.280 Enfield...Ahead of its time

[stanc]

Perhaps, but many seem to believe that the cartridge change for the Garand was due to, at least in part, the large amount of .30 ammo already on hand.

I agree. I wasn't saying that inferior armor defeat capability was a factor in the decision to opt for .30 caliber. I was only noting that .276 penetration was lacking, and perhaps inadequate for the diverse target array in WWII.

[stanc]

We could have avoided the whole M14 experience if they had just awarded the service rifle contract to the superior design in 1955. While I have an aficionado's affection for the M14 as you do, I still recognize the AR10 for what it offers over other designs.

No argument there. It's unfortunate the AR10 wasn't adopted instead of the T44.

We effectively already have a 3-caliber system when you look at how the SAW ammo is distributed and fed into the little pigs.

Nope, that pig won't fly. In WWII, packing and distribution was much the same as now, with .30 caliber ammo for the M1 rifle loaded in clips, and the same .30 caliber ammo loaded in belts for the M1917 and M1919 machine guns.

A two-caliber system does not become a three-caliber system just because packing is different for mag-fed (or clip-fed) rifles and belt-fed LMGs.

I still prefer 2, and think it can be done with the new multi-role LMG that replaces both the SAW and 240, while leaving the M4 alone.

Of course it could be done. The only question is how much performance reduction compared to 7.62x51 is acceptable? On that there is no agreement.

[stanc]

It is also easy to forget that proper bullet design would have erased any practical difference between the .280 and the 7.62X51 in the defeat of light armor.

Any advances made to improve .280 anti-materiel performance could also be applied to 7.62x51, thereby keeping relative performance the same.

However, there is one aspect of the .280 that, if changed, ought to have improved downrange performance. As best I can tell, the Brits used only flat-base bullets, whereas the Americans started out with flat-base projectiles but then switched to boat-tail designs.

[justified]

I retract the Ackley comment, I cannot find the reference. If I remember properly the .276 clips were directional and could only be inserted one way. I don't think there was an AR-10 when the m14 was adopted, at least not when testing began.

I also wonder if the manufacturing technology was ready to produce the AR-10 in large numbers.

[stanc]

P.O Ackley wrote about the .276's lack of performance in ballistic testing.

I haven't seen that. My info came from Hackley and Woodin, in History of Modern US Military Small Arms Ammunition, Vol. I.

If I remember properly the .276 clips were directional and could only be inserted one way.

That's true of the Pedersen rifle, but the .276 Garand used a clip that could be inserted either way.

I also wonder if the manufacturing technology was ready to produce the AR-10 in large numbers.

Good question. But I doubt that manufacturers would've had any more difficulties than they did trying to produce the M14.

[Tony Williams]

I think that the .280/30 would have been a better choice than the 7.62x51 simply because the significantly lighter recoil made auto rifle fire far more controllable. The M14 was originally meant to be a selective-fire rifle but the auto switch had to be disabled because the average soldier couldn't make use of it.

However, the .280/30 wasn't ideal IMO; its design was compromised by the desire to meet the US requirement for long-range effectiveness (the new round had to match the .30'06 for lethality at 2,000 yards). So the bullet was made big and heavy to achieve this, which meant that the initial velocity was quite low, giving it a steep trajectory. Incidentally, there was very little difference between the case diameters of the .280 and .280/30: the former was based on the 7.9x57 Mauser's, the latter on the .30'06 - pretty much the same but for a few thou.

I think that the .270 would have made a better basis for the new round, albeit with a different loading. The case diameter was more or less the same as the 6.5mm Grendel's, but it was 46mm long and 6.8mm calibre. Just about perfect for a general-purpose intermediate, I think. The problem was that the loading was optimised for short to medium ranges - 100 grains at 2,860 fps. It could have done with a bullet in the 120-130 grain range, which could then have had a good long-range performance.

My favourite "what if?" of the NATO ammo trials goes like this: the UK agrees to adopt the US 7.62x51 as the standard rifle/GPMG round, as long as the US agrees to the adoption of the .270 as a carbine round, to replace both the .30 Carbine and the SMGs. Chambered in a shorter-barrelled version of the EM-2 bullpup, this combination would have provided exceptionally compact and controllable firepower. Chances are that most British infantry would have ended up with the EM-2/.270 combo, with a .270 mag-fed SAW to follow-on, leaving the 7.62mm for belt-fed MGs and DMRs. One can only dream...

[stanc]

Incidentally, there was very little difference between the case diameters of the .280 and .280/30: the former was based on the 7.9x57 Mauser's, the latter on the .30'06 - pretty much the same but for a few thou.

So, the info on wiki that .280 rim diameter was 0.458" is wrong, and it was actually 0.470"?

I think that the .270 would have made a better basis for the new round, albeit with a different loading. The case diameter was more or less the same as the 6.5mm Grendel's, but it was 46mm long and 6.8mm calibre. Just about perfect for a general-purpose intermediate, I think. The problem was that the loading was optimised for short to medium ranges - 100 grains at 2,860 fps. It could have done with a bullet in the 120-130 grain range, which could then have had a good long-range performance.

I agree with all of that. Long-range performance could've been even better if boat-tail projectiles had been used. Were the British unable to make boat-tail bullets in that time period, or did institutional inertia cause them to stick with flat-base designs?

My favourite "what if?" of the NATO ammo trials goes like this: the UK agrees to adopt the US 7.62x51 as the standard rifle/GPMG round, as long as the US agrees to the adoption of the .270 as a carbine round, to replace both the .30 Carbine and the SMGs. Chambered in a shorter-barrelled version of the EM-2 bullpup, this combination would have provided exceptionally compact and controllable firepower. Chances are that most British infantry would have ended up with the EM-2/.270 combo, with a .270 mag-fed SAW to follow-on, leaving the 7.62mm for belt-fed MGs and DMRs. One can only dream...

Indeed. Nice dream, though.

[video=youtube;wtjVf724G7w]http://www.youtube.com/watch?v=wtjVf724G7w[/video]

[Tony Williams]

So, the info on wiki that .280 rim diameter was 0.458" is wrong, and it was actually 0.470"?

On checking Labbett's work on the 7mm, the rim diameter of the .280 was .458 (.455-.462) instead of .469 (.466-.473) for the .280/30, but the diameter of both cases above the extractor groove was identical at 0.471. So it was just a minor difference to the rim, not the case body.

I agree with all of that. Long-range performance could've been even better if boat-tail projectiles had been used. Were the British unable to make boat-tail bullets in that time period, or did institutional inertia cause them to stick with flat-base designs?

The .303 Mk VIII long-range MG loading (for Vickers guns) had a boat-tailed bullet and that was in service throughout WW2, so I don't know why they stuck with flat-based for the .280 series.

Indeed. Nice dream, though.

The first frame of this video shows the short-barrelled version of the EM-2, which is what I had in mind. I have never seen one in real life - they are exceptionally rare.

[LRRPF52]

I also wonder if the manufacturing technology was ready to produce the AR-10 in large numbers.

The AR10 is much easier to manufacture than a Garand, M14, or other steel receiver rifles, since the machining is done on aircraft-grade aluminum receivers, cutting tool time and increasing tool head life, then hardening through anodizing after they have been machined. Since aircraft-grade aluminum was machined in extremely large volumes back then, maybe more than ever in world history (thinking of the 1940's war efforts), there were no mass production challenges for the AR10. It actually offered streamlining and faster production times. Examples:

Receivers-already explained
Barrel-standard barrel-making procedures, + barrel extension
Furniture-Bakelite
Small parts-MIM

With the M14
Receiver-complex design than is difficult to machine, and must be fitted to the barrel using individual considerations for headspace and timing on each gun
Op-rod-also must be machined from steel
Furniture-wood individually profiled and cut by stock-makers
Heat shield-original was wood and caught fire under high volume, then made out of fiberglass

It is much easier to manufacturer and maintain an AR10/15 family weapon. The full-spectrum logistics advantages from the factory to the soldier's and armorer's hands is quite tangible.

[Tony Williams]

In my "ideal scenario" described above, the UK would have adopted 7.62mm rifles only for the sharpshooter/DMR role, with 4x scopes as standard. I think that the AR-10 would have been the obvious choice because of its accuracy. In fact, that's pretty much what the BA has ended up with now, with the L129A1.

One very minor detail of no military consequence whatsoever - I would have retained the Lee Enfields (preferably fully-stocked and nicely restored No.1 models) for the ceremonial role. Seeing the Guards in their 19th century parade uniforms, complete with bearskins, trying to perform the manual of arms with those little SA80s is just ridiculous...

[LRRPF52]

The .280 pushing a 7mm 168 VLD type bullet versus the 7.62 pushing a M118 173gr Special Ball leans in favor of the 7mm, and makes it a true 800m cartridge. That is with the 7mm 168 VLD starting 100fps slower at 2400fps and the M118 at 2500fps, which is book value for the M24 Sniper Rifle.

With the .280/30, we are looking at faster velocities that make the 7.62 NATO not worth looking at, and you have bullets of similar weights, similar velocities, with the sectional density and aerodynamic advantage clearly in the 7mm's favor. I just ran the numbers side-by-side with the G7 BC values for a 168 7mm VLD at .313, and the M118's .240 G7 BC. The 7mm retains 911 joules at 800m, while the 7.62 M118 only retains 692 joules at that range, having started 100fps faster at the muzzle.

Trajectory for the 7mm at 800m is 9.4 Mils, while the M118 is 10 Mils. Wind drift is 2 Mils for the 7mm at 800m, while M118 is 2.8 Mils at that distance. Another thing to look at is that the 7mm can still do better than the .30 bores with the 139gr bullets, at the same or even faster velocities, since a 139gr 7mm tends to have a higher BC advantage over the 168gr class .30 cal match bullets even.

For a DMR and LMG, the 7mm makes a lot more sense to me for trajectory and retained energy for that era, and the 7mm would still be filling the roles that 7.62 NATO has performed over the past 57 years, with machinegunners on the ground and in the air seeing less drop and drift at extended ranges, with lighter overall weight.

[Tony Williams]

You need to be careful where the performance of the 7mm British/Belgian rounds are concerned - they came with different loadings and case lengths.

The .280's initial loading was a 130 grain bullet at 2,450 fps (the same MV as the .303 Mk VII ball).

By November 1948 (after the switch to the .280/30 case in April), attention switched to 140 grain bullets to obtain the required steel helmet penetration at 2,000 yards. Muzzle velocity was 2,415 fps.

In the 1950 NATO trials held in the USA the steep trajectory was criticised so the MV was raised to 2,530 fps.

The final loading adopted in 1951 as the "7mm Mk 1 Z" was a 140 grain lead-cored FN bullet at 2,550 fps.

Other loadings (all using 140 grain bullet) were:

7mm Optimum: same case and bullet as Mk 1 Z but with bullet seated further out to leave more room for propellant and give the potential for higher velocities as required.

7mm High Velocity: cartridge case extended from 43.3mm to 49.5mm, MV 2,750 fps

7mm Compromise: cartridge case basically the US T60 .30 necked down; case length 51mm, MV 2,800 fps

7mm Second Optimum: based on Belgian 7mm Medium 2 (the only one to enter service - with Venezuela); case length 49.15mm, MV 2,755 fps.

[JASmith]

The AR10 is much easier to manufacture than a Garand, M14, or other steel receiver rifles, since the machining is done on aircraft-grade aluminum receivers, cutting tool time and increasing tool head life, then hardening through anodizing after they have been machined.

I will admit that I was about 10 years old when the M14 was going through final design and competition. But our family interest in firearms and my father being in the steel fabrication business brings couple of impressions strongly to mind: First, "only cheap and unreliable firearms used aluminum." and second, aluminum had not yet become popular outside the aircraft industry. Indeed, aluminum was only coming into popularity as a roofing material during that period.

At that time, accepting a firearm that employed an aluminum receiver would have been a serious break from tradition, representing a serious gamble on reliability and safety. Add to that we know that very few institutions evolve more slowly than the military firearms community, one can readily understand the reluctance to go with the new-fangled weapon. (Recall that the adoption of the M16 was viewed as a revolutionary step imposed from the outside.)

To be sure, other parts of the military R&D establishment were rather dynamic in trying new things. Even there, however, there were significant pockets of technological inertia in many areas, including some that I spent a significant part of my career working in.

Bottom line is that reluctance to adopt the AR10 in the mid-1950s would have been seen as a reasonable move by most of the folks that had even a rudimentary understanding of the business.

[LRRPF52]

You need to be careful where the performance of the 7mm British/Belgian rounds are concerned - they came with different loadings and case lengths.

The .280's initial loading was a 130 grain bullet at 2,450 fps (the same MV as the .303 Mk VII ball).

By November 1948 (after the switch to the .280/30 case in April), attention switched to 140 grain bullets to obtain the required steel helmet penetration at 2,000 yards. Muzzle velocity was 2,415 fps.

In the 1950 NATO trials held in the USA the steep trajectory was criticised so the MV was raised to 2,530 fps.

The final loading adopted in 1951 as the "7mm Mk 1 Z" was a 140 grain lead-cored FN bullet at 2,550 fps.

Other loadings (all using 140 grain bullet) were:

7mm Optimum: same case and bullet as Mk 1 Z but with bullet seated further out to leave more room for propellant and give the potential for higher velocities as required.

7mm High Velocity: cartridge case extended from 43.3mm to 49.5mm, MV 2,750 fps

7mm Compromise: cartridge case basically the US T60 .30 necked down; case length 51mm, MV 2,800 fps

7mm Second Optimum: based on Belgian 7mm Medium 2 (the only one to enter service - with Venezuela); case length 49.15mm, MV 2,755 fps.

Yes I've been reading up on all the variations of the British 7mm. If we're talking about a case based on a .458" rim diameter, that seems to be geared towards the intermediate cartridge concept more than a full-power cartridge like the 7.62x51, and would be limited in muzzle velocity with 7mm projectiles of weight in the 130gr plus range. If we're talking about the 7mm High Velocity, Compromise, and Second Optimum, we're basically looking at something very close to a 7mm-08, which would use the same receiver and magazines as an AR10, FAL, or M14. It's still too big for a service rifle for mission endurance, but viable for GPMG's, sniper rifles, and vehicle-mounted weapons, with measurable advantages over the 7.62 NATO.

[stanc]

The .280 pushing a 7mm 168 VLD type bullet versus the 7.62 pushing a M118 173gr Special Ball leans in favor of the 7mm, and makes it a true 800m cartridge. That is with the 7mm 168 VLD starting 100fps slower at 2400fps and the M118 at 2500fps, which is book value for the M24 Sniper Rifle.

With the .280/30, we are looking at faster velocities that make the 7.62 NATO not worth looking at, and you have bullets of similar weights, similar velocities, with the sectional density and aerodynamic advantage clearly in the 7mm's favor. I just ran the numbers side-by-side with the G7 BC values for a 168 7mm VLD at .313, and the M118's .240 G7 BC. The 7mm retains 911 joules at 800m, while the 7.62 M118 only retains 692 joules at that range, having started 100fps faster at the muzzle.

Unfair comparison. AFAIK, the US and UK have never used VLD bullets in infantry rifle calibers.

Try 7mm 168gr FMJ (w/tangent ogive) against M118SB.

(And your 2400fps MV seems a trifle optimistic, seeing as how the long, 168gr bullet would reduce powder volume.)

[LRRPF52]

Unfair comparison. AFAIK, the US and UK have never used VLD bullets in infantry rifle calibers.

Try 7mm 168gr FMJ (w/tangent ogive) against M118SB.

(And your 2400fps MV seems a trifle optimistic, seeing as how the long, 168gr bullet would reduce powder volume.)

I was actually comparing sniper rifles to sniper rifles, and appropriate projectiles for each. Even the hunting 7mm bullets with exposed lead tips have higher average BC's than the BTHP match .30 cal pills in the 150-175 weight ranges. A flat-based 139gr 7mm still has a G1 BC of .392, and since boat tail projectiles were adopted for the 7.62 NATO across the board, one can deduce that a 7mm FMJ with a boat tail would have been used then as well. Once you boat tail the 7mm, bullets almost 30gr lighter have the same or higher BC as their .30 cal BTHP match counterparts.

2400 fps is about 200-400fps mild when looking at the 7mm/.30 and other 7mm cartridges based on the .473" rimmed US cases, so I purposely handicapped the 7mm to show that it still has an advantage. The original .280 Enfield produced velocities in the 2530fps range with a 139gr projectile. With further powder development specifically for the .280 in any form, the US would most likely have developed loads with faster velocities using mixed powders, although the 7mm still smokes the .30 cals no matter how you look at it.

The .30 cal was a mistake in my opinion. Barrel availability isn't a limiting factor since entirely new barrels were made for the M14, FAL, AR10, and G3. The 7mm from a .473" rimmed case also enjoys about the same barrel life for accuracy as a 7.62 NATO, so there isn't a trade-off there either. It just made too much sense for big green pickle machine, so it wasn't adopted. That's my take on it. You can't fix the mindset of big Army brass. Stupidity is an eternal disease, I've concluded. It can't be helped, assisted, or corrected...only steered, and corrupt + stubborn + stupid makes a problematic mule.

[stanc]

I was actually comparing sniper rifles to sniper rifles, and appropriate projectiles for each.

How is a VLD appropriate? When has either the US or UK used VLD bullets in 7.62 sniper ammo?

A flat-based 139gr 7mm still has a G1 BC of .392, and since boat tail projectiles were adopted for the 7.62 NATO across the board, one can deduce that a 7mm FMJ with a boat tail would have been used then as well. Once you boat tail the 7mm, bullets almost 30gr lighter have the same or higher BC as their .30 cal BTHP match counterparts.

Granted that a boat tail bullet would likely have been developed, at least for sniper use. However, my point is that you were making an unfair comparison of 7mm VLD HPBT (secant ogive) vs 7.62mm Ball FMJBT (tangent ogive) bullets.

That's hardly apples-to-apples. If you wish to do a comparison with VLD in 7mm, it seems to me you ought to also use VLD in 7.62mm.

Or else show tangent ogive FMJBTs or SMKs in both calibers. For example, .284" 168gr SMK vs .308" 175gr SMK (M118LR).

But, 7mm VLD vs 7.62mm FMJ is apples-oranges.

[Buck2732]

Ok I need to confess I would like a rifle in this cal I have put in some time reading alot about it. So I offer this as some light reading.

http://www.quarry.nildram.co.uk/256brit.htm

Buck2732

[jbob208]

i aggree with the comments about aluminum, in that period most aluminum was being sand cast the alloys were simply not available at the time to make the high strength forgings. At the time aluminum was just highly refined dirt,(buaxite ore) to make it strong it had to be thick. Remember we were using a slide rule for caculations and adding a fudge factor in essence overbuilding everything. Now we have finiate element software that allows us to precisly determine a safety factor.

[LRRPF52]

For making conventional civilian market products, aluminum might have been viewed as weak, but for aviation, it was not cast. Aircraft-grade aluminum from WWII era is where Stoner really pushed things, even though the original rifle designs he was working with used steel stampings for the receivers.

The jump to aircraft aluminum made not only lightweight and strength a possibility, but dimensional uniformity under vast temperature ranges-something steel does not enjoy.

I'd still like to see a 7mm AR10 built in the original Armalite or Dutch pattern from the late 1950's. Those are great guns: