Polish AF: preparing for 1939

Canada began receiving Hurricanes September 1938, South Africa by November 1938, Yugoslavia by December 1938 ... so it was possible.

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It was certainly possible, but for every Hurricane that went to Britain's allies, it was one less for the RAF. The Hurricane was a finite resource.

I don't actually know if a more advanced fighter in the Polish air force would have made much of a difference - Shortround's right in that whatever it was would have to be in large numbers by September 1st. The Bf 109 was the best fighter in continental Europe and the LW bombers the most modern, but we also have to consider that it wasn't just superior airpower that defeated the Poles. A combined effort from the German armed forces - Blitzkrieg - the speed of Germany's advance caught everyone by surprise - in France and Russia subsequently. Although fighting continued into October, it is recognised that by September 17, the invasion was successful - that's seventeen days to take Poland out!

The Polish air force dispersed its fighters to satellite fields before the invasion so when the LW attacked its airfields, vital types were not wiped out. The Germans were quite surprised by the determination of the Polish pilots, largely because they weren't expecting such determined counter attacks, but it wasn't any more courage or more modern aeroplanes that could have saved Poland.

I agree that numbers were what was required, but the P-11 was just so close to obsolescence that it also created problems for the PAF over and above the numbers issue. two things really dogged the P-11s, slow speed and light armament. They lacked the speed to catch the German bombers, and even on those occasions that they did catch them, struggled because of the weak armament.

Just the same the P-11 had its uses, and given the limited supply of aircraft, in any alternate scenario, it should be retained to flesh out the Polish air strength.

So, any new fighter should not be viewed as a replacement, rather a reinforcement. And reinforcements can only come from additional money. In a cash starved country like Poland, they would need to make difficult choices as to what they sacrificed so that they could have more fighters. My opinion is that they sacrifice the naval expansion and bomber programs, and i now think they build Fokker DXXIs (with retractable U/C and possibly 2 x 12.7MG) and GIs.

Poland did not succumb to blitzkrieg as is popularly portrayed, though it has to be conceded that it had similar tactics and certainly similar outcomes. They did not go down the same way as France and the Low Countries. And it took longer than 17 days to overcome polish resistance. Certainly the back of Polish defence had been broken by September 17, but serious battles continued to rage right through September, including the Battle of Tomaszów Lubelski and the battle of Warsaw. A big factor in the Polish leaderships decision to look for its forces to escape rather than reform was the Soviet invasion.

The last resisitance did not end until 6 October. It is arguable, though conceded as unlikely that without intensive air support, the German encirclement movements, Kesselschlachts, might well have faltered and failed. If they had been forced to fight a ground slogging land battle, one or more of the encirclemeing mobvements may well have failed. if that happened, it would have been the German encircling forces that would have surrendered, rather than the Poles. And success in one sector would mean they (the Poles) could shift forces to relieve other encircled elements. this was certainly along the lines of the Polish battle plan, and it may well have worked except for the combined effects of tanks and air support. Take away the air support, and the Germa penetrations may well have been contained and defeated.

Certainly the back of Polish defence had been broken by September 17

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Well, that's still 17 days, Parsifal, which is still extraordinarily quick. You are right about the PZL P.11, and if they had a handful of Hurris or another type as reinforcements maybe things might have gone on for a bit longer, but the end result would have been the same, regardless of how long the resistance held out for. The German armed forces were too strong. In order to carry out the scenario you envisage, the Poles would have needed a pretty large number of fighters and bombers, so where do you stop in this scenario in terms of what you think they need as opposed to what they can get hold of beforehand?

From Wiki, but a good summary of the common misconceptions of the Polish campaign


The Polish Army fought German tanks with horse-mounted cavalry wielding lances and swords.

In 1939, only 10% of the Polish army was made up of cavalry units. Polish cavalry never charged German tanks or entrenched infantry or artillery, but usually acted as mobile infantry (like dragoons) and reconnaissance units and executed cavalry charges only in rare situations against foot soldiers. Other armies (including German and Soviet) also fielded and extensively used elite horse cavalry units at that time. Polish cavalry consisted of eleven brigades, as emphasized by its military doctrine, equipped with anti tank rifles "UR" and light artillery such as the highly effective Bofors 37 mm anti-tank gun. The myth originated from war correspondents reports of the Battle of Krojanty, where a Polish cavalry brigade was fired upon in ambush by hidden armored vehicles, after it had mounted a sabre-charge against German infantry.

The Polish Air Force was destroyed on the ground in the first days of the war.

The Polish Air Force, though numerically inferior, had been moved from air bases to small camouflaged airfields shortly before the war. Only some trainers and auxiliary aircraft were destroyed on the ground. The Polish Air Force, significantly outnumbered and with its fighters outmatched by more advanced German fighters, remained active up to the second week of the campaign, inflicting significant damage on the Luftwaffe. The Luftwaffe lost, to all operational causes, 285 aircraft, with 279 more damaged, while the Poles lost 333 aircraft.


Poland offered little resistance and surrendered quickly.

In the first few days, Germany sustained very heavy losses: Poland cost the Germans an entire armored division, thousands of soldiers, and 25% of its air strength. As for duration, the September Campaign lasted only about one week less than the Battle of France in 1940, even though the Anglo-French forces were much closer to parity with the Germans in numerical strength and equipment. Furthermore, the Polish Army was preparing the Romanian Bridgehead, which would have prolonged Polish defence, but this plan was cancelled due to the Soviet invasion of Poland on 17 September 1939. Poland also never officially surrendered to the Germans. Under German occupation, the Polish army continued to fight underground, as Armia Krajowa and forest partisans—Leśni. The Polish resistance movement in World War II in German-occupied Poland was one of the largest resistance movements in all of occupied Europe.

Poland succumbed to Blitzkrieg


It is often assumed that blitzkrieg is the strategy that Germany first used in Poland. Many early post-war histories, such as Barrie Pitt's in The Second World War (BPC Publishing 1966), attribute German victory to "enormous development in military technique which occurred between 1918 and 1940", citing that "Germany, who translated (British inter-war) theories into action… called the result Blitzkrieg." This idea has been repudiated by some authors. Matthew Cooper writes: "Throughout the Polish Campaign, the employment of the mechanized units revealed the idea that they were intended solely to ease the advance and to support the activities of the infantry…. Thus, any strategic exploitation of the armoured idea was still-born. The paralysis of command and the breakdown of morale were not made the ultimate aim of the … German ground and air forces, and were only incidental by-products of the traditional manoeuvers of rapid encirclement and of the supporting activities of the flying artillery of the Luftwaffe, both of which had as their purpose the physical destruction of the enemy troops. Such was the Vernichtungsgedanke of the Polish campaign."

Vernichtungsgedanke was a strategy dating back to Frederick the Great, and was applied in the Polish Campaign little changed from the French campaigns in 1870 or 1914. The use of tanks "left much to be desired...Fear of enemy action against the flanks of the advance, fear which was to prove so disastrous to German prospects in the west in 1940 and in the Soviet Union in 1941, was present from the beginning of the war." John Ellis, writing in Brute Force asserted that "…there is considerable justice in Matthew Cooper's assertion that the panzer divisions were not given the kind of strategic (emphasis in original) mission that was to characterize authentic armoured blitzkrieg, and were almost always closely subordinated to the various mass infantry armies." Zaloga and Madej, in The Polish Campaign 1939, also address the subject of mythical interpretations of Blitzkrieg and the importance of other arms in the campaign. "Whilst Western accounts of the September campaign have stressed the shock value of the panzers and Stuka attacks, they have tended to underestimate the punishing effect of German artillery (emphasis added) on Polish units. Mobile and available in significant quantity, artillery shattered as many units as any other branch of the Wehrmacht"......

nuuumannn said:

Well, that's still 17 days, Parsifal, which is still extraordinarily quick. You are right about the PZL P.11, and if they had a handful of Hurris or another type as reinforcements maybe things might have gone on for a bit longer, but the end result would have been the same, regardless of how long the resistance held out for. The German armed forces were too strong. In order to carry out the scenario you envisage, the Poles would have needed a pretty large number of fighters and bombers, so where do you stop in this scenario in terms of what you think they need as opposed to what they can get hold of beforehand?

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Polish resistance cracked on the day the Soviets intervened. its arguable as to why it cracked. Up until that point the Poles were making preprations for the Rumanian redoubt....a retreat to the south of the country into the rough terrain near the Rumanian borders. Thats still a strategy responding to defeat, but its not surrender either.

I dont think the answer lies in a few dozen foreign imports. The Poles needed several hundred additional fighters, and that really rules out bringing expensive imports. They had to build their new fighters, and they needed about 200 new fighters to have any real effect. That plus the 150 they already had would have given them 350 fighters, and 350 , along with a concerted effort by the western allies might well have unhinged the LW.

The problem with my ideas arent that they wouldnt be effective, its that the Poles would have needed crystal clear hindsight, much better support from their allies, and a German response no different to the historical. none of those assumptions are attainable, but within the limits of those faulty assumptions, if the Poles had done something along the lines of what im suggesting, I think it is very posible for them to pull off an upset. With 350 fighters, plus 1200 or so allied fighters in the west hammering away at the LW. , and a faltering encirclement battle on the ground, if the Poles could last until the winter, Germany might well find herself face with a true two front war from the very beginning. Who knows what might happen from there.

That's very interesting Parsifal and yep, looks like Blitzkrieg was perhaps not what we might call what they did, but nevertheless, the result was pretty swift (define Blitzkrieg - Lightning War). I'm under no illusion and never was that it was a cake walk for the Germans, but ultimately, the time it took for Poland to capitulate, despite the German casualties was remarkable. Advanced fighters might have slowed things down, but not been enough, which brings us back to this thread. Perhaps we should be asking what it would have taken to defeat the Germans in Poland, with the obvious limitations on technology and availability of equipment to the Polish armed forces? Would more advanced air power have been enough to do so?

My answer was to your informative post - and I definitely agree with you on your last one.

nuuumannn said:

That's very interesting Parsifal and yep, looks like Blitzkrieg was perhaps not what we might call what they did, but nevertheless, the result was pretty swift (define Blitzkrieg - Lightning War). I'm under no illusion and never was that it was a cake walk for the Germans, but ultimately, the time it took for Poland to capitulate, despite the German casualties was remarkable. Advanced fighters might have slowed things down, but not been enough, which brings us back to this thread. Perhaps we should be asking what it would have taken to defeat the Germans in Poland, with the obvious limitations on technology and availability of equipment to the Polish armed forces? Would more advanced air power have been enough to do so?

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Nah, not a chance. The big killer in the Polish campaign was the german artillery, mobility and numbers. there simply was no answer to that, given the forward defence policies insisted upon by the Poles. A fortified defence behins the Vistula, with better fortifications might have helped , but most of Polish industry was located in Polish Silesia......the Poles were in an almost imppossible situation....

I don't think anyone is under the impression better aircraft would have turned the tide in favour of Poland. As per tomo pauk's initial post, the idea is to think of Poland's best course of action.

I think if the British and French had of stepped in that could of taken some pressure off the Polish, but then again I don't think the British and French were really capable of giving enough help to change the Polish situation. From memory I don't think the British Expeditionary Force even started arriving in France until after Poland had fallen. Britain's strength was mainly in it's Navy and I don't think that even with the best of will that there was much any Navy could have done to aid the Polish. As for the French Army it was not ready to attack Germany, one of the French Armies biggest weaknesses was it's poor communications and this prevented it from organising a proper defence let alone an attack into Germany. The only thing I think the Western Allies could have done was possibly a bit of bombing, although I am not sure what they would have bombed or with what.
Basically the Germans had the Poles by the short and curlies in 1939 and there was nothing either they or their allies could do about it.
Maybe if the Polish had of invested more of their money in fortifications and fighters this may have slowed the Germans. As far as Polish fortifications are concerned a lot remain intact until this day as the Germans just went around them. More fighters esp something like the PZL P24 with canons for dealing with bombers would have been useful but they would really have needed efficient ground control to direct them towards the bombers, ideally radar. Perhaps though if the Poles had of been able to inflict more heavy losses on the Germans this could have effected later events in the west, but then a lot of the early equipment used by the Germans had been replaced by 1940 anyway.

parsifal said:

Saying that Hitler only decided to invade Poland after Poland sided with france, is the same warped logic as Hitler used. Poland had a non-aggression pact with Germany dating back to 1934, and before that there was the treaty of Locarno. the Poles had already demonstrated their good intentions towards Germany. Germany betrayed them, simple as that. As late as 1938, the Germans were professing their friendship towards the Poles, but at the same time making preprations for war, though the final decision to move came later, which is your entire casus belli.

All good and noble, but the world was already witnessing how the germans treated their "friends". That hitler could not be trusted was being demonstrated by event after event, culminating in the dismemberment of Czechoslovakia, and then finally the Czech rump. As those events unfolded, the Poles knew they could not trust the germans, and the germans were not genuine in their offers of friendship. Nearly every freedom loving nation in the world was realizing that at that time.

These statements of mine are not just my own, they were established at nuremberg after the war and were a precursor to being able to try the German leadership as war criminals. So I am conscious of your motivations here. Re-write history as to who is the aggressor nation, and you can establish that Hitler and the rest of his cronies were not war criminals, and disprove Germany's war guilt. sorry guys, not buying it, and it exposes you people for what you really are.

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Parsifal, I believe calling me a revisionist is uncalled for. I am a serious historian, who has spent more time reading about Nazi Germany than I would like to admit.
I am merely passing on information, which is available through a large number of primary and secondary sources. Hitler did often take up the idea of creating an alliance with Poland to fight Russia. In the end, he did not and instead massacred a large part of the Polish population.

But I will not take this kind of insult...

Kris

I apologise if you are offended, and was a little harsh on you, I can see. But harsh as my treatment of you was, that doesnt make me wrong to say what i said, and I dont retract it in any way. Thats because, perhaps without realizing, what you are saying is in sync with hitlers ideas. i am not accusing you of nazism, fwiw. Its just that Hitler was the agressor against poland. there was no choice for Poland. except perhaps to allow her people to die without a fight, which was never going to happen willingly. And saying you are offended pales to insignificance when you compare the monstrous nature of your opinion to the huge suffering inflicted on the Poles by the criminal aggression displayed by the Germans towards them.

Germany acted disingenuously toward Poland, and all nations that surrounded Germany in the end lived to regret it (even Switzerland). Any nation that tried to ally with Germany was always betrrayed in the end. Germany in the interwar period was a totally ammoral nation, no respect for the rule of law, and no peaceful intent whilst under Hitler. In just the same way as they presented a smiling friendly face to the Soviet Union, they always intended to dismmember Poland. Hitler in Mein kampf restated conservatrive racist german dogma already pursued from at least 1915, when he saw Poland, Lithuana and estonia as colonial frontiers of Greater Germany. He never made any secret of what he intended to do in these states. For a time, as he consolidated his power, he gave the impression of cultivating good relations with the Poles, and f rom time to time he toyed with the idea of using the Poles to attack the Soviets. But his base course was the same as that first suggested by Ludenforf in 1915, and stated very clearly in Mein Kampf.

Hitlers stated intent was virtually the same as that of Imperial germany, namely it was planned to annex territory in both Lithuania and Poland for direct colonization by German colonists after the forcible removal of the Polish and Lithuanian population. As early as April 1915, the Polish Border Strip plan against Poland, which was first suggested by General Erich Ludendorff in 1914, was approved as a German war aim by the Chancellor Theobald von Bethmann-Hollweg. The German historian Andreas Hillgruber argued that the foreign policy of General Ludendorff, with its demand for lebensraum to be seized for Germany in Eastern Europe during World War I, was the prototype for German policy in World War II. Lebensraum almost became a reality in 1918 during World War I. The new Communist regime of Russia concluded the Treaty of Brest-Litovsk with Germany, ending Russian participation in the war in exchange for the surrender of huge swathes of land, including the Baltic territories, Belarus, Ukraine, and the Caucasus. However, unrest at home and defeat on the Western Front forced Germany to abandon these favorable terms in favor of the Treaty of Versailles, by which the newly acquired eastern territories were agreed to sacrifice the land to Lithuania, Poland, and new nations such as Estonia or Latvia, and a series of short-lived independent states in Ukraine.

if you want to get upset because I dont compromise on German war guilt, thats your perogative. I dont want to fight with you. i dont mind discussing it. But neither will i compromiose on this issue, Ever. I dont make deals with the devil. I should not have made the accusation i did, but neither am i about to make any concessions about german war guilt. they are guilty as hell....

I dont see what war guilt has to do with it. I merely said that, at some point, Hitler was thinking of allying with the Poles to attack the Soviets.

You are right about everything you said and yes, Hitler would have backstabbed the Poles, but then again, allies is not the same as friends. You use them to your benefit as long as they are useful. I am sure the Poles had no illusions about this and decided not to team up with Hitler. As I said, they probably saw a division of power between Germany and Russia as a good thing. That turned out badly

Anyway, your rant was uncalled for and in no relation to my post. If you think you can just insult people and then justify it by saying you feel strong about these things, well, that just won't do. As a word of advice, try to keep your anger under control. I had the most respect for you up til today and I hope I was not wrong.

Kris

tomo pauk said:

Helo, gents,
What tecnological paths hould`ve been undertaken by the Polish air force in the 1930s, in order to be better prepared for the September war in 1939? Not that it would`ve changed the outcome, but just to give Polish air crews better chances once airborne.

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Getting back to the original question, the most practical engine solution would be a late model Mercury engine. The Poles already had a licence for an early version, they had a factory tooled up for the early version. It would have been the quickest and cheapest way to a 840-900hp engine. Unfortunately that is about the limit for Mercury without 100 octane fuel. Going to the 14 cylinder G-R engines might be the next step, depending on licence. The "K" series might be easily licensed (everybody and their brother was making it) and it might be able to be made on the Mercury machinery without too much trouble (same bore and stroke) but the "K" doesn't really offer much over a late model Mercury. The "N" series might be harder to license as it was the latest production version. From a manufacturing stand point it isn't really much different ( more and deeper fins, not sure what else) and some countries that Licensed the "K" developed versions close to the "N".
The Hispano engine offers more performance (with out trying to get into low drag radial cowlings in 1939) but may require the most money in manufacturing set up.

Using better propellers may help and it may be possible. The British had actually fallen behind the world standard and were playing catch-up so I would not use their time line as to when variable pitch ( two-pitch) and constant speed propellers were available.

For guns you are pretty much down to the standard MG used by the Poles or possibly the two 20mm cannon. Either pretty much the same thing as the German MG/FF (as used in some export fighters) or the 20 Hispano (or early version) IF they use the Hispano engine. Trying to be the first air force to mount Hispano guns in the wing is not likely to end well.

Retractable landing gear? The Poles can certainly design it and build it in prototype form, Large scale production? Please remember that many British and French aircraft companies bought the landing gear for their planes from specialist companies. Maybe they can and maybe the can't I don't know.

Some points about the Mercury


In early 1938 Roy Fedden (its chief designer) pressed the UK Air Ministry to import supplies of 100 octane aviation spirit (gasoline) from the USA. This new fuel would allow aero engines to run at higher compression ratios and supercharger boost pressure than the existing 87-octane fuel, thus increasing the power. The Mercury XV was a derivative of the Mercury VIII (with the same power output rating...I have read, however that the Mercury XV was capable achieving outputs of over 900HP with the 100 Octane and a boost of 9lbs) was first developed in 1938 and was one of the first British aero engines to be type-tested and cleared to use the 100-octane fuel. There is no reason to believe the Skoda (poland) production lines could not produce the Mercury XV. By early 1939 they were already building the Mercury VIII, with an 830HP rating. The Mercury VIII was first designed in 1935, so on the assumption that more fund are available, ther is no reason not to allow or consider reasonable the earlier introduction of this engine as well.

As indicated, the Poles were already producing the Mercury VIII in 1939 for the abortive P-11g. It arrived too late for the battles in September, but given that the engine was available from 1935, ther is no reason not to assume that given more money the engine could not have entered service in Poland from early 1938, and the mercury XV from early 1939. The great appeal of the Mercury for the Poles is that adoption of the improve models is seamless to production. They could seamlessly move from one model to the next without affecting production.

Retracts is a problem. However two Fokkers were modified to take retracts in the Finnish AF. It took about 3 months to fit the prototype, and they did give some problems to the Finns, in that the gear collased on one of the prototypes. Ive only seen one account of this test, and with retractable gear fitted, 200 lbs of weight was added to the aircraft, but an additional 15mph added to the top speed. that was with the lower rated Mercury VIs engines (645hp) fitted. with an 830hp engine fitted, you might get 2025 mph extra out og the Fokker with retracts. Again, given ideal conditions, I see it as very possible for the Poles, if they adopted the DXXI in 1937, to have a functional retract system in service by 1938. The Polish aero industry was working for the 6th biggest air force in Europe, and was quite efficient, certainly moreso than the FAL state factory at Timmpa.

I think the ideal weapon for the Polish DXXI and GI would not be in 7.7mm caliber. Neither do i see use of the 20mm cannon as all that optimal. Fitting and strengthening the wings for the DXXI might be a bit of a problem. The Danes had tried to fit 20mm madsen cannon to their DXXIs and it had not really worked, because it caused too much warping in the wings. But LMGs were too light as well IMO. I think the optimal would 2 x 12.7mg in place of the 4 x 0.303 Brownings. The Browning 0.303 weighed about 31 lbs, so total all up weight for the four guns would be about 125lbs. The Poles had a 12.7mm aircraft MG, but I dont know its weights. Assuming it was similar to the US 0.5 AN guns was about 61 lbs, so no weight penalty for the change of armamant. not sure about ammunition.

Civettone said:

I dont see what war guilt has to do with it. I merely said that, at some point, Hitler was thinking of allying with the Poles to attack the Soviets.

You are right about everything you said and yes, Hitler would have backstabbed the Poles, but then again, allies is not the same as friends. You use them to your benefit as long as they are useful. I am sure the Poles had no illusions about this and decided not to team up with Hitler. As I said, they probably saw a division of power between Germany and Russia as a good thing. That turned out badly

Anyway, your rant was uncalled for and in no relation to my post. If you think you can just insult people and then justify it by saying you feel strong about these things, well, that just won't do. As a word of advice, try to keep your anger under control. I had the most respect for you up til today and I hope I was not wrong.

Kris

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...and I would suggest that you both leave it at that. He apologized and you didn't accept his apology. Now move on.

Problems for the Poles are getting 100 octane fuel.

Again, the problem with retractable gear is not necessarily the design and fabrication of a few prototype sets but the manufacture of several hundred sets IF you don't have an industry set up for it. I don't know what the Poles had in place at the time.

Poles might be better off with six rifle caliber machine guns than using two .50s. I am not sure what the Belgians were getting for a cycle rate in 1938-39 but the US was only getting 500-600rpm even in an un-synchronized gun. .50 cal ammo is about 5 time heavier per round than rifle caliber ammo. ie, 250 rpg for four guns (1000 rounds total) of 7.9/.303/.30cal ammo weighs what 100 rpg (200 rounds total) does for TWO .50 cal guns. .50 cal ammo weighs about 30-31lbs per hundred.
Weight given for the US .50 cal varies but 61lb sounds like a bare gun while a 31lb browning .303 sounds like "as installed'. An installed .50 cal may well go over 71lbs.

Or the Poles could try the 20mm cannon (MG/FF clone) they were sticking in the wings of the export Pz 24s.

What the Polish AF was thinking and did already tried to improve the situation?

Problems for the Poles are getting 100 octane fuel.

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Quite possibly, I dont know enough about the supply side of the 100 Octane Fuel. But it had been sought after by Roy Feddon since 1938. Assuming that the Poles followed suit, what sort of time delays were there in securing quantities of the fuel from the US. Say orders were placed at the beginning of 1938, how long before they would receive any quantities of the new fuel?

Again, the problem with retractable gear is not necessarily the design and fabrication of a few prototype sets but the manufacture of several hundred sets IF you don't have an industry set up for it. I don't know what the Poles had in place at the time.

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The Poles were already designing and producing significant quantities of Retract gear for several models. The PZL-37 bomber had begun to enter service in 1938, used a home designed retract, more complex than those for most fighters. The PZL-46, of which 160 had been ordered and were in the pipeline, included a subtype with retractable undercarriage. The P-50 Jastrab had another design of retract. The Poles already had existing designs of retract gear, in service and under production. i dont see any major problems with building and adapting these designs to suit the light weight DXX1. The GI would most likley have needed to use an adaptation of the P-46, or it might even have used a lightreened single wheel version (as oposed to the double bogey version used) in the Pzl37)

Poles might be better off with six rifle caliber machine guns than using two .50s. I am not sure what the Belgians were getting for a cycle rate in 1938-39 but the US was only getting 500-600rpm even in an un-synchronized gun. .50 cal ammo is about 5 time heavier per round than rifle caliber ammo. ie, 250 rpg for four guns (1000 rounds total) of 7.9/.303/.30cal ammo weighs what 100 rpg (200 rounds total) does for TWO .50 cal guns. .50 cal ammo weighs about 30-31lbs per hundred.
Weight given for the US .50 cal varies but 61lb sounds like a bare gun while a 31lb browning .303 sounds like "as installed'. An installed .50 cal may well go over 71lbs.

Or the Poles could try the 20mm cannon (MG/FF clone) they were sticking in the wings of the export Pz 24s

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.

If the Poles go for 6 x 7.7mm, or a 20mm cannon version, they would need to strengthen the wings of the DXXI. i dont know if they would have time to do that. Assuming it can be done quickly, they would need to swing to the Pegasus, which was also available from local sources. They were already producing a 940 hp version for the Pzl 37, and had further developed it for the Pzl 46, which was in production but not yet in service as a replacement for the P-23. Some reports rate the redesigned version of the Pegasus at over 1000 HP. I was looking for quick easy conversions, because at the end of the day, the Poles needed a large number of fighters, of higher performance than the ones they had, and not a series of near prototypes. As I said, the Polish aeronautical industry was quite advanced, but time was limited.

Many thanks to the people contributing here, unfortunately I don't have time to do that by myself right now