In a study of recoil springs, I found that heavier recoil springs mean slower rearward travel but faster forward travel. Such action does not seem to change cycle times. If a shooter was to use higher pressure cartridges, such as, Buffalo Bore: 45 ACP Super 230 grain 1100/618 JHP #45S230 then the main focus would be to reduce felt recoil.

The thought is when using high-pressure loads then use extra-power recoil springs. Reducing felt recoil allows a shooter to shoot faster follow-up shots. However, rather than using a heavier spring it might be better to use a secondary spring, a smaller spring inside the main recoil spring.

 

You need a higher spring rate to slow the faster moving slide before it hits it's stop otherwise you will have slide or frame failure. I don't think a secondary spring will fit inside the stock spring as the recoil spring guide fits tight inside the stock spring.

I admit I haven't looked, but what limits slide travel on the JCP/JHP? Is it the recoil spring guide rod? If so it's also acting as a buffer and would get beat to death without a heavier spring.

Yes to the faster forward travel. A heavier firing pin spring is required to mod a 1911 for 45 super because the momentum of the faster forward travel overcomes the stock firing pin spring causing chain fires.

 

The Recoilmaster incorporates a strong secondary recoil spring that engages after cartridge case ejection to cushion the shock of the slide against the frame and extend the recoil pulse over a longer duration.

http://www.gun-tests.com/performance/jun96recoil.html

 

Sounds like a cool project.

We need lots of pictures.

Peace favor your sword,
Kirk

 

Quick question: Is the chamber of the JHP fully supported? If it is then you may be good-to-go with just a heavier spring (or a more massive slide if you can figure out a safe way to add mass). If it is not fully supported then I predict case ruptures.

Peace favor your sword,
Kirk

 

Quick question: Is the chamber of the JHP fully supported? If it is then you may be good-to-go with just a heavier spring (or a more massive slide if you can figure out a safe way to add mass). If it is not fully supported then I predict case ruptures.

What he saided. the C9 is fully supported and I've run up to 60k psi with no problems. Good thing to do when testing the really high reloads tho is to shoot it from a vise or something so your not so close, just in case it does blows up which I don't think it will but it's always better to be safe then sorry. I've put my c9 through a lot of hard hitting reloads and never even upped the recoil spring and I don't think it shows any signs of wear but a recoil spring won't hurt anything as long as you can cycle the slide other than that have fun and be safe.

Something I seen in a gun magazine once that I thought was pretty neat was a guy loaded some 305gr .45acp bulllets if you could push these fast enough they would make some bear stoppers, but the weight and increase bullet length would raise pressure quickly so a little bullet still might be better idk I don't have a .45 to play with........yet.

 

Quick question: Is the chamber of the JHP fully supported? If it is then you may be good-to-go with just a heavier spring (or a more massive slide if you can figure out a safe way to add mass). If it is not fully supported then I predict case ruptures.

Peace favor your sword,
Kirk

I don't know if it is or not. I'm casting today and decided I want to have some range fun with the 45 so I'm dropping a bunch for it. I'll play with my loads and see how much more I can squeeze out of it. When I'm done shooting it I'll teat it down and look it over real good, then make a plan for a 45 super hi point.

Agreed about shooting it from a vise, that will be part of the plan.

 

You are going to put your eye out!

Literally!

You start messing with those preasures and the polymer frame is going to turn loose of the nonferrous pot metal slide and take the side of your head off, along with fingers and chunks of arm.

You do not just put a new screen door spring in there and claim "good to go".

 

You are going to put your eye out!

Literally!

You start messing with those preasures and the polymer frame is going to turn loose of the nonferrous pot metal slide and take the side of your head off, along with fingers and chunks of arm.

You do not just put a new screen door spring in there and claim "good to go".

We'll see I assure you. I'm not worried about my head, fingers, hand, or anything else except the gun. No I'm not worried about the gun either, if it blows I've lost little and learned a lot and had a great time doing it. If you had read carefully you'd see it will have to go like a nuke to hurt me. Stay in bed.

 

Oh a heads up on the vise thing, I found it best to load a round and remove the mag as if it comes out of the vise there's a good chance it will disassemble your mag for you.Best of luck I'll be interested to see how this all turns out, and if you need any loads run through "quickload" just let me know.

 

Good advice. I figured I'd leave the mag out based on advice I got from AGI's free videos. It creates additional volume for the gases to expand into and lessens the results of a case rupture.

 

Well, I'm really curious to know how this is going to turn out.

Peace favor your sword,
Kirk

 

Well, I'm really curious to know how this is going to turn out.

Peace favor your sword,
Kirk

This wont take long to get done. The next time I have a few pennies to spend on reloading I'll get the brass and have at it! I got the stock for my Mauser project and that gets bumped to the front of the line, but in 3 or 4 weeks I'll see if the HP will blow up at 28,000 CUP.

 

any progress on the project? looking forward to your results.

 

Soon. My cowboy shoot ate all my play money, and one of my guns broke. I also wanted to get my Mauser project moving again. The Mausers ready to test fire, and I'm hunting for parts for the single action. I am going to do this so hang in there.

Edited a few hours later:

Well I decided to work on this project for a while. There is some math that needed done to ensure this is even possible, and since it's free I did some of it. The results didn't even come close to what I expected based on the math from this sight. http://www.orions-hammer.com/blowback/ That's supposed to be good math for determining bolt weight needed for a blow back design. Based on the results of my work today I need to confirm the info at that sight before using it.

Today I set out to:
1)Determine the weight of the slide on a JHP
I don't have an accurate scale large enough to weight the slide, so I applied a little engineering statics to get a good weight. Using a steel 12" rule I balanced the slide and a small bucking bar using a drill bit as the fulcrum. Because the slide and bucking bar are symmetrical is was easy to determine their center of gravity and therefore the lever arm from the fulcrum. The bucking bar is light enough I was able to get a good weight from my 610 gram triple beam scale. Applying a little algebra and I got a slide weight of 1.65lb. This is where the blow back site math breaks down. If you refer to the chart at that site a 45acp bolt needs to weigh 2.3lb. Since we all know the JHP works good something ain't right with the math at the site or there is something I don't understand. Using the math at that site to determine the bolt mass for the 45 Super I get 3.1lb. Obviously this needs to be figured out before I shoot the gun, because I'm really not trying to blow the gun up. More work needed here.

2)Determine the relevent forces of the recoil spring
I also don't have an accurate scale to determine the recoil spring rate. So I had to work something out. I mounted an 1/8" welding rod vertical in a detached drill press vise and placed the spring over the rod. I marked it's free length and then made two additional marks at 1in and 2in. I placed the vise on a digital car scale and zeroed the meter. I then depressed the spring 1in and got a reading of 4lb. This was confirmed at 2in with an 8lb reading. These readings repeated time and again. There is error here though because the scale only reads to the nearest pound. But this was all I had and the results make since. So I used a spring rate of 4lb/in for the calculations.
Recoil spring installed force determined by measurement of distance and calculation is aproximately 7.12lb or 7lb.
Recoil spring maximum operating force by the same method is aproximaetly 14.3lb or 14lb. I believe I've read the factory spec is 16lb and that makes since given the error in my scale measurement.
3)Determine the slide travel stop on the gun
This was easy it's the fwd edge of the barrel mount boss. I wanted to know this because I'll try to get a teflon buffer in there to absorb some shock.

So...Obviously HP is not using the recoil spring to delay slide travel. A spring capable of doing that would be much larger than 7lb at rest and 14 or even 16lb at max travel. And equally obviously the JHP works real good with 45acp with a slide that weights 1.65lb, oh I'm sorry 1.66lb with the striker and it's springs. I'm back to square one with my understanding of blow back math given the results of math done at that blow back site. The math there is fairly hairy and I'll have to relearn some things before I can determine if it's any good or not. I'm more confused than when I started, but it's been fun getting that way.

 

well good to hear that your doing some research and just not jumping in blindly as some people do(not saying I haven't). It's my understanding that the reason a heavy recoil spring is not used in the blow-back type gun is because the weight of the slide is relevant to the pressure that the gun will be firing and in your case the 230gr .45acp. So for example if your going to go from 900fps/414ft-lb to 1,100fps/618ft-lb there's really only two things you can do and that is increase the mass of the slide or run a heavier recoil spring . I don't know if you have a recoil spring tuner kit but that would be a good place to start and then just take your .45 super case and start working up. Start at the 900fps mark that the normal .45acp would produce and slowly climb and if you fell that the gun is starting to get battered move to a heavier recoil spring. This method should keep your gun from getting beat up but a buffer pad probably wouldn't hurt as long as it doesn't cause a problem with the last round hold open.

I think that your just over thinking this a little, or maybe I'm not thinking enough but with the increased rearward speed of the slide and increased forward pressure from a heavier recoil spring should equal out.

 

well good to hear that your doing some research and just not jumping in blindly as some people do(not saying I haven't). It's my understanding that the reason a heavy recoil spring is not used in the blow-back type gun is because the weight of the slide is relevant to the pressure that the gun will be firing and in your case the 230gr .45acp. So for example if your going to go from 900fps/414ft-lb to 1,100fps/618ft-lb there's really only two things you can do and that is increase the mass of the slide or run a heavier recoil spring . I don't know if you have a recoil spring tuner kit but that would be a good place to start and then just take your .45 super case and start working up. Start at the 900fps mark that the normal .45acp would produce and slowly climb and if you fell that the gun is starting to get battered move to a heavier recoil spring. This method should keep your gun from getting beat up but a buffer pad probably wouldn't hurt as long as it doesn't cause a problem with the last round hold open.

I think that your just over thinking this a little, or maybe I'm not thinking enough but with the increased rearward speed of the slide and increased forward pressure from a heavier recoil spring should equal out.

It would not be surprising at all to discover I'm over thinking this. I have done so many times with other projects. It's a survival strategy when dealing with dangerous things I know I lack knowledge for. In this case I have two goals and one is not to make a 45super HP because I know the gun wont do that for long. A couple years ago I worked up a rough design for a 357mag semi-auto rifle using a blow back design. The math I used is the math from that web site listed above. So I'm looking to get some practical blow back design experience from this experiment. If I don't have some idea whats going on I'll have no idea why it works or doesn't work. The other reason for the test is to SEE 45super at work. I was thrilled when you guys turned me on to it as it looks like a good round that can make a 1911 a decent 50 or maybe 75 yard hunting gun and a bear defense gun. A 230gr hard cast slug doing 1200fps will get it done.

 

Ya wish I could be more help but 9mm is my specialty, I've loaded everything from 55gr bullets at 2000fps to 173gr bullets and put them all through the C9, but when it comes to .45 I've only shot some Remington 230gr. I think you'll be surprised at how well these guns take a beating I really only use mine to test highend/crazy reloads anymore and it's ate everything I'm kind of temped to try to blow it up at this point. I'm guessing with as little as a recoil spring the .45 will handle .45 super rounds all day long but I could be horrible wrong, and it's always better to be safe then have a surprise hand grenade.

 

I followed your post about working up slow, and working with the recoil spring as I go. What bothered me most was there is something about the math I've been using for bolt weight I don't understand. It's one guys interpretation of established math from a 1950's era book quoted in the article. That math says you need a 2.3lb slide to shoot 45acp 230gr slugs, but my HP slide only weights 1.65lb. That's a huge difference, and I believe I understand blow back operation and springs enough to know the recoil spring don't have squat to do with it. A heavier spring is only required to keep the gun from beating itself to death during the cycle.

But without doubt if I raise operating pressures 8,000psi I need more slide weight. I've worked out a way to attach lead to the side of the slide without mechanical fasteners. There is a substance, I think originally developed by 3M that may do a great job of temporarily increasing slide mass. It's used extensively in aviation to seal fuel cells and pressurized cabins. But it's also used as a structural adhesive. We used it all over the F-111. It's a 10:1 epoxy sealant that is awesome tough and we used it for components loaded in shear, just like my leads weights would be. It could hold an 8 square foot RAM panel on at 2.5 mach, including resisting the heat.

I could make lead strips in various weights and use them as I increase pressure and learn by the ol "Cut and try engineering" method. Soon. I'm about ready to order the brass. This happens soon one way or the other.

 

If you still have fingers for typing, please update.

 

I'm way behind on this thread, I just saw it for the first time today. I have my 2 cents to offer.

I think it's very prudent for you to take the approach that you are. You seem to be thinking this out very carefully and that's a good way to stay safe and have fun at the same time.

At the risk of contradicting what I just wrote, I looked up the reloading data that I could find on 45 super (there's not a lot to be had) and the difference between it and 45 ACP seemed to be very modest. Basically the equivalent of 45 +P possibly a little more. I'm not sure I would mess around with lead weights on the slide. A beefier spring would be in my opinion the easier and possibly better route.

In my opinion a chronograph is going to be pivotal to the success of this project. Once I converted the gun I would start with a mild 45 ACP recipe and then slowly work up.

I have found in my experience that the weak point of the Hi-Point design is in the firing pin channel in the slide. Over time this channel begins to hourglass to the point where the firing pin first causes increasingly more frequent light strikes and then as the deformation continues the firing pin finally seizes. This will happen even using a light load, the only difference is that the lighter the load the greater the number of rounds that can be put down the pipe before the slid is cooked. Keep in mind that I put many thousands of rounds down the pipe of my Hi-Points so I realize that many people have not experienced this phenomena (yet).

That said, the heavier the recoil spring the better. The deformation takes place when the slide come to the rearmost position. The harder it slams to a stop the more the firing pin channel will deform. If you go with the heaviest recoil spring possible you will mitigate the damage from the slide coming to an abrupt stop.

Again just my 2 cents

 

Yup I still have fingers. George, thanks for the input. The data I've found puts the super pressures between 28,000 and 31,000 cup. And yes I agree a chronometer is a must to learn anything useful. I'm begging for one for fathers day.

 

I said I'd do it, but have been distracted by other priorities. Well the best way to push forward is to push. I just ordered the brass and slugs. That will give me something to think about.

 

When replacing .the firing pin on a Jimenez you have to cut a spring for the new firing pin. The Jimenez firing pin spring is what controls the cyclic rate of the gun. It took a lot of cutting and shooting to get the firing spring just right. 99% of Jimenez pistols that have timing issues can be fixed with a new firing pin spring and a lot of shells.

I would expect you to have the same experience with your 1911. This project is going to eat up some ammo. Bring at least twice as much ammo as you think it will take.

 

When replacing .the firing pin on a Jimenez you have to cut a spring for the new firing pin. The Jimenez firing pin spring is what controls the cyclic rate of the gun. It took a lot of cutting and shooting to get the firing spring just right. 99% of Jimenez pistols that have timing issues can be fixed with a new firing pin spring and a lot of shells.

I would expect you to have the same experience with your 1911. This project is going to eat up some ammo. Bring at least twice as much ammo as you think it will take.

You are late to the party, but absolutely correct a 1911 requires a firing pin and recoil spring change for a 45 super conversion. However this is more of an experiment in Hi Point strength and these will go through my JHP, shot from a vice of course.