Range Report: .62cal "RIFLED" GM Flint Barrel

[roundball]

19* and 10-15mph wind...sunrise was a big, fat, round blood red Sun...beautiful.

Decided to dedicate this trip to Goex 2F...seeing what the barrel would do with 80/90/100grns Goex 2F and Eddie May .600 cast balls, .015”/ .018”/ .020” patches, with and W/O .62cal Oxyoke wonderwads.

No bench but sitting in a chair was pretty steady with my elbow braced down against my side/chest...and I stayed at 25yds this first trip so I could sort out the variables easier and 25yds was protected from the wind. (50yds + was not).

.018” lubed pillow ticking with .62cal Oxyoke wonderwads gave the tightest groups.
Each successively larger powder charge was more accurate than the one before it and 100grns Goex 2F was the most accurate of the three, significantly so, turning in single ragged holes for 5 shot groups.

Shooting 40 strong hunting loads were enough for the morning and I was getting cold anyway, shooting with gloves on, etc...and if I never did another thing to it, this rifled barrel hunting load is already outstanding...I’ll see how it does at 50yds next weekend but I'll be shocked if it's anything less than outstanding.

.62cal GM Flint smoothbore barrel, then 'rifled' by Ed Rayl with .012" square bottom grooves @ 1:72" twist.

100grns Goex 2F
.62cal Oxyoke prelubed wad
.018” Oxyoke prelubed pillow ticking
Eddie May .600 cast ball

Ed Rayl did an outstanding job both with the rifling & crown, as well as the exterior...no indication whatsoever that the breechplug was removed, the barrel rifled, and the breechplug reinstalled except for his 1/4" witness mark underneath on the bottom flat at the breechplug/barrel seam...hard to believe that kind of quality & precision is available for $65.

 

[spud]

Do you have an address for Eddie May? thanks --Spud GREAT SHOOTING :applause:

 

[roundball]

Eddie May Round Balls
159 Ridley Rd.
Chatsworth, GA. 30705
706-581-8225
Please Call or Write to place Order

 

Congrats Roundball and thank you for all the help and advice you gave me in my TC big bore project!

Billy

 

[roundball]

Congrats Roundball and thank you for all the help and advice you gave me in my TC big bore project!

Billy

Do you know how much longer before he ships your barrel?

 

[Sharp Shooter]

I might have to do that!

 

[wtilenw]

I'm just curious why you didn't use .610 roundballs? .020 under boresize seems contrary to the norm.
Idaho PRB

 

[paulvallandigham]

Idaho: YOu may have read something wrong. Bore size( Land to land) in his gun is .620. .020 under that is .600, not .610. He is using the correct sized ball for his new rifle. As well as the patch, and the choice of using the wonderwad to protect the patch, and lube the barrel. I can't wait to hear his report on his 50 yd. accuracy.

 

[roundball]

I'm just curious why you didn't use .610 roundballs? .020 under boresize seems contrary to the norm.
Idaho PRB

Because GM .62cal bores are not .620"...GM actually makes them at .610"...GM manager himself confirmed that when I called to question it after micing the bore myself and getting only .610...I've owned three and they all mic'ed .610".

 

[wtilenw]

Thanks Roundball, that answers my question :v
Idaho PRB

 

[davy]

RB are these on the TC 1 inch barrel? Seems thin walled to be rifling unless its thin rifling, is the reason I ask! :hmm: :hatsoff:

Davy

 

[roundball]

RB are these on the TC 1 inch barrel? Seems thin walled to be rifling unless its thin rifling, is the reason I ask! :hmm: :hatsoff:

Davy

It's a large GM 1" x 33" octagon barrel.

Ed Rayl is a well known barrel maker and the first question I asked was if GM's 1" smoothbore barrel could have rifling added without it creating any kind of safety isses and he said no problem at all.

Similarly, GM makes .54cal deep grooved rifled barrels using 15/16" barrel stock.

 

[davy]

I am curious what a max load would be in a gun like that? :thumbsup:

Davy

 

[Rebel]

How long is the barrel? As much powder as will fill it and leave room for the ball. :grin: Just kidding you new guys.

 

[roundball]

I am curious what a max load would be in a gun like that? :thumbsup:
Davy

Well, first...for all the folks who like to jump too quick and/or have reading/comprehension problems, let's get a disclaimer out right up front:
this is just pure wild speculation on my part...pay no attention to it whatsoever.

BEGIN SPECULATION HERE:.

Knowing the buffer margins built into load data tables, and how proof loads are usually handled, if a .58cal published max load is 120grns Goex 2F, it should easily handle 150-175grns.

IMO, the .62cal would do likewise...projectile is an eyelash heavier than a .58cal but the bore volume is much larger too, off-setting pressures to a degree.

And remember, modern .45's & .50's are routinely using 150grns of powder now days in much smaller caliber bores with 250-300grns bullets...so the larger .62cal RBs at 325grns in todays good modern steel ML barrels would easily be able to do the same. (150grns)

Personally, my deer hunting load for this .62 is going to be 100grns Goex 2F...(same as for my .58cal)...and it's plenty enough for a kill shot on a deer at woods distances I'd normally be confronted with.
END SPECULATION HERE.

 

[faw3]

Just to ad to what roundball said Davy Ive shot at least 125 shots out of my 62 rifled 1" underhammer barrel with no probs at all and the barrel maker of mine said "sure its safe, youv been shooting for years so you know dont short start it. We tell people that 100 is tops because we cant controll how they will load it" I'll also ad he put on here a long while back he uses 5 balls in stake busting shooting race-is that safe ? but he's been doing it for years and is working today :rotf: Fred :hatsoff:

 

[davy]

Well good stuff guys .. just wonderin!

Davy :thumbsup:

 

[paulvallandigham]

Accoridng to the formula for determining maximum burning Black powder( 11.5 grains per Square inch of barrel, using a round ball, the maximum charge for a .600 bore gun, 33 inch long barrel, is 107+ grains. For the .620 bore gun, 33 inch long barrel, is 114.57 grains. In his 42 inch 62 smooth bore, Roundball could fire a maximum load of 145.8 grains.

Now that formula just determines the maximum amount of black powder that can be burned in that size barrel, shooting a round ball. . You can put more powder in it. With conicals, you will burn more powder, simply because of the delay caused by the weight and inertia of the heavier slug. ( More pressure must be achieved to begin to move a heavier bullet than a round ball. That extra fraction of a second of time allows more powder to burn. The increase in pressure raises the temperature in the chamber, causing more powder to ignite quicker, too.) The down side is that chamber and barrel pressure climb rapidly, and recoil also accelerates in direct proportion to the increase in velocity, and the weight of the bullet.

Roundball's one hundred grain load in his 33 inch barrel is probably going to be a very accurate, and relatively flat shooting load for that barrel length, and caliber, while leaving recoil down where he can handle it. Since he regularly shoots 80 grains of FFFg powder in his smoothbore, the 100 grain charge in the rifle should not deliver much more recoil to disrupt his shooting form, and aim. If he finds that it does, he can always reduce the powder charge, or switch to using FFg powder. Pin point accuracy is not needed to kill deer at the ranges he killed deer this past season.

 

Boy, it's not 1 in 48 twist, who knows how accurate it will be :rotf: :rotf: :rotf:

Bill

I started with nothing, and still have most of it left!

 

[jethro224]

Sounds like you got a real shooter there roundball. I'm glad to hear everything worked out so well for you. Enjoy! :thumbsup: