What causes this?

WoodSmith · Mar 19, 2010

I'm shooting 45 AR using 5.2 gr. Titegroup, 200 gr. Hornady FMJ C/T enc in a 25-2, at ~810 ft/s. These four pieces are typical of the fired brass, the two on the left show one side, and the two on the right show the other side of the brass. What do you think is the cause of the burn marks?

Skip Sackett · Mar 19, 2010

Too light of charge to obturate the case to the cylinder wall.

Dragon88 · Mar 19, 2010

Poor gas seal. 45 is a low pressure cartridge and the case doesn't always seal against the chamber properly, leading to those burn marks. I see it a lot on my 45 auto target loads. You might try a different powder or load, or a firmer crimp to help the powder burn.

Gun 4 Fun · Mar 19, 2010

I see this with a lot of 25-2's. I may be off here, but I believe that it is caused by a combination of things. First is the fact that an awful lot of 25-2's have oversized throats that run around .455"-.457". The second thing is that when you use bullets like the ones you mentioned, there isn't enough shoulder above the moth of the case to support the bullet in the throat.

When you fire rounds in an oversized throat then, the gasses can escape around the sides of the bullet (as well as push on the rear of it like they're supposed to) which doesn't allow the pressure to immediately reach the level that will expand and hold the brass against the chamber wall, thus allowing gasses to escape back around the side of the case that is in the "up" position at the moment of firing. I don't seem to get this in my guns that have correct throat/bullet fitment, but I get it in my 25-2, especially when using cast vesions of the same bullet that you are using. I even get it with loads that are rated just below +P levels in my 25-2.

bmcgilvray · Mar 19, 2010

smith crazy said:
Too light of charge to obturate the case to the cylinder wall.

I'm with Skip. Just as an experiment, carefully work up some heavier charges to see if the condition disappears.

Don't worry about it though if the handloads give the accuracy performance you desire.

epj · Mar 19, 2010

I see the same thing on both my autos and my 25-2 when using mouse fart loads. Tends to go away with heavier loads. Can't tell that it hurts anything other than making the brass dirty.

Skip Sackett · Mar 19, 2010

If it is a problem with the firearm, what are you willing to do about the problem? Send it back for a different cylinder? If the throats are too small you could have them reamed. If they are too big, do you weld them shut?

The reason is that the pressure isn't enough to obturate the case. Whether it is too small a bullet or too light a powder charge or too big of throats. There simply isn't enough pressure to seal off the case to the cylinder wall.

A quick test would be go to a soft lead bullet and run a maximum charge of powder behind it. Get some 45Colt bullets and try them, something that measures .454" or whatever.

Just as a second thought, do the bullets you have now drop through the cylinder? Does it take any push at all? If there is no resistance than that is an issue. If there is the least little bit though, move on to something else, that's not your problem.

Hope this helps.

WoodSmith · Mar 19, 2010

Thanks everyone for your expertise.

smith crazy said:
..........do the bullets you have now drop through the cylinder? Does it take any push at all? If there is no resistance than that is an issue.

The bullets drop thru' the cylinder throats with no resistance. So that's likely the major contributor to the burnt brass.

Since the gun shoots very accurately, and no damage is being done, I'll continue to shoot as is.

Thanks again.

Gun 4 Fun · Mar 19, 2010

I wasn't just typing before for the fun of it. I happen to know a bit about this issue. I have a 25-2 as stated and it does have oversized throats, though it does shoot pretty well. I have used .45 Colt bullets of varying diameter lots of times with lots of combos, but I still see this happening. I don't run powderpuff loads in my guns very often either. Like I stated, I use loads at max normal to +P loads regularly in it, and IT STILL DOES IT!!

The same loads are run through my custom 1911 that is set up for this type of shooting, and the cases don't suffer from this issue.

Having oversized throats essentially reduces pressures from max to somewhere below that, and that is a major contributing factor in this case.

You do need to try some .454"- .456" bulets and se if it alleviates some of the scorching for you.
Remington brand bulk lead bullets run .455" and 250 grains, while Winchester run .456" and 255 grains. Both are of a shallow hollow base design to help with obturation in the throats of older Colt SAA's and will do the same thing in oversized Smith throats. You may want to try MagTech lead 250 FP's as well. I have and they do work pretty well. They generally run from.454"-.455" and are also of a light hollow base design. They are available from Cabela's.

WoodSmith · Mar 19, 2010

Gun 4 Fun said:
I wasn't just typing before for the fun of it. I happen to know a bit about this issue.

I sure didn't think you were wasting your time replying to my question and I do appreciate your expertise on this issue. You sound offended and I don't understand why. I've made a note of your suggestion.

Thanks again.

Skip Sackett · Mar 19, 2010

WoodSmith said:
I sure didn't think you were wasting your time replying to my question and I do appreciate your expertise on this issue. You sound offended and I don't understand why. I've made a note of your suggestion.

Thanks again.

Squid, You will do better just to let it lay.

Gun 4 Fun · Mar 19, 2010

WoodSmith said:
I sure didn't think you were wasting your time replying to my question and I do appreciate your expertise on this issue. You sound offended and I don't understand why. I've made a note of your suggestion.

Thanks again.

Bob,
my comment wasn't directed to you in any way, and I'm sorry if it came off that way. I have no interest in getting caught up in the childish crap that smith crazy likes to stir up here either.

Skip Sackett · Mar 20, 2010

Bob,
Do you have access to some bigger bullets? What about some lead ones?

I have a new mold that throws bullets at .454". I could tumble lube some and send them. A few anyway for testing purposes.

It is a Saeco mould and is of a RN design. If interested, send me a pm with your address. I've sent some bullets of other designs to other members if you want to do a little checking first.

At any rate, I would shoot lead in it anyway. Lead will seal off better and give more consistent numbers across a chronograph if the throats are too big. Too big is a subjective thing. Too big to me would mean that in order to have a bullet that wouldn't push through the throats easily, when loaded in a case they wouldn't chamber either. Does that make sense? Some chambers in the Smith 45ACP revolvers are pretty tight and don't give you much flexibility.

So, if you are interested, pm me with your address. I'll be glad to send you 50-100 or so.

Sorry for the childish stuff, I guess I could have just bowed when I entered the thread and saw who posted then things would have been OK. Being a former serviceman you will understand the following analogy. Remember those folks that got all big headed when they hit E-4? Here it goes by post count. Some just seem to feel because they are on the forum from dawn till dusk, which gives them very little time to DO something with a firearm, they are the new "Corporal" so to speak. At 3500 posts in less than 18 months, it's a wonder there is any time left to do anything else.

Hoptob · Mar 20, 2010

Hi WoodSmith,

I just got myself a 4" bbl. 625 and was looking for a 200 gr. TG load that makes USPSA major. Your load seems close to what I'm looking for. Can you tell me what's the barrel length of your 625?

On your question, I shoot a lot of TG loads in 357mag and often see this kind of marks on the brass. I just ignore them -- it does not seem to affect anything.

Mike

Skip Sackett · Mar 20, 2010

Hoptob said:
Hi WoodSmith,

I just got myself a 4" bbl. 625 and was looking for a 200 gr. TG load that makes USPSA major. Your load seems close to what I'm looking for. Can you tell me what's the barrel length of your 625?

On your question, I shoot a lot of TG loads in 357mag and often see this kind of marks on the brass. I just ignore them -- it does not seem to affect anything.

Mike

Hey Mike,

Is 165 the Major floor? If so, 825fps with a 200gr bullet will do the trick. I'm not a big fan of Titegroup. It just seems to burn much hotter than other fast burning powders. I've had lead bullets, in a rifle, have their bases burnt off using it. Of course, that is with the 44Mag, so not quite apples to apples.
If memory serves me correctly, you shoot a lot of plated bullets, right? May not be a factor for you.

Good to hear from you again, been a while.

WoodSmith · Mar 20, 2010

Hoptob said:
Hi WoodSmith,

Your load seems close to what I'm looking for. Can you tell me what's the barrel length of your 625?

Mike

Mike, the barrel is 6.5" (it's a blue 25-2

)

-Bob

Anton Dee · Mar 20, 2010

Seen this happen a lot, and I think the advice given here about the throats is very good, but I'd like to ask this anyway:

Is this with handloads only?
As it IS possible that the dies do not align as exact as needed?
Sometimes the shellholders are just a bit out-of-zero?
(sorry; I cannot remember the right term in English)

Gun 4 Fun · Mar 20, 2010

Anton-

I don't shoot any factory stuff so I can't say whether or not it would hapen with it. I have seen it happen in mine and my friends guns, so I doubt that the dies are the culprit since we all use a different set.

buck460XVR · Mar 20, 2010

Hoptob said:
On your question, I shoot a lot of TG loads in 357mag and often see this kind of marks on the brass. I just ignore them -- it does not seem to affect anything.

Mike

Same here, altho I don't use TG. Used to get a lot more of it when I used Lil' Gun. Seems I get more with R-P brass than others also.

As for the childish bantering going on in this thread. Sheesh guys, it was a simple question...........the replies need not be contaminated and confused with spite. Grow up and take your personality conflicts elsewhere. If one is old enough to play with guns, one should be mature enough to respect another person's opinion.

Anton Dee · Mar 20, 2010

Gun 4 Fun said:
Anton-

I don't shoot any factory stuff so I can't say whether or not it would hapen with it. I have seen it happen in mine and my friends guns, so I doubt that the dies are the culprit since we all use a different set.

It has probably nothing to do eith handloading, but I was just wondering... And with my engineering background, I want to exclude all odds.

In 1990 I bought a brand new Model 625, and I cannot recall whether I ever shot factory loads in it.
But it DID give the same burnmarks on the brass. However, it was a superb shooter! I remember stepping into the bar, back from the shooting range with a somewhat confused look on my face. When the guys saw my target, the yelled ¨keyhole!¨ making fun of my new purchase. Than I told them that that ¨key¨hole was made by shooting a full cilinder...

When the gun shoots well and the pressures seem within limits, it probably does not matter that much?

What causes this?

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