Gas Checks Affect Pressure & Velocity?

[M71]

Greetings, I'm anticipating the delivery of 100 45-70 gas checked 470 gr. bullets, #2 Alloy, Lubed with Lyman Super Molly, sized to .458 (Lyman Mold # 32640671). The question I have is: How does having a gas check affect published load data without them? Specifically do they generate more or less pressure and velocity. I'll be experimenting for accuracy with 40-45 grains of Varget with these bullets. The barrel length is 34". I'm thinking the gas check will aid in keeping the bore cleaner too. Thank you.

[Bass Ackward]

Greetings, I'm anticipating the delivery of 100 45-70 gas checked 470 gr. bullets, #2 Alloy, Lubed with Lyman Super Molly, sized to .458 (Lyman Mold # 32640671). The question I have is: How does having a gas check affect published load data without them? Specifically do they generate more or less pressure and velocity. I'll be experimenting for accuracy with 40-45 grains of Varget with these bullets. The barrel length is 34". I'm thinking the gas check will aid in keeping the bore cleaner too. Thank you.



Gun specific question that would be more critical if you said you wanted to do this with Red Dot. Also might be more if this were a 22 bore.

Using Varget in a 45 pipe, my guess is that you will wonder why you had this concern.

[MtGun44]

Not so you'd notice any vel or press diff.

Cleaner, typically yes. "Sized to .458" Have you slugged your bore? Just "assuming" is
a poor practice in this situation. It is very common to require a .459 or .460 or even larger
boolit requirment based on your particular bore size. Just because the factory jbullets are
made in .458 has nothing whatsoever to do with what size boolits you need. Typically,
you need .001 to .003 larger than slugged groove diameter in rifles.

Bill

[StarMetal]

I would have to assume that neither the plain bullet or the gas checked bullet are going to leak lots of gas totally past the bullet. With that said the little extra weight of the gas check isn't going to be noticeable. Sure, a scientist could probably fine a minute raise in pressure.....but some are thinking the gas check will seal better and thus raise the pressure a tad....you are wrong.

[44man]

I would have to assume that neither the plain bullet or the gas checked bullet are going to leak lots of gas totally past the bullet. With that said the little extra weight of the gas check isn't going to be noticeable. Sure, a scientist could probably fine a minute raise in pressure.....but some are thinking the gas check will seal better and thus raise the pressure a tad....you are wrong.
Hey Joe, take two identical boolits, one cut for a check and one a PB. The PB weighs more.
Otherwise you are right, it depends more on boolit design for changes in pressure, not whether it has a check or not.
I am not talking about leaving a check off a boolit made for one.

[mike in co]

Hey Joe, take two identical boolits, one cut for a check and one a PB. The PB weighs more.
Otherwise you are right, it depends more on boolit design for changes in pressure, not whether it has a check or not.
I am not talking about leaving a check off a boolit made for one.

take two IDENTICAL boolits, put a gas check one one...it weighs more.

my limited personal experience is that a gas checked design boolit with out a gas check out shoots the same boolit with a gas check. the base of the cast boolit is better than the base of a boolit we put a gas check on....just my guess.

my limited experience is with 44mag loads in a srh....every time the bullet with out a gas check out shot its gas checked partner.
i have said it before i dod not think we put gas checks on as well as we can cast a base. the last thing the muzzle sees is the base or gas check.

[mike in co]

Greetings, I'm anticipating the delivery of 100 45-70 gas checked 470 gr. bullets, #2 Alloy, Lubed with Lyman Super Molly, sized to .458 (Lyman Mold # 32640671). The question I have is: How does having a gas check affect published load data without them? Specifically do they generate more or less pressure and velocity. I'll be experimenting for accuracy with 40-45 grains of Varget with these bullets. The barrel length is 34". I'm thinking the gas check will aid in keeping the bore cleaner too. Thank you.


my limited experience has been with revolvers and leverguns.

in a revolver, the gas checked produced aprox 30 fps more velocity than the non gc boolit.( same load, boolit weight 6gr more(?))

my guess, that on that big of a boolit with that long of a bore, it will not be an issue.

[StarMetal]

Hey Joe, take two identical boolits, one cut for a check and one a PB. The PB weighs more.
Otherwise you are right, it depends more on boolit design for changes in pressure, not whether it has a check or not.
I am not talking about leaving a check off a boolit made for one.

Jim,

But the factory doesn't do that, they cut the gas check bullet so that with the check it ends up pretty close to the weigh of the PB.

Again we're splitting hairs....not enough weight difference to make a hill of beans.

So I have to disagree on the weight difference. Now if you take the PB and cut a gas check shank out it, then the PB will weigh more, but that's not exactly what the factory is doing. Even if they did with the gas check on and lube they weigh pretty darn close to not make a difference.

[44man]

Jim,

But the factory doesn't do that, they cut the gas check bullet so that with the check it ends up pretty close to the weigh of the PB.

Again we're splitting hairs....not enough weight difference to make a hill of beans.

So I have to disagree on the weight difference. Now if you take the PB and cut a gas check shank out it, then the PB will weigh more, but that's not exactly what the factory is doing. Even if they did with the gas check on and lube they weigh pretty darn close to not make a difference.
I am not talking enough weight to worry about, just a small amount but both boolits need to be exactly the same. The copper is a small amount lighter then lead. So the hill of beans is a good analogy! :bigsmyl2:
Mike in co makes some points I do not agree with because it is still the alloy. Some need a check, others don't. Yes, if done right a PB shoots as good as a jacketed but so does a GC boolit. I see no difference at all.

[mike in co]

I am not talking enough weight to worry about, just a small amount but both boolits need to be exactly the same. The copper is a small amount lighter then lead. So the hill of beans is a good analogy! :bigsmyl2:
Mike in co makes some points I do not agree with because it is still the alloy. Some need a check, others don't. Yes, if done right a PB shoots as good as a jacketed but so does a GC boolit. I see no difference at all.

i said my experience is limited...but consisant.

i have tried three different boolits this way. a gas check boolit with and without a gs. complete load developement with each and in each case the gas check booolit WITHOUT a gc shot better than the same boolit with a gc.

the difference is small but consistant.
ww plus minor tin, cast at 750/775 water dropped. sized a tad under 432.
aa9 or wc820 powder. 7.5 ruger super redhawk.
original load was a 255 at 1340 or so.
with a gas check shot 3/4" without a gas check they shot 5/8.....small diff but consistant and cheaper without the gas check...short range either 25 or 50 yds.
similar with 265 and 300.
you may think alloy but its the base of the boolit ..its the last thing seen by the muzzle. my 2cents worth as cast is
"square'r" to the bore than the gascheck.
mike in co

[JJC]

I'm gona have to give that a try. My GC shank is a bit small and annealing helps but the GC still falls off at times. Any one know how ww would work at 1750 fps with out a gas check in 45-70? M71 do you buy your cast bullets? I have a stick of Lyman super moly you are welcome to, or any one else.

[JJC]

M71 have your PM sent you one back I think. Just went and loaded three rounds with out gas check in some cases I preped earlier. Only I did not prime them like the other batch. Took a minute to figure out what was falling out.

[JJC]

If you go to hawes.org thats Hawes Ranch Outfitters web site you can down load buffalo targets for that rifle your shooting up there. They are scaled down and to be placed close 15 yards I think, would be like shooting a buff at 150 yards. Have a bunch printed and use snap caps... one of these days it will be a real one

[StarMetal]

I am not talking enough weight to worry about, just a small amount but both boolits need to be exactly the same. The copper is a small amount lighter then lead. So the hill of beans is a good analogy! :bigsmyl2:
Mike in co makes some points I do not agree with because it is still the alloy. Some need a check, others don't. Yes, if done right a PB shoots as good as a jacketed but so does a GC boolit. I see no difference at all.

I agree with you again Jim....don't make this a habit :drinks: