28 nosler pressure and fouling

[Badgerclaw]

Was your chamber cut to saami or does it have a longer freebore?

It is saami. I looked up the chamber drawings and saw that it has a 3° lead angle to the lands. That has me wondering if I need to get a throat reamer and change that. Also wondering if I were to put some lapping compound on a cleaning patch and just run it back and forth over the freebore and the very beginning's of the lands if that might relieve some pressure

 

[highdrum]

The lead angle is aggressive, more so than any the nosler/ultra mag cases. I know guys who run them fast are usually running 0.230-.290 freebore which increases you powder capacity greatly reducing pressures. The bearing surface and BTO on the hornady bullets is generally a good bit longer than compared Bergers, which also makes pressure. If you don't have room, install a wyatt's box, and then ream the freebore by approximately another 0.05" and at the same time change lead angle to 1.5° or so. Only downfall is you'll be limiting bullet choices and throat wear will be faster. Keep the rifle cool, shot strings @ 3 rounds, cool between. I've read of guys chasing the lands up to 0.015 per 100 rounds when shot with hot barrel long strings.

 

[yobuck]

How tight is the neck?

 

[Badgerclaw]

Update. I seated the bullets back .090 off the lands and the longer jump relieved pressure, but the FOULING!!! 1 shot and there is copper build up. After 3 shots I can barely see any bare metal in between the copper. I borrowed a bore scope and I will try to upload a picture of what I found at the end of the chamber. It's a ring right before the lands that makes it look like the freebore is too large in diameter or my bore is too tight. Not sure if that's why it won't quit fouling or not.

 

[Badgerclaw]

Look right at the base of the lands

 

[Wedgy]

Do you have the 90 degree angle scope ?

 

[Badgerclaw]

Do you have the 90 degree angle scope ?

I dont have a scope at all. I was just borrowing that scope. Crazy thing about that ring at the end of the chamber is, yesterday I ran some 280 grit lapping compound over it, and it's still there

 

[Wedgy]

If you have developed a hard carbon ring it will need to be removed with an abrasive like Isso. Most mix a little on a tight patch with some Kroil and short stroke it right at the ring. Can also use the Isso blue brush, I have even used a cordless drill to spin it but don't get ridiculous with it. Their blue brush is not like a regular nylon brush, it is way more firm.

https://shop.brownells.com/gun-clea...MI1a-Zkay73AIVRpF-Ch2tEg6hEAQYASABEgKEN_D_BwE

 

[Badgerclaw]

Thank's for the info and advice everyone. I took it to someone with a 90° bore scope today and found out what the problem is. It appears like x-caliber used a rougher reamer and never put the finishing reamer in the chamber, so I have a 90° angle from my freebore to my lands. This explains my pressure problems and the copper fouling... it was probably sheering off half the jacket!!!! No wonder it fouled in one shot. I ordered a reamer from PTG today and will finish the chamber when my reamer gets here

 

[WildRose]

Badger you're using two pretty dirty powders so carbon buildup is likely an issue.

Did you use a good, thorough break in regime?

Len's thread on "carbon fouling' might be helpful for you.

 

[Badgerclaw]

Badger you're using two pretty dirty powders so carbon buildup is likely an issue.

Did you use a good, thorough break in regime?

Len's thread on "carbon fouling' might be helpful for you.

I did break in the barrel with my regular procedure, and when that didn't work I did a second break in with a different procedure. The rifle has gone six rounds at the most without being cleaned

 

[WildRose]

Update. I seated the bullets back .090 off the lands and the longer jump relieved pressure, but the FOULING!!! 1 shot and there is copper build up. After 3 shots I can barely see any bare metal in between the copper. I borrowed a bore scope and I will try to upload a picture of what I found at the end of the chamber. It's a ring right before the lands that makes it look like the freebore is too large in diameter or my bore is too tight. Not sure if that's why it won't quit fouling or not.

That sounds really odd. You may need to polish the chamber as there may be some imperceptible roughness in their catching carbon and copper.

Might be time to have a specialist look it over and give you some recommendations.

The "carbon ring" that usually causes pressure problems is usually 3-12" down the barrel, most commonly forming at 6-9" in front of the chamber. Yours is a different issue.

 

[WildRose]

Look right at the base of the lands

Great photo and very helpful.

I'm no expert but that simply looks wrong in that there is no gentle slope into the lands. It is so abrupt I would think it is causing excessive stripping of the jacket material on contact.

A gentle ride into the lands allows the grooves to be more pressed into the bullet rather than cut with a sharp edge.

I would again suggest maybe it's time to let an expert gunsmith look at it and to have them possibly gently ream it out just enough to remove that raised edge and create more of a gentle ride into the lands.

 

[jasonco]

Did you make? Seems to me, you're running a little TOO fast? I use Retumbo, under 79grs and after 3250fps, those bullets don't make it to the target, 175 & 180. FWIW