Hi all - copying a post I started in another thread regarding RPR 300WM Loads - 225gr ELD Match
Hi all - completed some initial load work-up and pressure testing of RPR in 300WM. IMPRESSED with this rifle. Under $1,400, and was grouping under 1/2 inch at 100 yards after the first few shots. It appears Ruger is performing barrel break in at the factory prior to shipping, as it was evident the rifle had been fired several times. Initial coating of copper, and cleaned easily.
Components:
Brass: Norma Factory (Neck tension 0.003 inch)
Powder: H1000
Primers: 210M
Projo: Hornady 225 gr ELD Match
I used a dummy round determine distance to lands, which measured Ogive (Og) of 2.801 inches;
Loaded three batches:
74.2 gr H1000: Og = 2.796 inches, 0.005 Jump - 3 rounds one hole, MV 2710, 2712, 2711 as measured with LabRadar
74.7 gr H1000. Og = 2.771 inches, 0.030 jump - 10 rounds, 1- inch group avg MV 2,721 fps Sd = 18
74.7 gr H1000, Og = 2.741 in, 0.060 jump - 5 rounds, 3/4 inch group avg MV 2,723 fps Sd = 13
The 0.005 jump looked the best in terms of tight group and Mv, so I built a pressure test with 0.005 jump running from 74.5 gr to 80.0 gr H1000.
74.5 gr H1000 - no data (radar not aligned properly)
75.0 - no data
75.5 - 2.765 fps (first three rounds same hole)
76.0 - 2,803 fps
76.5 - 2,800 fps (still printing in same hole - group less than 1/2 inch at 100 yds)
76.8 - 2,826 fps (bolt felt very slightly sticky from this point on - no signs of primer flattening)
77.0 - 2,833 fps
77.2 - 2,829 fps
77.4 - 2,825 fps (these last four shifted up 1/4 inch, but still substantially tearing into same hole as previous shots
77.6 - 2,855 fps
77.9 - 2,855 fps (impacts started to drift outside the centroid, 1/4 -1/2 inch)
78.2 - 2,869 fps
78.5 - 2,833 fps (moved to aim point since target was ragged hole, impact point exactly center, same as shots that started at 74.5 gr)
78.8 - 2,833 fps (low right, 1/2 inch - primers starting to show shallowing of primer impact cavity)
79.1 - 2,886 fps (low right 1 inch)
79.4 - 2,909 fps ( low right 1 inch)
79.7 - 2,909 fps (low right 1 inch or so, bolt significantly more sticky- so I quit at this point.
I ran some dimension checks on the brass when I got home, most would still chamber, albeit tight at higher loads. I resized the last shot (79.7 gr) with Hornady match die (0.333 bushing) to see if I could get the base back to spec. I then used Larry's collet die to work the belt region. The belt came back to spec and fit the chamber gauge properly, however the head had swelled about 0.003 inch dia so cartridge would not chamber in the rifle. I concluded this piece of brass was over pressured and trashed it. All other brass came back properly to spec. Cases for the hotter loads had stretched about 0.003 inches.
Bottom line -great rifle, forgiving loading conditions, and tight groups out of the box.
Based on these tests, I head to the 1,000 yard line in a few weeks with two batches:
74.7 gr and 76.2 gr.
I'll pass along the results then.
PS - rifle weighs 20 pounds fully loaded, recoil is comfortable (about like a 8 pound 308), though it got a bit more snappy at the higher powder wts, but nothing that affected my trigger finger.
Regards, Tim
