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 I’m 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...

 

[diggler1833]

Meanwhile, instead of spending all that money on a 'Vette, you can just start rocking the jorts and New Balances.

 

[Megalodong]

No holds bar

....

x-caliber carbon bull barrel

....

Defiance Tenacity Action

 

[610yd]

Is anyone digging on 300 PRC ELDM? Quick search pulls up some interesting threads (this site and sister sites). 1) some suggest 1:8 is just too fast for 225gr 300 ELDM, 2) others are suggesting accuracy issues because the Hornady ELDM's are not consistent from bullet to bullet.

Can 6 vs 5R barrel make a diff? I suspect it can. Here on this site:

What I do believe in is that the 5R (odd number of grooves) and the gentler angle on the sides of the lands help with distorting the bullet jacket less and this helps with bullet failure. Especially with some of the thin style match jacket bullets. Bullet failure is more of a problem for a long range shooter than a short range shooter.

I would perhaps start with slowing down the round, then after that try another bullet.

 

[Baron23]

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

View attachment 8685934

I'm no expert but all I see in this pic is fire cracking in the grooves and erosion of the lands in the lead. Is this not expected in a barrel with 400 rounds of 300 PRC thru it?

 

[71firebird400]

Meanwhile, instead of spending all that money on a 'Vette, you can just start rocking the jorts and New Balances.

Worst thing about Corvettes are the other owners

 

[Im2bent]

I'm no expert but all I see in this pic is fire cracking in the grooves and erosion of the lands in the lead. Is this not expected in a barrel with 400 rounds of 300 PRC thru it?

In the circled area the top edge of the land there's a deformation/ burr looking edge.

 

[610yd]

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.

That specific Berger calculator is flawed, it's only good to tell you if you don't have enough twist, it DOES NOT tell you that you have too much twist. Put in their 300 230gr, fps 5000, twist of 1, it says you are good to go.... blahhahahaha, BS.

Also not clear to me where the accuracy is failing, is it 100yds, or 1mi? I assumed this 300PRC build was for long distance.

More digging for punching one hole at long distance, is showing up that you choose a twist on the low end of rpm's that stabilize the bullet+muzzle fps, and when you get near max rpm's for bullet the accuracy starts to suffer. I myself cannot validate that, others can though.

 

[Baron23]

In the circled area the top edge of the land there's a deformation/ burr looking edge.

Thanks....but me?....I'm not seeing anything but erosion of the lands and fire cracking. Looks like on that part of the lead that the fire cracking has extended a bit into the land but isn't this as expected?

 

[TheBigCountry]

Meanwhile, instead of spending all that money on a 'Vette, you can just start rocking the jorts and New Balances.

Stop giving away all the secrets to life

 

[lash]

Thanks....but me?....I'm not seeing anything but erosion of the lands and fire cracking. Looks like on that part of the lead that the fire cracking has extended a bit into the land but isn't this as expected?

You need glasses then. This is a machining anomaly. Nothing to do with normal fire cracking.

Are you familiar with with machining?

 

[diggler1833]

Stop giving away all the secrets to life

My secrets to life stopped with: "Pants down, THEN shit."

^ Sometimes that one gets more difficult to remember after a hard night of drinking.

 

[adamthegrayt]

Wow guys! This thread got one or two comments in a month and then POW it goes nuts last night. First off, Thank you all for putting thought into this, even those who just want to subtly comment that i'm poor. It's still all appreciated.

Ill try to address comments in order and also give an update to what I have found.

The barrel twist ordered was 1:8 but I have not confirmed it. The rifling is 5R. My idea was to eventually shoot 250 atips and they have a minimum twist of 8.5

Always good suggestions to check all screw torque (action, rings, mount to rail, rail to action.) I also checked for interference with the recoil lug or if anything might be touching the barrel.

My suppressor was new. I cleaned it first with an ultrasonic cleaner and compressed air. I also cleaned it about 2 months ago. I also tried a muzzle brake (Area419 hellfire).

Wannashootit's comment about the "bellmouthing" is the best description of what I was initially concerned with. Ive never seen the start of lands and gooves look like that- but thats why im here. Ill try to get some better pictures. The firecracking looks normal to me.

Since first posting, I have done more testing. Yes, I can just buy another barrel and that might be what I will ultimately do, however my goal is to understand why its happening. Admittedly, I found that I was chasing my zero a bit. When the gun is cold, the first shot is way left, like a mil at 200yards, roughly like 8-10 inches. Then, without changing my scope or my point of aim, the next round would be about an inch to the right of the last one. This would happen for about 10 rounds with each round moving about an inch to the right @ 200yards without changing my windage or changing my point of aim. After 10 or so rounds, it groups nice.

After thinking about it, this had been roughly my experience the whole time. I would get to the range and be pissed that my first rounds were so far off from where I thought I had it zeroed. I would go recheck all torque and go through my checklists and maybe adjust my scope. Then by the end of my range session, I would get a decent group (not where I wanted the group but a decent group) and get my hopes back up again. Then it would repeat at the next range session.

So I stopped changing anything and just shot at the same spot without changing zero. So far I have done 4 different range days and they are all the same. Pictures show the last range day with me numbering my shots 10. Then the next image is the group shot after 10 rounds. So in 4 different range days it has grouped way left and crept back to center after about 10 rounds. Same with a brake on it. It must be heat related IMO. Good grouping at rounds 11-15 and 16-20 but those group centers would be still slightly moving to the right.

I took the gun to Ernie at Gunner's in Brookings Oregon and he said he thinks that some barrels will get a stressor in the barrel at some point. That stressor when subjected to heat changes the point of impact. He said he has only seen it one other time with a name brand carbon barrel.

I originally went with X-caliber because I thought they were a quality manufacturer. I have tried to call them and their mailbox is full and i'm not getting a response via email. I'm going to remove the barrel and I think get it magnifluxed and try to spot the issue. Might have to cut the carbon sleeve off if the stressor is not reveled on the outside.

 

[610yd]

That spot circled needs better pics. The scope obviously has set of small LED's making pics look odd.

 

[adamthegrayt]

That spot circled needs better pics. The scope obviously has set of small LED's making pics look odd.

Totally agree and thanks for spotting that.

 

[610yd]

The barrel twist ordered was 1:8 but I have not confirmed it. The rifling is 5R. My idea was to eventually shoot 250 atips and they have a minimum twist of 8.5

This has me worried. Min twist is not a thing, not the way you state it. You choose a twist based on bullet and muzzle fps. In other words, the bullet and muzzle fps are defining factors that help derive what twist is needed. The needed twist has a range from min to max.

Why 8.5min? Almost all 250gr near 2800 fps stabilize in 1:10 twists, and likely still do out to 1:12 twists.