Split brass Remington 760

[Berserker]

I have a 1980 760 gamemaster, that I removed the barrel to replace the oring on it few years ago. Shot couple hundred rounds through for it to1" with partions. I was firing this year and I was surprised how hot the the brass was. Note sure if this is just my memory forgetting it normally is or how the gas flows in a pump.

Out of 25 rounds I had 2 split at the shoulder. Last 2-3 I cleaned with rubbing alcohol, all I had on hand.

The brass was shot once before, sized few years ago. I don't remember lube. I tubled in media after sizing. Is lube the cause? Remington, WLR, IMR4350 54.5, noslet seating depths from website.

Also my cleaning has been primarily patches. I did since this, try to get a mop in chamber.

Suggestions on what to check? Should the brass be so hot? Thanks

 

[JmacD]

Also my cleaning has been primarily patches. I did since this, try to get a mop in chamber.

A buddy of mine rigged up one of those gooseneck flex things that goes in a drill to run a mop. He didn’t put it in his drill, but turned it with a 1/4 nut driver. It gave him the “3rd elbow” to get at it.

Possible it’s a “generous” chamber that some of those remmys we’re known for? My dads 742 is… “expansively proportioned”. Still knocks over a whitetail like nobody’s business! I’m more chiming in just to see suggestions since I’ve had a bit of similar experience with the 742

 

[jmorris]

Suggestions on what to check?

Check that you are not sizing the case too much.

Post a photo or two of the split cases.

 

[GeoDudeFlorida]

Check the age of your loads. You should probably also pull one apart and look for signs of degradation in the powder. Also, just to be extra cautious, check the date you loaded that ammo and make sure you’re not using very cold weather loads on unusually warm days. Temperature sensitivity is a small factor until you get into very hot loads made with powder that’s in the process of gassing out.

 

[243winxb]

Brass Heat normal, a split second after being ejected.
Neck cracks , brass problem.
Rubbing alcohol should not ever contact brass.

O-Ring never heard of it till now and i have a very old one. Newer 760's are different then mine.

 

[Berserker]

It was new powder. I just loaded few days before.

The 760/7600 have an oring,that rattles. Some years you can change it without taking barrel off. Mine you have remove barrel. I did it in 2016.

Only difference is was using partition protected tips, cause that is what I happened to buy years ago. This was first time with standard partition. Same load.

 

[Berserker]

Brass temp threw me, cause bolt brass is stone cold,and pump is so hot. I couldn't remember if this was normal .

Is there a path for the gas in pumps that needs to be cleaned?

 

[243winxb]

Is there a path for the gas in pumps that needs to be cleaned?

No gas tubes or ports. Just like a bolt action, except cleaning is from tne muzzle end.

Hoppe's Boresnake could be used for barrel cleaning, maybe? I would not. If cord breaks, to hard to remove from barrel.

 

[Berserker]

delete

 

[Berserker]

So have you got a chance to fire a bolt rifle, to see brass comes out stone cold?

 

[Chuck R.]

Check that you are not sizing the case too much.

Post a photo or two of the split cases.

As jmorris said, cracks at the shoulder are sometimes a headspace issue caused by oversizing.

Can you measure your loaded and fired brass at the shoulder to see how much expansion you're getting?

 

[jmorris]

So have you got a chance to fire a bolt rifle, to see brass comes out stone cold?

The longer the brass stays in there, the more heat the steel will absorb from the case and it will be cooler. If the barrel is already at a higher temp than the case, the opposite will occur and an unfired round that’s subsequently ejected will be hotter than when it entered despite not having been fired.

Just heat going where it’s cooler. Even a tiny .22 lr case will blister skin right after being fired. Probably one of the first things I learned was to not wear long sleeves with the SA-22 (bottom eject) and hold them like this…



The case thrown down the cuff onto a kids skin, it’s instantly recognizable as HOT!

 

[Berserker]

Shooting 300 win mag and 30-06 bolts. Brass is cold. Pump 30-06 is very hot. I can't remember if always like that.

22s are often semi auto, which is why I think they are hot

 

[Berserker]

I tried a no go gauge ,cause I had one. I'll leave one in bolt to see if it gets hot next time.

I measured neck of fired one. But no spec on fired in book that I saw.

I got some contact cleaner, I am going to clean the brass too.

As far as alcohol and brass, plenty do it not sure the issue.

 

[GooseGestapo]

Brittle brass! Probably got shorted on the production line by Remington.
I’ve seen it before with Remington .257Roberts brass.
Probably skipped the annealing step.

 

[AJC1]

I tried a no go gauge ,cause I had one. I'll leave one in bolt to see if it gets hot next time.

I measured neck of fired one. But no spec on fired in book that I saw.

I got some contact cleaner, I am going to clean the brass too.

As far as alcohol and brass, plenty do it not sure the issue.

If you have a case that fits over the neck and touches the shoulder you can compare datum. 40 or 10mm should work. A sized case is probably more accurate for spec comparison

 

[Berserker]

I have loaded a bit of Remington brass. 2 in 25, which might have not assocation with batches. Something else to this.

I just dont remember the hot brass before.

 

[tightgroup tiger]

The case thrown down the cuff onto a kids skin, it’s instantly recognizable as HOT!

Yeah, or a 9mm case going down the back of your neck. Hot potato!

 

[Berserker]

But that is semi auto with the gas. My bolts stone cold. 300 win mag and same load in another 3006.

I'll try leaving brass in couple seconds longer in case I am cycling bolts faster on bench. I really have my doubts it makes a difference. When you compare bullet lying on ground while I search for it, and still hit

But think some people need to do some shooting.

 

[Chuck R.]

If you have a case that fits over the neck and touches the shoulder you can compare datum. 40 or 10mm should work. A sized case is probably more accurate for spec comparison

Also, I'll add decap that piece of brass.. sometimes the fired primers have ridges where the FP hit and will throw your measurement off. Ideally you'd use something like this:

Lock-N-Load® Headspace Comparator & Anvil Base Kit - Hornady Manufacturing, Inc

Lock-N-Load® Headspace Comparator & Anvil Base Kit Lock-N-Load® Headspace Comparator The Lock-N-Load® Headspace Comparator extends brass life, improves accuracy, and enhances safety. The gauge measures...

www.hornady.com

Which is what I use to set up my dies to just "bump" a couple .001s. The above will let you know FF you're oversizing. You're looking for the delta between fired brass and your sized brass.. Measure about 5 of each and use averages.

We shot yesterday, 60 degrees, practicing from 400-750 yds, running 5 tgts in a series. I was using my 6mm SLR and a 300WM and noticed no what I'd call "hot" brass, and that was running a bolt pretty quick.

 

[Berserker]

Still my question is,do you have hot brass when shooting a pump rifle like 760.

 

[Slamfire]

I believe @GeoDudeFlorida is on the correct tack, but of course a picture will likely change the failure analysis direction.

The thing is, old gunpowder outgasses NO2. Nitrogen dioxide is a horrible oxidizer and it will ruin brass. Typically the first sign the powder has gone bad in the case, is excessive case neck cracking. Body splits are not uncommon either.

example of old pulled IMR 4895 causing neck splits and case head separations in a gas gun

this IMR 4895 was new when I loaded it, and conventional wisdom was that gunpowder is immortal. Conventional wisdom is wrong.

Gun Club President sold me a 300 Win Magnum and tossed in ammunition he loaded. When I saw this cartridge, and I know he still has WW2 IMR 4831, I suspected the powder had gone bad in the case.

powder did not look bad, but appearance means nothing in terms of gunpowder stability. What matters is the amount of stabilizer left in the gunpowder, and I don't have a gas chromatography machine to test that.

Vihtavuori powders came into the US in the 1990's (plus or minus) and various powder lots have been going bad twenty years later.

However, without more information, it is next to impossible to diagnose your problem. Brass fails all the time, sometimes it is over worked. Sometimes bird poop causes season cracking. Saw a picture of a brass or bronze outboard boat propeller with one blade cracked off. Bird poop did that. Dirty birds! There are lots of causes of brass enbrittlement, but I doubt you ever thought old deteriorated gunpowder could cause it.

Old gunpowder will also blow up your gun, given enough tries. If you ever experience high pressure indications with old gunpowder, stop using the stuff. The October 2023 Guns Magazine has an interesting article in which a Garand was blown all to hell with reloads and unstable gunpowder. The article is "Know thy Gun, know thy Gunshop" The Gunshop that sold the Garand was giving customers store credit if they supplied the gunshop with "remanufactured" ammunition. A failure analysis of the reloads indicated that "the remaining kernels of unburned powder could not be matched up to any known gunpowder". That's a clue the customers were probably using ancient pull down powder. Or maybe, just ancient gunpowder. The reloaders got store credit, and the buyers of their "remanufactured ammunition" had blowups. What a deal.

 

[conan32120]

As jmorris said, cracks at the shoulder are sometimes a headspace issue caused by oversizing.

Can you measure your loaded and fired brass at the shoulder to see how much expansion you're getting?

If OP recently replaced barrel as he said I would lean toward headspace issue that neck sizing only the unsplit brass might add a clue. Does brass in a pump gun get hot? Well yes and no depending on what one calls hot. If you can pick it up I don't call that hot and the pump gun brass should be similar to a bolt gun in that respect. To hot to touch might be the the hot gasses enveloping the brass as it expands to find the chamber walls

 

[Berserker]

New gun powder. I have fired couple hundred rounds probably since I removed barrel and reinstalled. Been 7 years. Not that it hasn't crossed my mind.

Rounds I loaded in past were hot too. I was really hoping to hear from someone who shoots a pump I don't recall brass being hot before.

New powder, same load in other rifles,but different bullets.

Brass had only been loaded once

 

[Berserker]

I need to clean the rest of brass and examine. Haven't decided if I will even reload it