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22 ARC   General Military Discussion

Started 23-Nov by smg762; 1067 views.
smg762

From: smg762

23-Nov

on youtube there are the designers of the new 22 ARC, saying that the bullet has a higher BC than 224 valkyirie (assuming the same weight) , and yet the two bullets appear to have an identical shape. can anyone explain why this is?   would it be related to the boat tail or shape of the tip?

as i said the ogive length is identical so i don't know how they can claim a higher BC

In reply toRe: msg 1
EmericD

From: EmericD

26-Nov

smg762 said:

on youtube there are the designers of the new 22 ARC, saying that the bullet has a higher BC than 224 valkyirie (assuming the same weight) , and yet the two bullets appear to have an identical shape. can anyone explain why this is?   would it be related to the boat tail or shape of the tip?

Could you gave us a link to those claims?

The new ELD-VT line of bullets seems to use the jacket of heavier bullets, with a truncated lead core.

For example, the G7 value of the Hornady 88 gr ELD-M is given at 0.274, for a sectional density of 0.251 and a form factor of 0.916.

Now, if you take the same jacket but use a truncated lead core in order to reach a weight of only 62 gr, then the G7 BC of this bullet will be around 0.193, very close from Hornady claim of 0.199 for the 62 gr ELD-VT (first claim was 0.191).

That's independent of the cartridge used, but you need a 1-in-7" twist to be able to use this light bullet.

If you have a .22-250 or a .223 with a 1-in-12" or 1-in-9" twist, you would be able to use 62 gr bullets with a BC of only [0.15 - 0.16], because those bullets are traditionally shorter.

In reply toRe: msg 1
nincomp

From: nincomp

26-Nov

smg762 said:

on youtube there are the designers of the new 22 ARC, saying that the bullet has a higher BC than 224 valkyirie

The most likely answer is that even though the 22 ARC and 224 Valkyrie cartridges have the same overall length of 2.26" (same as 223) the 22 ARC's case is shorter.  This allows the 22 ARC to use bullets with longer ogives ( which have potentially higher BC's).     Although I have not yet seen the SAAMI drawing for the 22 ARC, I have seen reports that the max case length is 1.52".  The 224 Valkyrie has a slightly longer case of 1.6".   If magazines are not an issue, both cartridges would be loaded to a longer OAL with longer-ogived bullets.

smg762

From: smg762

1-Dec

visually they appear identical. could it be related to the boat tail or the tip of the bul;let

In reply toRe: msg 4
EmericD

From: EmericD

1-Dec

That's exactly what I explained. 

They are comparing the .224 Valk firing a 60 gr bullet of "old" design, versus the .22 ARC firing the new 62 gr ELD-VT, which is a 75-88 gr class bullet with a shorter core (to reduce weight, but keeping the very good form factor or Hornady latest design).

It's very similar to the excellent Soviet 5.45 mm 7N6 bullet, which was around 25 mm long but with a weight of only 3.4 g (partly due to the use of a steel core, partly due to the air gap inside the bullet nose).

For the 75 gr offering, they are also comparing the .224 Valk loaded with the old BTHP designed to be used with the .223 Rem, and the .22 ARC loaded with the ELD-M, which is way longer & slender.

So, the short version is that Hornady currently load the .22 ARC with "more modern" bullets than the .224 Valk (surprise, surprise), but when you are using the same bullet in both cartridge (like the 88 gr offering), the .22 ARC still have the edge due to a slightly higher case capacity, even if you need to run the .22 ARC to a slightly lower pressure than the .224 Valk (due to the limitation of the AR-15 bolt).

Nothing magical here.

In reply toRe: msg 6
nincomp

From: nincomp

8-Feb

The drawings for the 22 ARC are now up on the SAAMI website.   This is the first time I have seen it. Grendel-length case rather than the shorter one used for the 6 ARC.  Freebore is .1314" (3.338mm) long at .2245"  (5.702mm) dia.   

https://saami.org/wp-content/uploads...2024-01-29.pdf

nincomp

From: nincomp

8-Feb

smg762 said:

on youtube there are the designers of the new 22 ARC, saying that the bullet has a higher BC than 224 valkyirie (assuming the same weight) , and yet the two bullets appear to have an identical shape. can anyone explain why this is?   would it be related to the boat tail or shape of the tip? as i said the ogive length is identical so i don't know how they can claim a higher BC

Now that the SAAMI specs are available, we can answer this.  As we suspected, the 22 ARC can use bullets with longer ogives.  The "head height", or the max projection of the bullet from the neck of the case of the 22 ARC is  0.735" (18.66mm).  For the 224 Valkyre, it is 0.66" (16.76mm).

nincomp

From: nincomp

8-Feb

To put this into context: 

EmericD said:

For the 75 gr offering, they are also comparing the .224 Valk loaded with the old BTHP designed to be used with the .223 Rem, and the .22 ARC loaded with the ELD-M, which is way longer & slender. So, the short version is that Hornady currently load the .22 ARC with "more modern" bullets than the .224 Valk (surprise, surprise)...

Bullets designed for the 223 Rem have a maximum ogive length of only 0.500 (12.7mm).  

For what it's worth, it is useful to learn that suspiciously round numbers like 1" or, in this case .500" tend not to have any serious engineering rationale behind them (technical term:  "rough guess" or "ass-pull"). Over the years, one of the biggest ballistic limitations of the 223 and the 5.56x45 has been the short head height, which seems to have been fairly arbitrary.

In reply toRe: msg 9
gatnerd

From: gatnerd

15-Feb

Some first chrono data for 22 ARC.

https://www.ar15.com/forums/ar-15/22-ARC-75-ELD-M-Factory-Ammunition-Velocity/121-784696/

75gr 22 ARC 20" = 2949fps

Velocity is comparable to the 77gr 5.56 Shell Shock's from Black Arc, although obviously 22 ARC has a higher BC projectile. 

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