7 prc 180 ELDM Bullet tumbling

[RiverRatMatt]

Sighting in my bergara mg lite in 7 prc this weekend and ran into what I believe is an issue. If you zoom into the top impact you can see the lead in the hole. The bottom right impact doesn’t look clean either. This happened after around 15 shots and doesn’t seem right considering the paper was stapled to cardboard.

Curious to what caused this and how can it be prevented.

 

[eoperator]

Is your bergara one of the smooth bore models?

 

[swavescatter]

Do you have access to another magnum rifle that shoots sub-MOA? Put together some "proof" that you can actually shoot before contacting Bergarbage customer support, otherwise they'll just accuse you of sucking and refuse to honor their BS sub-MOA guarantee. That's what they did to me.

Don't waste more ammo chasing your tail here - if bullets are tumbling I don't think that's a simple fix like checking action screws, muzzle devices for tightness, etc.

 

[RiverRatMatt]

Is your bergara one of the smooth bore models?

Let’s hope not

 

[RiverRatMatt]

Do you have access to another magnum rifle that shoots sub-MOA? Put together some "proof" that you can actually shoot before contacting Bergarbage customer support, otherwise they'll just accuse you of sucking and refuse to honor their BS sub-MOA guarantee. That's what they did to me.

Don't waste more ammo chasing your tail here - if bullets are tumbling I don't think that's a simple fix like checking action screws, muzzle devices for tightness, etc.

I don’t. If it means anything this was initially at 50 yards as I walking it out to my 200 yard zero.

 

[wind gypsy]

I'd use a cleaning rod to measure actual twist rate of the barrel. Only other things I could think of are brake or suppressor contact with the bullet or bullet jacket failure. The jacket failure would likely have to be occurring just shy of the target to get results like that? ELDms are known to be a little more prone to jacket failure than others but i sure wouldn't expect it on a fresh 8 twist PRC barrel.

 

[swavescatter]

You can reach out to Bergara to find out what ammo they use for accuracy testing. Do you have a chronograph?

If it initially shot well then something may have changed. Muzzle devices or even try a deep clean.

 

[RiverRatMatt]

You can reach out to Bergara to find out what ammo they use for accuracy testing. Do you have a chronograph?

If it initially shot well then something may have changed. Muzzle devices or even try a deep clean.

Yeah bergara recommended this round or 170 grain federal terminal ascent. The rifle is suppressed if that matters. I guess it’s worth nothing I did run a bore snake through in between shots 10-15.

Average was 2802 on the chrono

 

[RiverRatMatt]

I'd use a cleaning rod to measure actual twist rate of the barrel. Only other things I could think of are brake or suppressor contact with the bullet or bullet jacket failure. The jacket failure would likely have to be occurring just shy of the target to get results like that? ELDms are known to be a little more prone to jacket failure than others but i sure wouldn't expect it on a fresh 8 twist PRC barrel.

Surely there would be viable damage in the suppressor if it was making contact right?

 

[TxLite]

Surely there would be viable damage in the suppressor if it was making contact right?

You should notice something, but it could be minor. When I made contact with my suppressor it absolutely launched. There was no question on whether or not there was contact.

Pull the bolt and look down the bore and see if you can see the suppressor.

 

[5811]

Did you shoot it without the can? Have you shot the same can on other rifles with success?

 

[Koda_]

Check your barrels actual twist rate with a cleaning rod, ive read its not uncommon for them to be off. Check your bullets SG stability factor in Bergers Stability calculator, especially if your at a higher elevation...

A very very slight graze on the supressor would do it and not leave a mark for a while. I would test without it....

 

[RiverRatMatt]

Did you shoot it without the can? Have you shot the same can on other rifles with success?

Shot with the can only. This is my only threaded rifle.

 

[RiverRatMatt]

Check your barrels actual twist rate with a cleaning rod, ive read its not uncommon for them to be off. Check your bullets SG stability factor in Bergers Stability calculator, especially if your at a higher elevation...

A very very slight graze on the supressor would do it and not leave a mark for a while. I would test without it....

What’s the solution if the twist rate is off? New barrel?

 

[Jason Snyder]

What’s the solution if the twist rate is off? New barrel?

That or a lighter bullet.

 

[Koda_]

What’s the solution if the twist rate is off? New barrel?

As mentioned above, new barrel or much easier to select a lighter bullet.

 

[SloppyJ]

Take the can off first and try it.

 

[RiverRatMatt]

As mentioned above, new barrel or much easier to select a lighter bullet.

Id much rather shoot the 170 terminal ascents but can’t find them locally

 

[Koda_]

Id much rather shoot the 170 terminal ascents but can’t find them locally

Availability is always a factor, whenever you pick a new bullet always check its SG stability factor with your actual twist rate before buying. A lot of people dont. I dont know how often it happens bt have always hear a rifles actual twist rate can be off from its advertised twist rate, if even just a little and one selects a bullet listed for the advertized twist rate things can tumble. Its best to pick a bullet with a twist rate slower than your barrels for best stability.

Odds are your barrel is 8 twist as its advetized, your bullet is advetized an 8 twist... it "should" work but what if your barrels actual twist is 8.2...

It still could be your suppressor is not perfectly concentric or something. I would still test without the can to rule that out.

 

[TxLite]

Odds are your barrel is 8 twist as its advetized, your bullet is advetized an 8 twist... it "should" work but what if your barrels actual twist is 8.2...

8.2 vs 8 isn’t going to keyhole at 200 yards and cause jacket separation. At most I’d expect reduced BC or poor groups. Something else is going on here