Gas Check bullets tip without checks

[Irascible]

I have a Ruger #3 rebarreled to a 32 special in an 8mm barrel. The twist is 1 in 18. It shoots the Saeco 180gr # 081 bullet VERY WELL. When I try the same bullet without the checks it is tipped when it hits the 100yd targets. WHY? I posted this question on the ASSRA websight and got some theorys, but nothing deffinate. One fellow thought that by leaving the GC off I was creating a boatail and that was doing it. I theorized that without the GC there was less pressure and that made less velocity? A mute point probably, I have ordered a new Borton-Darr flat base bullet mould. But that hasn't cured my curiosity!

[leftiye]

See Bass ackward's thread which concerns muzzle issues with cast in the thread "RPM and Bore size" in this same forum. These effects would be enabled and exascerbated when the gas check was left off.

I might guess that your load that is accurate with a gas check might be buggering up the boolit base when not used with a gas check. You don't say what the pressures are, nor the burning rate of the powder is, nor the boolit hardness, so this is just a guess.

Theoretically, the rear driving band acts the part of the boolit base when there is no gas check. Even if it had an effect like a boattail, it would still be very square due to being cast that way, and should not tip yer boolit.

Shortened bearing area due to lack of a check might well destabilize your boolit's design though.

[runfiverun]

shortened bearing area, and the fact that the check area is the last thing to
leave the case neck,possibly tipped,or forced not straight.

jmy02

[Leftoverdj]

Gas check protects the bullet from gas cutting. Leave it off and there is no such protection. A few people report being able to get GC bullets to shoot accurately without GG at very low velocities and pressures. I ain't one of them, but that may be because I decided right quick that it was not worth my time and effort. Gas check designs get GCs, and I have PB moulds for when I don't want to use a GC.

[Irascible]

13-15gr of 5744, 4227 or 4759. 15/5744 is the most accurate. It's about 1400fps. Alloy is 10lb ww + 1 lb of 50/50. Groups with gas checks are 5/8" to 3/4" at 100yds and that is a consistant grouping not a fluke.

[44man]

I guess I have posted this about 1000 times! :mrgreen:
You lost a drive band and the boolit is no longer compatable with the twist rate and load. In effect, you shortened the boolit.
If you don't want to use a check you must remove that portion from the mold and make it a PB.

[joeb33050]

Greenhill tells us that a .323" barrel with 1:18" twist will stabilize a bullet .87" long MAX. Estimated weight of that bullet is 168 grains. You're on the edge of stability here, particularly at low velocities.
I shoot ~208 grain 311299/314299 in 10" and 12" barrels, without gas checks, without problem.
Try a shorter bullet.
joe b.

[Bret4207]

Leaving the check off changes a bunch of things AND leaves you with a non-square, non-full size base. I've had good results at short range with out GC, but only with the Lyman 311316 in the 32-20. Bad luck sans GC with anything else IIRC.

[725]

All the above and this too. I suspect that the effects of gas at the muzzle at the time the boolit leaves the barrel don't excape at exactly the same time. Rather like having a bad crown. Gas lets go a nano-instant on one side before it does on the other. Uneven release = wobble / tipping / keyholeing. Just a thought. I might be whistling through my hat again.