to Gas check or not to Gas check??

[crackerjack57]

Quick question all..... im running a 7.62x39 bolt gun. alliant 2400 underneath the lee 155 gn cast boolit and if I remember correctly its cruising about 1850 fps. I am currently using gas checks. i know I don't need a Dacron filler but I want to start using about 3/4-1 gn of the filler. I loaded some and did see a bit of improvement in accuracy, getting about 1 1/2" at 100 y. what my question is do you think i absolutely need the gas check using the filler?? when i fire a shot there is a puff of clean unburnt Dacron puffing out of the barrel. Im wondering if the filler would protect the boolit base? Im sure that some of you have thought of this already so just wanting your 10 cents.

Thanx
Dan

[Whiterabbit]

why not try it and see?

[MtGun44]

Only Mr. Target knows the answer for your exact combination of barrel dimensions, velocity, alloy, design,
lube, boolit dimensions, hardness, powder speed, pressure, bore smoothness, twist and your uncle's hat
size - [which is rarely an issue, but I swear that sometimes it may play into the mix ;-) ].

Ask Mr. Target - he ALWAYS gets the right answer.

Bill

[44man]

The gas check is to stop skid at the base, not protect the boolit. But it also adds to boolit length that you can lose by omitting it, changing match to twist.
Filler does not alter that, it changes powder ignition. You do not make a filler act like a check but it might plug gas leakage and I am not so sure a tuft of anything will hold back high pressure gas. It is like asking for a lube to seal a boolit. TOO MUCH PRESSURE, like an engine that uses expanding rings to seal and uses lube to prevent ring wear. It is not the lube that prevents oil from going past worn rings when an engine fires, but doing a compression test will show a little more pressure if you stick in oil, low pressure! If rings are worn, the oil goes by the rings very happy to burn. I was a mechanic and I will tell you if rings are worn (boolit that does not fit) no oil on earth will seal the rings. An engine does not even equal a gnats butt to gun pressure so you can read and believe all the nonsense.
Other fillers like corn meal might compress into a hard slug and hold back gas. Can of worms I stay away from.
If the boolit needs a check, use it and at that velocity I don't think a PB with a filler will work either if the boolit skids. If it does not skid, a PB will work but you change boolit length by leaving off the check.
I was shooting a 30-30 Tender with a GC boolit and was hitting pennies at 100 yards, ran out of checks and loaded without. Every single boolit went through the paper sideways at 50 yards.
My answer is to try it. It might work or fail big time but don't think it is the filler.

[Sensai]

It all boils down to "try it and see".

[runfiverun]

keep them on.
if the load got better with the Dacron.
you could try raising the powder the same amount of weight, as the Dacron weighs and omit that.

[FLHTC]

Hey 44man, wasn't there a time in the distant past when wax sheets were marketed as gas check material? I know there were many items that actually worked but fell out of favor over the big name brands. I understand your point on holding back extreme pressures but how do plain base bullets do it when the pressure is up close to 30,000 cup? I believe pressure is a weird phenomena and one which can't be predicted but often it seems as though pressure has no rule to follow. I've heard of hunters bulging a shotgun barrel from shooting too close to a snow covered limb. Now that's effecting the pressure without even being an obstruction.
How can a double powder charge explode a steel cylinder without venting all its energy out the barrel behind a lead bullet. Yet a dry lube, which is exponentially weaker than the gas check ( akin to the cylinder and the lead bullet) cannot hold back pressure?
You sound very adept to explaining the scientific aspects of escaping pressure and id like to hear more.

[williamwaco]

At that velocity, accuracy is going to suffer without the gas check.

Keep It.


If you just want plinking loads around 1500 you can omit it but again accuracy will suffer

My experience is based on the .30-30 in a Thompson Contender with loads from 1000 fps to around 1900 fps.

[MaineJim]

I completely agree with 44man and williamwaco.
I have tried shooting boolits without gas checks in different guns ,including the TC Contender 30-30 without much success.
I tried them hard,soft and anywhere between 1000-1500 fps.They shot ok for 25 yard plinking but 50 yards and beyond ,no go.And I was using filler.
I use 3/4-1 grain Dacron on all my loads because I find them more consistently accurate ,not to protect the boolits base.

[MtGun44]

My experience, too, says that GCs likely to be needed for rifles, but I
still think that if someone is up for testing, give it a try. PROBABLY the
accuracy will not hold up, but maybe the combo of alloy, design, barrel,
lube, etc MIGHT work.

Expect problems, but see what happens - and please report back.

Bill