naja302
Well-Known Member
- Joined
- Jun 28, 2013
- Messages
- 160
Hey, first post here. Mostly I just come here to learn by reading other posts, but this is bugging me so I figured I ask for some advice.
I gave up on the 338 Lapua after not being able to get acceptable accuracy with 3 different guns...the last of which being outrageously expensive (problem must be me). So I figured I would try this 7mm mag thing that everyone seems to think is so good (despite my pre-conceived notion that its basically equivalent to a 30-06).
I have a sour taste from expensive guns that shoot 2MOA, so I bought a Remington 700 long range in 7mm mag for $750. I wanted fancy brass so I bought 100 pieces of Norma brass.
Facts:
I am definitely seeing pressure signs, but I think the brass is just soft down in the belt region and its probably not actually a high pressure load or I would see faster velocities to go with the extreme pressure.
I loaded some in some once fired R/P brass and group size doubled, but velocity increased by 150fps without ext trouble.
I am a believer that pressure equals velocity. SO I am thus convinced that the norma brass is expanding excessively under normal pressures...Anyone agree?
If I didn't own a chronographs I would be really happy cause this thing is shooting very well, but there is a big difference in 2825 and 3025 FPS (at least in my mind).
Should I be happy with 2825 FPS?
Should I sort and prep R/P brass and hope to get good accuracy with that AND more velocity?
Thanks, and I hope the above makes some sense.
Danny
I gave up on the 338 Lapua after not being able to get acceptable accuracy with 3 different guns...the last of which being outrageously expensive (problem must be me). So I figured I would try this 7mm mag thing that everyone seems to think is so good (despite my pre-conceived notion that its basically equivalent to a 30-06).
I have a sour taste from expensive guns that shoot 2MOA, so I bought a Remington 700 long range in 7mm mag for $750. I wanted fancy brass so I bought 100 pieces of Norma brass.
Facts:
- I have fired less than 200 rounds through the gun
- I am new to the 7mm Rem Mag
- I have fired 13 different 5 shot groups under MOA and 6 of those were roughly .5MOA. This is outstanding and I have never had this kind of repeatable accuracy with anything.
- I have shot mostly 168 bergers and they shot best at Zero clearance
- Velocity is very slow and when I get to 2900 fps extraction is very stiff and I had to use a cleaning rod to remove several rounds.
- I neck sized the brass and they would not chamber (without a fair amount of force) These rounds when chambered scraped the case immediately in front of the belt.
- 150 barnes TTSX shot great but same severe extaction trouble at 2850-2900 FPS (loaded with .050" clearance and I did not try any other depths)
- Remington Factory 150 cor-lokts shot fine and chronographed 3112 without ext trouble
- R/P brass is 10-15 grains heavier than the Norma brass
- Norma brass varies by about 2 grains in weight
- R/P brass varies by about 10 grains in weight
- My chronographs reads normal type velocities with the other guns I am shooting so I don't thing that it is significantly off.
- I was expecting 3000-3050 FPS with the 168g (maybe that's just not reasonable)
- 68g H1000 with Norma brass and Fed 215 GMM primers @ 2744 FPS (69 and 70 grains gave significant extraction trouble)
- 68g Retumbo with Norma brass and Fed 215 GMM Primer @ 2825 FPS (69 and 70 grains gave significant extraction trouble)
- 150g TTSX with 59g H4831SC, Norma Brass, Fed 215 GMM primers @ 2672FPS (60 grains and above gave extraction trouble)
- 168 VLD, R/P brass, Fed 210 GMM, 70g Retumbo @ 2970FPS without ext trouble but poor accuracy
I am definitely seeing pressure signs, but I think the brass is just soft down in the belt region and its probably not actually a high pressure load or I would see faster velocities to go with the extreme pressure.
I loaded some in some once fired R/P brass and group size doubled, but velocity increased by 150fps without ext trouble.
I am a believer that pressure equals velocity. SO I am thus convinced that the norma brass is expanding excessively under normal pressures...Anyone agree?
If I didn't own a chronographs I would be really happy cause this thing is shooting very well, but there is a big difference in 2825 and 3025 FPS (at least in my mind).
Should I be happy with 2825 FPS?
Should I sort and prep R/P brass and hope to get good accuracy with that AND more velocity?
Thanks, and I hope the above makes some sense.
Danny