BHN and Gas Checks

[Black Wolf]

Quick question - and I feel sort of dumb asking since I've been casting for about 5 years. Anyhow, Lee Precision's BHN tester has a chart for BHN relative to the diameter of the dent imprinted on the bullet with the tester. Along those same lines, every talks of BHN regarding their bullets.

Question: When you (and Lee Precision) discuss BHN and their applicability to the rifle or handgun is it with or without a gas check? Or is BHN not relative when using a gas check since the check supports the base and hardness is no longer an issue. I guess in short, does BHN (bullet hardness) important when using a gas check?

[fourdollarbill]

I think - yes, it does make a diff.

I tried using 50/50 ww/lead mix on a 165gr lswc w/gc and shot them at magnum pressures out of a 6" 357mag. They were all over the place. Also the few that had a soft landing I picked up and found the were way shorter then original.

I switched to straight ww alloy and water quenched them. They are shooting very well at magnum pressures.

These were heavy loads of 2400 and H110. I'm not sure how a softer gas checked bullet will work with medium pressures.

You would probably have to ask Lee for the other specifics.

[Black Wolf]

Maybe I wasn't clear in my former msg, let me ask it this way. I know that obturation is necessary to seal the bore to prevent gas cutting and subsequent leading of the bore.

What relevance does BHN have if you install a gas check on the bullet?

I can certainly understand that hardness would be an important aspect of casting if a gas check wasn't used. But does not the gas check protect the base of the bullet thus rendering the issue of bullet hardness mute?

TIA.

[GP100man]

You have to factor in the tuffness of the alloy to grab the rifling to start spinnin!

If ya over speed an alloy accuracy suffers checked or unchecked .

Here`s the catch let`s work with the 357 magnum , if ya got an alloy that`s 10.5 & ya size em 357" these boolits won`t stand as much speed or pressure as a boolit sized 359" ,
the titer boolit helps "wedge" the boolit & thus supportin the pressure & speed better .

I know there`s better ways of puttin it but this is how my febble mind conceves the issue & it took a chronograph & close observation of load development to actually see this .

Hope this helps even if a little!

[fryboy]

a gas check supposedly helps protect the base - not the bore ,yes u can shoot a softer alloy with a gas check on it but gp pretty much hit it , no matter checked or not u still have to keep the velocity within it's pressure limit , take a rain coat for example , keeps u dry when it's lightly rainin but jump out in a hurricane with the same raincoat expecting it to keep u dry would be sheer foolishness but it would keep u drier than no coat in the same hurricane not much drier but ...( weird parable i know .... ) i have a soft alloy i use for low velocity loads works great with 45 acp hollow points and low velocity 38 wadcutters cast it in a 22 add a check and trying to fire it at medium to higher pressure it doesnt do too good ..however loaded at low velocity/pressure it does decent ,the lee tester is still new to me ..had it about a month

[Black Wolf]

Ok - both of the last 2 posts makes sense. To summarize, regardless of the gas check, the alloy must be hard enough so it doesn't skid through the rifling versus gripping and subsequently start it spinning (like a foot ball). Too soft of an alloy and it doesn't engage the rifling deep and strong enough to allow it to start it's spinning journey down the bore.

Slow the bullet it down and it has less pressure pushing it and subsequently allowing it to (once again) engage the rifling.

Good stuff guys. Thank you.

It would seem logical to me then, if you have a rifle that has poor/shallow rifling that a softer bullet alloy may assist in accuracy.

Thanks again.

BW

[Rico1950]

As stated here many times before. Boolit fit is KING.

[303Guy]

Well..... here's a harder boolit fired in a two-groove 303 brit. Note the degree of rifling shear.

http://i388.photobucket.com/albums/oo327/303Guy/Two-GroovePP30grAR220957grBran.jpg


Here is a softer alloy boolit with all else being equal.

http://i388.photobucket.com/albums/oo327/303Guy/SizedCore208gr.jpg

Soft alloy with half patch - still better than the hard one.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-757F.jpg


It seems it's not cast in stone.:holysheep

[missionary5155]

Good morning
The boolit still has to be of sufficient strength BHN to support the pressure applied.
The gas check gives the base that Hard BHN but if the rest of the boolit fails under to high base pressure / acceleration it colapses upon itself in the chamber. Much like a pure lead boolit getting wacked in the base by a healthy load of 2F. Now when all that reaches a revolver gap and has to get mashed through the forcing cone then begin to get spun violently lead gets stripped and accuracy gets irregular.
BUT on the other side I personally like a softer boolit (but strong enough for the applied pressure) as I want expansion in target and not a shattering explosion . I generally shoot 50-50 until I find evidence ( inspection of fired boolits) that I need a harder alloy.