How do we get a heavy (120+ grain) 6mm bullet made?

[wind gypsy]

6 creed already is what PRCs are in their respective bore size.

I saw the comments on 25 PRC on the hide as well. Who is Ledzep over there? Miles N?

 

[ACHILLES]

6prc is more overbore than a 7prc by a ways. 25prc is more overbore than a 7prc but not by much.

 

[ACHILLES]

One of the Hornady guys over on the Hide stated they wouldn’t do a 25 PRC due to it being overbore so that pretty much leaves the 6 PRC as a wildcat.

I saw that and thought that was an interesting statement considering the 22creed and 25prc are almost identical using the overbore index.

 

[CMP70306]

6 creed already is what PRCs are in their respective bore size.

I saw the comments on 25 PRC on the hide as well. Who is Ledzep over there? Miles N?

I believe so

I saw that and thought that was an interesting statement considering the 22creed and 25prc are almost identical using the overbore index.

Technically they didn’t make the .22 Creed, Horizon Firearms and an untold number of wildcatters did and it gained enough of a following to justify them putting up the SAAMI expense to start making factory ammo for it.

If somebody were to market and sell the 25 PRC well enough to justify an ammo run then maybe they would consider it.

 

[crich]

Sort of related but I asked Sierra when they plan on making another run of 95 TMKs and he said they dont plan to in the foreseeable future.

Asked about 115+ 6mm offerings and didnt acknowledge the question so theres that.

 

[Rippey715]

https://appliedballisticsllc.com/wp-content/uploads/2021/06/Understanding-Long-Range-Bullets-Part-1-The-Nature-of-Scale.pdf

Read this. For real. Understanding the nature of scale for bullets. But then there are other factors. Barrel twist, performance gained, seating depth and mag length for industry short actions. Bigger bullet is bigger. Now you can’t seat boat tail to shoulder for long range ideal. Maybe go smaller cartridge so you can seat long, but. Now you don’t have the velocity and maybe worry about pressure to get close to desired speeds. Is it even efficient? Litz really explains this point well in his chapter about the problem with 30 cals in his 2014 book vol 1.

 

[Dobie07]

https://appliedballisticsllc.com/wp-content/uploads/2021/06/Understanding-Long-Range-Bullets-Part-1-The-Nature-of-Scale.pdf

Read this. For real. Understanding the nature of scale for bullets. But then there are other factors. Barrel twist, performance gained, seating depth and mag length for industry short actions. Bigger bullet is bigger. Now you can’t seat boat tail to shoulder for long range ideal. Maybe go smaller cartridge so you can seat long, but. Now you don’t have the velocity and maybe worry about pressure to get close to desired speeds. Is it even efficient? Litz really explains this point well in his chapter about the problem with 30 cals in his 2014 book vol 1.

Thanks for sharing this. If I’m reading the example right tho, it shows the scaled up and down bullets at equivalent weights for respective caliber. Given that at each caliber example listed there’s already a heavier bullet than used in the example (.224- 90 gr, 6.5-142 gr, 7mm-175 gr, .308- 220 gr) except for 6mm which lists the heaviest grain currently available: 115 gr. Doesn’t that kind of speak to there being a gap at the top of the 6mm bullet range?

 

[Dobie07]

I actually took Litz’ calculation to extrapolate a scaled up 95 gr .224 bullet to a 6mm.
- 6mm/5.56mm = 1.079136690647482
-cubed that equals = 1.256565343671
- then multiply 95 grains by that value to arrive at 6mm scaled equivalent that weighs: 119.37 grains
If we scale that again up to 6.5mm then we arrive at a 151 grain bullet. Still less than the 156 gr EOL that exists. Scaled to 7mm it comes out to a 189 grain bullet, again there are heavier 7mm options that exist.

So yes, according to Bryan Litz formula for scaling bullets there theoretically should be a 119-120 grain 6mm bullet that would be in line with the heaviest 22 cal, 6.5 cal, 7mm caliber bullets that already exist.

 

[Rippey715]

Thanks for sharing this. If I’m reading the example right tho, it shows the scaled up and down bullets at equivalent weights for respective caliber. Given that at each caliber example listed there’s already a heavier bullet than used in the example (.224- 90 gr, 6.5-142 gr, 7mm-175 gr, .308- 220 gr) except for 6mm which lists the heaviest grain currently available: 115 gr. Doesn’t that kind of speak to there being a gap at the top of the 6mm bullet range?

So this is where the next part about twist rate, seating depth, mag length, and ideal velocity come in. In this case think about the 156 in 6.5cm. You need a faster 1:7 twist ideally which isn’t normal. Going to have to seat it deeper for chamber and mag length issues which isn’t ideal for precision. Might have to throat the chamber longer. Lower velocity around the low to mid 2600s which is much slower for the average creedmoor. This combo though supposedly shoots amazingly but it is decently far outside the norm of anything factory. Some times there is the perfect heavy bullet but no cartridge yet. Litz talks about this with the 300WM vs 300 PRC and creating the 215. So overcoming those same variables with a given, heavier for caliber, 6mm and then is the performance actually worth it or there at all. Just saying there are other reasons involved. And I say all this while shooting a 25CM 1:7 with 134 ELDs.

 

[wind gypsy]

So this is where the next part about twist rate, seating depth, mag length, and ideal velocity come in. In this case think about the 156 in 6.5cm. You need a faster 1:7 twist ideally which isn’t normal. Going to have to seat it deeper for chamber and mag length issues which isn’t ideal for precision. Might have to throat the chamber longer. Lower velocity around the low to mid 2600s which is much slower for the average creedmoor. This combo though supposedly shoots amazingly but it is decently far outside the norm of anything factory. Some times there is the perfect heavy bullet but no cartridge yet. Litz talks about this with the 300WM vs 300 PRC and creating the 215. So overcoming those same variables with a given, heavier for caliber, 6mm and then is the performance actually worth it or there at all. Just saying there are other reasons involved. And I say all this while shooting a 25CM 1:7 with 134 ELDs.

Berger's stability calculator says the 156 is fully stable with an 8 twist @ 2600 FPS @ 2000' elevation.

With 6mm i feel like OAL is less of a thing too because bullets are not going to be as long as the heavy 6.5s. 2.950" is pretty dang long for a 6 creed. I doubt a high form factor 115-120 bullet would have notably longer bearing surface than say a 115 DTAC which has run well in many current 6mm freebore configurations.

I do wonder what twist such a bullet would require.

 

[Dobie07]

I do wonder what twist such a bullet would require.

@wind gypsy I looked up the DTAC and it’s OAL is 1.344. Even if we say to get an additional 5 grains we have to bump it to 1.38, Bergers twist calculator says the bullet is fully stable in a 1:7.5 twist barrel at 2000 ft elevation.