Texan 7mm

Have you had a chance to look at the 288-135-HP bullet mould?

https://noebulletmolds.com/site/product-category/284-7mm/288-135-fn-f1/

I tend to believe that it is fairly close to what you originally described in your posting today.

In the non HP version with the flat pins installed it is as close as you are likely to get with a current NOE design that has been made before …

With a touch less tin in your alloy you can end up throwing a slightly heavier cast bullet… should you choose to do so.

With the HP pins mine tends to be right about the 128 Gr cast bullet with wheelweight alloy as originally designed.

I’ve had pretty good luck with that particular NOE cast bullet design … in my various 7 MMs.

Looking at the remainder of your posting … I would like to ask… if I may…

You noted that you wanted your new request to be like the 258-75…  which I tend to believe is designed as an Air Gun bullet, with said design alloy specified to be cast of pure lead not a wheelweight alloy…

https://noebulletmolds.com/site/shop/257/258-75-fn-bq6/258-75-fn-bq6-rg2-cavity-bt/

May one ask what exactly are you looking for?

If you are also looking for a cast bullet with a boat tail design any gas check utilized would need by design to be smaller than the normal standard 7 MM GC…

One would basically be putting on a much smaller gas check, & unfortunately any benefit from said GC would basically be negated by the boat tail design… as the gas check would not protect the entire base of said cast bullet…

You might possibly tend to be better off casting with a much harder alloy… then of course one would have to do the match calculations to estimate the final cast bullet weight of 135 – 138 Gr when cast with a very hard alloy like linotype.. As an example a 165 Grain cast bullet in wheelweights would only weigh in at around 156 Grains in linotype…

Thus your initial wheel weight alloy design (Flat Nose HP version) (Boat Tail or not) would basically need to weigh in somewhere around 146 grains … when cast in wheelweight alloy to throw an ~ 138 Gr Cast bullet when cast in a linotype alloy …

Take Care & Stay Safe …

On the air gun basis I ran some numbers using the same software design program that NOE utilizes.

In order to get to a 286 Caliber 138 Gr BT HP design the cast bullet design would most probably need to be around .845 in length.

With a flat pin the mould is predicted to throw a 142 Gr cast bullet when cast in pure lead…

With an HP pin the same mould design is predicted to produce a 138 Gr cast bullet using the same pure lead alloy…

Apparently the NOE forum is still apparently not allowing drawing attachments.

Take Care, & Stay Safe…

May I ask what specific type of cast bullet & bullet weight are you looking for? 

Air gun projectiles basically by design have been traditionally called out by NOE as being cast of pure lead. The alloy used to cast the projectile changes the end bullet weight.

Is this design request for said projectile … actually for an airgun…  (thus Pure Lead for its natural softness and its BHN of 5….  in comparison to normal cast lead alloys) … which all tend to be much harder than pure lead… and thus lighter…

If not what specific cartridge case are you planning to utilize… to mount this new design projectile into to create the reusable internal combustion chamber?

Looking up your referenced barrel mfg (BarTlein), ( I believe that may be with a “T” in the spelling) & utilizing a 7MM barrel with a 1 to 9 twist would tend to indicate that you could potentially stabilize up to a 170 grain projectile … using the standard barrel twist vs caliber calculations.

Mixing a fast twist by comparison… with a much lighter bullet tends to mean that one will not be tending to produce the best accuracy combination… My 7MM Rem Mags group best with a 175 Gr projectile.

The cast bullet design software allows me a good bit design & size latitude… as to designing the cast bullet – Airgun or Otherwise …

However one must by definition also match bullet weight cast or otherwise to the barrel twist to tend to get the best of the accuracy marriage between the two…

Said Quick Design Software will however … Not allow one to gauge the velocity that one can predict that one can drive the cast bullet at…

One can design the projectile & its predicted end bullet weight … However the Propellent (Air) or some kind of Internal Combustion Propellant (containing its own O2) is not included in the bullet design parameters…

That is strictly up to the end user … as to what type of propellent or propellent reservoir you are intending to use…

Now you are getting into another type of program such as quickload … which unfortunately does not include air or air pressure as one of its documented propellents…

With a powder charge one can thus select the burn rate of the individual powder type to help regulate the end velocity of the projectile … as it leaves the muzzle…

I tend to believe that you originally requested a bullet weight of something like a 138 GR HP design…

Your nome de plum according to Rsterne … suggests an air gun advocate vs a cartridge firearm… I.E. Texan 7MM 

Is this a valid assumption on Rsterne’s part or not?

If so I would tend to defer to the Airgun Guru to recommend a cast bullet weight for your airgun design request endeavor and wished for velocity… and the pressure needed to propel said cast bullet weight to your desired velocity…

If this is for a specific 7MM cartridge chambering then post the 7 mm cartridge type or PM me and I will try to help you with a quickload program to try to select a proper powder type propellent…

Remember also that NOE PM’s allow for no attachments…

I will leave you to it…

Take Care, & Stay Safe…

IMO 320 FPE on just 3200 psi would be a remarkable achievement…. Using a seldom achieved 50% efficiency, my lofty goal calculation is 290 FPE…. I have never achieved 50% on any of my custom PCPs, even when tuned for a maximum power shot, with every subsequent shot at lower velocity….  Good Luck…. 

Bob

I’d lose the antimony component … if you can … Then you might be close to the BHN numbers that you originally stated.

If you go with just tin with your pure lead + .5 % of your Tin with your stated percentages you just might be close to your stated BHN numbers…

That should put you in the 30:1 neighborhood…

Nuff said…
I’ll leave you to it…
Take Care, & Stay Safe…

I use rotometals 40:1 (ie 2.5% tin) for all my airgun bullets…. It runs about BHN 7-8, which is plenty soft enough…. If you want a softer bullet, you can reduce the tin content…. but if you go down to 1% the bullets will tarnish after about a year…. Pure lead, of course, goes dull within a month or two…. not that it matters if you shoot them right away…. It’s only an appearance thing…. Adding at least 1% tin allows the lead to flow better and you get better fills….

I recommend you try sizing your bullets from 0.001″ over groove diameter down to 0.002″ under, to see what shoots best…. Outside those sizes I have found that the velocity tends to decrease slightly…. but of course accuracy is the main concern…. You may even need to sand out a bushing to an in between size for best results…. but 0.001″ steps will put you in the ballpark….

Bob