pressure curve, I probably won't blow anything up.

ruger438,

What was the light like when you did the chronographing? One of my chronographs is 4-5% faster under a high sun than when shooting under clouds. This was confirmed one partly cloudy day when shooting a 10-shot string as a few clouds periodically passed in front of the sun.

Hornady Interlocks usually result in lower pressures (and hence velocities) than other bullets of the same diameter and weight.

I did not know that, and you know I'm a Hornady fan...why is that??? jacket alloy or some such?

Short bearing surface, especially on lighter-for-caliber bullets.

OK...dat makes sense...

According to a ballistic lab tech I know, the only bullets that create less pressure are the lighter-for-caliber Triple Shocks. He often has to switch to a faster powder to get up to speed with light TSX's.

I've seen the same thing.

What kind of chronograph are you using? Do you have a known load you can test your chronograph with? Like MD said light conditions etc. can give false readings. As you can see I'd question the chronograph first. OTOH some rifle can be hard to understand. Some years ago I had a factory M700 7RM that was just plain lazy and there was nothing I could do about it. With factory 150gr Rem loads it just barely broke 2900fps. With reloads I had trouble reaching 3000fps with 150gr bullets. What I had was a loud, hard kicking .270 so it went down the road.

I don't think he's pushing too hard yet. My 308's like a bit over 47 gr. of Varget with flat base 150 Interlocks in Lapua brass, lit by a CCI 200 or BR2.

Yeah.....don't work to fire wall with a 338-225 Hornady, then switch to a 225 Nosler P without a substantial load reduction....ask me how I know...

Ooops! Gee...what's that funny smoke?..... where'd that primer go?

[quote=Mule Deer]ruger438,

What was the light like when you did the chronographing? One of my chronographs is 4-5% faster under a high sun than when shooting under clouds. This was confirmed one partly cloudy day when shooting a 10-shot string as a few clouds periodically passed in front of the sun.

Mule Deer,
Any idea which condition gave the more accurate reading?

My pet .308 load is 45.5 grains of Varget, winchester brass, WLR primer, and a 165 NBT or Sierra BTSP. Out of a 98 Mauser with 22 inch Wilson barrel she get @ 2650-2725. I do not sweat the velocity as he will shoot bug sized groups and kill well out as far as I care to take game.
The best I have ever gotten out of 150's from this rig was @2800 with a max dose of IMR4320. It was fast but I would rather have bullet weight than the little extra speed. The 165/168 grain bullets hit a sweet spot in the .308 for me. They fly plenty flat, are very stable, and usually outshoot 150's in the .308's I have shot. Particularly at distances over 200 yards.

Cloudy.

lots of good reading here since i posted

Miles- I think I may end up at 45 grns but we will see

MuleDeer- The cronograph was in the shade with the plastics shades on because I though the white background would allow the screens to pick up better.

Thats interesting that you found Hornady to produce lower pressure, because the Hornady data runs milder loads of Varget than other data like barnes, Hogdon and Speer for intace max out at 47 grns where Hornady data stops at 44.8 grn with 150's.

But that does explain the results

SuperT- its the cheapest Chrony and last year seemed to be in line checking 17 HMR ammo, but for kicks and giggles I may buy a box of factory 308's just to see.

It seems nothing is wrong so 45 grns at 2680 will make me happy for deer and black bear in places I hunt.

But I'm still going to re-shoot 45 grn and 46 grns Varget just to satisfy my curiosity

If I might make a suggestion, shoot more than two shots of each. If the true velocities of the different loads are close, it will take a larger sample to detect the difference.

My South Carolina (I think, new anyway) M-70 Fwt 308, 22" barrel produces 2743 with 46.0 Varget, Win WLR primer, Win brass and a Sierra 150 flat base. Hornady bullets produce less pressure in both the 308 and 7mm08 for me, based on both speed and primer flatness. This over an old Pact Chrono/Timer with diffusers over the screens. I need to start recording the cloud conditions when I chronograph.

Yeah, it helps.

I record everything I can about conditions during any range session, including temperature, wind direction and velocity (taken with a Kestrel), whether I put out wind flags, which chronograph was used, the scope, how many shots had been fired from the rifle since the last cleaning, etc. etc. Oh, and I also check the actual distance to the target with a laser rangefinder. It's kind of a PITA but quite often the info is useful.

This is the correct response. Your sample study is far from being statistically valid. Not meant to flame, but you need more data before you can draw any conclusions. I collect chrony data every time I am out to make sure things remain consistent.

yup, thats why I will shoot more, but did not want to load up 10 rounds of each load if there was a potential problem.

ruger438, please let us know how things turn out.

SuperT-FWIW,finally got a chance to re-shoot some over the chrony.

Also bought a box of Federal Blue box 150's as a reference

10 shots each, cloudy this time with diffusers up 22" 70 Featherweight 308.

Federal Factory Load 150grn
2733-2761 ave. 2744

150 Hornady Interloc BTSP
44 grn Varget
2563-2612 ave 2591

45 grn Varget
2643-2702 ave 2683

46 grn Varget
2712-2751 ave 2719

All loads shot well 1- 1 1/4, smallest was the 44 grn load and Federal factory load.

Cloudy conditions seem to have given better results with the chrony, so I was fun to experiment a little.

Now after all that fooling around I am sticking with the original 44 grn load since it does kick noticeably less and have enough ooomph to pop deer.

Why not just stay with the factory stuff?

Because of the red highlighted line, and I have thought a 300 Savage would be about right.

Likely doesn't matter but notice that at pushing 4000 feet toward the headwaters of the Missouri air pressure equivalent to 14.7 psi at sea level works out closer to 12.7 psi - this might change external ballistics some along with the presence or absence of humidity (hydrogen is a light gas) so even results fired at the same spot might vary between a dry winter and a hot wetter summer.

Maybe we could have a predicted velocity rifle match for those of us loonies who can't shoot for accuracy?

FWIW, I just found a good long range target load of the Nosler 168 BTHP and 46.0g of Varget, which I chronographed at 2740 fps from my 26" barrel.

GPerry

Wow, some of you really need to look in the mirror and realize that what's printed in a reloading book or posted on a forum is not the end all, be all, of velocities.

99% of you shoot off the rack hunting rifles. The bullet velocities will vary by several hundred fps because of the chamber size, free bore, barrel diameter, bullet, primer, brand of case used, how far from the nuzzle you measure the velocity, elevation, air density etc.

For Christ's sakes, lighten up!

When I started using Re 15 in the 303 British and 308 Win/7.62 x51mm in 1999, I found big differences between rifles from different manufacturers. I did not believe that there was a problem; just variances between rifles.

Relax. A 100 or 200 fps swing does not mean that there's something wrong with your rifle, barrel or recipe.

We now return you to your regularly scheduled (ill informed) discussion.

Ruger
I own a 1963 FW 308. I did the same as you and used a factory load to establish a baseline and went from there with 150 gr bullets.
Where I live in New England there have been many volumes of deer that died quite nicely from 30-30s. So I loaded up what shot well and went hunting. Same choice as you. The slower loads looked good on paper. No need to kick myself silly on a 150 yard or under shot that is all I will see in my rifle hunting here.
It even worked in East Texas when I had the lucky chance to hunt Hogs for 7 days on a really nice property. Every hog that a bullet hit in the front 1\3rd died within 40 yds of where it was hit. (These were 06 rounds out of a push feed model 70, but at the same speed as my 308 loads).
No knock on going faster. Just an example of 1 that found dead game at the end of the day with speed closer to some of the old classic rounds.
I like knowing what the speed is but dont need it to be max to hunt deer here.
Enjoy your fall hunting.

Ruger, my old Mauser 308 has a 24 inch barrel. I shoot 44g of AR2208/Varget over 150g bullets, including Corelokt and Interlock.

I get ave 2575fps consistently. So your results don't surprise me at all.

Factory ammo eg 150g Corlokt chronies right on the advertised 2800+ fps. I just think the 44g figures in the Hodgdon/ADI data are not all that relative to some rifles.

That's the beauty of a chrony - now we know.

seems like I've read this thread before - anyway, 47.3 or 47.5 gr of Varget work great for me with 150 gr Horn SP and also Barnes TTSX. The 165 gr load that works best in my 308 is 50.0 gr 2000MR at about 2830 fps using either 165 gr Fusions or 165 gr Interbonds. Great velocity and accuracy with both. I am currently using my 284 win shooting 120 gr NBT's into itty bitty groups as my longer range round and the 308 shooting the 165 IB as my woods stand load. Great thing about hunting here in Mid-MO, you have a pretty good idea of what you can expect for shot length, based on which stand you hunt.

Fwiw...my factory rem vtr has a ton of jump to the rifling. When I combo this with generous room in win brass I need about 2 grains more powder than much data I see in manuals and the inet.

I run 47.o gr Varget with Speer 150 spitzer HC's at 2,850 fps in a 22" PN tube.

That sounds like a dandy MM,I'll load some up today!