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10mm powder

I also put an NPZ 24lb recoil spring and guide rod in it as even the light loads of BE-86 and Longshot under a 160gr powder coated lead bullet had cases flying 20' to the 4 o'clock with the OEM 17lb recoil spring assembly in place.
If there’s one thing I don’t love about 10mm, it’s chasing the brass. Particularly at public ranges, I’m always asking the guy 10 bays down if I can police up at his feet 🤣.
 
Good to see another brand of 200gr. bullets available. I be ordering some since I can't find 200gr. Hornady XTP any more lately. thanks for posting!
 
If there’s one thing I don’t love about 10mm, it’s chasing the brass. Particularly at public ranges, I’m always asking the guy 10 bays down if I can police up at his feet 🤣.

Heavy spring, heavy slide, and then adding a good brake is the cure. It does make the 10mm loud, but a decent brake does more to delay unlocking and tame the slide speed than just about anything else in most 10mm pistols. And that's not just about chasing brass; keeping the barrel/slide locked up a fraction of a second longer makes full power loads safer, and controlling slide speed improves reliability.

Of course in a 1911 you've also go the option of a flat bottom firing pin stop and a heavier mainspring - if you do that you can avoid the heavy recoil spring battering the barrel feet. But no such option in a Glock or most other platforms.
 
Got 49 of the 50 loaded up last night with 9.1gr of BE-86, but I ran into an odd piece of brass.

Appears to be nickel plated Starline and it just will not get all the way up into the die to resize the whole case. I'm using Dillon carbide dies with their spring loaded, and non-adjustable for height, decapping rod system, but I don't think it's a case of the decapping rod sticking in the flash hole and stopping the case from going deeper into the die. It took a primer easily, but I broke the round down after tumbling the lube off for 15min when I saw the ring around the bottom and it wouldn't chamber.

Also, may a pox be put on the man/men who decided small primer 10mm was a good idea. The 1,000pcs of range pick-up I bought seem to be 20-30% small primer :mad: I think I'll end up culling those along the way and just buying virgin large primer from Starline or another manufacturer in the future.

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That piece looks like it was about to separate on the next firing. Good thing you caught it.
It's good thing to have the Lee bulge buster die especially if shooting the Glocks in 10mm and 40S&W which is notorious for leaving bulges in brass. I had the G40 for awhile then migrated to the fine 1911 series and my brass are in better shape for reloading. BE-86 is a good powder as I am using AA #9.
 
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Got 49 of the 50 loaded up last night with 9.1gr of BE-86, but I ran into an odd piece of brass.

Appears to be nickel plated Starline and it just will not get all the way up into the die to resize the whole case. I'm using Dillon carbide dies with their spring loaded, and non-adjustable for height, decapping rod system, but I don't think it's a case of the decapping rod sticking in the flash hole and stopping the case from going deeper into the die. It took a primer easily, but I broke the round down after tumbling the lube off for 15min when I saw the ring around the bottom and it wouldn't chamber.

Also, may a pox be put on the man/men who decided small primer 10mm was a good idea. The 1,000pcs of range pick-up I bought seem to be 20-30% small primer :mad: I think I'll end up culling those along the way and just buying virgin large primer from Starline or another manufacturer in the future.

View attachment 8200377View attachment 8200378
A belted magnum!
 
Got 49 of the 50 loaded up last night with 9.1gr of BE-86, but I ran into an odd piece of brass.

Appears to be nickel plated Starline and it just will not get all the way up into the die to resize the whole case. I'm using Dillon carbide dies with their spring loaded, and non-adjustable for height, decapping rod system, but I don't think it's a case of the decapping rod sticking in the flash hole and stopping the case from going deeper into the die. It took a primer easily, but I broke the round down after tumbling the lube off for 15min when I saw the ring around the bottom and it wouldn't chamber.

Also, may a pox be put on the man/men who decided small primer 10mm was a good idea. The 1,000pcs of range pick-up I bought seem to be 20-30% small primer :mad: I think I'll end up culling those along the way and just buying virgin large primer from Starline or another manufacturer in the future.

View attachment 8200377View attachment 8200378

Yeah that brass is bulged pretty bad.

While you could force it through a Lee “Bulge Buster” kit (basically a 40 S&W FCD with the top removed), it won’t fix the integrity of the brass. I’ve done that and then sectioned the pieces; the brass ends up with some scary thin spots that aren’t safe.

Chances are that may have had a loose-ish primer pocket anyway.


The small primer brass is stronger, primer pockets don’t loosen as easily, but can be a real pain when mixed in with LP brass.
 
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Thats the main reason why I had Barsto make me a match barrel for my G40 and sent it in for them to do the full fitting with my dangerous game loads. I bought the G40 and worked up these 200gr Montana HC-GC loads to carry this in a chest rig in the back woods while I fly fish all over the country... While I wasnt seeing any issue like that with my 1175fps 200gr HC-GC loads, I wasnt going to test it any further until I got my Barsto barrel with a fully supported chamber....
 
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Thats the main reason why I had Barsto make me a match barrel for my G40 and sent it in for them to do the full fitting with my dangerous game loads. I bought the G40 and worked up these 200gr Montana HC-GC loads to carry this in a chest rig in the back woods while I fly fish all over the country... While I wasnt seeing any issue like that with my 1175fps 200gr HC-GC loads, I wasnt going to test it any further until I got my Barsto barrel with a fully supported chamber....

It's hard to tell for sure, because the sizing die might have changed the appearance, but that bulged case above looks like it happened because of early unlocking rather than an unsupported chamber. That's more common with hot 10mm loads than is generally understood IMO, especially now that 10mm has been making a comeback and becoming more mainstream again. Most 10mm semi-auto pistols are still set up to cycle reliably with the common "FBI Lite" loads - you know, the cheaper ammo that's basically 40 S&W ballistics from the longer 10mm case. When a lot of those pistols are used with real full power 10mm loads, unlocking happens too early and we start to see bulged cases either at the feed ramp or all the way around like the one above.

It also could have been from a blowback action - they're pretty prone to case bulges all the way around due to early opening with hot 10mm loads as well. (On a similar note, I experimented with a blowback 357 Sig carbine for a bit that was not only bulging cases, but pushing shoulders forward too for the same reason. Not a good scenario!)

The G40 is one of the few though that doesn't have as much issue with that; you can feel pretty comfortable that it'll handle much heavier loads than you've been using. Nothing wrong with going to a Barsto barrel, just be realistic to the fact that all tilt-breech 10mm pistol barrels are "unsupported" to some degree at the feed ramp. Most of the horror stories with Glocks though came from the earlier guns, gen 2 and 3. By the time gen 4 guns came around, Glock had put a lot more support back in the feed ramp area, especially in the 10mm barrels. With the right powder choices the standard gen 4 G20 will handle a 200gr @ 1200 fps safely, and the G40 will run a bit faster with the same load of course. Some of the earlier guns would bulge brass way before you reached that point because the feed ramps were too generous.

Also keep in mind that BarSto barrel will probably build more pressure with the same load, as you'll see evidence of in the higher velocity.
 
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It's hard to tell for sure, because the sizing die might have changed the appearance, but that bulged case above looks like it happened because of early unlocking rather than an unsupported chamber. That's more common with hot 10mm loads than is generally understood IMO, especially now that 10mm has been making a comeback and becoming more mainstream again. Most 10mm semi-auto pistols are still set up to cycle reliably with the common "FBI Lite" loads - you know, the cheaper ammo that's basically 40 S&W ballistics from the longer 10mm case. When a lot of those pistols are used with real full power 10mm loads, unlocking happens too early and we start to see bulged cases either at the feed ramp or all the way around like the one above.

It also could have been from a blowback action - they're pretty prone to case bulges all the way around due to early opening with hot 10mm loads as well. (On a similar note, I experimented with a blowback 357 Sig carbine for a bit that was not only bulging cases, but pushing shoulders forward too for the same reason. Not a good scenario!)

The G40 is one of the few though that doesn't have as much issue with that; you can feel pretty comfortable that it'll handle much heavier loads than you've been using. Nothing wrong with going to a Barsto barrel, just be realistic to the fact that all tilt-breech 10mm pistol barrels are "unsupported" to some degree at the feed ramp. Most of the horror stories with Glocks though came from the earlier guns, gen 2 and 3. By the time gen 4 guns came around, Glock had put a lot more support back in the feed ramp area, especially in the 10mm barrels. With the right powder choices the standard gen 4 G20 will handle a 200gr @ 1200 fps safely, and the G40 will run a bit faster with the same load of course. Some of the earlier guns would bulge brass way before you reached that point because the feed ramps were too generous.

Also keep in mind that BarSto barrel will probably build more pressure with the same load, as you'll see evidence of in the higher velocity.
I agree that the jacked up case in my pic was probably from an action unlocking earlier than it should have, due to the fact that the donut is uniform and goes around the entire case. If it was a case of an unsupported chamber I would expect to see the bulge limited to where the feed ramp was.

I'm hoping to avoid this issue by way of a KKM threaded G40 length barrel and the aforementioned 24# NDZ recoil spring. I've read elsewhere the KKM barrels support the case a bit more than OEM Glock ones do.

I had a bunch of .40S&W from the CBP range in AZ when I lived there and it was pretty obvious which cases came from Agents shooting Glocks compared to other firearms on the line. I invested in a Lee Bulge Buster die before I eventually got out of .40 all together.
 
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Springs tends to get beat up faster in the 10mm when using near max loads so it's good idea to replace them more often and might be good to go up on springs pressure like +2lb over what you have in now. Spring packs in different weights is cheap insurance.
 
Springs tends to get beat up faster in the 10mm when using near max loads so it's good idea to replace them more often and might be good to go up on springs pressure like +2lb over what you have in now. Spring packs in different weights is cheap insurance.
The NDZ recoil rod and spring pack I went with had 20, 22, and 24lb springs in it. I went with the heaviest and we'll see how it goes next time I hit the range with the 160gr loads over 9.1gr of BE-86.

https://ndzperformance.com/ndz-epr-guide-rod-glock-gen-1-3-20-20sf-21-21sf-ndz-g20-g3-epr/

I can always get a 26lb or heavier spring and swap it out if I'm still getting cases launched into the next county.

As this is my first 10mm, what kind of ejection pattern should I be seeing from a properly sprung pistol with full house 10mm loads? I realize it's kinda like reading tea leaves, but any insight/experience would be appreciated.
 
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I use 180/200gr. bullets exclusively in the 10mm and 165/180 in my top tier 40S&W as I know the slide velocity is bit too fast on the lighter bullets. I bet the brass is launched a long ways.
Ejection should be about 4-5 oclock. if they ejecting straight back then its too weak spring.You should feel the difference with slide to frame battering.
 
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The NDZ recoil rod and spring pack I went with had 20, 22, and 24lb springs in it. I went with the heaviest and we'll see how it goes next time I hit the range with the 160gr loads over 9.1gr of BE-86.

https://ndzperformance.com/ndz-epr-guide-rod-glock-gen-1-3-20-20sf-21-21sf-ndz-g20-g3-epr/

I can always get a 26lb or heavier spring and swap it out if I'm still getting cases launched into the next county.

As this is my first 10mm, what kind of ejection pattern should I be seeing from a properly sprung pistol with full house 10mm loads? I realize it's kinda like reading tea leaves, but any insight/experience would be appreciated.

I have the NDZ recoil pack and rod for my G40...I forget which spring I tested but it caused feeding issues. Went back to the stock recoil pack and no issues...

I have to test the other springs.
 
If there’s one thing I don’t love about 10mm, it’s chasing the brass. Particularly at public ranges, I’m always asking the guy 10 bays down if I can police up at his feet 🤣.
Ain't that the truth.
My 1076 has an erratic ejection pattern and I end up losing more than I find.
Had a 1911 that would fling brass out of sight.
My solution:
IMG_20230810_080115585.jpg
 
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I agree that the jacked up case in my pic was probably from an action unlocking earlier than it should have, due to the fact that the donut is uniform and goes around the entire case. If it was a case of an unsupported chamber I would expect to see the bulge limited to where the feed ramp was.

I'm hoping to avoid this issue by way of a KKM threaded G40 length barrel and the aforementioned 24# NDZ recoil spring. I've read elsewhere the KKM barrels support the case a bit more than OEM Glock ones do.

I had a bunch of .40S&W from the CBP range in AZ when I lived there and it was pretty obvious which cases came from Agents shooting Glocks compared to other firearms on the line. I invested in a Lee Bulge Buster die before I eventually got out of .40 all together.

I have a 10mm KKM barrel and there is literally no difference in support compared to a factory Gen 4 G20 barrel. I'm loading 10.0gr of Longshot under 180gr Gold Dots that chrono over 1300fp and the brass looks the same from the factory barrel and the OEM barrel. I'm also just using the factory recoil spring.
 
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I have a 10mm KKM barrel and there is literally no difference in support compared to a factory Gen 4 G20 barrel. I'm loading 10.0gr of Longshot under 180gr Gold Dots that chrono over 1300fp and the brass looks the same from the factory barrel and the OEM barrel. I'm also just using the factory recoil spring.

I didnt see any brass bulging in my Gen4 G40 barrel but I didnt shoot anything over 1200 so far.

I got a Dan Wesson Bruin 10mm not long ago. Took it out one time to test it out and its pretty damn sweet. Time to do some load workup on that with this Longshot.

One big different I found between my Gen4 G40 and this DW Bruin.. Is the Bruin will not feed my G40 200gr HC loads... They hang up every time the slide rips one off the mag and tries entering the chamber. From diagnosing it and doing a little testing, the 1911 style Bruin wont feed the longer COAL 200gr HC rounds..

I load my Montana 200gr HC loads to book COAL of 2.26. They feed 100% with zero issues in my G40. No go in the Bruin... So, I measured up some factory Underwood 200gr HC and those measure 2.245" COAL. I wonder if they make them that way to properly feed in many different 10mm guns, specifically 1911's?? Hmm..

I took some of my G40 200gr HC rounds and shortened them to match the Underwood @ 2.245" COAL and sure enough, they now feed fine in my 1911...
 
I agree that the jacked up case in my pic was probably from an action unlocking earlier than it should have, due to the fact that the donut is uniform and goes around the entire case. If it was a case of an unsupported chamber I would expect to see the bulge limited to where the feed ramp was.

I'm hoping to avoid this issue by way of a KKM threaded G40 length barrel and the aforementioned 24# NDZ recoil spring. I've read elsewhere the KKM barrels support the case a bit more than OEM Glock ones do.

I had a bunch of .40S&W from the CBP range in AZ when I lived there and it was pretty obvious which cases came from Agents shooting Glocks compared to other firearms on the line. I invested in a Lee Bulge Buster die before I eventually got out of .40 all together.

A KKM (or any other brand) barrel won’t prevent that early unlocking type of bulge like that case in the pic, but it will have a tighter chamber and gives you threads at the muzzle.

You’re not likely to have too many issues with early unlocking in the G40 anyway, because of the heavy slide, but the heavy recoil springs are a good idea for heavy loads. I use 22 and 24 lb springs in mine (not much functional difference between them).

The biggest improvement to ejection distance and keeping the action locked up longer is a muzzle brake/comp; since you’re using a threaded barrel it’d probably be worth trying. It’s not very necessary if you’re using relatively mild loads like what Padom mentioned, etc, but can help a lot with the heavier stuff. That’s also where denser powders like AA9 and AA7 are at their best; the added powder mass works the brake more.

As a side benefit, I’ve found that my braked 10mm pistols handle a wider range of loads; the brakes tame down the really hot loads, but then don’t have as much edge with the milder loads because of the smaller powder charges. My long Glock with a brake, for example, handles the 200gr @ 1,375 comfortably, but also cycles 40 S&W reliably too. But when my G20 or converted P16 Para (no brakes) were set up to work with the heaviest loads, they didn’t work well with milder stuff. YMMV of course.

Ejection distances with my long Glock with a brake and heavy loads are about the same as a G19 or 17 with minor power factor loads; about 3:30-4:00 and maybe 6-8 feet. Without the brake it’s more like 15-20 feet, and even farther for the G20.

*My long Glock is a Gen 3 “G20L” aftermarket slide, built before there was a G40. With a G40 here as well though I’ve compared dimensions with a digital caliper and weights on a postage scale; they’re so close it almost seems like Glock copied that slide - it’s functionally identical to the Gen 4 G40.
 
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A KKM (or any other brand) barrel won’t prevent that early unlocking type of bulge like that case in the pic, but it will have a tighter chamber and gives you threads at the muzzle.

You’re not likely to have too many issues with early unlocking in the G40 anyway, because of the heavy slide, but the heavy recoil springs are a good idea for heavy loads. I use 22 and 24 lb springs in mine (not much functional difference between them).

The biggest improvement to ejection distance and keeping the action locked up longer is a muzzle brake/comp; since you’re using a threaded barrel it’d probably be worth trying. It’s not very necessary if you’re using relatively mild loads like what Padom mentioned, etc, but can help a lot with the heavier stuff. That’s also where denser powders like AA9 and AA7 are at their best; the added powder mass works the brake more.

As a side benefit, I’ve found that my braked 10mm pistols handle a wider range of loads; the brakes tame down the really hot loads, but then don’t have as much edge with the milder loads because of the smaller powder charges. My long Glock with a brake, for example, handles the 200gr @ 1,375 comfortably, but also cycles 40 S&W reliably too. But when my G20 or converted P16 Para (no brakes) were set up to work with the heaviest loads, they didn’t work well with milder stuff. YMMV of course.

Ejection distances with my long Glock with a brake and heavy loads are about the same as a G19 or 17 with minor power factor loads; about 3:30-4:00 and maybe 6-8 feet. Without the brake it’s more like 15-20 feet, and even farther for the G20.

*My long Glock is a Gen 3 “G20L” aftermarket slide, built before there was a G40. With a G40 here as well though I’ve compared dimensions with a digital caliper and weights on a postage scale; they’re so close it almost seems like Glock copied that slide - it’s functionally identical to the Gen 4 G40.

Thanks for all of that. Very helpful from a powder and firearms perspective.

My 10mm Glock is a Gen 3 G20 P80 build and the KKM G40-length barrel will just be going in that G20 slide. I won't get the benefits of the longer/heavier slide, but I might look into a brake for the G40-length barrel when not running it with a can. I wanted to stick with the G20 slide as I already have a holster that will hold it and my Gen 4 G21 and I need another holster like I need another hole in my head, haha.
 
Thanks for all of that. Very helpful from a powder and firearms perspective.

My 10mm Glock is a Gen 3 G20 P80 build and the KKM G40-length barrel will just be going in that G20 slide. I won't get the benefits of the longer/heavier slide, but I might look into a brake for the G40-length barrel when not running it with a can. I wanted to stick with the G20 slide as I already have a holster that will hold it and my Gen 4 G21 and I need another holster like I need another hole in my head, haha.

Ok.

Heads up though - the milder 10mm loads m will be fine will be ok (although loud) with a suppressor, but it’d be very inadvisable to use it with real full power stuff. We already have to be careful of early unlocking in hot 10mm pistols, without a suppressor booster in the mix.

The booster in your can does exactly the opposite of a brake; it creates recoil, and hot 10mm loads are excessive for pretty much any commercial booster out there (all of which, I’m pretty certain, are designed around 40 S& W). If you want to intentionally cause case bulges like your picture above from early unlocking, this is how you do it.

If you insist on trying it, at the very least remove the magazine from the pistol when testing, so the blown case can vent down an open mag well. It’ll save your hand.
 
I use Accurate #7, 12.0 grains with a Hornady 180 XTP. Using R-P brass, Midway or Starline is better brass for heavy loads. Run it thru my Glock 20C.
 
Ok.

Heads up though - the milder 10mm loads m will be fine will be ok (although loud) with a suppressor, but it’d be very inadvisable to use it with real full power stuff. We already have to be careful of early unlocking in hot 10mm pistols, without a suppressor booster in the mix.

The booster in your can does exactly the opposite of a brake; it creates recoil, and hot 10mm loads are excessive for pretty much any commercial booster out there (all of which, I’m pretty certain, are designed around 40 S& W). If you want to intentionally cause case bulges like your picture above from early unlocking, this is how you do it.

If you insist on trying it, at the very least remove the magazine from the pistol when testing, so the blown case can vent down an open mag well. It’ll save your hand.

Well, after getting the KKM G40 barrel in I don't think I'll be putting a can on the end if for no other reason than it'll look ridiculous. Might look into a brake or maybe getting the barrel ported.

Ref a can and booster generating issues, would running a can sans booster alleviate the issue? I know tilting barrel pistols normally need the booster in order to ensure function due to the extra mass on the end of the barrel, but if the 10mm is working with so much energy to begin with, could the can using a fixed barrel mount act somewhat like a brake or comp in that it's adding non-reciprocating weight for the action to move around?

If not a full size 45ACP can, perhaps a K can would be the right balance of added weight without adding too much. I imagine much like addition of a brake, the addition of a non-boosted can might require the recoil spring to be reduced in strength.

Never messed with anything besides 9mm and 45ACP as far as suppressed centerfire pistols go, so happy to learn anything I can from those who've done so.

G40.jpg
 
Well, after getting the KKM G40 barrel in I don't think I'll be putting a can on the end if for no other reason than it'll look ridiculous. Might look into a brake or maybe getting the barrel ported.

Ref a can and booster generating issues, would running a can sans booster alleviate the issue? I know tilting barrel pistols normally need the booster in order to ensure function due to the extra mass on the end of the barrel, but if the 10mm is working with so much energy to begin with, could the can using a fixed barrel mount act somewhat like a brake or comp in that it's adding non-reciprocating weight for the action to move around?

If not a full size 45ACP can, perhaps a K can would be the right balance of added weight without adding too much. I imagine much like addition of a brake, the addition of a non-boosted can might require the recoil spring to be reduced in strength.

Never messed with anything besides 9mm and 45ACP as far as suppressed centerfire pistols go, so happy to learn anything I can from those who've done so.

View attachment 8204610

Yeah, it is possible to run a very light can solidly mounted without a booster (talking about tilt-barrel recoil operated pistols of course - Glock, 1911, etc). I had some opportunities to try this, and found that a 3 oz 9mm can, for example, worked well on a stock Glock 19 with heavier subsonic loads.

Presumably the maximum suppressor weight to do this would be heavier for hot 10mm loads than for a 9mm, but I don't know what that weight would be.

The other side of the coin though is that hot 10mm out of pistol barrels doesn't suppress all that well. IMO supersonic 9mm is not bad, but 10mm can be pretty loud. YMMV and depends on the load of course. Personally though - this is the main reason I don't bother with a suppressor on my 10mm pistols, even though 40 S&W can be OK with the right setup.
 
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My 10mm choices include Longshot, Blue Dot, Power Pistol and BE-86 depending on which bullet I use.
 
I HOPE that I am not "resurrecting a Zombie thread", here.
I'm wondering if any of you more seasoned 10mm reloaders have tried Alliant Herco as a propellant in 10mm. For those not familiar with it, Herco is a slightly slower-burning version of Unique/BE-86, which tends to give notably higher velocities in equi-baric loads in 10mm, 9mm, .38 Super, and the original magnum revolver rounds, but with similar economy (rounds per pound). Without the benefit of equipment for a rigorous analysis, I would estimate Herco's burn rate as roughly midway between that of Unique/BE-86 and Blue Dot. If not midway, then closer to the Unique/BE-86 end of the scale.
I have reloaded roughly 200 rounds of 10mm, for someone else (in the process of teaching HIM how to reload for himself), and the propellant of choice was (then) Hercules Blue Dot. Without pushing things too hard, we managed to launch 205 gr. cast RNFPs at just over 1150 f/s. The lengendary "Big White Ball of Fire" proved to be a detriment in low(er) light conditions. Back then, flash-suppressed propellants were not available to private reloaders, so I opined that a slightly faster-burning powder might mitigate at least SOME of the flash. I had little hope that Unique would provide the requisite velocity with 200+ gr. projectiles but opined that Herco might be a decent compromise. While neither Unique nor Herco have reputations for being "low-flash" propellants, it was difficult for me to imagine that either of them would "light up the countryside" in the way the Blue Dot did.
My 10mm shooting friend was untimely transferred out of state before we got to try it, and I used the remainder of my Herco supply in .357 Mag. reloads. I've nonetheless wondered if Herco might have worked, so I thought I would ask the 10mm shooters who might actually know.
Thanks in advance for your input.
 
I HOPE that I am not "resurrecting a Zombie thread", here.
I'm wondering if any of you more seasoned 10mm reloaders have tried Alliant Herco as a propellant in 10mm. For those not familiar with it, Herco is a slightly slower-burning version of Unique/BE-86, which tends to give notably higher velocities in equi-baric loads in 10mm, 9mm, .38 Super, and the original magnum revolver rounds, but with similar economy (rounds per pound). Without the benefit of equipment for a rigorous analysis, I would estimate Herco's burn rate as roughly midway between that of Unique/BE-86 and Blue Dot. If not midway, then closer to the Unique/BE-86 end of the scale.
I have reloaded roughly 200 rounds of 10mm, for someone else (in the process of teaching HIM how to reload for himself), and the propellant of choice was (then) Hercules Blue Dot. Without pushing things too hard, we managed to launch 205 gr. cast RNFPs at just over 1150 f/s. The lengendary "Big White Ball of Fire" proved to be a detriment in low(er) light conditions. Back then, flash-suppressed propellants were not available to private reloaders, so I opined that a slightly faster-burning powder might mitigate at least SOME of the flash. I had little hope that Unique would provide the requisite velocity with 200+ gr. projectiles but opined that Herco might be a decent compromise. While neither Unique nor Herco have reputations for being "low-flash" propellants, it was difficult for me to imagine that either of them would "light up the countryside" in the way the Blue Dot did.
My 10mm shooting friend was untimely transferred out of state before we got to try it, and I used the remainder of my Herco supply in .357 Mag. reloads. I've nonetheless wondered if Herco might have worked, so I thought I would ask the 10mm shooters who might actually know.
Thanks in advance for your input.

You’re looking at too fast of a burn rate, and want to be at Blue Dot or even on the other side of it. Unique isn’t even slow enough for full power 40 S&W, much less 10mm, and Herco isn’t that much better.

AA9 is your huckleberry for real 10mm loads with flash suppression. That and AA7 both give minimal flash; AA7 is good for the lighter bullet weights.

If you just have a bunch of Herco you want to use, yeah it’ll go bang, just keep the loads mild; most pistol powders can fit that role. But it’s not one of the good 10mm powders.
 
I use 800x strictly for 200gr bullets and Longshot, Power Pistol and AA9 for 180 bullets as i don't use bullets under 180 since it doesn't make any sense. I save my Herco for my midrange snubnosed S&W 44 mag.
 
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I use 800x strictly for 200gr bullets and Longshot, Power Pistol and AA9 for 180 bullets as i don't use bullets under 180 since it doesn't make any sense. I save my Herco for my midrange snubnosed S&W 44 mag.

Why not use the AA9 for 200+gr bullets as well? It’s even better suited for those than the 180gr range, and IME better than 800X for both ballistics and ease of use, as well as low flash.
 
Got a bit more velocity with lot Less flash and softer recoiling.

Compared to AA9? Interesting, I've always gotten exactly the opposite in regards to flash and velocity. What barrel length(s) are you using? I work with the G20 stock length a little but mostly with a 6.5" barrel for my old longslide gun. That could account for some differences in flash results but I always felt 800x was kinda bright. IIRC the Tanfo and 1911 10mm barrels I used to use were somewhere in between those two.

In the 200+gr range, especially with cast bullets, the top end for pressure with AA9 is right about 105% case fill, i.e. just a little compressed, giving the perfect fill and better velocity than any other powder in my experience. I think a lot of people end up stopping with AA9 before they get there though, and maybe I did the same with my 800x experiments. I felt it metered too poorly to be safe at top end loads though, where AA9 seems to work best at that top end and meters perfectly.

AA9 does use heavier charge weights though so recoil can be a little more with a bare muzzle. If you're using a brake that flips around though; the heavier charge weight works the brake more, making the gun shoot softer and track flatter. Lots of people don't like a brake though, and I get it, it's loud, but makes my longslide a sweet shooter.

Regarding flash, I've been thinking of some video ideas for a youtube channel, and that'd be a good one; some sort of flash comparison for common powders for a few different cartridges. I've done a fair bit of that for my own use but never shared it with the world.
 
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Compared to AA9? Interesting, I've always gotten exactly the opposite in regards to flash and velocity. What barrel length(s) are you using? I work with the G20 stock length a little but mostly with a 6.5" barrel for my old longslide gun. That could account for some differences in flash results but I always felt 800x was kinda bright. IIRC the Tanfo and 1911 10mm barrels I used to use were somewhere in between those two.

In the 200+gr range, especially with cast bullets, the top end for pressure with AA9 is right about 105% case fill, i.e. just a little compressed, giving the perfect fill and better velocity than any other powder in my experience. I think a lot of people end up stopping with AA9 before they get there though, and maybe I did the same with my 800x experiments. I felt it metered too poorly to be safe at top end loads though, where AA9 seems to work best at that top end and meters perfectly.

AA9 does use heavier charge weights though so recoil can be a little more with a bare muzzle. If you're using a brake that flips around though; the heavier charge weight works the brake more, making the gun shoot softer and track flatter. Lots of people don't like a brake though, and I get it, it's loud, but makes my longslide a sweet shooter.

Regarding flash, I've been thinking of some video ideas for a youtube channel, and that'd be a good one; some sort of flash comparison for common powders for a few different cartridges. I've done a fair bit of that for my own use but never shared it with the world.
I have very little of AA9 left and have not seen it on the shelf with the exception of AA 5/7. AA9 will work better on the longslide but not much so with my carrying piece in 5" from experience with it. Agree that the longer the barrel the better AA9 works especially in Glock 40 respectively.