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338 Snipe-Tac - Load Evaluation Wanted

 
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  #8  
Old 06-18-2008, 06:27 PM
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Based on your first day's data, and looking at the targets, I would have worked in the 136-138 gr range. You indicated you thought you were .015 off the lands. I would play with seating depth until you find something that looks good to you. Make sure you know where your bullet is in relation to the lands. Are you able to control neck tension? What is the nk dia of the chamber? What type of dies are you using.
For the most part, your ES from the first day of shooting looks good.

When doing load development, I take the measurement of a virgin piece of brass, and monitor the growth, stretch, to determine max load. For instance, a Norma .340 WBY case measures .508 just above the belt, that piece of brass will expand as you increase your charge. You will know you're approaching max load before the tell tale heavy bolt lift.
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  #9  
Old 06-18-2008, 06:47 PM
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Quote:
Originally Posted by Just Learnin View Post
Marine Sniper: Our local range is stuck right up into a draw, which gives a shooter some time past sunrise to still shoot in the shade. I saw a lot of mirage on the first day (shooting in the sun) and none the second day (got there an hour earlier and shot in the shade).

I set up my bench and chrono right off the side of the parking lot with my truck about 10' away. But yes, on the first day I picked up the rifle and set it in the shade of my truck each time in a vertical position to aid in the cooling down. Seemed to work ok, the barrel was never hot but never totally cooled down either. I do very little shooting from benches and really don't have a clue what proper protocol is, just what feels right, you know?

I shot the load workup round robin as it gives me a little more comfort factor. If I mess up a shot (which I try not to do ) I'm reasonably confident that the others will be correct, that I can hopefully make some assumptions off the aggregate, as well as chrono data.

Thanks for the compliment, btw. -- Don
You will get lots of advise on your loads, I will offer some on your shooting. Pick a load you want to shoot a 3 shot group with and shoot 3 shots without getting off the rifle. Every time you pick up the rifle and move and then come back and set it down you will never get everything the same as the shot before. I understand that rifle must build a lot of heat in the barrel. I have a 300 Weatherby and 408 Cheytac; they get the barrel hot quick also. No problem with you letting the barrel cool, but stay on the gun until you shoot your 3 shot group with one load. Let it cool and shoot 3 more with a load you want to test.
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  #10  
Old 06-18-2008, 07:56 PM
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I'm not surprised that your second effort was not as sucessful as your first when shooting your load development. I personally find that to be the rule and not the exception - at least for me. I agree that moving your entire rig to keep it in the shade is more effort then will prove productive. If you want shade that bad, bring an umbrella to the range and set it up to cover the barreled action (keeping the ammo in the shade is far more improtant then keeping the barrel in the shade. Additionally, you don't want to chamber a round and then let it cook in a hot chamber any longer then necessary in regular circumstances, but especailly when doing load development (I'm talking cooking it 20-30 seconds, not 3-5 seconds).

I'll hazzard a guess that the 50BMG powder is one of Hodgden's Extreme Powders, so its probably going to be fairly consistent as far as temp swings go. That having been said, I'm always nervous developing a load in the spring that I intend to shoot in the summer.

I learned this lesson in Houston when developing a 6.5x284 load in March (45 degrees 35% humidity)for use in June (95 degress with 75% humidity) and had heavy bolt lift and primers popping all over the place - nasty. Same story for the load that I developed and shot for F-Class in my 7WSM last December, January, and February in Vegas. That load is now shooting like crap at 110 degress in the Las Vegas desert, so I get to develop something to use in the summer.

I suspect that the lighter load (136-138 grain) will work its way up towards if not above 3,200 fps at 80 degrees, and may well be the one to consider for your load.

just a thought.....


JeffVN
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  #11  
Old 06-18-2008, 09:05 PM
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Joel, thank you for the info concerning the brass. I still have my brass from the second day's shooting in order so I can measure those. Is there a general rule as far as expansion that I can go off of? I got my die from Dave Viers, made to the reamer spec I believe. I would have to check with him on the neck diameter. I will play with the seating depth and see if that'll help. Thanks again. -- Don
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  #12  
Old 06-18-2008, 09:07 PM
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Marine Sniper, thank you for the shooting advice. I will implement your advice and I appreciate you pointing it out. -- Don
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  #13  
Old 06-18-2008, 09:13 PM
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.005" on the brass expansion.

Go out and re-shoot those loads I mentioned earlier, then play with seating depth all at the same shooting session.
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  #14  
Old 06-18-2008, 09:22 PM
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JeffVN, the temperature was something that I had planned on experimenting with. These colder temperatures in the morning is closer to what I might expect to experience during hunting season, but certainly not during the summer busting rocks (which is when I'll likely shoot it the most). We've got some warmer days coming up that I thought I'd run a round or two through the chrono. Reminds me of when I worked up a great load for my son's 270wsm once (in the spring of course) and completely forgot about summer heat. We were shooting at one of the steel targets one evening and he said "Dad, the bolt's kinda sticky." :eek: I had to use some force to open the bolt. I'll accept my mistakes but boy I hated thinking of something dumb I did hurting my son. So needless to say that load is just for hunting in the fall and kept in a separate box.

I appreciate the comments and advice. It sure is nice to be able to access all the knowledge on this site. -- Don
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