FireFlyFishing
Well-Known Member
What chronograph are you using and do you trust it?
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Irregular velocities with 7prc loads
- Thread starter Johrichal
- Start date
Help Support Long Range Hunting Forum
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- Feb 18, 2007
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The short of it is, the firing pin needs guidance but it doesn't need to drag or bind. When you have a firing pin that is dragging you can hear it with a trained ear when you dry fire it.
You will need to clearance where it's dragging. Not a kitchen table gunsmith job.
I generaly don't go to Mag primers unless it's over about 80grs of powder. I never had much luck with Mag primers, with most of my loads in 264 WM, 7mm R M.,308NM and 338Wm are in the 75gr areas. I use Fed 210 primers. the Mag primer seen to expand the groups in my rifles. I don't have any rifles that hold much more than about 75 grs anyway.
I don't know what your barrel lenght is so that doesn't help. I would look at H 4831 or H4350 powders. Faster than the H1000 powder. I like the H powder and use them mostly. Most double base powders have problem temp change. So change over 1.5fps per degree in temp change. That can be a real problem on longe ranges.
Other problems are case length, neck tension. Annealing helps on neck tension, and case also helps. setting your primer depth, flash hole cleaning and deburring. Finally volume fill your cases and check to see if there much differents in volume weight.
Changing out or using different primers is one that needs to be look at or tried. I have just gotten a brick of White River LRP in. I haven't use them yet, Interesting on your load info.
Following!
I don't know what your barrel lenght is so that doesn't help. I would look at H 4831 or H4350 powders. Faster than the H1000 powder. I like the H powder and use them mostly. Most double base powders have problem temp change. So change over 1.5fps per degree in temp change. That can be a real problem on longe ranges.
Other problems are case length, neck tension. Annealing helps on neck tension, and case also helps. setting your primer depth, flash hole cleaning and deburring. Finally volume fill your cases and check to see if there much differents in volume weight.
Changing out or using different primers is one that needs to be look at or tried. I have just gotten a brick of White River LRP in. I haven't use them yet, Interesting on your load info.
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I also just started loading for the 7PRC, in a Weatherby Accumark. I matched 30 Hornady new Unfired cases, then made a light load of IMR 4831 to FIRE FORM, the new cases to the new rifle. IM Just wondering if your results, which are not bad, are the first firing out of your cases???? Might they have benefited from a "fireforming session", prior to loading and testing?? Just wondering.
My 7 PRC absolutely did not like H1000. Velocity was inconsistent and the only charge that grouped at all was a very slow load running around 2600 fps.
Koots
Member
Maybe this can help a bit? I am just finishing load development with my 7mm prc. When I was doing my break-in I started with a light load of 66 g of N565. Just over minimum charge. I was getting weird slower velocity spreads and ejector marks which didn't make sense at such a light load. I switched to ram shot grand and my highest velocities are over 3150 with no pressure signs great node at 67.5 and 3000fps. Might be a low charge/powder/primer combo? My velocities have spead up from what's in the picture with barrel break-in but the es and sd are the same.
ADG brass
Br2
Ramshot grand
Eldx 175
.002
67.5 g
ADG brass
Br2
Ramshot grand
Eldx 175
.002
67.5 g
Attachments
I've got Ramshot Grand on the shelf and really looking forward to trying it. Down to my last 1.5 lbs of RL26...
Johrichal
Member
@RockyRandy - I had the same thought at the range a few weeks ago I found a guy with a Labradar that let me compare my Garmin side by side and it was within 3fps every time
Okanogan
Well-Known Member
Another vote for trying different primers and if that doesn't work, different powders. During load development for my 7 PRC, I cut the SDs in half by switching from F215M to F210M. CCI250s were better than the F215M but not as good as F210M. I think you'll find numerous posts on the forum from people who found their 7 PRCs like F210s.
I didn't have much luck with H1000 with my 7 PRC but many others have claimed good results. Hornady app says the max charge for 175 ELDX is 67.1 g and I could not even hit 2850 fps out of my 22" barrel with H1000 with a 0.5g over max so I gave up on it. For all of the powders I tried my SDs tended to reduce to a low sweet spot at a particular charge weight and then increase as I increased charge weight past the sweet spot. I never saw the wild swings in SD for only 0.2 g variation that you report however, which makes me question your sample size and if the results were repeatable.
You mentioned you have some N565 coming and hopefully that will work well for you. I tried N570 but couldn't get the velocities I wanted without going extremely compressed and that gave me poor SDs.
I didn't have much luck with H1000 with my 7 PRC but many others have claimed good results. Hornady app says the max charge for 175 ELDX is 67.1 g and I could not even hit 2850 fps out of my 22" barrel with H1000 with a 0.5g over max so I gave up on it. For all of the powders I tried my SDs tended to reduce to a low sweet spot at a particular charge weight and then increase as I increased charge weight past the sweet spot. I never saw the wild swings in SD for only 0.2 g variation that you report however, which makes me question your sample size and if the results were repeatable.
You mentioned you have some N565 coming and hopefully that will work well for you. I tried N570 but couldn't get the velocities I wanted without going extremely compressed and that gave me poor SDs.
Johrichal
Member
That is correct that was the first head scratcher moment
That looks like a great load! I suppose it could be due to low pressure charge but find it unlikely as I have worked up to above Hornady max load data
@Mike Matteson - I'll update when I shoot some more of the white rivers I can tell you they seem to be slightly larger diameter than most LRP's I use a hand primer and they require quite a bit more pressure to seat
mtank
Well-Known Member
- Joined
- Jan 29, 2015
- Messages
- 216
My 7 prc shoots the 160 LRX very well. I just received a box of 165 Norma's to try as well.
ewnanney
Active Member
I had poor results with H1000 in my 22" Proof 7prc, never got velocity I could get with V560 and Grand. Its just too slow for 22" barrel.
SAM55
Well-Known Member
I've also been on a 7PRC load development journey. After trying H1000 & N565 I settled on H4831SC, which gave me my most consistent results. I use ADG brass, crimp with a Lee crimp die, and magnum CCI primers, but I will try some standard primers to see how that works out. One big detour I caused myself was by annealing with my Dewalt drill and two propane torches - a very inconsistent process. After a couple of rounds of annealing my neck tensions were all over the map causing very wide SDs and poor groups. I had to throw away several batches of brass. I finally broke down and bought the AMP annealer, solving my annealing problems. The AMP devise is an amazing piece of equipment.
If you have an acquaintance with a 7PRC and chronograph, I suggest you run some of your loads in his rifle over his chronograph. That would at least rule out a rifle or chronograph issue. Just my 2c worth!
If you have an acquaintance with a 7PRC and chronograph, I suggest you run some of your loads in his rifle over his chronograph. That would at least rule out a rifle or chronograph issue. Just my 2c worth!
