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The Amazing 270 Win - revisited

 
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  #1  
Old 11-05-2012, 08:53 PM
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The Amazing 270 Win - revisited

During the hunting season my son who inherited my 270 Win, built in 1966, rebarreled in 2005 was giving him problems.

I think we reloaded cases that were neck sized from being fired in the original barrel. When the cartridge chambered with difficulty and fired, it had to be removed with even more difficulty.

After shooting at a coyote one morning he carried a stuck case rifle till we got home.

I took it upon myself to FL resize all brass. Brass in all W-W brass from years ago. About 50 cases.

Some cases received considerable resizing as indicated by effort necessary to run them through the FL die.

The go to load has been 58.5 grains of RL-22 and Hornady 140 SPBTs for years. They are a great bullet consistently printing around 0.25 MOA 200 yard 3-shot groups @ around 3200 MV.

There is a thread, which I can't find at the moment or I'd post there, regarding use fo 7828ssc in the 270 Win. Outlandish velocities have been reported. Thought I'd give it a go.

From its original build in 1966 until now the barrel has been fully bedded. It has never been floated and has never changed POI over the decades.

Knowing this rifle better than I know my wife I dove into the 'new era'.

Bullet of choice is the 140 Berger VLD Match. Knowing that they usually don't like to jump into the rifling I was leery about accuracy due to magazine length.

The Hornady spire point loves jump and provides unmentionable group size with the 3190 FPS MV.

Having shot thousands of rounds through this rifle, each round being pushed pretty hard, I feel I know what "pressure" looks like from primer appearance. By watching that I am able to remain below extraction problem pressures.

I modified the Mauser extractor years ago to keep from loosing brass when firing at game and it now slips off stuck cases fairly easily. However, back in the day, I was able to get multiple shots off in pretty quick order and end up with cases for each shot in my hand. I have no idea of how I did it. I just did it. . .

Magazine length is 3.305" so I set the Base to Tip length short enough to give free loaded cartridge movement. This length from base to point is 3.295". I cycled the 5 cartridges that fills the magazine several times with out hang up.

Then used a prepared dummy case to seat the 140 VLD by chambering. Letting the throat seat the bullet resulting in a Base to Point OL of 3.371" way too long for the magazine.

With these settings bullet jump is about 0.076" presenting a cause for concern.

Loading 4 cartridges with progressively increasing charges of Reloder - 22 was intended to validate pressure/velocity with this new, for the rifle, bullet.

And one cartridge each with 4831sc and 7828ssc.

Atmos temp = 60*
Cartridge temp = 57* for all shots
Chamber temp = 71* for all shot (sun increased rifle temperature above atmosphere)
Chrony @ 10'

All shots @ 200 yds.

RL-22 Loads and velocities
57.0 gr - 3150
57.5 gr - 3144
58.0 gr - 3207
58.5 gr - 3200

4831sc load
60.0 gr - 3222

7828ssc load
60.0 gr - 3265

All shots except the 7828ssc load were dispersed in the horizontal direction. No shots even "tended" to group.

The 7828ssc load went spot on horizontal but higher than the other shots. See images below.

RL-22 velocities and pressures were inconsistent. One case case, loaded with 57.5 gr was difficult to extract. There was nothing I liked about RL-22's performance.

4831 and 7828 peak pressures appeared significantly lower than the RL-22 loads.

As I liked what the 7828ssc compared to the others I loaded 3 more of 60 grains.

7828ssc 60 grains - 140 VLD 3322/3384/3382. Hmmmm, why the increase in velocity. It may well be due to the low sun this time if year. It was not possible for me to have both chrono view ports shaded which tends to keep the chrony honest.

The group showed a major vertical stringing component, about 1.7 MOA @ 200 yds. This is a good sign to me as the lower velocity loads showed a major horizontal tendency. Thus a significant drop in powder should produce a horizontal string.

Dropped 1 grain to 59 grains
Shot 1 - chrony error (the chrony wasn't parallel to line of fire. Corrected that)
Shot 2 - 3414 FPS (WTH! Difficult bolt lift. I have no explanation)
Shot 3 - 3357 FPS

A nice triangular 0.55 MOA group was produced.

Loaded 3 more to validate group.
Velocities: 3355/3378/3489 Where are these 3400 + velocity readings coming from. There was no noticeable, primer or extraction pressure indications.

Another ~0.55 MOA group was produced.

Will use a second chrony tomorrow to compare.

If these velocities are valid it will be pretty sweet. While the rifle is capable of much better than 0.55 MOA groups this is good enough for the stuff I shoot at.

Plus 7828ssc is much more temperature stable.

JBM says that at these velocities 900 yards can be reached with a 5 MIL drop which would be pretty sweet also. And only a few clicks to 1K.

We'll see what further testing reveals.
Attached Thumbnails - Click to View Larger
The Amazing 270 Win - revisited-pic-1.jpg   The Amazing 270 Win - revisited-pic-2.jpg  

The Amazing 270 Win - revisited-pic-3.jpg   The Amazing 270 Win - revisited-pic-4.jpg  

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Old 11-06-2012, 07:03 AM
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Re: The Amazing 270 Win - revisited

Wow, It will be interesting to see how the drop testing and further chronograph tests go. My chrony goes nuts with a low battery or low light.

I can't get 3300 with my 270WSM with 130's(well one w/magpro). I am going to develop a new load with the 130g Berger Classic Hunter for my 270WSM if I can sneak it in by Thursday. I think I will try the 7828ssc as I have some and it is listed as a good load for the 270WSM(it likes Retumbo but 110% fill w/130). Sometime I will have to try it in my 270 also.

I used to use RL22 in my 150g partition elk loads for the 270 which gave pretty decent numbers! Good enough that when I sold that rifle to my buddy and handed him those loads he gave them back!

I am going hunting and I ran out of time after developing new loads for my 7RM and 45/70 with the 168 Berger Classic Hunter and 325 FTX respectively. I also wanted to work up some new loads for my 6.5/284 and 270WSM but have been way too busy. Guess I am going to have to leave something home. I have 4 tags for the trip.

Sounds like you have found a great load for your rifle regardless. I may try to duplicate it as I have all the components sitting here ready!
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  #3  
Old 11-06-2012, 07:13 AM
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Re: The Amazing 270 Win - revisited

Sounds like you have a rather tight barrel and are rather high or over pressure with most all of it, causing your rather poor accuracy on some targets. I can't get over 3100 fps with 130's with rl22 or either 4831 in two different 270's. I don't burn short cut powders but use regular 7828 with a 150 for 2850 fps.
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Old 11-06-2012, 08:39 AM
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Re: The Amazing 270 Win - revisited

Maybe this is more about 7828ssc than the 270 Win

Here's a pic of load density w/59 gr of 7828ssc

No drop tube needed for either 59 or 60 grains.
Attached Thumbnails - Click to View Larger
The Amazing 270 Win - revisited-load-density-59-gr.jpg  
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Old 11-06-2012, 02:42 PM
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Re: The Amazing 270 Win - revisited

Lookin forward to what you find Roy. Is there any what I could persuade you to compare a couple of charges by changing the powder temp? Maybe shoot a couple at ambient and put a couple close to your body to heat em up say 20 degrees warmer or Vic-verca.
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Old 11-06-2012, 06:33 PM
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Re: The Amazing 270 Win - revisited

I think I read it here or another forum where some guys who are much smarter than I am in this reloading game have mentioned that IMR7828 burns the same as surplus 4831 that O'Connor used.

The last time I bought 7828 was around 1992. I may have to revisit this SSC version. I recall reading the Speer load manual in the 270 where they got highest velocities with their 130 and 7828.

I don't need to get any right now but may try some in the spring. Until then, I wait for your confirmatory chronograph data.
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Old 11-06-2012, 08:29 PM
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Re: The Amazing 270 Win - revisited

Wooda posted this evening but the videos are taking forever to upload to photo bucket..

Leaving for a day chasin' woofs in a few moments. Tomorrow will be a good day!!

Not to keep ya hangin'.

59 gr 7828ssc (fills case about 1/2 way up shoulder) Berger 140 VLD MV 3366 FPS was confirmed spot on @ 448, 590 and 750 yards w/a 200 yard zero. @ 6600 feet this load makes the 270 Win a 1k shooter with a drop of 5 MILs @ 980 indicated w/1855 FPS and 1070 FPE

My thanks to Berger, JBM, Shooter and Jack O'Connor. . .

Good night and good huntin'
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