Help with 10mm heavies for subsonic use...

[bigfelipe]

Hello fellow 10mm aficionados...

I'm looking to develop as heavy a 10mm subsonic round as possible. I realize this goes against the grain with most 10mm shooters  but I have a reason. I have a threaded barrel and suppressor for my GLOCK 20. This is my RV gun when I travel. My "one gun" for that purpose. Something for everything. I want a heavy cast boolit for subsonic use. The thinking is it'll be quiet but still penetration will still be good. A sledgehammer round if you will.

I'm looking for something 250-300 grains @1000fps. The higher the weight, the better. I'm not sure what is possible while remaining stable with the slow twist of 10mm. I'm sure others have had similar thoughts. Can't find a mold anywhere close to what I want. I have played with Mountain Molds design page but it's limited. I do some coated boolits, hi-tek and PC. So, I think a tumble lube or no lube groove design.

I don't know what will fit in the case with enough room for powder to get enough velocity...

Thoughts?


Edit: not interested in just using 180-220gr projectiles and calling it good...

[bigfelipe]

I worked this up on Mountain Molds...

Sorry. Wrong mold. That one was bumped up to 45 caliber by accident. It gives you an idea though.


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[Muskrat]

Maybe you're looking for a project, but if not, there's no point in reinventing the wheel.

Rim Rock 220 grain bullets generally run heavy...all mine have been 226 grains. Push it to 1000~1050 fps and you don't have to worry about k-booms. I'm sure it's possible to find and load heavier bullets, but don't see any point to it. If anything I think you'll just run into stabilization issues, as well as the potential for unsafe pressures.

[The_Shadow]

Well if you want heavy without gaining length forget the lube groves, PC coat the bullets, also if bullets get too long you will likely see pressure spikes or the bulge where the bullet sits inside the case that may cause feeding issues... 

[sqlbullet]

So, even though that Mountain Mold page starts with 10mm/40, the as cast diameters have been pushed up to 45ACP sized bullets.

If you trim the diameter back down to .403", then the in-case length gets well above 0.500".  In my test at MM I came in at 0.567" inside the case with a 0.270 nose and a 270 grain bullet, two groove.  (Shadow is right, if max weight is the goal, go no lube groove and powder coat, but Mountain Mold doesn't allow you to delete lube grooves.)

Here is my take...

A 220 grain loaded within published data doesn't get above 1000 fps, and the reported pressure at max is nearly 37,000 psi.  So, a 220 grain gets you very subsonic. 

[bigfelipe]

Well if you want heavy without gaining length forget the lube groves, PC coat the bullets, also if bullets get too long you will likely see pressure spikes or the bulge where the bullet sits inside the case that may cause feeding issues... 

Yup, I stated in the OP that I coat bullets and was looking so no lube grooves or at most tumble grooves. Obviously I don't want to blow up one of my guns. Been there with a case head failure that trashed the frame of a new Glock in the middle of a stage during competition. That's why I'm looking around for as much information as I can to make educated starting guesses. I was hoping being a 10mm dedicated forum someone may have been down this rabbit hole before. Maybe not...

[bigfelipe]

So, even though that Mountain Mold page starts with 10mm/40, the as cast diameters have been pushed up to 45ACP sized bullets.

If you trim the diameter back down to .403", then the in-case length gets well above 0.500".  In my test at MM I came in at 0.567" inside the case with a 0.270 nose and a 270 grain bullet, two groove.  (Shadow is right, if max weight is the goal, go no lube groove and powder coat, but Mountain Mold doesn't allow you to delete lube grooves.)

Here is my take...

A 220 grain loaded within published data doesn't get above 1000 fps, and the reported pressure at max is nearly 37,000 psi.  So, a 220 grain gets you very subsonic.

Yeah. It was late and I had been messing with that mold site for awhile. Accidentally bumped up the diameter. It was just to give an idea. That site doesn't allow you to mock up PC-type rounds.

[Muskrat]

...
A 220 grain loaded within published data doesn't get above 1000 fps, and the reported pressure at max is nearly 37,000 psi.  So, a 220 grain gets you very subsonic.

Where did you find published load data for 220 grain bullets?

[The_Shadow]

Muskrat, probably the data that was obtained in the pull down documentations as found in the UW, BB, DT ammos.
There was 205 grain data in the Accurate Arms in the past...

Here are the various Pull Down Documentations

DT Double Tap 230gr Hard Cast10mm Auto
Muzzle Velocity: 1120 fps
Muzzle Energy: 612 ft. lbs
LongShot Weight: 7.2 grains

UW Underwood 220gr Hi-Tek Coated Hard Cast FN 10mm Auto
Muzzle Velocity: 1200 fps
Muzzle Energy: 704 ft. lbs
BE-86 8.0

UW Underwood 220gr Cast WFN 10mm Auto
Muzzle Velocity: 1237 fps
Muzzle Energy: 747 ft. lbs
LongShot  8.4 grains

UW Underwood 220gr Hard Cast(reduced)
10mm Auto
Muzzle Velocity: 1240 fps
Muzzle Energy: 750 ft. lbs
LongShot Weight: 8.0 grains

BB Buffalo Bore 220gr Hard Cast 10mm Auto
Muzzle Velocity: 1175 fps
Muzzle Energy: 674 ft. lbs
Power Pistol Weight: 8.4 grains

[Muskrat]

Gotcha.

I gotta say, unless the round is for poaching rhinoceroses, I don't see a single reason for going heavier...and a lot of potential issues. Whatever winds your watch I guess.

[The_Shadow]

I agree with you Muskrat, I do like the 200 grain bullets and my cast ones are about 208 grains.
I do also like several other weights for my purposes.

Just wanted to post the data found in the pull-downs of the commercially sold ammo as a reference

[cwlongshot]

I like the idea of heavy for caliber bullets, ALWAYS HAVE at least since I have learned "better".

No need for subs in my house but I understand. I tried PP, Longshot and Blue Dot. For me although the others metered better, BLUE DOT was my champion.

I use GT bullets 220g HP. It's quite a long bullet. ZERO stabilization issues from factory G29, G20 @ G40 bbls or from aftermarket Lone Wolf Or KKM bbls.

I started at 7.0g and worked to 8.5. I stopped cause I hit my target velocity. But no problems AT ALL where witnessed. Cases are fine. Primers fine and pockets live for additional loadings just fine. (Some are on there third loading)

Of coarse your results can differ and always stark low and work up.

But I'm real happy with these results.

GT bullets offers many diameters and a couple hardnesses. I take there standard alloy it measures 12BHN and expands beautifully in wet paper at 1200 FPS ALMOST to base of HP shaft.
They also sell "AS CAST" and this is what I buy cause mine are all
Powder coated. Then sized .402.

CW

[sqlbullet]

Where did you find published load data for 220 grain bullets?

Hodgdon reloading website.

[The_Shadow]

Just got my new Alliant 2020 manual and they show only one load for 220 cast FP coated using Sport Pistol Powder 4.7 grains @ 929 fps
They also show a load used in the 40S&W 220 cast FP coated using Sport Pistol Powder 2.9 grains @ 728 fps

Sport Pistol powder was said to not react with the coatings on the PC coated bullets

The sad thing is that they make no reference to barrel length for the test and still no pressure values...

Also there is no 200 grain Gold Dot or any other 200 grain bullets listed in the book only the 190 gr Federal JHP

[Muskrat]

Where did you find published load data for 220 grain bullets?

Hodgdon reloading website.

Thanks...wonder when they added that bullet to their charts?

Interesting that the go-to powders for 220 grain aftermarket loads (800X and Longshot) aren't even on the list. Also interesting that Hodgdon lists max pressures at velocities WAY below what Underwood is generating. From a 6" barrel I get 1,226 fps from the Underwood 220 hardcast...almost 25% faster than anything Hodgdon publishes.