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Discussion Starter · #1 ·
Okay guys I need some help. please tell me what I'm doing wrong. I'm loading 150 grain Nosler Ballistic tips. I have a Winchester model 70 in .300 win mag.
I'm using the Nosler 5th edition reloading guide. It say 70 grains of IMR 4350 in a winchester case and a Federal 215 primer, COL 3.35 inches. This should give me 3240 fps.
I used everything they said. I even bought a new RCBS digital scale and made sure the load was exact. I shot 5 through my chronograph. I got 3004,3058,2869,2753, and 2869 fps in that order. Not even close to what the guide said and a 305 foot extreme spread.
I bumped up the charge to 72 grains of IMR 4350. The guide said I should get 3330 fps. I got 3151,3066,2943,3051,and 2957.
The acuracy with the 70 grain load was excellent, and the recoil very mild. The 72 grain load had pretty good acuracy too but the recoil was a bit stiffer.
Can someone tell me what I'm doing wrong? Why such a difference in their velocity compared to mine? Also, is that much of a spread in velocity from shot to shot normal?
One last thing, I have a 26 inch barrel. Their guide shows a 24 inch barrel. In theory shouldn't I get better velocities?
Would appreciate any help you can give me......Thanks;
Tony
 

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With a spread like that I don't think I would trust your chrono too much, especialy if you say accuracy is good. I would say a 300 fps spread would be crap for accuracy. I would take a good hard look at your chrono. And dont expect your loads to match the books, in my experience they usually dont. KN
 

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Lyman 47th Handbbook
Winchester Cases, Winchester 8-1/2-120 LP Primers O.A.L. 3.340"
Hornady 150 Grain SP #3031
IMR 4350 68.0 [email protected] to 76.0gr. (factory velocity duplication) @3290 fps.

Nosler 165 Grain SP #16330 O.A.L. 3.340"
IMR 4350 67.0 gr. @2865 fps to 74.0 gr. @3194 fps

Jim
 

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Sounds like your chrony might be too close to the muzzle...

I found that the acceptable loading range for 150's is:
IMR-4350 From 60.3 grains to 80.0 grains
Winchester WLR Primer

But the following was better...
RL-22 From 69.5 grains to 81.5 grains
Winchester WLR Primer
 

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I have never had a velocity come close to what the manuals say. I did have a friend who had a "fast" .308 Ruger one time that put a 150 gr. bullet at about 2900 fps within pressure limitis and within book guidlines.

Before you give up try puting a slight crimp on your rounds. A friend of mine just got a SD of 181 with some .375 Win loads out of his contender. He bought a Lee crimp die and put a slight crimp on them. The next trip back to the range with the same batch of ammo produced a SD of something like 18 or 19. All over a new Oehler chrono. It made a believer out of me.

Beau
 

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Also, are you using new or once fired/mixed hulls not previously shot out of your gun? If you are using mixed brass or once fired brass that you do no know the history of, you may be getting varying bullet pull. Different brands of brass have different hardnesses and thicknesses. Also if you picked up some once fired brass somewhere, it may have been fired several times and have necks that need anealing. Try some new brass. Your SD needs to be 20 or less. Oftentimes it is only one little thing that needs to be changed to get you back on track.

Beau
 

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Discussion Starter · #7 ·
Thanks for the replies, Just for the record, Im using once fired Winchester cases. They have only been fired in my gun. I'm going to try moving my chronograph farther away. If that doesn't help I'll try a crimp die.
Thanks;
Tony
 

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I don't know what the test barrel length listed with your loading data is, but if it is longer than YOUR barrel, that would account for at least some of the loss in velocity. However, what you are experiencing is not at all unusual. It is quite common to find velocities less than the books say, especially when factory test barrels were used. There are just too many variables... Line one of the other replies said, I have seldom ever come up to the "advertised" velocities listed in most of the manuals. You are not doing anything wrong... however, if the velocity is your target, you may need to change powders in order to find the one that will give you your desired velocity... Just IMHO
 

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Velocity differences could be due to your chamber or barrel being not as tight as the barrel the loads were developed in. Is your headspace the same, or have your once fired cases now have just a bit more internal capacity? Also temperature, barometric pressure, altitude, humidity, etc, all play into the velocity actually achieved. Are you using a different lot of powder? Are you using a different lot of bullets. Lots of variables can account for the differences you observe from published data (besides the questions raised about your chronograph). That's why the manuals always say start low and work up. You don't know which side of the equation your particular firearm/cases/powder/primers/bullets fall on.
 

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Find a Speer Manual

Find Speer Manual with an article titled "Why Ballistitians Get Gray" or something close to that and read it over. There are a ton of variables involved and its inevitable that individual guns and loads will perform differently. Powder age and moisture content, production variances in bullet, case, primer, rifle. Temperature of your ammo vs load book ammo, altitude, etc. etc. ad nauseum. But I would expect you loads to be a little closer to the book given my experience with my HS Precision .300 win. I think the suggestion to move your chrony farther away is good. Also, I usually use a "blast shield" - a wood pallet with a 10 inch gap to shoot through. I place it about 2-4 feet in front of the muzzle to dissipate the muzzle blast and protect the screens which are 2-6 feet further from the pallet.

I used to work with statisticians a bit and I've been thinking it would be neat, but totally unaffordable, to use 5 or 10 rifles of each chambering to generate more statistically valid data. Man I used to hate all the extra samples we had to take to fully address all sources of bias and variability. (We called them the bias police.) When I think about it, its amazing how some of the load data seems to only use only one gun or very few guns- seems a little dangerous - certainly not a good statistical sample [maybe I'm wrong on this?].
 

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Discussion Starter · #11 ·
I moved the chronograph farther away from the muzzel and things improved. I'm now getting a fairly consitant 3150 fps. The extreme spread has reduced also. I still get the ocasional high or low velocity but for the most part they are within 40 or 50 feet of each other.
Thanks for all the help.
Tony
 
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