Pressure at Starting

[deertroy1]

How did it act with another powder?

The same. I tried RL-16 and 95gr Bergers. Maxed out about 3-4gr and 200-300 fps low.

 

[LCazador]

No I did not have any extra capacity. The capacities are almost equal. I said I can load three more grains of powder in the Savage without any pressure signs!

I misworded that. The fact you can load three more grains of powder in Savage without pressure signs indicates some sort of chamber or bore problem with your Cooper. In my case with my Cooper it was a short chamber. Maybe you have a short freebore in the Cooper?

 

[deertroy1]

I misworded that. The fact you can load three more grains of powder in Savage without pressure signs indicates some sort of chamber or bore problem with your Cooper. In my case with my Cooper it was a short chamber. Maybe you have a short freebore in the Cooper?

Freebore is only slightly less than the Savage. I'm leaning more towards a tight or rough bore or both.

 

[deertroy1]

What throws me is that it usually takes a certain amount of pressure to achieve a certain amount of velocity. However in this case I'm seeing the pressure without a corresponding rise in velocity?

 

[dellet]

What throws me is that it usually takes a certain amount of pressure to achieve a certain amount of velocity. However in this case I'm seeing the pressure without a corresponding rise in velocity?

I posted earlier with this exact scenario. Tight chamber and first few inches of bore, the area where peak pressure will occur and showing in the brass, followed by a loose bore where pressure/velocity is lost and shows on the target after a few rounds..

I have seen a few barrels that the bore was basically barrel shaped. Tight on both ends and loose in the middle

An overly tight bore could also drop velocity due to higher friction.

 

[EOD Rob]

I posted earlier with this exact scenario. Tight chamber and first few inches of bore, the area where peak pressure will occur and showing in the brass, followed by a loose bore where pressure/velocity is lost and shows on the target after a few rounds..

I have seen a few barrels that the bore was basically barrel shaped. Tight on both ends and loose in the middle

An overly tight bore could also drop velocity due to higher friction.

Dellet,
I am following the thread to learn. This is something I have never dealt with and have followed everything. Please correct me if I am wrong! So what your saying is, in a nut shell, it would be like a barrel being burned out in the middle? (but not really burned out!) Same principal? If more suitable please PM. I would really like to know.

 

[dellet]

Dellet,
I am following the thread to learn. This is something I have never dealt with and have followed everything. Please correct me if I am wrong! So what your saying is, in a nut shell, it would be like a barrel being burned out in the middle? (but not really burned out!) Same principal? If more suitable please PM. I would really like to know.

First post indicates loads a grain over max, with minimum load velocity. Low velocity compare to same load in another rifle. That’s problem number one. A slow barrel.

Pressure signs and a hard bolt lift is problem number two.

They may or may not be related, but high pressure, low velocity is opposing symptoms in general.

I think somewhere in the last couple pages the OP mentioned that the chamber checked fine, but the throat was shorter than the other rifle. That may explain the pressure sign, different chamber different pressure. Happens all the time.

A slow barrel compared to another is not uncommon. Chamber and bore dimensions vary. Happens all the time.

The combination is more rare.

Barrels burn out from the throat forward. So not likely to have a barrel burnt out with high pressure.

Tight chamber and normal or tight bore for the first maybe two inches could explain pressure sign. How do you burn out the middle of a barrel? You don’t. You either have a problem when it was bored, rifled or more likely when it was hand lapped.

You end up with normal ends of the blank and a worn out center. It should be caught at the quality control department before it leaves, but things happen. Maybe find it with air gauging, if you pull the barrel. Might feel a loose spot with a tight patch. Maybe a skilled eye with a bore scope, but it will need to be confirmed.

Pushing a soft lead slug or bullet through the bore will also provide the feel needed.

A captured bullet could give a clue. It would likely have carbon deposits ahead of the base, confirming gas blowing by. That blow by is velocity loss.

I think he may have two problems, one in the chamber, one in the bore. As I added to the post a tight bore can also slow down a bullet. So re chambering the barrel may ease the pressure signs, but the velocity drop might be more likely in the bore.

 

[NorCalMikie]

The pressure sign is ejector mark on the case head.

???? First thing that comes to mind is??) (and I've said it a million times) Case too short for chamber, when fired, case gets slammed back against the bolt head and you get ejector mark. So, maybe you're NOT actually seeing pressure signs?
And something else to check. Try loading long, bullet stuffed .010 INTO lands to hold the case against the bolt head.
Once fired, the issue may go away when the case gets formed to the chamber. And make sure you don't push the shoulders back too far again and you end up with the same problem all over again.
I single feed all my ammo (except my gas guns) and it's all loaded INTO the lands and I have pulled a few bullets when opening the bolt on a live round BUT, I knew it was coming so the barrel is pointed UP so the dumped powder didn't cause "much" of a problem.
It's been my experience that if you load with a jump to the lands with a given powder charge, you may see pressure signs.
Take that same powder charge, with the OAL set to a jam INTO the lands, you may not see any pressure signs and can actually go higher with no ill effects. YMMV.

 

[deertroy1]

???? First thing that comes to mind is??) (and I've said it a million times) Case too short for chamber, when fired, case gets slammed back against the bolt head and you get ejector mark. So, maybe you're NOT actually seeing pressure signs?
And something else to check. Try loading long, bullet stuffed .010 INTO lands to hold the case against the bolt head.
Once fired, the issue may go away when the case gets formed to the chamber. And make sure you don't push the shoulders back too far again and you end up with the same problem all over again.
I single feed all my ammo (except my gas guns) and it's all loaded INTO the lands and I have pulled a few bullets when opening the bolt on a live round BUT, I knew it was coming so the barrel is pointed UP so the dumped powder didn't cause "much" of a problem.
It's been my experience that if you load with a jump to the lands with a given powder charge, you may see pressure signs.
Take that same powder charge, with the OAL set to a jam INTO the lands, you may not see any pressure signs and can actually go higher with no ill effects. YMMV.

I've had the headspace checked. It's good. I'm also barely bumping the shoulder.

 

[NorCalMikie]

I've had the headspace checked.

It's NOT a head space issue. Think brass issue.

 

[deertroy1]

It's NOT a head space issue. Think brass issue.

This would have been my conclusion as well but the same brass will stand max to even more than max in the Savage?

 

[deertroy1]

It looks like the problem is still a carbon ring. I scrubbed the crap out of the first 6" or so of my barrel with both RG-1 and JB-Bore paste on a nylon brush wrapped with a patch. After doing this COL with a Hornady 65gr V-Max measures about 2.920" however, after firing about 10 rounds the COL measures about 2.850" or about 0.070" less. This leads me to believe I'm not removing the entire carbon ring but only enough for the bullet to clear slightly. Once it returns my bullet isn't being measured to the lands but rather to the carbon ring. I'm not sure how to fix it?

 

[Texas10]

I have a Cooper M54 in 6mm Rem. that shows signs of pressure a grain or so above published starting loads. I tried a couple different powders and same thing. Velocities however are close to starting load velocities (Oehler 35). The barrel had a carbon ring just ahead of the chamber when I got it which I thought was causing the pressure issues but after cleaning it out (still waiting for borescope to confirm) the issue remains.

Example:
Hodgdon starting load 24" 40gr IMR 4064 Sierra Bullet = 3355 fps

My load 24" 40.5gr IMR 4064 Sierra 70gr Bullet = 3262 fps shows ejector mark

Same load in my 22" McGowen barrelled Savage was able to reach Hodgdon max of 44.5gr and over 3600 fps no signs of pressure. Same components, same brass. Savage has a slightly longer throat but both loads are nowhere near the lands.

I've been loading for 30 years and this one baffles me!

Ideas?

My first thought is to ask if you've calibrated your powder scale recently?

Regarding the carbon ring, this was my recent experience with a new (to me) 6BR. I was tuning a load by shooting 5 shot groups with powder charges varying by .3 gr over 1.2 grs total. All loads shot pretty much identically and all about .3 moa.

Never experienced that before!

Thoroughly flummoxed as I was shooting the last group, I ejected the last round before firing and noticed the bolt was very hard to pull back. Once the round was ejected, I noticed engraving marks on the ogive that suggested a carbon ring in the throat.

Once home, the borescope confirmed my suspicion, big fat carbon ring that had the effect of smoothing out the starting pressure. In effect all the loads were starting out tightly jammed, and powder charge changes made little difference. Very interesting!

 

[deertroy1]

My first thought is to ask if you've calibrated your powder scale recently?

Regarding the carbon ring, this was my recent experience with a new (to me) 6BR. I was tuning a load by shooting 5 shot groups with powder charges varying by .3 gr over 1.2 grs total. All loads shot pretty much identically and all about .3 moa.

Never experienced that before!

Thoroughly flummoxed as I was shooting the last group, I ejected the last round before firing and noticed the bolt was very hard to pull back. Once the round was ejected, I noticed engraving marks on the ogive that suggested a carbon ring in the throat.

Once home, the borescope confirmed my suspicion, big fat carbon ring that had the effect of smoothing out the starting pressure. In effect all the loads were starting out tightly jammed, and powder charge changes made little difference. Very interesting!

How'd you get it out?

 

[shoot4fun]

How'd you get it out?

You bought the rifle in used condition if I read you correctly. What did the previous owner do? Did you contact him to see if he was having the same issue as you?
Just how many rounds did the previous owner really send thru the barrel?
Was the rifle always a 6MM Remington? Could it have once been, say, 243 or 6BR?
When a barrel gets fire cracked to a certain point and is then rechambered without cutting off the original tenon there can be immediate and dangerous pressure issues occur. I had it happen when I had a barrel that had a fairly high round count of 6 Dasher redone with a 6 Creedmoor reamer.
I duo think, if all the above are answered, you have a carbon ring issue. AS for suggestions on removal, check out this article from Tom at Alpha Brass:

Carbon Ring Build-up, Resulting Problems and a Cure | Alpha Munitions

alphamunitions.com

I tried it on an older 6 Creedmoor barrel and it worked wonders.

 

[deertroy1]

You bought the rifle in used condition if I read you correctly. What did the previous owner do? Did you contact him to see if he was having the same issue as you?
Just how many rounds did the previous owner really send thru the barrel?
Was the rifle always a 6MM Remington? Could it have once been, say, 243 or 6BR?
When a barrel gets fire cracked to a certain point and is then rechambered without cutting off the original tenon there can be immediate and dangerous pressure issues occur. I had it happen when I had a barrel that had a fairly high round count of 6 Dasher redone with a 6 Creedmoor reamer.
I duo think, if all the above are answered, you have a carbon ring issue. AS for suggestions on removal, check out this article from Tom at Alpha Brass:

Carbon Ring Build-up, Resulting Problems and a Cure | Alpha Munitions

alphamunitions.com

I tried it on an older 6 Creedmoor barrel and it worked wonders.

I pretty sure this is the original unaltered factory barrel. I bought the rifle from a dealer and have no idea who the original owner/owners are.
I seen the article from Alpha. However, I live in rural Canada. No Simichrome anywhere up here. Amazon Canada has it for $37 a small tube! I can get Flitz and Brasso.

 

[shoot4fun]

I pretty sure this is the original unaltered factory barrel. I bought the rifle from a dealer and have no idea who the original owner/owners are.
I seen the article from Alpha. However, I live in rural Canada. No Simichrome anywhere up here. Amazon Canada has it for $37 a small tube! I can get Flitz and Brasso.

If you have a place to buy Iosso Gunbrite that will work well too.
I have used it for carbon rings and for wiping carbon off muzzles behind the radial brakes of my BR guns.

 

[deertroy1]

If you have a place to buy Iosso Gunbrite that will work well too.
I have used it for carbon rings and for wiping carbon off muzzles behind the radial brakes of my BR guns.

Oh, I have access to it all. Most of it is around $10 and another $20-$30 for shipping. About the only thing I can get here is Flitz but there are report of barrels being ruined with it due to it polishing the leade (not good)! Free shipping from Amazon Canada LOL!

 

[shoot4fun]

Oh, I have access to it all. Most of it is around $10 and another $20-$30 for shipping. About the only thing I can get here is Flitz but there are report of barrels being ruined with it due to it polishing the leade (not good)!

No Flitz for sure.
I think it is going to take a lot of work to get that ring out. Sounds like it had been building (previous owner) for quite some time.
Good luck!

 

[243winxb]

OD of loaded rounds neck? OD of fired neck of brass that shows ejector marks?

Thinking the brass is not releasing the bullets. Just a guess.

If answered, i missed it?