7mm Spitfire guns

[drewwizard]

The British 7mm was as mature as it was going to get in 1913-14, It had already been through a number of variations.

Altering the shape of the case does little or nothing despite some peoples claim to the contrary. It may make the cases harder to form.

Lowering the powder charge does work, but then "underpowering" the cartridge seems to be defeating the purpose. Making the velocity difference between the .303 and the .276 closer means a closer trajectory path and less difference to justify the change.

The difference in trajectory for long range rifle shooting has little application in air to air combat where the effective distances are much shorter. A few inches difference in impact on an aircraft fuselage?

The Japanese may have been happy with much less than eight .303s, the Italians were not, shifting to a pair of 12.7mm machine guns in the early/mid 30s, before the Hurricane and Spitfire first flew. The 12.7 was roughly 3 times more powerful on a round to round comparison.
The Italians failed to increase the rate of fire as time went on, although they did try using HE ammunition. The pair of synchronized machine guns might be equal to 3-4 synchronized .303. When mounted in the wing one 12.7 might be equal to two .303s. Yes less than eight .303s but the Itialians weren't happy" about it, they simply didn't have the engine power to carry any more. Their primary fighter engine, the Fiat AR 74, made roughly the same amount of power as the Bristol Mercury in the Gloster Gladiator.

They also tried fitting additional 7.7 machine guns at times.

Here is a bit of internal ballistics (what happens inside the gun) information. It is a bit simplified but bullet velocity is dependent on the pressure applied to the base of the bullet vs the weight of the bullet per unit of area (sectional density).

What this means is that using similar powders (to keep the burning curve the same) is that, due to the difference in diameter, you can accelerate a 145 grain 7mm bullet to the same speed as a 174 grain .303 bullet using the same pressure. If you want to use a 165 grain bullet in the 7mm you need more pressure, if you want higher velocity you need more pressure.

The smaller diameter bullet will have less room inside for incendiary materiel and it's AP qualities may be suspect, especially at anything other than a 90 degree impact. Long skinny bullets not doing so well at oblique impacts or penetrating after intermediate barriers. The US .50 having trouble with that one for instance.

The British, after the BoB, moving to a mix of 50% AP and 50% incendiary ammunition as fast as production would allow.

The difference in ballistics at fighter ranges is very large. Look at a ballistic table, and see what a 500 yard drop is like between the two cartridges. We are likely talking 10s of feet. requires a little better ballistic compensator for the slower round. The deal breaker is the energy left at 500 yards. You either need speed and weight (14.5mm Russian), or explosive head (20mm and above) to deliver damage.

 

[Shortround6]

The difference in ballistics at fighter ranges is very large. Look at a ballistic table, and see what a 500 yard drop is like between the two cartridges. We are likely talking 10s of feet. requires a little better ballistic compensator for the slower round. The deal breaker is the energy left at 500 yards. You either need speed and weight (14.5mm Russian), or explosive head (20mm and above) to deliver damage.

Actually the .276 brings little to the table. Please do play around with a ballistic calculator or two.
Please look at the ballistic chart in a previous post. Near sea level the MK VII round didn't rise more than about 4.3 feet above the line of sight out to 600yds. At higher altitudes it would be flatter, lower air density means less drag which means the bullet has a shorter time of flight to a given distance. It also means it hits harder.

measuring "drop" is using the wrong parameter. The guns will be pointed upwards a bit, wing guns will cross the line of sight somewhere between 200 and 300yds for most planes. This means the bullets will not be more than a foot or a foot and half from the line of sight for several hundred yds at the least and perhaps as much as 400yds. this distance is NOT from the muzzle of guns but starts 150-200yds in front of the fighter.

I sincerely doubt the difference in "drop" between the ,303 and the .276 was 10s of feet at 500yds in any case. It might only be 9 feet between the .276 and the old round nose black powder loaded .303. With a spitzer bullet and cordite propellent the difference in drop may only be 3 feet.
How big is an He 111 fuselage?

 

[drewwizard]

I finally got some time to look up a ballistic table. Just a simple comparison, the
1940 .276 Enfield at 500 yards. Velocity 2011 Ft/S, energy 1617 FT-lbs, drop 56.08 inches. Better than I thought.
Enfield 303 at 500 yds. 1578 Ft/S, Energy 962 Ft-lbs, -64.9 inches.

.276 muzzle velocity - 2640, energy 2786
303 muzzle velocity - 2400, energy 2225
Not sure I would see a lot of difference between these two as aircraft armament. both are light on energy for WWII.
.5 BMG is 6201 Ft lbs at 500 yards, 2055 Ft/S and a bullet drop of 46 inches

 

[Clayton Magnet]

The .303 cartridge was obsolescent prior to WWI, and straight up obsolete by WWII. It only remained in service so long because a couple pesky world wars popped up and interfered with the re-tooling. The Boers out-shot the Imperial troops, at least as far as I have understood, primarily because of the rapid reloading from 5 round stripper clips. The Lee-Metfords of the era were issued with magazines, tethered to the rifle, and required single feeding to reload. combined with the fact that the rifles were poorly zeroed with respect to the ammunition used. As a result, the Boers were able to maintain a higher volume of fire, and more accurately at distance.

I assume, perhaps erroneously, that HAD the 303 been replaced, the British would have explored the .50 Vickers as a possible aircraft armament.

 

[The Basket]

Not sure about the weight and rate of fire. The Boers had the advantage in range.
Weapons and ammunition made in huge numbers does tend to stick around.
I wouldn't say the Lee Enfield was obsolete in 1940. Obsolescent but since the enemy also had bolt actions then it wasn't a deal breaker.

 

[Glider]

BTW these are two of the rifles I own.
View attachment 470541
View attachment 470542

The bottom one is a converted No 4 Enfield and will make anybody who claims that "rear locking lug rifles won't shoot" a liar.

.

Is the top one an Anchutz?
I have used a civilian version of the Lee Enfield L42A1 on the long ranges at Bisley a couple of times and I did better than I expected up to 800 yards. I cannot tell you why, but the rifle gave me confidence that it would do well. I hope yours is as good

To be honest the 303 was a very good round and when matched with the Lee Enfield was at least as good as any other bolt action rifle. The round was an almost perfect match for the Lee Enfield which is why many people considered it to be the best sniper rifle of the war.

I can only go from my own experience, but I hadn't shot a full bore rifle for many years and at 800 yards scored 86 which was a group of about 26 inches. Most of the others were a lot better than me but they were regular shooters. I had to score 80 at 300 yards before I was allowed to shoot at 800 yards. I don't know the score it was a pass or fail test.

Another fact which may be of interest but I like you used peep not telescopic sights. Some used the telescopic sights but I didn't as I was used to peep sights on my 0.22 target rifle

 

[Clayton Magnet]

which is why many people considered it to be the best sniper rifle of the war.

The No.4(T) was considered the "best" sniper rifle of the war because they were bedded and accurized by H&H, not because of the cartridge. The .303 comes up short against the 7.92x57mm and .30-06 in ballistics.

 

[Clayton Magnet]

Most sniper rifles at that time were simply rack grade rifles quickly fitted with optics and sent off to the units.

 

[Shortround6]

The .303 cartridge was obsolescent prior to WWI, and straight up obsolete by WWII. It only remained in service so long because a couple pesky world wars popped up and interfered with the re-tooling. The Boers out-shot the Imperial troops, at least as far as I have understood, primarily because of the rapid reloading from 5 round stripper clips. The Lee-Metfords of the era were issued with magazines, tethered to the rifle, and required single feeding to reload. combined with the fact that the rifles were poorly zeroed with respect to the ammunition used. As a result, the Boers were able to maintain a higher volume of fire, and more accurately at distance.

I assume, perhaps erroneously, that HAD the 303 been replaced, the British would have explored the .50 Vickers as a possible aircraft armament.

The difference between the 7mm Mausers and the .303 Lees has been somewhat exaggerated, perhaps to cover up poor training, doctrine, tactics and supply?

1. Both used round nosed bullets of rather similar ballistics/trajectory. Both changed to lighter spitzer bullets of higher velocity between the Boer war and WW I.
2. The Lee Metford may have been loaded with single rounds from the top but that was changed to using 5 round stripper clips in the top.
However, doctrine/training called for single loading with a magazine cut off used to hold the magazine in reserve. Just in case the Boers decided to use a Zulu style charge, the British could flip the cut off outoff the way and every soldier would have a full magazine.
3. It took a while for the British to get into dispersing troops and not trying to form up 'squares" or other out dated tactical formations.
4. Some sources state that the rifles as supplied from store/factory were not properly zero'd which certainly affects long rang accuracy.

Note that changing rifle or cartridge changes none of these problems.

 

[Shortround6]

Is the top one an Anchutz?
I have used a civilian version of the Lee Enfield L42A1 on the long ranges at Bisley a couple of times and I did better than I expected up to 800 yards. I cannot tell you why, but the rifle gave me confidence that it would do well. I hope yours is as good

To be honest the 303 was a very good round and when matched with the Lee Enfield was at least as good as any other bolt action rifle. The round was an almost perfect match for the Lee Enfield which is why many people considered it to be the best sniper rifle of the war.

I can only go from my own experience, but I hadn't shot a full bore rifle for many years and at 800 yards scored 86 which was a group of about 26 inches. Most of the others were a lot better than me but they were regular shooters. I had to score 80 at 300 yards before I was allowed to shoot at 800 yards. I don't know the score it was a pass or fail test.

Another fact which may be of interest but I like you used peep not telescopic sights. Some used the telescopic sights but I didn't as I was used to peep sights on my 0.22 target rifle

top rifle is an RPA 2000 quad lock. (four locking lugs at the front of the bolt) It is a single shot action and the only opening in the tube that forms the receiver is the loading/ejection port on the right hand side. I did use this rifle twice at the Canadian National matches about 17-18 years ago and such custom rifles had all but displaced the converted military rifles.

The rules of the game are/were such that you had to use non-optical sights to compete in the open catagory. If you used a telescope you got put into a different catagory and were not eligible for some awards (bragging rights, nobody every made money shooting rifles).

 

[Clayton Magnet]

The Lee Metford may have been loaded with single rounds from the top but that was changed to using 5 round stripper clips in the top.

Very true, the charger bridge was added shortly thereafter, but the rimmed cases never functioned perfectly well in the clips. It was an improvement, no doubt, but the Mauser's worked better. Wartime manufactured ammunition had slightly beveled rims, to help with the rim-lock issue, so soldiers could force a round into the chamber. But try that with modern factory brass, and the rifle will lock up solid.
Rimmed cases are a relic of the 19th century, with only the Russians still fielding the ancient 7.62x54R

 

[Clayton Magnet]

I should clarify, I personal love the Lee Enfield, and own 3 of them. One 1916 BSA No.1 Mk III, one 1945 Long Branch No.4 and a 1946 Fazakerley No.5

 

[The Basket]

Apart from the danger of using Google to look up rimmed I don't see any problem with a rimmed cartridge.
Still goes bang.

 

[Clayton Magnet]

I don't see any problem with a rimmed cartridge.

Unless you are very careful stacking the magazine, a rimmed case will grab the rim of the cartridge below it and lock up the rifle. A decidedly poor turn of events.

 

[Shortround6]

Clayton Magnet is quite right, this is often called a double feed. The two rounds both move forward in the magazine and the bottom one actually gets it's nose on the feed ramp and the two rounds are wedged together. This can happen with rimless rounds (been there) but is much more common with rimmed.

 

[The Basket]

I am certain aware of rimlock.
How big of a show stopper it is is the key.

 

[Shortround6]

Haven't had it happen on an Enfield (due to not using the magazine much) but you may be able to clear it by dropping the magazine and dumping the rounds involved.
Clearing a double feed on some other rifles gets a lot harder. Had it happen on a Win 70 that has a magazine floor plate release, solved the problem but all round not involved are dumped on the ground and you pretty much start over.
One Mauser I believe you can unlatch the magazine floor plate by inserting a bullet nose into a hole in the floor plate? Takes a lot longer.
please remember that if this happens you do NOT have a single shot rifle, you have a club.

 

[Clayton Magnet]

View: https://www.youtube.com/watch?v=MOYTdoQkFrM

 

[Clayton Magnet]

Might not have been a big deal, but it wasn't ideal. Again, there is a reason that rimmed cartridges are a thing of the past in Military use. Obviously 303 is still popular as a hunting round, likewise with 30-30

 

[tyrodtom]

I managed to get my #4 Mk1 to rim jam, but it was all my fault. At the time I was ignorant of the mechanics of rim jam, or double feed.
Had a scope on it, so I had to hand load the magazine. plus the magazine was a poorly made aftermarket 5 round magazine.
It tried to double feed.

I never had that problem with the original 10 round magazines, even though they were dented.