7PRC -Prone to Pressure Signs and Carbon Ring Buildup?

Blue_dog

FNG
Joined
Sep 20, 2022
Messages
58
I have some hornady eldx in 7prc that’s been popping primers out. I’d say about 1/4 of the primers end up in the mag on average suppressed. I’m going to shoot with a brake tomorrow.
Just to update folks that might be interested. Federal eldx was blowing out 1 in every three primers and the velocities were nearly 2900 in an 18in barrel.

Switched to hornady and the fps came down a bit. Fixed a mounting issue in the scope and ran the gun out to 1,000 yards. Headed to the sheep mountains.

Anyone need 3 boxes of federal cheap?
 
Joined
Jul 17, 2013
Messages
697
Pure ******* ignorance yet again. And proof that shooting a lot doesn’t really make you an expert in anything. I’d put you as juuuuust less of a charlatan than Cortina. He probably shoots as much as you do, but actually puts his name out there and has skins on the wall. He’s built his entire reputation/persona on precision and he treats his gun like his ass, cleans it after every use.


The 6.5 PRC that after 150 rounds of ammo loaded in the exact same way, with same lot materials, all of a sudden had extremely hard bolt lift with no velo increase, and it went away after a thorough cleaning wasn’t a carbon ring???!?!?

The 22 GT that shot great for the first 500 rounds, then would blow up ~5% of bullets if I went more than twice without cleaning, then at
800+ rounds is blowing up 8-10% regardless?? Nope! Bullets never blow up and cleaning doesn’t matter because some anonymous moron on line said so! 🙄


Anyone reading this thread I would look up what someone like @Frank Green has to say. Again he’s someone who looks at 1,000’s of barrels a year for his living. Not just someone who “sHoOtS a LoT!1!1” and made a name for himself by dropping things…
"At the core of all anger is a need that is not being fulfilled."

Everything okay at home @Megalodon ?
 

Fyaman1

FNG
Joined
Jan 13, 2022
Messages
56
Location
California
Im getting random velocity spikes in my 7 prc barrel. Im in the load development phase, i just hit 100 rounds through my barrel Im loading 68-70.3 grains of retumbo shooting a 160 copper rose, virgin adg brass chamfered and mandrelled to 1 thousandth under caliber, fed 215 primers. Getting a nice gradual velocity increase between 2980-3120 fps. At 70 rounds(last cleaning was 40 rounds ago) i started seeing random pressure spikes between 3250-3300 fps along with more felt recoil. 7 velocity spikes total in the past 25 rounds.
 

Shooter Mike

Lil-Rokslider
Joined
Dec 7, 2021
Messages
236
Im getting random velocity spikes in my 7 prc barrel. Im in the load development phase, i just hit 100 rounds through my barrel Im loading 68-70.3 grains of retumbo shooting a 160 copper rose, virgin adg brass chamfered and mandrelled to 1 thousandth under caliber, fed 215 primers. Getting a nice gradual velocity increase between 2980-3120 fps. At 70 rounds(last cleaning was 40 rounds ago) i started seeing random pressure spikes between 3250-3300 fps along with more felt recoil. 7 velocity spikes total in the past 25 rounds.

What powder thrower are you using? That’s quite the large spread. Have you scoped your barrel?


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Fyaman1

FNG
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Jan 13, 2022
Messages
56
Location
California
Rcbs chargemaster 1500. I always double check the charge weight, (pull it off and put it back on to confirm the weight on the same scale) and anything higher is a compressed load so im doubting that is the issue. And negative never scoped the barrel.never had a reason to own a barrel scope lol

What powder thrower are you using? That’s quite the large spread. Have you scoped your barrel?


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What powder thrower are you using? That’s quite the large spread. Have you scoped your barrel?


Sent from my iPhone using Tapatal
 
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Shooter Mike

Lil-Rokslider
Joined
Dec 7, 2021
Messages
236
I had a very similar problem previously with another caliber. I have another scale, though, that I used to verify the charge, and low, and behold the thrower was incredibly inconsistent. If your velocities are inconsistent, and not just each successive shot being faster than the last, I think it is a reloading issue, and not a barrel or caliber issue.


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Fyaman1

FNG
Joined
Jan 13, 2022
Messages
56
Location
California
I had a very similar problem previously with another caliber. I have another scale, though, that I used to verify the charge, and low, and behold the thrower was incredibly inconsistent. If your velocities are inconsistent, and not just each successive shot being faster than the last, I think it is a reloading issue, and not a barrel or caliber issue.


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Im struggling to get over 3100 fps without running out of room for powder in my case Which is kind of why im leaning away from the amount of powder being the issue. And all my other loads are within 20 ES or less. But im no expert. Just in the past 2 years ive been trying to learn and become a more serious rifleman and reloader. Maybe ill look into getting a better scale to confirm these charges.
 

Shooter Mike

Lil-Rokslider
Joined
Dec 7, 2021
Messages
236
I’m confused. I thought you said your velocities were between 2890 and 3120. That is not an ES of 20.

Have you tried a different powder? And what is your barrel length?


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Fyaman1

FNG
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Jan 13, 2022
Messages
56
Location
California
I’m confused. I thought you said your velocities were between 2890 and 3120. That is not an ES of 20.

Have you tried a different powder? And what is your barrel length?


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22” barrel. I've tried staball hd but my ES was pretty high but that was before i started using the neck expander too. Sorry that was confusing im saying between all my load workup my loads have been between those numbers which is why when i get a velocity spike at 3200+ it really stands out. Heres my info from yesterday.
 

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TaperPin

WKR
Joined
Jul 12, 2023
Messages
3,535
and mandrelled to 1 thousandth under caliber,
Many folks would say that’s not enough neck tension and .003” to .005” is much more common. I would bet lunch that will help your velocities even out.

Everything we do and all the components vary a little bit - tolerance stacking can quickly use up that .001” so the bullet is just flip flopping and might be into the lands if the load is compressed and it squeezes the bullet out.
 

Fyaman1

FNG
Joined
Jan 13, 2022
Messages
56
Location
California
Many folks would say that’s not enough neck tension and .003” to .005” is much more common. I would bet lunch that will help your velocities even out.

Everything we do and all the components vary a little bit - tolerance stacking can quickly use up that .001” so the bullet is just flip flopping and might be into the lands if the load is compressed and it squeezes the bullet out.
Okay i can try that, the bullet manufacturer suggested one thousandth under caliber.
 

The Guide

WKR
Joined
Aug 20, 2023
Messages
1,044
Location
Montana
Okay i can try that, the bullet manufacturer suggested one thousandth under caliber.
With a super light neck tension, your bullet can get started towards the barrel just by the primer impact before any powder can be burned. Also, if you are magazine feeding the cartridges every shot can cause the bullet to move in the casing and not always in the same direction. Neck tension of 0.001 is really light for a hunting round. I would not be comfortable using it.

Jay
 

Fyaman1

FNG
Joined
Jan 13, 2022
Messages
56
Location
California
With a super light neck tension, your bullet can get started towards the barrel just by the primer impact before any powder can be burned. Also, if you are magazine feeding the cartridges every shot can cause the bullet to move in the casing and not always in the same direction. Neck tension of 0.001 is really light for a hunting round. I would not be comfortable using it.

Jay
Copy, im single feeding them, what is your suggestion for neck tension?
 

The Guide

WKR
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Copy, im single feeding them, what is your suggestion for neck tension?
Most guys speak of neck sizing to within 0.002 of the caliber to get a 0.003 neck tension with brass spring back. You would need to measure you actual neck ID and calculate what your spring back is and then adjust from there. I would look for a measured neck tension of 0.003 to give you a variance of 0.002 to 0.004 depending on bullet consistency.

Jay
 

Fyaman1

FNG
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Jan 13, 2022
Messages
56
Location
California
Most guys speak of neck sizing to within 0.002 of the caliber to get a 0.003 neck tension with brass spring back. You would need to measure you actual neck ID and calculate what your spring back is and then adjust from there. I would look for a measured neck tension of 0.003 to give you a variance of 0.002 to 0.004 depending on bullet consistency.

Jay
After further investigation i have 2 thousands neck tension. .284 cal bullet measured using my calipers, and inside neck diameter after brass spring back was .282. Still think thats likely to cause bullet jump from the primer?
 

TaperPin

WKR
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Jul 12, 2023
Messages
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After further investigation i have 2 thousands neck tension. .284 cal bullet measured using my calipers, and inside neck diameter after brass spring back was .282. Still think thats likely to cause bullet jump from the primer?
As you probably noticed, it’s really hard to get a good inside measurement with calipers because the contact surfaces are flat while the case is curved, and the design of calipers doesn’t have a self zeroing feature like an outside measurement does (cheap calipers are likely to not be exact between the inside and outside contact surfaces). Outside measurement before and after seating the bullet will generally be more accurate.

.002” is still not much neck tension, but there’s a chance the number is closer to .001” because of the inside measurement. It will be worth measuring a number of loaded cases because bushing dies on cases that aren’t turned to an exact neck thickness can have thin and thick necks in every batch, causing tighter and looser neck tension. Maybe it doesn’t make any difference, and maybe your neck tension won’t make any difference, but the number of things slightly off increases the odds of it effecting something.

You’re doing good, don’t let it put a downer on your enthusiasm - this is a great learning experience.
 

The Guide

WKR
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Messages
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After further investigation i have 2 thousands neck tension. .284 cal bullet measured using my calipers, and inside neck diameter after brass spring back was .282. Still think thats likely to cause bullet jump from the primer?
To properly measure your case neck I.D. you would need a snap gauge, an inside ball micrometer, or pointed inside measuring tool due to the round nature of the neck. These are more specialized tools than the dial calibers are.

Jay
 
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