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Thread: Velocity that "requires" gas checks.

  1. #1
    Boolit Mold
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    Velocity that "requires" gas checks.

    Is there a velocity that requires gas checks? Or is it basically different for all situations? I'm tired of gas checking bullets,. and I know that if you have a lapped barrel (freedom arms comes to mind) they say it's actually pretty hard to make a barrel lead as long as you are using any type of lube at all. For both 357 and 44 mag,. I've used gas checks and driven them to "standard velocities" (for those of you who are young,..I mean what was standard when the cartridges came out....i.e... over 1500 fps.).

    I've recently bought some tumble lube molds for each of them,. and I'm going to go ahead and give them a try. Am I going to be in for a surprise? I know alox isn't the nicest looking lube in the world, but I would imagine that is the only reason commercial mfgrs. do not use it. I also know that the coating probably do not work in higher velocity magnums like they do with 40s and 45s, and 9s.

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    Boolit Grand Master GhostHawk's Avatar
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    When I first started reading here I noticed several people give 1400 fps as the best point to switch to gas checks.

    Now, some people with the right bullet, right lube, right rifle may have gotten higher without issues.

    Me I figure if I'm going over 1400 fps I go with a gas check and a bit more or better lube. Thus far it has worked well for me. But I sure you will hear all kinds of answers.

  3. #3
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    I’m not “Ant-man” so I can’t really describe or video the innards of the chamber and bore when a round goes off but many have the misconception that hot gases from a cartridge attack the base of the bullet. The objective of gas checks isn’t so much defending the base but more so the very outer circumference where that bullet is supposed to seal (obturation). “Fit” in a bore is more important than “fashion”. Yes of course you want the bullet base to be strong but that seal is more important. Like the rings on a piston. Anyway I’m getting between 1800 + 2100FPS out my AR using no gas checks. Sometimes in my 500 Smith I use no checks but I get 0 leading. I do powder coat those twice. At first when I thought I needed a bullet with like 80 BHN (serious?) THATS when I got serious leading because the bullet couldn’t make itself at home down a half inch pipe.


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    1172 FPS is the absolute cut off for needing a gas check- at 1173 your boolits will tumble your barrel will lead and your gun may melt without them.....please note that this was an attempt at humor.

    A major contributor to various gun rags states often that around super sonic gas checks are required; and they often are unless they are not. It really is a case by case basis I’m amazed at some speeds my pal gets in 9mm carbines with no check, as always FIT is king alloy and powder used play a role and powder coating sort of changed the game .
    I know personally in a 44mag lever action similar boolits in the 250-260 range one GC the other not can be driven to the same “standard” velocity of around 1300 with and both shoot well and don’t lead- that was not the case before I PC’d, but Alox just may not have been up to the task.
    The pal I mentioned gets about top non +p 9mm velocity with plain base boolits and says there is no trick to it, he uses a fairly soft alloy; some are pcd and some not various nose profiles but sizes to 3 diffrent sizes for 3 diffrent weapons systems...fit is king

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    In most of my rifles somewhere between 1900 and 2100fps is where i need a check to retain accuracy
    The larger the dia of bullet the faster i could go YMMV
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  6. #6
    Boolit Master
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    so far ive only gas checked rifle calibers and never really had any problems. but I also factor time in, if you spend 10 minutes gaschecking a group of bullets is that really worth it over using a borebrush for a bit. that's for you to decide you might spend more time trying to prevent leading than remove the leading.

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    I will start off by saying, when it comes to understanding gas checks I know of no person that knows more about gas checks than Charlie Darnall the designer & maker of the Freechex gas check making tools. Charlie will tell anyone who wishes to listen that if you powder coat and do it properly the PC replaces gas check.

    To test the limits of PC I loaded 25 full power rounds of 22-250 with PLAIN BASE PC 55 grain bullets. The same load I have used with copper jacketed bullets. I did not take my chronograph, but I can assure you the velocity exceeded 3500 fps. All rounds fired without incident and there was no barrel leading. Accuracy is what I would expect with a lopsided cast bullet, not bad at 50 yards, but very poor at 100 yards. But the powder coating sealed and protected the bullet and protected the barrel from leading. I don't know what the velocity limit is with PC, but I own no firearm that is faster than my 22-250. So Charlie is right, from a ballistic standpoint, a proper PC replaces the need for a gas check. From Charlie's tests, my test and many others who have tested full power PC loads, velocity is not an issue with powder coating.

    I believe there are some accuracy issues where a check should be used. First, if the base of the cast bullet was designed for a gas check. Second, if a gas check is installed absolutely perpendicular and completely flat it can correct the imperfect sprue cut base of a cast bullet. However, a gas check or PC alone is not going to correct the inherent problem of a lopsided cast bullet.

    I PC and make my own checks, so my cost is as little as it gets, but I personally don't use a check on any bullet I don't have to and don't have or would use a GC handgun mold because accuracy past 25 yards with a handgun is not something I am going to pursue. At least that is my take on gas checks.

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    I haven't done any empirical research on this because all my 'rifle caliber' molds are gas-check designs. On the other hand, I shoot PC'd boolits without checks in both my leverguns - a .44 Marlin 1894 and a .357 Rossi '92 - at 1400-1500 fps without any hint of leading. But, I also push fairly soft (9-10 Bhn) uncoated boolits up over 1400 fps from my .38-55 Highwall without checks so, for me, I'll go with what works until I find something better.

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  9. #9
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    Quote Originally Posted by Kraschenbirn View Post
    I haven't done any empirical research on this because all my 'rifle caliber' molds are gas-check designs. On the other hand, I shoot PC'd boolits without checks in both my leverguns - a .44 Marlin 1894 and a .357 Rossi '92 - at 1400-1500 fps without any hint of leading. But, I've also push fairly soft (9-10 Bhn) uncoated boolits up over 1400 fps from my .38-55 Highwall without issue, too.

    Bill
    1400 in 38-55 with no issues; awesome so with lever guns and bolt actions I’ve pushed it pretty fast with plain base boolits as I mentioned above- once I sized correctly it worked more often than not; as in acceptable accuracy and no leading. Did your success come with shear luck or did you tinker and get everything just right; as in correct powder charge; appropriately sizing and correct
    Lube?- no dig at you and totally not a baiting question , my first attempts at cast boolits in 45 and 44 mag were not good- decent accuracy until leading went to epic proportions and stinky smoke and a dirty gun; found out Allx isn’t the best; alloy was much to hard- didn’t need to water drop; and I was sizing to 452 and 429; making all the pieces fit was the deciding factor in success. Not simply a FPS threshold

  10. #10
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    That '1400 fps' load actually chrono'd at 1418 fps (10-shot string) and consisted of a 304 gr. RN cast from 50/50 range scrap/Pb+a bit of Sn, (pan)lubed with Emmert's, and loaded 'as-cast' over 20.2 gr. H4198, fired from a Taylor & Co. (Uberti) Highwall with a 30" barrel. I've since backed the powder down just a bit to improve accuracy but, otherwise, haven't changed a thing...still no substantial leading. And, yeah, it took me a while to develop that load. Mold is an old NEI, most likely designed for the .375 H&H, reworked by Buckshot to remove the GC shank and reduce weight a bit. After experimenting with BP for a while, I tried 3 different smokeless powders...AA5744, AA2015, and H4198 both with and without dacron fill before hitting a formula that worked for me. Off sandbags, on a calm day, will print under 2 MOA until my eyes start getting tired.

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  11. #11
    Boolit Master
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    Reading this thread it seems to me we have 2 different concepts of why you "need" to put on a gas check. So do we put it on to reduce or prevent leading? Or do we use it to improve accuracy?

    I've been one of those folks who have advised that in my experience somewhere around 1400 fps seems to be where I started "needing" a gas check. I was not thinking leading when I said this: I was purely thinking accuracy. I don't even know if the gas check reduces leading because I so seldom get any particular amount of leading. What I have observed is that for boolits that shoot OK either with or without a gas check, somewhere around 1400 to 1500 fps is where my non gas check accuracy starts being significantly less than my gas check accuracy. Virtually all my experience has been with conventionally lubed boolits. And the little shooting I have done with PowderCoated boolits has me thinking that they also need the gc to maintain best accuracy as velocities go on up, though I don't know where that velocity limit is.

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    Boolit Mold
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    As far as "needing" to put on a gas check. I am not going to kid myself and say that I shoot straight enough to tell. HOWEVER,... I do know that gas checks don't help with accuracy unless your bullets are the wrong hardness or wrong diameter. If they fit correctly, and are not too soft,.. they usually shoot a little better than gas checked bullets....at least I've read that over and over. But, like I said,.. I don't shoot near well enough for that. I am just concerned with keeping the leading down. I don't get much leading in most of my guns,.. but if my kids ever decide they like 357 more than 38 special,..then I guess I better know the answer because I'll be loading a lot more 357 and I really don't have the patience to do gas checks when that happens.. Like most kids, mine think their purpose in life is to be lead dispensers.

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    Quote Originally Posted by pukester View Post
    I do know that gas checks don't help with accuracy unless your bullets are the wrong hardness or wrong diameter. If they fit correctly, and are not too soft,.. they usually shoot a little better than gas checked bullets....at least I've read that over and over.
    I also have read that, but that is exactly the opposite of my experience.

    And if you are shooting 38's and 357's, you are still down in the velocity range where you aren't going to need a gas check. I was thinking we were talking rifles where we wanted to get 2000 fps or so out of our casties.

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    Quote Originally Posted by pukester View Post
    As far as "needing" to put on a gas check. I am not going to kid myself and say that I shoot straight enough to tell. HOWEVER,... I do know that gas checks don't help with accuracy unless your bullets are the wrong hardness or wrong diameter. If they fit correctly, and are not too soft,.. they usually shoot a little better than gas checked bullets....at least I've read that over and over. But, like I said,.. I don't shoot near well enough for that. I am just concerned with keeping the leading down. I don't get much leading in most of my guns,.. but if my kids ever decide they like 357 more than 38 special,..then I guess I better know the answer because I'll be loading a lot more 357 and I really don't have the patience to do gas checks when that happens.. Like most kids, mine think their purpose in life is to be lead dispensers.
    The rule of thumb...you don't NEED GCs.

    I no longer use a GC on any boolits for pistol ammo.

    I will use a GC on any boolits for Rifle ammo, with the exception of very low velocity loads, because those are loaded for close range plinking or low noise varmint dispatching.

    The theory of a GC improving accuracy is in regards to creating a perfect base, so when the Boolit leaves the Barrel, there are no imperfections to nudge the boolit off course, much like an imperfect muzzle crown will do. While I highly doubt this will be noticeable at typical pistol shooting distances (25 yards or less), it is surely noticeable at typical Rifle shooting distances (100yds or more).

    I'm curious where you "read that over and over" about Plain base boolits "usually shoot a little better than gas checked bullets"?



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    Quote Originally Posted by earlmck View Post
    I also have read that, but that is exactly the opposite of my experience.

    And if you are shooting 38's and 357's, you are still down in the velocity range where you aren't going to need a gas check. I was thinking we were talking rifles where we wanted to get 2000 fps or so out of our casties.
    My velocity for 158s, is just under 1600 fps in my 6" 357s. Less in the shorter ones. If I recall, in my 92, the velocity tops 1800 but my numbers are not right in front of me.

  16. #16
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    In my 38-55, one of my hunting loads is 9 Bhn, PC, plain base at 1600. No leading yet after using it for a couple years.

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    Id say accuracy wise (and a lot of this depends on alloy) that about any lead alloy is going to do better gas checked. over 1400-1500 you step into an area where it takes a whole lot of work and luck to find accuracy with plain based bullets. Im not saying it cant be done. Ive done it myself. But in the long run the gas checks are going to proabably be cheaper then all the components you waste chasing accuracy. Leading is easy. You can pc dead soft, shot it at 1500 fps and not get leading. Now doing that and punching tiny groups with those bullets is two different things. Unless your bored or want to prove a point when speeds approach 1200 fps its time to step up to harder alloys and yes gas checks.

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    Boolit Mold
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    I use hard alloys with gas checks, but it seems like a read somewhere that with gas checks you actually do not need a hard alloy. Not that I'm going to shoot soft lead over gas checks. It just seems like I read that somewhere.

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    Is there a velocity that requires gas checks?

    Or is it basically different for all situations?

    You answered your own question. Lot's of opinions from all on when they "need" or don't "need" a GC. I have my own opinion too.....fathom that

    I use a GC if the mould is made for one. I use a GC'd bullet if I want a velocity with a soft alloy that I want to expand. I don't find the use of a GC to be a PITA. I make my own GCs and use lots of commercial ones. Most of my handgun bullets are flat based (PB) but I do use GC designs on +P and magnum level soft cast bullets that I expect expansion out of, especially HPs. I shoot flat base (PB) cast bullet in rifles but only from 300 fps up through 1200 fps most often and sometimes 1400 +/- fps. Above that I use a GC'd bullet. There are a couple exceptions though.
    Larry Gibson

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    Boolit Grand Master Outpost75's Avatar
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    My use and experience with plainbased bullets parallels Larry's. I would offer additional clarification:

    1. Bullet "fit" is critical.

    In using GC design bullets without a GC, the base band must be large enough to seal the throat or ball seat. This is necessary to prevent powder gases from leaking past the bullet and causing base deformation and leading. Soft alloys about 8-10 BHN used with faster-burning powders such as #2400, IMR4227, SR4759, Herco are able to upset and give less trouble in this respect. Very fast powders such as Bullseye, TiteGroup, 231, WST also work as long as velocities are limited to about 1200 fps and pressures below ab out 20,000 psi.

    2. Slower rates of twist are more forgiving.

    In black powder cartridges such as the .32-40, .38-55, .44-40, .45-70, using soft alloy such as 1:30 tin-lead, in barrels of traditional twist rate, velocities up to 1600 fps are possible with good hunting accuracy with suitable powders which don't exceed SAAMI MAP for the cartridge, usually below 20,000 psi.

    3. Faster rates of twist and less than perfect mil-surp barrels require a different approach.

    In "dark but strong" or "frosty" mil-surps somewhat harder bullets which "fit" such as wheelweight alloy, give good results up to about 1250-1300 fps if the bullet is well lubricated, but leading and keyholes become apparent very soon after practical mechanical limits are reached.

    4. Dacron fiber-fill and "grease cookie" under base of bullet helps.

    Using "medium" burning rate extruded tubular "rifle" powders, such as RL7, IMR3031, IMR4895, IMR4064, RL15 or Varget, you can get good hunting accuracy up to about 1700-1800 fps using wheelweight alloy plainbased bullets that "fit" using charges about 75% of a jacketed charge for the same weight bullet, in cartridges such as the .30-30, .303 British, 7.62x54R Russian, .30-'06 and 7.9x57.

    5. Revolvers are more limited by pressure than velocity.

    It has been my experience that GC bullets are of less advantage in revolvers UNLESS bullets are sized to fit the cylinder throats. Otherwise powder gases leak past the GC in transitioning from the cylinder into the barrel forcing cone. If the bullet is of sufficient length that its front driving band impinges against the origin of rifling before the properly fitting GC bullet exits the cylinder, then the GC will help. But if the sized GC permits gas leakage around the bullet, or if the bullet is short enough, or the barrel forcing cone deep enough, that the bullet base exits the cylinder before its forepart is engraved by then rifling, leading and poor accuracy is likely. My experience has been that with bullets which "fit," plainbased revolver bullets in wheelweight alloy will perform well even in full charge .357 and .44 Magnum loads.
    Last edited by Outpost75; 03-10-2019 at 12:31 PM.
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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