Brass ejection distance tuning, on 10mm 1911

[GhostX]

I have a new Kimber Eclipse Custom II that I've been trying to tune so that it can handle full-house 10mm loads. I've tried various things--increasing the mainspring weight from the factory 21# up to 25#, installing a flat-bottomed EGW firing pin stop with a very small radius (less than 1/16") beveled onto the hammer-contacting edge, and tapering the face of the FPS so that the hammer makes better contact with it at rest.

 

Using what's probably the weakest commercial 10mm ammo available (Prvi Partizan 180gr JHP), my spent brass is ejecting anywhere from 12.5 feet (with the EGW stop, beveled but untapered, with the 21# mainspring) up to 17.5 feet (with the EGW stop, beveled and tapered, with the 21# mainspring). I didn't find that a 25# mainspring made any significant difference in ejection distance, so I'm next going to try a 30# mainspring. The difference between a 21# and a 30# mainspring, curiously, is only about a quarter of a pound heavier trigger pull, as I measured with my Lyman gauge.

 

One thing that I do not want to do is increase the weight of the recoil spring. The factory spring is 18.5#, which is at the limit of my comfort level for preventing excess battering of my slide and barrel when returning to battery.

 

My question is, what sort of ejection distances are you all seeing with your 10mm 1911? Even a rough estimate would be appreciated. Please tell me what brand of ammo is giving you that distance, what modifications, if any, you've done to shorten that distance, and what spring weights are in your gun. My goal is to get that ejection distance with the Prvi ammo down as short as I can possibly get it (say, less than 5 feet), before I start beating on my gun with full-house loads.

[sqlbullet]

I have a Para-ordnance 16-40 converted to 10mm. I run a 22lb recoil spring, a 25 lb mainspring, and an EGW FB FPS with no radius or taper. Brass for full power loads is 25'-40' at about 4 o'clock. Practice loads are about 15'-25', same direction.

 

I have not altered the ejector in any way on my gun.

 

My personal opinion is you are not going to get anywhere near 5' with 10mm or 40S&W loads without increasing the slide mass several ounces, increasing spring weights to the insane or radically altering the ejector. The first two options will make the gun very ammo sensitive, and the last option will be trial and error to get a profile that reliably ejects.

 

I am thinking about buying some netting and creating a frame to mount it on that I can stand up beside/around me to act as a huge brass catcher. Tired of spending half my range time combing the desert for brass only to come home with 60% of it anyway.

[GhostX]

I have a Para-ordnance 16-40 converted to 10mm. I run a 22lb recoil spring, a 25 lb mainspring, and an EGW FB FPS with no radius or taper. Brass for full power loads is 25'-40' at about 4 o'clock. Practice loads are about 15'-25', same direction.

 

I have not altered the ejector in any way on my gun.

 

My personal opinion is you are not going to get anywhere near 5' with 10mm or 40S&W loads without increasing the slide mass several ounces, increasing spring weights to the insane or radically altering the ejector. The first two options will make the gun very ammo sensitive, and the last option will be trial and error to get a profile that reliably ejects.

 

I am thinking about buying some netting and creating a frame to mount it on that I can stand up beside/around me to act as a huge brass catcher. Tired of spending half my range time combing the desert for brass only to come home with 60% of it anyway.

 

Thanks for those observations, sqlbullet, that is helpful. Wow, that's amazing that you get 40 feet of ejection with full-house loads!

 

The range officer where I shoot actually suggested me that I get a brass catcher, when he saw how far my brass was ejecting. He told me they sell such things made for that purpose, though I've never seen one.

 

I actually don't really care about having to chase down my brass, since I usually shoot in an indoor range--I'm just using ejection distance as an indicator of how much of a beating my gun is taking. So I wouldn't have any interesting in modifying my ejector. I figure that if I'm getting 15' of ejection using very weak ammo, then my gun is going to get beaten hard when I use hot ammo.

 

I'm wondering now if anybody gets short ejection distances with their 10mm 1911, or if it's just the nature of the beast.

[sqlbullet]

It seems to be the nature of the beast. I inspect my gun carefully for signs of battering. I have three 10's each with about 4,000 rounds on them. None show any signs of battering that cause me concern. Your mileage may vary and all that.

 

I also hear you on abuse going into battery as well as at the end of rearward travel. I inspect the slide stop pin and corresponding hole in the frame for evidence of issues as well as the frame block and recoil plug. So far, so good.

[GhostX]

It seems to be the nature of the beast. I inspect my gun carefully for signs of battering. I have three 10's each with about 4,000 rounds on them. None show any signs of battering that cause me concern.

Thanks, that is reassuring.

 

I had never considered using an EGW firing pin stop that has no bevel at all. I assume you're not noticing that it is causing any undue wear on your hammer, with such a sharp edge on the bottom of that stop? I may try that myself, and see if it works better than my small-radius stop.

[sqlbullet]

Well, to look at a picture you would think yes:

 

 

But, that is exactly what the hammer looked like when I bought it. And you can't feel any irregularity at all if you run your thumbnail over that spot.

[TaosGlock]

M Kimber SS Target II has a flat bottom fps and 20# spring. Still flings em' 25 feet with hot loads.

 

Like sqlbullet says it is the "nature of the beast."

While my G20 is a bit less, it's still a flinger.

[GhostX]

Well, to look at a picture you would think yes:

 

 

But, that is exactly what the hammer looked like when I bought it. And you can't feel any irregularity at all if you run your thumbnail over that spot.

 

Your hammer actually looks pretty good to me. It looks like that EGW stop is doing its job well.

 

My hammer came with the typical raised MIM mark that Kimbers have, on that surface that contacts the firing pin stop. It peened my brand-new EGW stop the first time I manually racked the slide (I hadn't noticed the MIM mark until that happened), which annoyed the hell out of me, so I filed the hammer smooth.

 

Thanks for posting that photo!

[GhostX]

M Kimber SS Target II has a flat bottom fps and 20# spring. Still flings em' 25 feet with hot loads.

 

Like sqlbullet says it is the "nature of the beast."

While my G20 is a bit less, it's still a flinger.

Thanks, Taos, that was useful to hear a fellow Kimber owner's results. I could live with 25' ejection distance with hot loads. I suspect that my Kimber would eject much farther than that though, if I am getting 15' with very weak loads.

 

When you say you're using a 20# spring, are you referring to your recoil spring, or did you lighten your mainspring to that weight (to improve your trigger pull)? What weight is the other spring? Also, I'm curious to know if you beveled the edge on your FPS?

[TaosGlock]

Thanks, Taos, that was useful to hear a fellow Kimber owner's results. I could live with 25' ejection distance with hot loads. I suspect that my Kimber would eject much farther than that though, if I am getting 15' with very weak loads.

 

When you say you're using a 20# spring, are you referring to your recoil spring, or did you lighten your mainspring to that weight (to improve your trigger pull)? What weight is the other spring? Also, I'm curious to know if you beveled the edge on your FPS?

20# recoil spring. Stock mainspring. I don't recall beveling the FPS. I had to file it slightly (as it was oversize) to fit. I got it from Brownell's in 2005 when I bought it used.

I did replace some of the MSM parts.

One odd thing was my ejector snapped off. It seemed long when I got it. It lost, and I am guessing, 1/8" or more IIRC. I did file it smooth at the break point and with the proper angle.

But worked perfect so far. A few years back I posted a thread on the topic.

The Kimber is in storage as I am doing CCW with my G29 as opposed to the usual Kimber.

[GhostX]

20# recoil spring. Stock mainspring. I don't recall beveling the FPS. I had to file it slightly (as it was oversize) to fit.

So that's probably a 21# mainspring that you're running then. It will be interesting to see how my 30# mainspring compares with your ejection distances. I'm contemplating installing an extra-strength firing pin spring to try to counter some of the heavy force produced by that mainspring, though I'm not sure if that is anything I need to be concerned about. I just don't want to start getting primer wipe because my hammer is being held too tightly against that firing pin.

 

It's interesting to hear that 10mm users are not beveling their EGW firing pin stops, as the gunsmiths over on forum.m1911.org have been recommending for years. If people are not seeing that an unbeveled stop is not causing any damage to their hammer, that gives me more incentive to try an unbeveled FPS myself.

[GhostX]

So that's probably a 21# mainspring that you're running then. It will be interesting to see how my 30# mainspring compares with your ejection distances. I'm contemplating installing an extra-strength firing pin spring to try to counter some of the heavy force produced by that mainspring, though I'm not sure if that is anything I need to be concerned about. I just don't want to start getting primer wipe because my hammer is being held too tightly against that firing pin.

 

It's interesting to hear that 10mm users are not beveling their EGW firing pin stops, as the gunsmiths over on forum.m1911.org have been recommending for years. If people are not seeing that an unbeveled stop is not causing any damage to their hammer, that gives me more incentive to try an unbeveled FPS myself.

 

I tried out that 30# mainspring today, with a new unbeveled, and untapered, EGS firing pin stop. I am really perplexed as to what I am observing... I found that the 30# mainspring makes no significant difference to my brass ejection distance, compared to the factory 21# mainspring. It's ejecting in the 13-15' range with either spring. It should make a big difference.

 

I am also noticing no difference at all between an unbeveled EGS firing pin stop and a tiny-radius tapered FPS. The bizarre part is that when I put the factory FPS (with its huge radius) back in, my ejection distance decreases by about 2 feet. The trajectory of the ejection is more of a parabola though with the factory FPS, seeming to eject at about 45 degrees (if 0 degrees is straight up, and 180 degrees is straight down). With the EGW stop, the ejection angle is more like 90 degrees.

 

I'm not sure which trajectory is better. My thinking is that the 45 degree angle must be better because it makes the ejecting brass less likely to hit the edges of the ejection port as it ejects, but I'm not sure. If that's the case, then the factory FPS works better than the flat-bottom FPS. That shouldn't be the case. I understand the physics behind the flat-bottom FPS, and it really should reduce the slide velocity significantly. Maybe there's something peculiar about Kimbers than makes the geometry of the hammer and slide stop interact differently.

 

I'd really love to see somebody try to replicate my experiment, if they have a Kimber 10mm. To summarize, measure the average ejection distance (from the ejection port to the point on the ground where the brass first hits before it bounces), and see how the flat-bottom FPS compares with the factory FPS.

[sqlbullet]

The distance makes sense once you describe the angles. Takes a lot more ejection velocity to cover that similar distance when the elevation is 45° compared to flat.

 

I would guess the different ejection angle is related to your extractor. I am gonna guess it is not holding the brass tight against the breech face on extraction. With the factory FPS, the higher slide velocity means the brass is higher on the breech face when it hits the ejector. The slower slide velocity of the flat bottom stop gives the brass time to slide down, so the ejector strikes it closer to the mid line.

 

Just guesses without high speed photos though.

[GhostX]

The distance makes sense once you describe the angles. Takes a lot more ejection velocity to cover that similar distance when the elevation is 45° compared to flat.

 

I would guess the different ejection angle is related to your extractor. I am gonna guess it is not holding the brass tight against the breech face on extraction. With the factory FPS, the higher slide velocity means the brass is higher on the breech face when it hits the ejector. The slower slide velocity of the flat bottom stop gives the brass time to slide down, so the ejector strikes it closer to the mid line.

 

Just guesses without high speed photos though.

 

Thanks for those thoughts, squlbullet. Yeah, I too had the thought that if the brass if following a more parabolic trajectory, then it is covering more distance than if it ejects straight toward the ground, and therefore represents a higher slide velocity even though the brass is hitting the ground in the same place. I'm glad you confirmed that idea.

 

I'm still not sure which trajectory is preferable though. It seems that if it is ejecting at 90 degrees (i.e, directly to the right of the ejection port, and a bit rearward), then the brass is just going to be hitting the bottom edge of the ejection port. One thing that I noticed is that with the 45-degree ejections (the more parabolic trajectories), is that the brass seems to be ejecting a bit more inconsistently, with some cases landing quite close, and others a couple of feet farther away in a somewhat different direction.

 

As for the extractor tension, what you said makes perfect sense, so I just now went and checked the tension on my extractor with a quick-and-dirty observation... I slipped an unfired round underneath the extractor claw, pushed it up as far as it would go along the breechface (toward the top of the slide), and then shook the slide in my hands. The nose of the bullet moved up and down a millimeter or two, but the round stayed in place. I had to shake it quite hard to get the round to fall out. An empty case would of course be held in place even more firmly than my unfired round. I don't really have a sense for how hard that extractor should be grabbing a 10mm round, but to me this seems like adequate tension. Feel free to comment if you disagree, as I'm sure you have more experience with this than I do. I'm not particularly inclined to try tightening the tension (by bending the extractor), since I have never experienced a failure to extract or eject, so I figure it's probably best to leave well enough alone.

 

So I am now sort of leaning back in the direction of thinking that the flat-bottom FPS may indeed be reducing the slide velocity. What I still don't get though is why going from a 21# mainspring to a 30# mainspring seems to make no difference at all to my ejection distance. That 30# spring really is quite heavy, and I had a hell of a time installing it in the mainspring housing.

[sqlbullet]

I agree that I wouldn't mess with the tension on the extractor if you are happy with it's performance.

 

A loaded round may stick better though. The weight of the bullet will tend to pull the rim of the case into the edge of the extractor giving it a better bite.

 

My main take away is that ejection distance is not a reliable indicator of slide velocity. We KNOW it takes more energy to compress a 30 lb spring than a 21 lb spring. And we know that energy comes from the slide velocity budget. So, slide velocity has to be lower.

 

So either the change is not significant, eg the energy requirements to compress the springs are miniscule compared to the available budget, or other factors are having an affect we have not accounted for.

 

I am wondering if it is the first. The momentum budget for a 45 ACP shooting 230 grain ball ammo is 207,000 Gr-ft/Sec. For a full power 200 gr 10mm it is 260,000 gr-ft/sec. (Yes, I know the units are non-standard, but they are easily derived and uniform). This gives the 10mm a 25% addition to 45 ACP. And, people were already selling shock-buffs for the 45 acp. For light target loads of 45 ACP, many shooters dropped to a 12 or 14 lb spring. The 200 gr light loads are generally in the neighborhood of 100,000-120,000 gr-ft/sec, or about half of a full power load.

 

The problem we seem to have is I don't know that we have a good idea where that budget goes. How much goes into unlock, resisitance, recoil spring compression, mainspring compression, etc. At least I don't. Might be a question for a guy like 1911Tuner over a the high road.