Thread: My 7mm PRC is driving me nuts…

Some background:

Tikka action,
Hardy steel barrel 24”, profil similar to a medium Palma. Manson M1 reamer
Shooting suppressed.

Jumped on the new trend early when we only had Hornady brass. Made developing a load nightmare.
Tested H1000, H4831sc and Staball.
Finally found a load grouping well with h4831sc (66.3gn in middle of a 0.8gn nod) adg brass, 180eldm, fiocchi primer, 2990fps. Consistent sub 0.5moa five group shot, sub 0.3moa three group at distance up to 600m. Single digit ES among 20shot.
In short a shooter

I always let barrel cool down every three shot.

At around 400 rounds, it started to throw split group. Consistent 2 in one hole and one 1inch away. Every single group.
So far This is what I checked:
-different stock and chassis
-different action screws torque
-different scope
-different scope ring
-proper clean and bore scope inspected
-shot a new seating depth ladder from 85th to 10th
-shot it without suppressor
-I anneal every time
-not new to reloading

After that I was around 500 ish rounds. Measured throat erosion and it grew 55-60th from new.
Talked with some reloaded who do this for a leaving. That lead me to start questioning the load. Even if I had absolutely zero pressure sign this load was 2.3gn above Hornady book. We ran number on GRT and it is definitely well above max pressure. ADG has a podcast where they warn people their brass is stiffer than most brass and you won’t see usual pressure signs until it is way past max pressure.

So… if you still reading… shot another load ladder and found a nod between 63.6 and 64.2gn, sub Moa but all also grouping two in one hole one around one inch away. 64gn put me at 2900 which is almost bang on what Hornady gives for this charge. This is max book…

Reloaded a few pill and went to the range again. (Scope roughly zeroed as I did one last scope swap to make again sure it was not the scope).
Shot one group of 4 then 2x group of three (making sure barrel cooled down in between)
See the pic below. It is getting interesting when you superpose them. One main group of 4 then 3x separate group of 2 around it.

I’m out of options, two mates are professional reloaders and have worked on hundred of rifle, they said we pretty much tested everything. I’m now at 680rounds. I know it will still be a dead deer at distances but I’m struggling to leave something I can’t explain alone.
Anyone seen this before, could it be the barrel starting throwing shot consistently in different spot….?

While I can’t help I feel for you iv played these games and I never got to the bottom of it I no Dave at CST is having endless troubles with his and he’s very clever he’s at 700odd rounds just trying to get it right everytime he’s close it throws a wobbly very frustrating

That would bug me too, I’ve heard more bad things about hardy barrels than good but you initially got a good load running which then turned sour.

Do you by any chance have access to a bore scope in order to have a good look inside the barrel?

I stopped reading at “hardy…

Yep I got mine chambered at the same time as Dave, he his a mate.

I would definitely start looking at the Hardy's barrel, they arent that popular for a reason.

Have you tried shooting it fouled?

Yep we had a look nothing unexpected for the round count, not much firecraking. No carbon ring ect.

Dave removed his proof and getting a Bartlein done by Greg

Originally Posted by whanahuia

Have you tried shooting it fouled?

Yep no change. Unfortunately. They carbon foil fast suppressed as other magnum.
Tried copper fouled, cleaned ect the whole
Spectrum

Originally Posted by 7mmsaum

I stopped reading at “hardy…

The barrel shot good before, what do you have in mind? Just average steel and the barrel already throwing shot at 600round. I thought about that, I did shoot a hot load with a fast powder for the caliber

Watch Hornardy podcast #50. No such thing as a node. You were and are seeing a standard statistical dispersion due to increased sample size. Sad but true. I have a Hardy barrel just about to be fitted, I aint holding my breath .
. .

Bedding ? Any shite in recoil lug slot ?

Nope, was my first check, my chassis is skim bedded, swap
Stock with another rifle and used another caliber in the chassis no change.

Originally Posted by Tentman

Watch Hornardy podcast #50. No such thing as a node. You were and are seeing a standard statistical dispersion due to increased sample size. Sad but true. I have a Hardy barrel just about to be fitted, I aint holding my breath .
. .

I stopped listening to anything coming from Hornadys mouth a long time ago… especially after measuring 2gn spread in a same batch of branded match ammo. Different powder in same batch of match ammo ect.

I repeated this experiment three time and found the same nod every time for those same charge on a rather large sample

Does your head in that kind of shit. Even if you cant fix it its good to know whats causing it