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7mm PRC Optimal powder charge help... update... I give up!!! ... updated again!

infoman jr. said:
An off center chamber will definitely cause pressure issues as the bullet changes directions trying to find the bore. I've seen it many times over the years. I'm guessing they didn't proof fire the gun, or they should have seen the pressure signs.
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Exactly....

But why the heck will it still shoot good???? I would have figured an off cut chamber would shoot like crap. During load workup, the WORST group I got was 1.5 inches, and most groups were under 1in. I'm hoping they will admit what the problem is in addition to fixing it!
 
Not to go into to great detail, a friend of mine ordered a Impact Precision in 7mm PRC, 24" Carbon Bartlein barrel, Nightforce scope. Here is the best load we found, we tried 3 other powders but H4831sc came out on top, we started at 65.5 wound up at 69.5 grains of H4831sc pushing a 180 Berger VLD, Lapua case's, with no pressure signs, bolt lift is fine, no extractor mark. Chronograph average 3004fps. I don't have but a 300 yard range here behind the shop and rifle shoots extremely well with that load. Like you I believe your groups would be worse and more erratic with an off cut chamber. Hope you get your problem taken care of.
 
I threaded a barrel and installed a brake on a rifle several years ago. I was amazed at how much runout the barrel had while holding the breech and muzzle on center. It was a factory sporter barrel and shot well. I had to shoot it afterwards just to see for myself. I was amazed.

As to the off center chamber, you would think the chamber reamer was piloted and should have stayed on center. However, some smith's drill/bore the chamber first and ream with a finish reamer. This method leaves a lot of variables on the table. Saving the cost of a piloted rough chamber reamer just isn't worth the chances of ruining a barrel. Also, as land diameter is variable between barrels, reamer pilots should be changed to a diameter that closely matches the land diameter with the appropriate clearance of course.
 
They received the rifle Monday (lag in shipping on my end because of my local FFL)

Already done and being shipped back

Their response
 

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Just thinking out loud. If the chamber is off-center, as was suggested, recutting it will make it sloppy because metal was previously removed and not replaced. Redrilling a hole tends to remove more metal and make it deeper if desired. The only way around that would be to weld it up before recutting, which is an absolute nono. The other would be to set the barrel back, rethread it and cut a new chamber. That would only work if the shank were long enough and the barrel would be physically shorter. I'd rather they install a new barrel.
 
Finally got some low 60s temps in south MS to test it out since it came back from the factory.

Factory 175 eldx at 2775fps and 1in group

Factory 180 eldm at 2750 and 1 in group.

My prior handloads 175eldx now at 2725fps and 1/2 in groups, no erratic pressure.

I guess recutting the chamber to center it dropped velocities by average of 50fps, but I now think I have a LOT of room to work up on.

The 190 a tips I loaded for ladder velocity string and had to abandon back in April due to pressure signs at pussycat loads, I finished out. Got over 2 grains higher than when I had to stop earlier, but no pressure signs. Have to keep working up, then after finding optimal charge, work on seating depths. Hopefully we get some more cool weather so I can get it dialed in before deer season!
 
Another update.

Worked up a load with the 180 ELDMs (thanks to all of you who suggested to use them over 175 ELDXs with staball HD. Got them up to 2800 fps while still grouping 1/2in at 100 yards. About 8 out of 10 are fine, 2 out of 10 will give faint ejector marks, but the load is on the warm side for sure.

Load gives me 1.5in groups at 300y, and 2in groups at 400y, so it's holding up. Didn't get to shoot it at 500 yet.

We've taken 4 deer with that load so far (between 100 and 200y) and the bullet is just devastating. 3 out of 4 dropped on the spot, the one that ran made it 25 yards. Massive wound channels extending all the way to offside shoulder, but only one bullet (or just a piece of it actually) exited. Not sure I would want this bullet for elk up close, but for whitetails it does just fine.

Still have 2 jugs of VV n570 to play with, so when I get some time I'm going to see what it will do, but for now, I'm pretty much all good with current load for this season.
 
Can you summarize what loads, speeds, & groups sizes you are dealing with now with the rework done.

So did CA return the rifle to your local FFL. Previous when I had work done on a gun of mine they were able to return the gun back to me directly (no FFL).

Thanks,
 
megalomaniac said:
Another update.

Worked up a load with the 180 ELDMs (thanks to all of you who suggested to use them over 175 ELDXs with staball HD. Got them up to 2800 fps while still grouping 1/2in at 100 yards. About 8 out of 10 are fine, 2 out of 10 will give faint ejector marks, but the load is on the warm side for sure.

Load gives me 1.5in groups at 300y, and 2in groups at 400y, so it's holding up. Didn't get to shoot it at 500 yet.

We've taken 4 deer with that load so far (between 100 and 200y) and the bullet is just devastating. 3 out of 4 dropped on the spot, the one that ran made it 25 yards. Massive wound channels extending all the way to offside shoulder, but only one bullet (or just a piece of it actually) exited. Not sure I would want this bullet for elk up close, but for whitetails it does just fine.

Still have 2 jugs of VV n570 to play with, so when I get some time I'm going to see what it will do, but for now, I'm pretty much all good with current load for this season.
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The eldm is a straight killer.


Glad you got it up and running.
 
trap55555 said:
Can you summarize what loads, speeds, & groups sizes you are dealing with now with the rework done.

So did CA return the rifle to your local FFL. Previous when I had work done on a gun of mine they were able to return the gun back to me directly (no FFL).

Thanks,
Click to expand...
I'm getting 2810fps with (gasp) 25fps ES with the 180 EldMs over high 60s g (rather not say exact load as i am warm) Win Staball HD.

Despite the ES, it's consistent 1/2 MOA out to 400y.

I had no problem getting half MOA out it before I sent it off, just erratic pressure at what were mild book loads.

When I contacted Christenson arms, they insisted I ship it back to them through an FFL dealer.

In the past, I've been able to ship myself directly to an ffl gunsmith, he just provided me a copy of his ffl and I included it in the case. Not sure why Christenson arms insisted it ship from an ffl to them? Maybe rules have changed?
 

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