My Lapua 300 prc brass experience......

highdrum

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I had a 7/300 prc built by Dallas Lane. Terminus helios lite, rock creek 8tw 23" carbon barrel in an Alterra carbon stock. I initially fireformed 100x pcs ADG brass. Necked down and formed with a false shoulder, 74gr H1000 184 bergers going 2830-2840. Shoulder was coming ahead 6-7k upon forming. No ejector marks or psi signs. Minor load development was done with H1000 and N570.

Received 100pcs of Lapua last week. Upon initial measuring, the shoulder is only 1k short of my current shoulder bump dimensions, excellent! Necked down 16 cases just enough for slight resistance on bolt closure. Measured loaded neck diameter: 0.3165, adg was 0.314, my chamber is 0.321, another win! Measured case weights on my scale and lapua was 10gr lighter, so assumed slightly more volume.

Used my prior forming load of 74gr H1k, 184 bergers they went 2860-2870, figured normal as barrel sped up from forming ADG. I was getting light ejector marks on ever case, I figured it was due to forming, bolt face slape, but headspace wax pretty tight, wasn't too concerned. I found a few velocity flat spots potential accuracy nodes in ADG and wanted to try hit them with lapua brass.

ADG H1000 190 LRHT
76.5 2992,2994
77.0 3004,2999
77.5 3027,3033 shadow ejector, no lift
80.0 3044,3051 ejector marks, light click

ADG N570 190 LRHT
79.0 2994,2995
79.5 3004,2989
80.0 3023,3022
80.5 3028,3040
81.0 3055,3051
81.5 3063,3071 shadow ejector, no lift
82.0 3099,3074 ejector marks, light click

Lapua H1000 190 LRHT
76.4 949,939 ejector
76.7 961,965 ejector
77.0 3000,951 ejector
77.3 993,3001 ejector
No bolt lift/click

Lapua N570 190 LRHT
80.4 992,3012 ejector
80.7 3012,3019 ejector
81.0 3041,3027 ejector
81.3 3033,3045 ejector
No bolt lift/click

So my assumption that lapua holds more volume was correct, it took more powder to achieve the velocities compared to ADG. The bad.......every single round showed noticeable ejector marks. The primer were all hand decapped, the top charges in lapua popped free with very little effort, telling me that the pockets were loosening after 1 lower psi forming load and one hot load.
The lapua brass is smaller in the web dimension than ADG. My chamber is oversize from saami prc to accommodate adg brass and it's tight fit to saami Chambers. Maybe the lapua brass in smaller dimensions isn't gripping the chamber as well? I don't know. What I will say, in this comparison, adg is tougher brass than lapua. I was pretty disappointed in my findings as I was very anxious to use lapua in this rifle as well as my 65 prc. At this point in time, I will continue to run ADG brass in my magnum case head cartridges. Anything utilizing the 588 lapua case head, Lapua brand brass is absolutely fantastic, never tried ADG in my norma.
 

wasskeet

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Thanks for your write-up as it is very informative. I would not have expected that much difference between Lapua and ADG. More powder for Lapua for same velocity - yes, loose primer pockets that early - no.
 

highdrum

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I will also note I did some neck thickness measurements, 10 random cases with a mean thickness of 0.0155, lowest was 0.0147 and highest was 0.0163. All dimensions conducted with a tubing micrometer verified with calibration block. This is in new 30 cal form. May be a lil tight in saami chambers but after a skim turn would be excellent.
 
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Lenwood901

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are you using bushing dies to size the necks i notced the other day that od diameter loaded round of adg was 315.5 and the lapua was 316.5
 

highdrum

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are you using bushing dies to size the necks i notced the other day that od diameter loaded round of adg was 315.5 and the lapua was 316.5
Yes I used a 324 then 314 bushing. Loaded od on lapua is 3165 and adg 3145 with my mitutoyo outside micrometer. Your lot of ADG must be thicker than mine.
When I necked down the ADG, I used a 324 bushing, then ran into a FL 7saum non bushing die. The FL die may have flowed some the brass into the shoulder. Idk
 
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Lenwood901

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Okay I have some high hopes for the Lapua haven’t tried either one yet as my gun is still waiting for a barrel thanks for your report
 

2ndson

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I've shot them 2950ish in my 37" barrel just seeing how fast they'd go and no problems. It's a half-dozen of one, 6 of the other thing with the 230 vs. 250. Slightly better wind vs. less elevation. By 2000yd they're about the same thing.
 

7MMMagnum

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I've shot them 2950ish in my 37" barrel just seeing how fast they'd go and no problems. It's a half-dozen of one, 6 of the other thing with the 230 vs. 250. Slightly better wind vs. less elevation. By 2000yd they're about the same thing.
37” barrel. Do you have pictures. Would like to see that.
 

SteveBurton

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Thank you for the write up. I'm hoping the Lapua brass does better in my 6.5 PRC than the Hornady brass I've been using. Your observation of the primer pockets and ejector marks has me a bit worried.
 
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