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# Recoil Question

Discussion in 'Caliber Corner' started by PghJim, Mar 7, 2010.

1. ### PghJim

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I have a couple boxes of 45 ACP 230gr +P HST's. I found out today with my chronograph that these rounds come out of my 4" XD compact at the same velocity the non +P is rated out of a 5" barrel.

My question is that assuming both guns weighed the same and one had a 5" barrel and the other a 4". If I shot +P out of the 4" and non +P out of the 5" gun and the velocity for the 230gr. bullets were the same, would I feel the same amount of recoil between the two guns? Let's also assume the volume of powder is the same in both the non +P and the +P rounds.

2. ### Brent10mm

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inverse it and you might be spot on.
why?

well first off, +P means more pressure, more velocity, and recoil. now your putting it in a smaller lighter, shorter gun...? (4") then yes.

just because a 5" barrel beats it, its still operating at lower pressures doing so. the increase in barrel length negates the extra powder that makes a +P round +P, or the reason to go +P... more velocity.

assuming powder volume is the same between (P) and (+P) are the same is illogical at best. +P is made by adding a bit more powder, nothing more.

now would you notice the difference? maybe. I can tell between Win Ranger T's and Fed HST's fired out of my G36, but only slightly.

50-75 fps? difference between T's and HST's, roughly a +P increase, but the T's I have are still standard pressure.

Last edited: Mar 7, 2010

3. ### PghJim

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I know there is a formula for calculating recoil, I just cannot seem to find it. I made the guns the same weight and the powder charge just to negate those variables. I know in the recoil formula the weight of the powder charge is used somehow. I was hoping someone had the formula.

4. ### Brent10mm

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for expamle...

plug in;

a G21 weights 2.375 lbs fully loaded, not close to the 1911 id guess.
a G36 " 1.67 lbs.

a P rounds might have 10 gr, and a +P 11gr.

the impulse, velocity and energy are far greater in the smaller weapon.

5. ### PghJim

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Thanks that answered it. Except for the small difference in powder charge between +p and not +p, the only reason I would feel more recoil in my 4" XD is because the gun is lighter than a 5" XD, as long as the bullet exits with the same velocity. It does not matter that I started with a +P load, other than the small difference in powder charge which is insignificant.

6. ### Brent10mm

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yes the powder charge is insignificant, in terms of measuring recoil impulse... as far as weight is concerned. however, it increases pressures.

realize that a bullet exiting a 4" barrel @ the same velocity of a 5", requires a higher pressure load. Hence +P, now that +P load not only increases velocity, but recoil. Chamber pressures and rearward slide velocity.

think of it in beer terms....
A 16 oz. busch will get you "said" amount of alcohol.
while a 12 oz. ice beer will get you the same end result in a smaller package. but in so doing, packs bit more bite.

speaking of, I need another beer....

7. ### fredj338

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You can get a higher pressure load by changing powders as well, not just dding more. Though in most cases, you go to a more slower powder to get higher vel w/ acceptable pressures. Recoil would be about the same w/ +P in a 5" heavier guns vs std pressure in a lt.wt. 4" gun. It's one reason I will only shoot +P in my heavier 5" guns & use std. pressure loads in my shorter/lt.wt. guns. Recoil just goes up to a level that slows my follow up shots unacceptabley.

Last edited: Mar 8, 2010
8. ### Glolt20-91

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Powder amount affects recoil and is a part of recoil software. As an example in .45auto/230gr, 10.0grs of Blue Dot will yield an MV of mid to upper 900s. Change to 7.4grs of Power Pistol, MVs remain the same, slide speed is slower as evidenced by ejected brass falling closer to the shooter and felt recoil is less.

In this particular comparison, 2.6grs less powder from a faster burning powder gave 30fps more velocity with less recoil;

Given the same pistol/bullet weight, velocity and powder amount, recoil will be the same . . . chamber pressure is a non factor.

Bob

9. ### Glolt20-91

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Different powders at the same case volume will not give the same weight.

Bob

10. ### Brent10mm

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-changing powder, albeit differing from the O.P., would change Pressure, sure.
- +P in 5" = P in 4" recoil wise, is why I said, " inverse it and you might be spot on."

Good response,

I guess its my assumption, that Factory loads would use the best +P powder/load combo, and then decrease powder volume from there to make the P version.
It would have all the benefits of higher velocity, less recoil.... ect.

If one given powder performs best in said categories, then it would assuredly surpass others in a reduced load.

11. ### PghJim

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That is what I said, the fact that it is a +P round does not effect recoil when the velocity, gun weight and bullet weight are the same, powder could go either way. So the only recoil advantage a 5" gun shooting regular pressure 230 grs over my 4" shooting +P, is that the 5" gun maybe heavier. The +P round only gets me to the same velocity as a regular load in a 5" gun. If my 4" gun weighed the same, there would be no difference.

12. ### Glolt20-91

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This is where things can get a little sticky. If I load a regular velocity 230gr JHP in the ~890fps range, upper load range of 6.0grs Universal Clays gives the best accuracy in 4 separate .45auto barrels. Reducing Power Pistol loads to yield ~890fps also decreases accuracy in my testing.

This load reduces 1911 recoil into G17 territory or less depending on load;
Bob

13. ### Glolt20-91

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Just affirming what you wrote.

Bob

14. ### THplanes

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This gives the formula for calculating recoil.

With the OPs stated conditions the +P would have a tiny bit more recoil because the gas at a higher pressure would lead to a higher gas velocity. So the gas would have a little more momentum than the standard pressure load.

15. ### AJSully421Armed Citizen

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I just want to know what type of world you live in where a 4" barreled gun and a 5" barreled gun weigh "about the same"?

Also, how you get a +p from the same ammo manufacturer who uses the same powder without increasing the volume of the powder charge?

Your question is nonsensical. Besides... velocity does not wound.

Terminal ballistics show that the +p and standard HST are too close to matter in any real world situation. There is a list floating around that shows standard 230 HST does 14.4 deep and .86 wide while 230+p does 14.6 deep and .85 wide... if 0.2" deep or 0.01 wide makes the difference between life and death, you were screwed before you got out of bed that morning.

16. ### PghJim

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Thanks for your non-contribution. I was trying to understand recoil and if a higher pressure load matter if the bullets were going the same velocity. But to also address the stupid assumtion that a +P round just has a little more of the same powder, it is not necessarily the case. They could use a faster burning powder for whatever reason on the +P that has less powder volume. That is why I said the powder influence could go either way.

This was more of a scientific discussion. Maybe if we had pictures you could have gotten more out of it.

Also, a 5" XD compact weighs pretty close to a 4" kimber stainless compact, so you could find guns with the same weight, but that was not the point.

I would like to thank all of the rest of you for helping me understand how recoil is caculated.

17. ### AJSully421Armed Citizen

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While it is certainly standard procedure for home reloaders, and even smaller companies like DT or GA to use different powders for different individual loads, you have to realize that for a company like ATK who owns several ammo companies, with likely hundreds of different loads, and they manufacture millions of rounds per year, it does not make much sense for them to use completely different powders for a .45 ACP 230 grain, and a .45 ACP 230 grain +p, 200 grain, 200 grain +p.........

They will typically standardize as much as they can. Having four different powders for four different .45 loads is not good for business. I do not work for an ammo manufacturing plant, but I would be willing to guess that they use the same powder, just a little more of it.

And you do not have to get so testy, I was just screwing around with you. If you are soooooo worried about the recoil of the .45, maybe you should switch to the 9mm so it does not hurt your girly wrists.

Either way, I hope that you never have to use any of this, and that many years from now, you pass on warm in your bed, having never fired a shot in self defense.

18. ### Glolt20-91

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Your opinion is based upon a constant gas expansion velocity of 4,000fps, which may be or maybe not. Using recoil software is more accurate and a lot easier.

Interior ballistics is a lot more complicated than your posted formulas.

Bob

19. ### Glolt20-91

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You are very kind in your response.

Bob

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