Author Topic: Does this photo show “gas blow by”? (Read 5584 times)

Flint62Smoothie · « **on:** February 13, 2018, 04:52:31 PM »

Here’s a picture of a 13yo shooting my left-handed 50-cal half-stock by Brian Anderson of VT. My hunting load is 80-grains, but for range use I lower it to 55-grains. I took videos of the boy shootin’ my rifle and when reviewing each frame, I noticed what looks to be evidence of gas blow by.

I did’t post the frames before & after this picture, but it does appear that red hot gas is escaping the muzzle before the roundball charge does. I know all about patch/lube/charge combos ... so I don’t need that info, jist looking for comments if this is what I’m seeing. For the record, that 55-grn load put 4-shots into a nickel-sized ragged hole group w/ 1-shot right next to it, offhand at 25-yds, so the load will certainly shoot! And the boy hit both gongs, one 2”x2”, using a rifle he’s never shot before.

What say you?

lightshot

smylee grouch · « **Reply #1 on:** February 13, 2018, 05:22:57 PM »

It would almost look like it. What patch thickness are you using? Great photo by the way.

Flint62Smoothie · « **Reply #2 on:** February 13, 2018, 05:54:53 PM »

Quote from: smylee grouch on February 13, 2018, 05:22:57 PM

What patch thickness are you using? Great photo by the way.

Red-striped pillow ticking from Joanne’s Fabrics, measures 0.016” after washing twice to remove any sizing. Lube was 4-drops per patch of Hoppes BP lube (can shoot all day without cleaning).

Just for ‘fun’ I may try a thicker patch combo, but was just more curious about the flame exiting the barrel ... apparently before the roundball. This rifle does have square-bottom grooves, so maybe it warrants a better sealing patch/load.

But I sure can’t complain about the groups it currently is capable of printing, whether using 55 or 80-grn loads!

OldMtnMan · « **Reply #3 on:** February 13, 2018, 06:13:29 PM »

I don't think it's possible to stop all gas blow by with a PRB.

smylee grouch · « **Reply #4 on:** February 13, 2018, 06:44:44 PM »

Forgot to mention it Flint 62 but thanks for getting the young one shooting, hope he enjoyed it.

Standing Bear · « **Reply #5 on:** February 13, 2018, 06:47:54 PM »

I can see why you suspect blow by but

?? I really can’t say. IMO the best if not only way to tell - without very high speed photography - is by examining everything fired patches.
TC

Marcruger · « **Reply #6 on:** February 13, 2018, 07:34:38 PM »

No need for guess work. Show us pictures of the fired PATCHES. They tell the tale. I cannot believe no one posted this before now.
I would also note that you posted the cloth thickness. Is it 100% cotton? Can you see sunlight through the weave when held up to the sun? For example, Burlap is thick, but the weave density is awful. Think canvas when looking for weave density.
Also, 25 yards tells you little. A loose loaded smoothbore will group okay at 25 yards. Go to 50 and then 100. If you are getting blowby, you will see erratic groups due to velocity variations and fouling.

I hope this helps. God bless, Marc

thelongrifle · « **Reply #7 on:** February 13, 2018, 07:51:05 PM »

If it is shooting good and you are hitting with it jus keep shooting and don't try to fix what ain't broke.

WadePatton · « **Reply #8 on:** February 13, 2018, 08:00:08 PM »

Quote from: Marcruger on February 13, 2018, 07:34:38 PM

No need for guess work. Show us pictures of the fired PATCHES. They tell the tale. ...

This. Gases cannot get past the ball without leaving indications on the patch.

OldMtnMan · « **Reply #9 on:** February 13, 2018, 08:00:33 PM »

Is a picture available showing a PRB leaving a muzzle with no gas blow by?

Flint62Smoothie · « **Reply #10 on:** February 13, 2018, 08:58:46 PM »

All good questions. As stated, I usually don’t load that low and at higher BP charges, my patches are fine, with outstanding accuracy to 100-yds.

As for the boy ... he’s hooked on flintlocks; doubt he’ll ever own a ‘cap gun’ , haha!

hanshi · « **Reply #11 on:** February 14, 2018, 02:05:31 AM »

A prb can come close to being a gasket but cannot completely seal the bore 100%. Even modern cartridge firearms often show evidence of a bit of gas escaping using slo-mo photography.

RichG · « **Reply #12 on:** February 14, 2018, 03:28:03 AM »

I believe Lyman had some high speed photos of a prb out of a musket showing gases exiting the muzzle before the ball. I know Sam Fadala also talks about it at length in his handbooks.

Daryl · « **Reply #13 on:** February 15, 2018, 01:21:33 AM »

Fired patches will show scorch marks in the groove marks on the patch, if there is blow-by. Serious blow-by usually, causes anything from burns to incineration of the patch, depending on how

bad it is. In order to keep his patches from being incinerated, Sam had to use a wad-type barrier between his patched ball and the powder. Try it, it will work. When I tried using a wad in my

small bores - under 50cal. I found a reduction in accuracy. Only my 14 bore rifle showed it was impervious to accuracy changes with a wad between patched ball and powder. I was testing for

hunting loads with respect to protecting the powder from the lube in the patch. I found through experience, that the barrier wad was not necessary.

I suggest you try a barrier wad if you are having trouble with accuracy, burned or scorched patches & cannot load a tighter combination, the easiest solution is to simply use a thicker patch or

larger ball. I found I was able to use a thin .017" to .018" patch, when I went to a bore-sized ball. A nice smooth crown makes loading these loads possible.

Accuracy shooters (bench, cross-stick, chunk, plank) use bore sized or up to .007" larger than bore sized balls, with .020" patches. These guns usually have false muzzles, but not chuck or plank -

not allowed there.

Sharpsman · « **Reply #14 on:** February 15, 2018, 03:04:20 AM »

25 yards is spitball range! $:-\$

Even with centerfire rifles....there will be gas exit the muzzle prior to the bullet exit!

Just how do you know the bullet hasn't made an exit prior to some of that flame??

Like others stated....check your patches!

D. Taylor Sapergia · « **Reply #15 on:** February 16, 2018, 04:15:39 AM »

Correct me if I am in error. What I see in the photo is a left hand flintlock...I see a jet of flame coming out of the vent - not the muzzle. It is being deflected up by the lip of the pan. If the fire in the image was from the muzzle, it would appear to be pointing downward, in relationship to the muzzle rising from recoil.

So no, we are not seeing blow-by from the bore.

Flint62Smoothie · « **Reply #16 on:** February 16, 2018, 04:27:41 AM »

Quote from: D. Taylor Sapergia on February 16, 2018, 04:15:39 AM

If the fire in the image was from the muzzle, it would appear to be pointing downward, in relationship to the muzzle rising from recoil.

It is a LH rifle and if you look immediately ahead of the muzzle, you can see orange flame. Whether the ball already left or not ... I don't now, the still frame before and afterwards don't prove anything.

To the others ... I know all about reading patches et al and as stated, one hole groups out to 50-yards using this low 55-grn load is well good enough for me!

I just thought the photo was interesting and pretty cool ... that's why i posted it.

D. Taylor Sapergia · « **Reply #17 on:** February 16, 2018, 05:06:06 AM »

I see flame above and forward of the shooter's left hand, and the rifle is pointed at the target - not up into the trees. I am not convinced that any of the flame in the photo is from the muzzle. And it doesn't matter. It is an excellent photo!

Flint62Smoothie · « **Reply #18 on:** February 16, 2018, 05:21:39 AM »

... right below the target frames you can see an orange glow exiting from the muzzle.

Daryl · « **Reply #19 on:** February 16, 2018, 09:49:49 PM »

Flint62 - I see the glow from the muzzle you are talking about, but at this point in time, the ball has either 'gone' or is still in the bore - we cannot really say with any degree of certainty as we need higher resolution to see exactly where the ball is of is not.

Due to the pressure at the muzzle, which is likely well over 200 atmospheres, as soon at the sealing of the patched ball in the bore is no longer holding it back, the flame would blast out well past

the ball as it was then unrestricted and could travel at much higher speed than the ball that was holding it back.

Need better, sharper photograph. Like Taylor said, it's a great photo, non-the-less.

D. Taylor Sapergia · « **Reply #20 on:** February 17, 2018, 03:59:55 AM »

And the answer to your original post question, "Does this photo show gas blow-by?" The answer is "no, it does not."

duca · « **Reply #21 on:** February 17, 2018, 07:29:06 AM »

The photo looks like it’s coming from the Touch hole

Anthony

rich pierce · « **Reply #22 on:** February 17, 2018, 04:57:37 PM »

Quote from: duca on February 17, 2018, 07:29:06 AM

The photo looks like it’s coming from the Touch hole

Anthony

On the money

Daryl · « **Reply #23 on:** February 17, 2018, 07:06:39 PM »

You can see he was aiming at the steel plates, not the targets. You can see the vent flash - yes - it is huge & that is what everyone seems keyed on.

You can also see the flame coming from the muzzle of the rifle (the barrel and forestock is pointed down and to the left of the targets - as the orange steel plates. We do not know where the ball is,

in relation to that muzzle flash/glow.

Dennis Glazener · « **Reply #24 on:** February 17, 2018, 07:07:28 PM »

Enlarge the photo and look at the muzzle, sure looks like the flash is from muzzle and not fro touch hole.
Dennis

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Author Topic: Does this photo show “gas blow by”? (Read 5584 times)