Barrel wear or a manufacturing problem?

[adamthegrayt]

After turning 40, I decided that instead of a Corvette, I would build my dream bolt gun. No holds bar, I wanted the best money could buy but alas, I have had nothing but troubles with accuracy.

300PRC

x-caliber carbon bull barrel- 1:8 twist 5R 26" with the cryo treatment. This was a blank that I had a local (reputable) gunsmith fit and chamber for me.
Shooting Hornady 225 ELDM and its a 3-5 moa gun. I reload and made a hand load but it only gets slightly better.

I understand a sub moa gun in a 2 moa shooters hands will not get sub moa results.

I also understand that its a game of variables and that if something in the system is wrong (ie contact with the barrel to chassis) it will not have good results.

I have completely exhausted everything I can think of from shooting technique (if I didn;t have another gun- 6.5 prc that shoots amazing- I would doubt my ability to shoot) to ammo to the rest of the gun. I have a barrel cooler (motorized fan) that I let cool the barrel down.

I finally got a bore scope and was pretty amazed at how poorly my throat looked. Does this look like normal throat wear? Or is this a possible manufacturing issue? Or a gunsmithing issue? There is about 450 rounds down the barrel and like I said, I didnt abuse it with excessive heat or hot loads. The gun has never shot well. Below is a image of the throat of the 300 prc. I will also include an image of the throat of my proof 6.5 prc barrel with 120 rounds down it for comparison. Thanks for the help.

 

[BenE]

Appears the chamber wasn’t cut concentric to the bore.

 

[adamthegrayt]

The throat looks about the same all the way around. If it was cut non concentric to the bore- I would assume that one side of the throat would look different to the other side.

Im going to take the barrel off the action and test it for runout.

Any other comments/ opinions are appreciated

 

[adamthegrayt]

More rifle specs:

Nightforce 7-35 ATACR
Area419 match rings
Defiance Tenacity Action
TriggerTech Diamond Trigger
MDT Chassis and bipod
X-Caliber .30 cal barrel 1:8 5R 26" Heavy contour with their cryo treatment
Chambered by Trevor at Cold Barrel Precision in Medford, Oregon
CGS Hyperion Suppressor on their taper mount muzzle device.

Getting around 2830fps using a garmin chrono. This is from factory Hornady 225gr eldm. I also loaded 225gr Hornady in Hornady cases with 77gr of H1000- CCI magnim primers- with what I thought was about 0.020" of jump to the lands with the same velocity of 2830 fps.

 

[BenE]

The throat looks about the same all the way around. If it was cut non concentric to the bore- I would assume that one side of the throat would look different to the other side.

Im going to take the barrel off the action and test it for runout.

Any other comments/ opinions are appreciated

Yes, it would. Between the shadows, glares, wear points and converging lines something looked off.

 

[610yd]

1:7 for a long barrel with 225gr bullet @ 2800fps ?
Verify my math, but shouldn't it be more like 1:10 or 1:12 ?

What type of paper punches is it leaving at 100 200 300yds?

 

[whatsupdoc]

If the chamber/throat is not concentric to the bore you would see a difference were the lands
begin. Minimum twist for the 225gr is 1:10 and faster. I would first check that all action, scope
and mount screws are tight.

Next shoot with the suppressor removed using a different bullet. Check the actual twist rate of the barrel.

 

[Wannashootit]

That third photo has me baffled, I've borescoped too many barrels to count and I can't tell what the fuck I'm looking at there.
The center land looks as I'd expect, but the ones on either side look "bellmouthed" which is impossible- as I look closer, it appears to be dark discoloration on either side of those lands. Possible hard carbon fouling there in the leade?

What's your cleaning regimen?

Firecracking as I'd expect for the round count, but still should be good for at least another 1K rounds.

 

[John Glidewell]

That third photo has me baffled, I've borescoped too many barrels to count and I can't tell what the fuck I'm looking at there.

That looks like residual carbon to me.

I would do as others have stated, Good cleaning. Shoot without suppressor with different ammo and see what happens. How many rounds on the suppressor too? They need to be cleaned every once in a while.

 

[roostercogburn98]

Shoulda bought a vette

 

[610yd]

1:7 sounds too fast to me., that has to be near de-jacketing rpm's.
Also, Hornady site is not 100%, but their PDF for the 300 prc eldm does say "best terminal performance with 1:8", that still sounds a bit fast to me. I just not finding many posts anywhere where 225gr anything @ near 2800fps muzzle running fast 1:7 twist, I find a few 1:8, and lots of 1:9 1:10 and 1:12 setups. 1:7 @2800fps is spinning that 225gr at 288,000 rpm !

It aint right folks. It goes almost 2x faster at 100yds? Nice try Hornady. LOL.

 

[John Glidewell]

His (OP) orig and subsequent posts say 1:8 twist. Where are you getting 1:7 from

 

[610yd]

His (OP) orig and subsequent posts say 1:8 twist. Where are you getting 1:7 from

Not sure then. Maybe it was edited? I swear I read 1:7.
x-caliber carbon in 300 26" does come 6 or 5R rifling, be good to know which version it is.
Hornady specs are from a 26" 1:8 BARRET MRAD, not sure what rifling that is though.

I find a lot of accuracy issues end up being related to rpm's. Doing online searches for sniper stuff I see 225's near 2800fps using 1:9 1:10 barrels. I surely can be wrong, might be worth a try to load some slower 300's just to see if lowering rpm's helps or not. Trying to find a nick or scratch in throat that accounts for accuracy issue is gonna be tough. Doing a concentric test will help, but it came from a reputable machinst?

 

[lash]

Is it just me or is this an anomaly in the lands?

 

[Aftermath]

Seems like you have an ammo problem. By that, I mean the ammo and rifle are not compatible in some way. Far cheaper, at least up front, to change the ammo. I have serious doubt the twist rate is causing any issue at all.

I'd do some seating depth tests starting with bullets just barely touching the lands. Shoot some and see what you get. I like the number 10. Seat 0.005" deeper and shoot 10 more. Repeat. I'd also go deeper than 0.020" just to see what happens. You already know that ain't working for ya.

I'd also try some other bullets. Try some 210 VLD's.

 

[Aftermath]

1:7 sounds too fast to me., that has to be near de-jacketing rpm's.
Also, Hornady site is not 100%, but their PDF for the 300 prc eldm does say "best terminal performance with 1:8", that still sounds a bit fast to me. I just not finding many posts anywhere where 225gr anything @ near 2800fps muzzle running fast 1:7 twist, I find a few 1:8, and lots of 1:9 1:10 and 1:12 setups. 1:7 @2800fps is spinning that 225gr at 288,000 rpm !

It aint right folks. It goes almost 2x faster at 100yds? Nice try Hornady. LOL.
View attachment 8685920

The bad magic number is 300KRPM. If you go to Berger site and enter the data for the ELDM...even 1:7 is stable. Caveat is I guesstemated the bullet length. I'd have to dig deep to find a Hornady bullet. At 300KRPM, jackets can start to fly off.

 

[Aftermath]

 

[lash]

View attachment 8685947

We’re going to have to ask you to stop posting facts. It interferes with our theories and SWAGs.



What’s interesting to me is that this thread unintentionally reminded me to address the possibility that my suppressor is involved in an issue having. I may go back to square three and test the variance when using it on a particular rifle.

 

[ma smith]

Shoulda bought a vette

TFW you save $100k not buying a car,
but don't want to buy another bbl...

 

[Ty21]

Just buy another barrel from proof or anything company you like… I know I like pva barrels always half moa for me…. If you weren’t going to worry about money how come you went with a man x-caliber barrel? Just curious I’ve looked at them but always went with another company proof,pva.

 

[JAS-SH]

Is it just me or is this an anomaly in the lands?

View attachment 8685934

Assuming that what I'm seeing on the right side of the image is your rifle's free bore that's just fire cracking and it's perfectly normal on high power cartridges.

 

[Evlshnngns]

I have a 300nm prefit from xcaliber(not carbon), its a shooter. I went 10 tw 5r, 26", 7 contour. All I've put through it after fireforming is 225 eldm.


I would try a different bullets like the 215 and 245 berger. You'll know in 5 shots if its worth chasing. Some barrels are duds.

 

[stello1001]

Should've bought the vette...