Freebore Rifling?

[Ekupp]

I have a new 7PRC Rifle with 40 rounds of factory ammo shot through it. The rifle has shot 3/4 moa when clean but opens up and becomes erratic past 3-4 shots to at least 2 moa. There is etching in the freebore where the bullet is contacting leading in to 2/5 lands it looks like the lands are contacting prematurely. Additionally, the rifle is shooting 150 fps slower than all of the hype for this ammo, bits of powder remaining in the barrel. Has anyone seen anything like this, is the case sitting crooked in the chamber or is this chambering not concentric, bad ammo? The rifle is an off the shelf model that features a barrel by a prominent barrel company, should I engage the rifle company or the barrel company to resolve? They have both offered to look at it but not sure where to start.

Your opinion/feedback will be helpful so I know what to ask for when I send this to the manufacturer.

 

[sable tireur]

The rifle is an off the shelf model that features a barrel by a prominent barrel company, should I engage the rifle company or the barrel company to resolve?

The very first thing for you to do is contact the rifle maker. They built the rifle and need to see where you think the problem is. But, in any situation such as this, I prefer to ask questions of the manufacturers rather that state what I think the problem is. It sets a better tone to getting information and a probable fix.

Concentrate on getting the best information first from the manufacturer and then establishing their cooperation in the resolution of the problem.

Best of luck!

 

[Ekupp]

The very first thing for you to do is contact the rifle maker. They built the rifle and need to see where you think the problem is. But, in any situation such as this, I prefer to ask questions of the manufacturers rather that state what I think the problem is. It sets a better tone to getting information and a probable fix.

Concentrate on getting the best information first from the manufacturer and then establishing their cooperation in the resolution of the problem.

Best of luck!

Thanks for replying, was hoping to get more feedback, I am very curious to see what people think about bullet contact in the freebore and what causes that. The etching in the pictures is not from chambering it is engraved and a result of contact before hitting the lands when fired.

In this case I had already been in touch with the manufacturer and part of their wishy washy delayed response was that I should also reach out to the barrel manufacturer as well. Feeling like I am about to get the run around from all parties so trying to educate myself on what is going on also curious.

 

[MagnumManiac]

I do not see an issue other than the roughness, this is perfectly normal on a factory barrel.
The etching, as you have called it, is not from bullets engaging the rifling, it is what's leftover by the chamber being cut.
More pics of the throat would be helpful, but if you're concerned, then by all means send it back for inspection.

Cheers.

 

[Barehandlineman11]

Id get more then 40 rounds on it not even broke in yet. A lot of barrel's don't start speeding up until 100 rounds. That one picture doesnt show much fyi. It also might not like the factory rounds

 

[WapitiBob]

Chamber centricity or lack thereof shows up really well on the lands as well as the groove/freebore blend line.

 

[Ekupp]

I do not see an issue other than the roughness, this is perfectly normal on a factory barrel.
The etching, as you have called it, is not from bullets engaging the rifling, it is what's leftover by the chamber being cut.
More pics of the throat would be helpful, but if you're concerned, then by all means send it back for inspection.

Cheers.

The photo is not the best, I have a video that would show better the situation, link below. The "etching" was not there prior to firing the rifle. The 2 etched lied start at one end of the free bore and run straight in to the lands (only 2/5). The etching appears to be the same wear that you see in the rifling. They even have a slight twist/angle that would indicate they were part of the lands that were not properly machined smooth or as Wapitibob indicated shows a lack of concentricity. I do not have any other barrels that show bullet contact in the free bore prior to the lands.

In the video you will see powder, in the chamber as well as concentric circles in the freebore. The rough circles left over from machining are not an issue if no contact with the bullet, they are a catalyst for fire cracking though and in my opinion should not be there.

As for velocity, I agree, 40 rounds is too early to tell, with that said, I have 4 other barrels from this manufacturer and they say you do not need to break in their barrels and that has largely been true, from shot one they have all been within ball park of expected velocity not 150 fps off. Also if the barrel requires handloading to get any reasonable results something is not right. PRC is designed to be OK to good accuracy if barrel and ammo are reasonably within tolerance. Especially when using the ammo from the designer of the cartridge.

Factory ammo could be the velocity issue especially when seeing powder in chamber. I do not have a way to check concentricity accuracy but when rolled it does not appear to have any hops and would not account for being that

My main issue is accuracy, velocity is another issue that may or may not be related. Finally, rifle was sent to manufacturer, had to start somewhere, not expecting much but will see what they find.

Video

 

[HandgunHTR]

I can't help you in the freebore department, but in regards to the velocity, what ammo are you using? What barrel length is your barrel? What is the published velocity data? What chrono are you using to verify your speeds?

These are all questions that could help determine if there is truly a problem.

Also, in regards to accuracy, you say that it opens up to 2MOA after 3-4 shots. Does that mean that you are shooting longer strings and subsequent shots are opening up, or that after 3-4 shots, it opens up regardless of the strings you are shooting?

 

[Bob Wright]

Sounds like what you are describing is the chamber is not concentric to the bore/rifling in your photo. All the other problems with speed and accuracy are a symptom.
I wouldn't waste ammo. Just contact the manufacturer and ship it back.

 

[V35BTC]

I looked at video, looks like it was not dialed in tru to the spindle. There is one more land peeking through the bullet didn't touch. It also looks like there was some reamer chatter.

 

[Dirtrax]

I had a similar issue with a "manufacturer". It was a good bit more obvious that the chamber was not concentric with the bore. Upon contacting them they were quick to respond and rectify the problem. Shoots very well now, cost me nothing, and it only took 3 weeks door to door. IMO you're just prolonging the agony by procrastinating.

 

[Ekupp]

I can't help you in the freebore department, but in regards to the velocity, what ammo are you using? What barrel length is your barrel? What is the published velocity data? What chrono are you using to verify your speeds?

These are all questions that could help determine if there is truly a problem.

Also, in regards to accuracy, you say that it opens up to 2MOA after 3-4 shots. Does that mean that you are shooting longer strings and subsequent shots are opening up, or that after 3-4 shots, it opens up regardless of the strings you are shooting?

The rifle has been shipped to rifle manufacturer even though there was a suggestion to talk to the barrel company from the rifle company. Couldn't waste any more time and ammo trying to sort it out.

To answer your questions ammo box stated velocity is 3000 fps in 24" barrel. I have a 22" barrel getting 2810 fps ave for 3 shot groups as measured with a magnetospeed. Other barrels from this barrel company perform very well and require little break in. I would expect near 2950 after break in but initially 2875 at the worst. Ammo could also be the issue.

After cleaning to metal first 3 shot group is .75 moa without working at it. 2nd 3 shot group will have a flier. Any further groups are random and 2-3 inches. I repeated this 3x meaning after I got to 2 moa + accuracy I cleaned to bare metal. I did some swabbing between groups for the first 10 shots accuracy still dropped but returned after cleaning to bare metal (copper and carbon eliminated per bore scope).

 

[Pdvdh]

I had a throat looked like that. Two grooves were cut deeper than the other three by the cudtom barrel manufacturer. And that barrel did not shoot well for me.
The barrel was sent back to the manufacturer and their Rep said there was nothing wrong with their barrel. Even though my gunsmith could measure the difference in the depth of two of the 5 grooves. Two of the 5 grooves were visible across the length of the throat, because they were cut deeper than the reamer cut the throat.