aluminum vs brass for gas checks?

[wileynet]

any difference in performance between the two, will be using these in 303 British and 308, have noticed the aluminum is cheaper

[Lloyd Smale]

my biggest complaint would be that ive never seen a aluminum check that actually crimped on and i dont want checks falling off my bullets in flight. Other then that im sure the material its made out of doesnt matter a bit.

[Flash]

I shoot them in my 25-20 and they work fine but, I make my own checks. Like Lloyd mentioned, the aluminum checks are made by someone with their own dies to do so and they could be too large for the base of your bullet. The punch size will determine the inside diameter of the check and if the base of your bullet is much smaller than the check, they won't crimp on. I had my tooling made for the bullet I'm shooting and they crimp on fine.

[Land_Owner]

i dont want checks falling off my bullets in flight.

Why?  What would be wrong with the check falling away?

My thinking in a check falling off is akin to the wad of a shotgun round, which falls away after doing the job it was intended to do.

[AtlLaw]

Ya know, that's a pretty darn good point the LO... I never thought of it that way.   
 
Any info out there on the aerodynamics of a GC bullet w or w/o the GC?   

[smokehouserex]

 
 
  Hey AtlLaw:
 
  Have considered this myself and have always had a question mark as to the difference from bullet to bullet in flight, one with no check and the one that stays on??? Just a question of accuracy as you said about the areodynamics of them.
  I have not had good success with a GC designed bullet with no GC as far as accuracy is concerned. I have limited experience, only shot 30 cal., 357 &44's.
  Would appreciate some info on this also.
  thanks
  HM 

[smokehouserex]

 
 
  Hey Land_Owner:
 
  My thoughts on the comparison of the wad/slug is not the same as a GC designed bullet. The GC bullet has a recess around the base and is designed to have the GC which not only serves the purpose of preventing melting lead as well as limiting blow-by, GC are supposed to stay on, The slug is pretty flat on its base and is designed for the wad to seperate upon it's exit from the bbl. and many of them are hollow base. Not many SG will shoot with the same degree of accuracy as the cast rifle bullets will.  JMO
  HM

[mtbugle]

I would suppose if some stay on and some fall off would open a group up a bit.
Thanks Don.

[wileynet]

gas checks let you load to higher velocities than plain base bullets by keeping hot cases from blowing bye or cutting the led and reducing velocity by blowby, for my handgun bullets where i keep velocities usually  under 900 fbs the other thing with higher velocities is a harder bullet with the gas check to keep deformity down

[smokehouserex]

 
 
  Hey wileynet:
  You said you were shooting the 303, are you having the checks made or doing it yourself and are you using alum.checks.  I have seen them on u-tube with the alum. One guy is shooting a 7.5 Swiss Rifle and gives favorable reports. I am thinking about making some of these for my castings if I hear more good reports, sometimes if someone is selling something they cannot be totally objective, so I am asking around before committing to it.
  thanks
  HM
 

[wileynet]

there is a guy on ebay selling them he has a formula for check thickness based on bullet shank diameter, he offers i think 4-6 different thicknesses in all calibers, he will even send you(mine are coming) samples to make sure the thickness will work for your application pretty rare for a ebay'er ill give a report after i get them

[Land_Owner]

Some brain scratchers to think about in regard to gas checked bullets in flight. 

1.)  If a lead bullet has a GC and the GC stays securely crimped to the bullet across its entire flight regime, that is "normal" for these discussions.

2.)  If a lead bullet does not have a GC, but needs one, its rear end is going to get burned and misshapen going up the bbl.  That does affect its flight making it aerodynamically less stable and less accurate.  I think we in general agree in this.

3.)  Using rocket science terminology, if the GC "stages away" from the bullet upon exiting the muzzle, then, depending on the method of that staging (below), the flight of the bullet may or may not be affected.

     3A.)  If the GC tears away, one side has more friction than the other, releases later, or in any way creates uneven drag across the rotating bullet surface, that will negatively affect aerodynamics, trajectory, and accuracy.

     3B.)  If the GC falls away similar to a shotgun wad or the properly released stage of an orbital rocket, which we have all seen, the as-discharged shape of the bullet's rear end (a slight recess that used to contain the thickness of the GC) should act similar to a boattail, with an increase in aerodynamics and accuracy.

How to "test" these hypotheticals is left for discussion and for those with unlimited budgets, high speed cameras, and time for experimentation.

[smokehouserex]

 
 
  Hey Land_Owner:
 
  Thanks for the reply, good things to consider,  as stated this was just my opinion so, I cannot prove anything scientifically. I do know that I have not had good results in shooting the GC designed  bullets without one. Maybe I didn't do enough testing in that area in order to find a accurate load???
  I normally get really good accuracy when using 4227 with cast and jackets in 06 cast as well as 44's and 357 acst and jacketed bullets. The reason that I started using 4227 so much was that a old reloader/shooter/caster friend recommended it. I'm sure there are other powders that work as good or better but thats what I've used for ~40yrs.
  On the base of the GC bullet and it's shape, I feel like the abrupt shoulder causes the areodynamics to be altered and would cause a different drag effect than a smooth boat tail design or one that had the GC in place, and may therefore upset the airfoil/airflow over the projectile, possibly a rough base,   maybe?  Also I would think that the break-away of the GC may also have a uneven base due to the GC being crimped on and thus would probably not be a smooth base as a result of this. I have read that different angles on BT bullets effect them also.I am assuming the GC stays on til it exits the bbl.   Like I said, this is just an opinion,,, no hard evidence,, just not having any success shooting the GC designed bullets without a GC, accurately.
  OK, I repeated what you said in, #'s 1,2,3,3a, but we part ways on 3b, it seems to me that the Rocket, BT bullets ect, are designed to act in this manner, the GC bullet is not designed to function properly after loosing the GC.
  thank you for your input,  I am not being emphatic in these comments, my opinion only.
  You are exactly right that we cannot know for sure even tho we may do our own tests and acheive satisfactory results, in our favor.  Again, Good Ideas and thanks for your thoughts. Would like to see it on a hi-speed camera.lol
  HM

[Land_Owner]

Smokehouse, 

Good thoughts.  Empirically, I get your point with regard to aerodynamic drag after losing the GC, although I don't understand the physics of it. 

Still, the drag created by the null space behind the lower pressure ring is, to my thinking, far exceeded by the drag created behind the bullet base.  In the case of a lost GC, the air flow down the side of the bullet begins to bend, toward the bullet base, which is now inward and reduced in diameter.  This, in a small way, is akin to a boattail, don't you think?

I am no physicist, just an inquisitive engineer, but maybe the null space drag is a zone of stagnation pressure that is bending the air flow over its influence area toward the reduced diameter bullet base.


OR


The drag could be upsetting the air flow in advance of the influence of the now reduced diameter bullet base, which could be causing all sorts of misunderstandings in bullet trajectory and accuracy.

Just pondering the minutia of aerodynamics and penning my thoughts out loud...

[Blackhawker]

The melting point of aluminum is a lot lower than that of brass.  It's still about 600 degrees F higher than straight lead but I don't know how hot the gasses from a magnum or rifle round gets.  If it gets hot enough to start melting the aluminum, I suppose one might "aluminum" their barrel rather than lead it.   

I don't think the gasses from ammunition get hot enough though.  I believe the melt point of Al is about 1200 degrees F.

[wileynet]

i have gas checked bullets in both my 45/70 and 308 i have recovered some from the dirt behind 100 yard targets and the gas checks(brass) were still in place, gas checked bullets have a (shank) that is smaller than the diameter of the bullet, i have noticed on some of the recovered rounds that it appears the gas checked is "shoved" up into the base of the bullet and the grooves are shallower on the check as opposed to the bullet

[smokehouserex]

 
 
  Hey Land_Owner:
 
  I understood some of what you said and I do think that the diminished size of the base would have to have a similar effect as the BT, but I am only speculating, and as far as the drag, I would have thought there would be a turbulance at the rearward portion which could cause a variance in stability of the projectile. JMO
  I will yeild to someone with more knowledge than I have. I have read some of the articles ect. in the reloading manuals but do not understand Exterior Ballistics to any depth.
  I enjoyed your comments, very interesting, thanks for the reply.
  HM
 

[smokehouserex]

 
 
  Evening wileynet:
 
 I too have dug the bullets from the target burm and found what you mentioned about the GC being shoved up into the bullet, I have never noticed the difference in the diameters of them, I do think the copper GC seem to have a inner lip that causes them to bite into the bullet. I have melted down a lot of range lead,  maybe I should have kept some of the GC's and reused them. I am a believer in using everything that I can.
  I took some measurements today and checked on some alum. for GC's, I'm fixing to draw up the plans/prints for the GC dies and plan to make at least one set right away.
  safety first
  HM

[wileynet]

let me know how it goes, i ll post my results also, i think with the aluminum checks i shoot thru butgher paper at 25,50 75 and 100 if the gas check leaves the bullet i should see it mark the paper

[Lloyd Smale]

all i know in the case of gas checked bullets loosing there checks is the old lyman checks didnt crimp on and about any load ive ever shot using them opened up compared to a crimp on hornady check. I seen at my range where gas checks were littered from about 20 feet in front of the bench to the 25 yard backstop. Im sure if a check left the bullet the exact same way each time it would do much to effect accuracy but thats sure not the case. Also consider the drag on one side of a bullet if the check peels away from that side first. For a nanosecond it would act like a sail on that side of the bullet. this is no doubt mostly speculation as i obviously dont have equiptment to watch a bullet in flight but like i said the group sizes dont lie and ive seen groups sizes double. I also know that alot of users of tools like the freecheck tool will use a dab of superglue to make sure the check does stay on.

[linoww]

I have shot about 3000 aluminum 30 caliber checks in a  Pats Green tool (decent tool poor service). With bullets from .310 to .314 dia in bolt guns with no difference in accuracy to Hornady ones.The aluminum must be .014 dia or they will fall off.I have also used them in two autoloader 308's(Saiga and FN FAL) with no ill effects at 2000 fps and good accuracy.(under 2MOA and sometimes much smaller)

Horacio

[Larry Gibson]

I make my own GCs, both aluminum and brass.  I also use lots of Hornady and Lyman crimp on GCs and even have the older Lymans that don't crimp on.  I have run many extensive accuracy tests with several different cartridges at different velocities (1200 - 2600+ fps) with all the different kinds of GCs. The crimp on brass GCs and my own made from .015 brass shim stock give superior accuracy in most cases.  Even with .014 aluminum sheeting the aluminum ones do come off in flight and they do not come off evenly.  This causes yaw in the bullet and can  adversely affect accuracy.  However, not all of them come off in flight and with some that fit very tightly on the bullet GC shank they don't come off.  For example; I have one bullet I size at .314 for use in a Russian MN and many of the aluminum GCs come off right away causing the groups to open to 3 moa.  The same bullet with a brass  GC of my own or with a Hornady GC will group into 1 - 1.5 moa with the same load.  I can size the bullet at .312, which gives the GC a much tighter grip on the shank, for use in my Finn M39 MN and the aluminum GCs very seldom come off in flight and accuracy is the same as with crimp on brass GCs. 
 
Also over 2400 fps the aluminum GC do not do well in my .308W Palma or my .22 CFs.  The aluminum GCs are harder and more brittle than brass GCs and seemingly do not hold up well so far.  However, most users of GC'd cast bullets use them in the 1200 - 2000 fps range so that may not be a consideration.
 
Land owner left one thing out; the GCs, if they come off the bullet right away, can cause havoc and severe damage to a chronograph or skyscreens.
 
Larry Gibson

[Land_Owner]

Land owner left one thing out; the GCs, if they come off the bullet right away, can cause havoc and severe damage to a chronograph or skyscreens.
 
Larry Gibson

Dang.  That WOULD be a bad day at the range...  Good point.  Well taken.  I will give careful consideration to not using AL GC'd boolits when using the chronograph.

[Tom W.]

When I had my .454 I shot AL gas checked bullets chronographed @ 1760 fps from an Encore pistol. They crimped on quite well and maybe I was lucky, but the bullets went where they were supposed to go.I never did recover any of the bullets that I fired, so I cannot say if the gas checks stayed on downrange or not, but I got good groups. I never noticed any difference in the groups that were copper checks or Aluminium.
I even tried some that were double thickness pepsi cans. They seemed to lock on better than the .014 checks did.

[Larry Gibson]

I have shot about 3000 aluminum 30 caliber checks in a  Pats Green tool (decent tool poor service). With bullets from .310 to .314 dia in bolt guns with no difference in accuracy to Hornady ones.The aluminum must be .014 dia or they will fall off.I have also used them in two autoloader 308's(Saiga and FN FAL) with no ill effects at 2000 fps and good accuracy.(under 2MOA and sometimes much smaller)

Horacio

I did not intend to totally contradict you.  I should have mentioned that the diameter of the GC shank on bullet must be a good fit for the .014 aluminum GCs to not come off.  Obviously yours are a good fit as they are on mine with about half of my .30/.31 cal moulds.  It's on the bullets that they don't fit tightly on that they come off. 
 
Larry Gibson

[linoww]

 
"I did not intend to totally contradict you.  I should have mentioned that the diameter of the GC shank on bullet must be a good fit for the .014 aluminum GCs to not come off.  Obviously yours are a good fit as they are on mine with about half of my .30/.31 cal moulds.  It's on the bullets that they don't fit tightly on that they come off"

I agree on shank size.I have been lucky so far and i too shoot them in Mosins sized .314 with accuracy down to near MOA. The 8mm tool I have  makes checks that wont fit most of my 8mm shanks well at all.Groups are double the size compared to Hornady or even old Lyman Ideal non crimpers.A buddy slightly flared the back end GC shank of his .314 AK bullet (with a deburing tool !!) so he could shoot the cheap checks.He now has good accuracy and they stay on.I sent some to a friend to try in a very accurate Stolle  in 30 BR and sized to .309 they shot near 1/2 MOA 10 shot groups at 200 yards @2100 fps.

Horacio
 

[35Whelen]

  I've made and shot LOTS of aluminum .30 caliber checks. Unless I'm in a hurry to size and load and don't happen to have any aluminum checks made, (in which case I'll just use factory Hornady checks) I very much prefer aluminum checks.
  I started out with a FreeChex I and when I used aluminum "Garage Sale" type signs (.013"- .014") it made perfect checks that stayed on the bullet. The neat thing about the FreeChex I is the piece that forms the cup can be altered in a lathe or on a drill press to make the ID of the cups just about whatever you want.
 I have since made my own that threads into a single stage press and stamps checks out in one stroke. The piece that forms the cup is made from a 5/16" bolt whose tip can be made different diameter to form different ID's on the checks.
  For those of you whose checks fall off, try thicker aluminum. The thickest I've found that works is aluminum guttering. It's about .017" - .018". That's about the thickest material I could stamp out with the FreeChex I.
 
 35W

[PigBoy Crabshaw]

Speaking of gas checks...do any of you know about making them
as I saw on this site about checkmaker dies from PatMarlin?
http://castboolits.gunloads.com/showthread.php?t=89742
 
-gary