ADvertise hereRotoMetals2Lee PrecisionInline Fabrication
MidSouth Shooters SupplyRepackboxWidenersTitan Reloading

Page 1 of 7 1234567 LastLast
Results 1 to 20 of 134

Thread: Gas Check Boolits without Gas checks ???

  1. #1
    Boolit Buddy Fire_stick's Avatar
    Join Date
    Jan 2009
    Location
    Spanish Fort
    Posts
    413

    Gas Check Boolits without Gas checks ???

    If your bullet is sized properly for your gun,
    and if the pressure is sufficient to obturate the bullet per the bullet hardness.

    Is there a need for a gas check? Even at elevated velocities?

    From what I have been reading, I suspect the answer is, or could be no.

    Although I also suspect powder burn rates may play a role in determining whether a GC is needed. Maybe it is simpler to use a GC and not worry with all the variables.

    Please help me understand.

  2. #2
    Boolit Buddy camotruck's Avatar
    Join Date
    Feb 2009
    Location
    Frederick MD
    Posts
    160
    Me too, help me understand, I thought that the limiting factor was the speed the pill was pushed down the tube and the friction generated on the bearing serfaces. Are we balancing beteen cooking the pill from the back and heat generated by friction?

    Thinking.....................

    The harder alloys let us get faster speeds and overcome friction and the GC lets us use more power / powder/heat to up the velocity.

    Yes......No......

  3. #3
    Boolit Master

    Join Date
    Apr 2008
    Posts
    4,947
    I had thought, mix some alloy, put on a gas check, and crank up that puppy.
    Well, I learned better.
    I believe, the gas check being harder than the boolitt, does prevent gas checking to an extent. Sizing is an issue here.
    Useing copper as an example, it is harder than lead alloy. I am not sure how much as checks are thin. However, it does some scrapeing, and will fill the back of the casting as it travels down the bore. I am no expert, and I would love to find an alternative to swageing. I paper patch with great results in my .30s. No leading, good accuracy, fairly simple once the original point is achieved.
    Specifically, how the gas check works is a mysery to me. I believe it does seal the bore, but with the loads I use for paper, the same load gas checked is a waste of time and lead.
    I bet someone knows for sure here. I am interested in finding out also.

  4. #4
    Boolit Master
    Join Date
    Mar 2005
    Location
    Base of the Blue Ridge
    Posts
    1,145
    I don't know why GC's work. It's enough for me to know that they do. A while back, I honchoed a double run of .25 cal moulds. The two bullets were identical except that one was GC and the other PB. Accuracy with the PB bullets vanishes ar somewhere between 1200 and 1400 fps, depending on rifle and load. The GCed bullets still shoot well at 2400 fps.
    Sometimes you gotta wonder if democracy is such a good idea.

  5. #5
    Boolit Master Slow Elk 45/70's Avatar
    Join Date
    Feb 2009
    Location
    Clear, AK
    Posts
    1,289
    I would like to know the real answer also, I've been trying to find the answer for years, and the only thing I can see that makes much sense to me is that the GC protects the base of the CB from the propellant burn when fired at higher than 1700fps +- . I agree that it helps seal the bore.

    I can't really prove this , just my theory from my humble experiences using PB & GC....
    So if someone knows the real answer, please share
    Slow Elk 45/70

    Praise the Lord & Pass the Ammo

  6. #6
    Perma - Banned


    Bret4207's Avatar
    Join Date
    Mar 2005
    Location
    St Lawrence Valley, NY
    Posts
    12,926
    Quote Originally Posted by Leftoverdj View Post
    I don't know why GC's work. It's enough for me to know that they do. A while back, I honchoed a double run of .25 cal moulds. The two bullets were identical except that one was GC and the other PB. Accuracy with the PB bullets vanishes ar somewhere between 1200 and 1400 fps, depending on rifle and load. The GCed bullets still shoot well at 2400 fps.
    And great design they are! We're all still in your debt for that run DJ!

  7. #7
    Perma - Banned


    Bret4207's Avatar
    Join Date
    Mar 2005
    Location
    St Lawrence Valley, NY
    Posts
    12,926
    Quote Originally Posted by Fire_stick View Post
    If your bullet is sized properly for your gun,
    and if the pressure is sufficient to obturate the bullet per the bullet hardness.

    Is there a need for a gas check? Even at elevated velocities?

    From what I have been reading, I suspect the answer is, or could be no.

    Although I also suspect powder burn rates may play a role in determining whether a GC is needed. Maybe it is simpler to use a GC and not worry with all the variables.

    Please help me understand.
    I'll give you my understanding, it'll be in simple terms and is only my opinion.

    Yes, there is a need for gas checks once you pass a certain point. That point varies from load to load and gun to gun, even ambient temp can affect it so your summer load might need it and your winter load not.

    Obturation is an iffy thing, sometimes it happens and good results follow, other times it happens and bad things follow. Same for when there is no obturation. In a perfect world the would be no obturation- the boolit wild precisely fit the throat area and the powder would gently start the boolit down the barrel without distortion. That's why Harry Pope and Zischang and Schoyen and all the other old time lead boolit shooters used a false muzzle and muzzle loaded their guns. Most of us won't do that. We prefer fixed ammunition, so we try and hit a happy medium.

    Different powders, primers, case shapes, throat shapes, seating depth, alloy, boolit design and size , rifling type and condition, even ambient air pressure can cause variations in the burn rate and pressure curve of a given load. SOME plain based boolits in SOME guns will be extremely forgiving of all those variables and will tend to shoot good up to somewhere around 2000 fps. At least those are the claims that have been made. You will occasionally hear of someone who gets 22-2300 fps for 5 shots or so. If this is true, these guys shouldn't even bother picking up a lottery ticket, they've used all their luck up!

    In an average rifle those variables will stack up in a seemingly random order and usually limit your plain base shooting to under 1600 in general no matter how good a fit you have. That 1600 fps can be 1200 in some guns, 1700-1800 in others, larger calibers tend to be more forgiving. If, IF you go to a slower powder, a harder alloy, maybe a little larger boolit and a super lube and a filler you can up the speed. Maybe. It might work one day and not the next.

    In handguns the PB generally works up to 11-1300 fps given good fit, etc as with rifles. Cartridges like the 45ACP can be used at factory velocity with PB with little problem, same for the 32 ACP and 380 ACP. Low pressure! Take a 9mm and you're good to a certain point and then it's lead city. Same for the 38, 357, 40S+W, 44 Special and Mag and of course the any of the other hotter rounds. Pressure seems to be the bad guy here and to me at least, it seems to work a little differently in handguns than in rifles.

    A gas check just makes achieving higher velocity at a higher pressure easier. IMO boolit bases do not, and have never "melted". There isn't time enough , even under the pressures involved, for the heat transfer to take place. IMO what happens at the base is that the pressure pushes the lead around and like a rock thrown in mud there is some splashing. The rougher and weaker the base and alloy the more splash. Lead alloy is ductile and if you've ever hit an ingot with a hammer you can see that you don't get a smooth surface when you've hit it. I believe this takes place and the "splashed" particles are minute, maybe microscopic in size even.

    The same general theory goes for the sides of the boolit once it's moving- only now you have hot gases trying to rush past the boolit through any gap between boolit and barrel. The alloy doesn't "melt", the gases abrade the boolit surface (and of course a rough barrel can help this happen too) and the particles of alloy are blown onto the barrel surface and pressed on by pressure. At least that's my understanding. There can also be the instance of lube failure where the alloy is actually rubbed into the barrel surface. I call it lube failure, but it may actually be something else.

    So what does the GC do?

    1- Provides a scraping action to the barrel. The edge of the check theoretically scrapes lead from the boolit ahead of it away from the barrel.

    2- Provides a seal of sorts in a properly sized gas check/barrel interface. An undersized gas check is a waste of money. What the tolerance is depends on the gun and load, but as a general rule I want my checks at least bore size and preferably closer to groove size. If the check is under bore size it's effect is drastically reduced, may not work at all and is wasted money.

    3- Provides a much stronger base to the boolit and one that remains square throughout the boolits journey up the barrel. This I've seen- seat a check crooked and shoot several groups with crooked checks and square checks. It don't take a genius to see the difference.

    4- Makes achieving higher velocities at higher pressures EASIER. That doesn't mean the sky is the limit. There comes a point where the alloy can't take the pressure/velocity/rifling anymore and you get leading and wild shooting. But the GC makes it easier to go faster using pressure to boost speed.

    That's my understanding at this point. 10 years ago I had a different opinion, 20 years ago it was different than that! I used to think hard, hard, hard!!! I thought that would solve all the problems. Not so. A GC won't solve it all either, but it does reduce the variables in most cases.

  8. #8
    Moderator Emeritus


    Join Date
    Mar 2005
    Location
    SW Montana
    Posts
    10,452
    Veral claims a check will aid the base in strength and prevent it from stripping out in the twist. I would add that to Brets excellent points.
    [The Montana Gianni] Front sight and squeeze

  9. #9
    Boolit Bub SlamFire1's Avatar
    Join Date
    Aug 2006
    Location
    AL
    Posts
    62
    In a 30-06, I tried Lyman 311299 and 311284, lyman #2 alloy, with IMR 4895 without gas checks. Measured velocities were between 1700 and 1800 fps.

    Without gas checks I got six foot by six foot groups.

    With gas checks, the things shot much better.

    I am sticking with gas checks.

  10. #10
    Boolit Buddy Papa smurf's Avatar
    Join Date
    Oct 2005
    Location
    East Springfield Pa.
    Posts
    166

    Check or no

    In relation to just accuracy with or without a gas check , I think the gas check gives the boolit a more uniform base . A good crown will give better accuracy than a poor one , therfore a good base will give better accuracy and the gas check being stronger as well as uniform will allow this. Any and all replies please
    Good shooting---------Papa Smurf

  11. #11
    Boolit Master Cap'n Morgan's Avatar
    Join Date
    Jun 2008
    Location
    Denmark
    Posts
    1,109
    The two bullets were identical except that one was GC and the other PB. Accuracy with the PB bullets vanishes ar somewhere between 1200 and 1400 fps, depending on rifle and load. The GCed bullets still shoot well at 2400 fps.
    Noticed the exact same thing with a 2-in-1 mold (PB + GC) I made for my 375 H&H. I cooked up a load in the 1600 fps range and shot a nice group with the checked boolits - the plain based, however, couldn't stay within an A4 sheet at 50 yards.

    This was with a 325 grains bullet. My gut-feeling tells me a heavy bullet amplify the problem, but I don't know for sure.
    Cap'n Morgan

  12. #12
    Boolit Master on Heavens Range
    felix's Avatar
    Join Date
    Mar 2005
    Location
    fort smith ar
    Posts
    9,683
    It's for sure, Cap'n. It is much harder to rotate a heavier projectile. ... felix
    felix

  13. #13
    Boolit Buddy Fire_stick's Avatar
    Join Date
    Jan 2009
    Location
    Spanish Fort
    Posts
    413
    Thanks guys for all of the replies. This is just what I needed.

    Bret4207 - thanks for your thorough post. This helps me begin to tie everything together a little better.

  14. #14
    Perma - Banned


    Bret4207's Avatar
    Join Date
    Mar 2005
    Location
    St Lawrence Valley, NY
    Posts
    12,926
    I'm a little amazed no one told me I was completely wrong about all of it!

  15. #15
    Boolit Master
    Join Date
    Jan 2009
    Location
    Southeast Louisiana
    Posts
    587
    Quote Originally Posted by Bret4207 View Post
    I'm a little amazed no one told me I was completely wrong about all of it!
    Okay, you're wrong. Naw. I think you gave a pretty good indepth explanation. Thanks. It's something we all wonder about I'm sure. I would like to add one thing to Bret's though. Many feel that the harder the bullet, the less leading. This is not true. Even with handgun cast bullets you can get leading if you drive your bullets to hard. A softer bullet at a lower velocity will many times cause less leading than a harder bullet at a higher velocity. The bullet will skim over the lands and give greater leading issues. You have to find the right mix of hardness, pressure and velocity. Velocity is not always the key factor. It takes time and experimentation. But it's all part of the fun of what we do as a hobby or an art. We should worry more about accuracy from our cast boolits, not velocity from the weapon. The one that you hit and drop won't know if your bullet was traveling a couple of hundred fps faster or slower anyway. Neither will the one you miss.

  16. #16
    Boolit Master Slow Elk 45/70's Avatar
    Join Date
    Feb 2009
    Location
    Clear, AK
    Posts
    1,289
    Thanks Bret for your insight, and others, this has always been a point to ponder for me, so now I can chew on all this for a while, I am leaning toward your pressure theory along with most of the other points, there is no simple answer..... It seems to be a compilation of several factors affecting the boolit

    I will keep using the GC on mine over 1600+ ,
    Slow Elk 45/70

    Praise the Lord & Pass the Ammo

  17. #17
    Perma - Banned


    Bret4207's Avatar
    Join Date
    Mar 2005
    Location
    St Lawrence Valley, NY
    Posts
    12,926
    Quote Originally Posted by Slow Elk 45/70 View Post
    Thanks Bret for your insight, and others, this has always been a point to ponder for me, so now I can chew on all this for a while, I am leaning toward your pressure theory along with most of the other points, there is no simple answer..... It seems to be a compilation of several factors affecting the boolit

    I will keep using the GC on mine over 1600+ ,
    Ah Grasshopper, the light at the end of the tunnel is no longer the oncoming train!!!

  18. #18
    Boolit Buddy
    Join Date
    Nov 2006
    Location
    Queen Charlotte Islands
    Posts
    294
    Maybe check with the guys who shoot the single shot matches at the CBA - they certainly get respectable results. I suspect we've lost a good deal of that technology.
    Grouch

  19. #19
    Boolit Grand Master


    Larry Gibson's Avatar
    Join Date
    Jul 2005
    Location
    Lake Havasu City, Arizona
    Posts
    17,493
    Quote Originally Posted by grouch View Post
    Maybe check with the guys who shoot the single shot matches at the CBA - they certainly get respectable results. I suspect we've lost a good deal of that technology.
    Grouch
    Grouch

    I don't think we've lost any of that "technology". I doubt any of the single shot match shooters shoot over 1600 fps and doubt many of them shoot over 1400 fps. At least the shooters in the single shot matches here don't.

    Larry Gibson

  20. #20
    Boolit Master
    Join Date
    Sep 2005
    Location
    Dyer, Tn
    Posts
    1,118
    If i ever get around to publishing the pics. I have shot my MM brass mold 255.41 many times with out the cg and it does just fine out of a handgun no clue yet as to the rifle-- but mine at least will shoot very well with or with out in a 5.5" Rhawk .41 AA#9 15.5 gr bullet weight is about 248+- so yes they can or so it seems

Page 1 of 7 1234567 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check