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Retumbo or H50BMG in 32" 300 RUM?

 
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  #22  
Old 09-20-2013, 09:32 PM
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Re: Retumbo or H50BMG in 32" 300 RUM?

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Originally Posted by Tumbleweed View Post
Well, I set up the chronograph this early this morning and fired three rounds of 102 grains. Unfortunately I did not get a reading on any of the shots. I guess I was a little early and did not have enough light. Having to get this done before taking the kids to school put a time crunch on things. 2 shots at 275 yards were .75" apart with the other up slightly making the group 2.25". Not fabulous but I will play a little more witht the 102 load and make sure to get speed readings next time. With a 100 yard zero and input velocity of 3240, shooter called for 2.0MOA at 275 yards. My group center was near perfectly centered with my POA. This tells me that I have to be above 3200fps.
Time to invest in a Magnetospeed
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  #23  
Old 09-20-2013, 11:30 PM
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Re: Retumbo or H50BMG in 32" 300 RUM?

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Originally Posted by MontanaRifleman View Post
Time to invest in a Magnetospeed
I like the idea behind them eliminating all of the lighting issues. However I understand they will change point of impact and possibly grouping.. With barrel life and component costs/shortages to consider, I always collect target data at the same time when I chronograph.
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Old 09-21-2013, 10:06 AM
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Re: Retumbo or H50BMG in 32" 300 RUM?

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Originally Posted by Tumbleweed View Post
I like the idea behind them eliminating all of the lighting issues. However I understand they will change point of impact and possibly grouping.. With barrel life and component costs/shortages to consider, I always collect target data at the same time when I chronograph.
Most of what I have read on them says they have very little to no affect on groups and have little affect on POI if any. A lot of guys are using with good results. They may even actually save you barrel life, gas and time by giving you good info in any condnitions so you don't have to make multiple trips to the range. Once you have a good load you like, in 3 to 5 shots you can get an accurate velocity range and not have to bother with it anymore. I'll be getting one before too long.
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Old 09-21-2013, 10:07 AM
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Re: Retumbo or H50BMG in 32" 300 RUM?

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Originally Posted by Tumbleweed View Post
I like the idea behind them eliminating all of the lighting issues. However I understand they will change point of impact and possibly grouping.. With barrel life and component costs/shortages to consider, I always collect target data at the same time when I chronograph.
That's precisely the reason we gave up my the chrono's my father built years ago; he was building chrono's before the optical ones were really available. They used two laminated foil plates and Dad built/ programmed the electronics to measure the time between plates and arrive at a speed. They were accurate and had great shot to shot consistancy due to the way he built the stand, but you couldn't see a downrange target through the foil plates so you shot for speed/uniformity then for group. The plates also had to be replaced every dozen shots or so so if you were doing a bunch of stuff you may have to be chrono'ing for a while if the range was busy.
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  #26  
Old 09-23-2013, 02:42 PM
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Re: Retumbo or H50BMG in 32" 300 RUM?

Well, I got out and began shooting 3 shot groups starting with 102 grains RL33. I also sent a group at 103 and 104 grains. I had good conditions for the chronograph to perform well. The groups were shot at 275 yards and ranged from 2"-3". I noticed that velocity did not improve over 102 grains as the barrel simply couldn't burn any more powder. 104 ended up being a max safe load. Velocities with all three loads averaged around 3250fps. Accuracy was obviously not good enough as I'm looking for .5MOA or under. Here's the awesome thing, I backed down to 101.5 and groups calmed right down but the velocity stayed at 3240fps average. No pressure signs at all on the case head. The 275 yard group measured 1.125" with two in the same hole. I took it out this morning to shoot 700 yards before the wind picked up. I had a very slightly shifting 1mph wind. The 700 yard group measures 4.5" and vertical spread measures a whopping .375". The shifting wind could have easily moved the left bullet out of the group. I'm settling on this load.

275 Yard Group
Retumbo or H50BMG in 32" 300 RUM?-275-yards.jpg
700 Yard Group
Retumbo or H50BMG in 32" 300 RUM?-700-yard.jpg
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Old 09-23-2013, 03:17 PM
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Re: Retumbo or H50BMG in 32" 300 RUM?

Great! That stokes me up for some RL33 load development!
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  #28  
Old 09-24-2013, 02:06 PM
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Re: Retumbo or H50BMG in 32" 300 RUM?

Mighty fine shooting for a 10 power scope.
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