P16 to 10mm
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Old 04-06-2010, 12:51 PM   #1
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Default P16 to 10mm

I've done some Google-fu on this but I want the opinion of our resident gunsmiths. I have an older Para P16 Signature (built before the PXT power extractor) and I'm toying with doing a 10mm conversion. Based on what I've read, it's just a matter of re-chambering the barrel and switching to a heavier recoil spring. My question is (since 10mm ammo is $$$), could I still shoot .40 ammo through it or would I be better off to have a separate barrel (Brownell's has one in stock)...

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Old 04-06-2010, 05:29 PM   #2
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Seeing that the case length of the .40S&W is .850 and the case length of the 10mm is .992 you would be depending on the extractor to hold the cartridge in place. IF the extractor is tuned right it SHOULD hold it but I'd not want to take the chance of shooting .40 in a 10mm barrel. All you can do is try it and see if the extractor will hold it good enough. I've been shooting .45 out of my .460 Rowland barrel but with less than stellar results. That's even using a .45 weight recoil spring too.

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Old 04-06-2010, 05:33 PM   #3
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Thanks Bear, as I was thinking the same thing. If I go this route, I'll just buy an extra barrel. During my searches I found that the conversion was easy but nobody talked about being able to shoot .40 S&W after the chamber is reamed. The thought of 17 rounds of 10mm in a 1911 style package is very tempting...

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Old 04-06-2010, 05:39 PM   #4
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I had a Para P-14 in .45 with Colt 1991 slide and an STI (early) frame with a Colt Delta slide chambered in .40. The frame should hold the 10mm ammo. My STI mags would hold 10mm ammo. The P-16 is a stainless steel frame, correct? I would tend to over spring it, run a 20+ lb recoil spring to help prevent frame battering.

DO NOT shoot .40 S&W ammo out of a 10mm barrel!!!! Headspace is non existant and bad things WILL eventually happen.

A simple barrel swap is feasable. The ejector may need to be swapped out as the 10mm uses a much shorter part than the .40.

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Old 04-06-2010, 05:44 PM   #5
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Originally Posted by robocop10mm View Post
I had a Para P-14 in .45 with Colt 1991 slide and an STI (early) frame with a Colt Delta slide chambered in .40. The frame should hold the 10mm ammo. My STI mags would hold 10mm ammo. The P-16 is a stainless steel frame, correct? I would tend to over spring it, run a 20+ lb recoil spring to help prevent frame battering.

DO NOT shoot .40 S&W ammo out of a 10mm barrel!!!! Headspace is non existant and bad things WILL eventually happen.

A simple barrel swap is feasable. The ejector may need to be swapped out as the 10mm uses a much shorter part than the .40.
My P16 is an older black finished steel gun with the normal fire control group (not the LDA). I saw a spare barrel at Brownell's this morning so I'm going to have to consider this - like I need another caliber...
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Old 04-06-2010, 11:22 PM   #6
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Why bother changing calibers at all.. just put a heavier recoil spring in the P16, and load your 40's as long as a 10 mm and work up your loads to match 10 mm performance. The gun can handle bullets up to the length of 10 mm anyway as is.. you just need load longer/heavier bullets seated to 1.260". I can't see why you;d actually want to change from a readily available caliber to a rare/expensive caliber.. As long as the ammo you load is as long as the 10 mm, I see no issue since you will not be able to load it into any standard 40 length gun (ie Sig, Glock, S&W, etc).

I load ammo long for my 610 that fits perfectly in my P16 in 40.. and I only use 40 S&W brass to do so..

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DO NOT shoot .40 S&W ammo out of a 10mm barrel!!!! Headspace is non existant and bad things WILL eventually happen.
This only applies to semi-autos as the 610 can fire any length 40 S&W or 10 mm due to it's use of moon clips. But you likely already knew that.
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Old 04-06-2010, 11:31 PM   #7
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Why bother changing calibers at all.. just put a heavier recoil spring in the P16, and load your 40's as long as a 10 mm and work up your loads to match 10 mm performance. The gun can handle bullets up to the length of 10 mm anyway as is.. you just need load longer/heavier bullets seated to 1.260". I can't see why you;d actually want to change from a readily available caliber to a rare/expensive caliber.. As long as the ammo you load is as long as the 10 mm, I see no issue since you will not be able to load it into any standard 40 length gun (ie Sig, Glock, S&W, etc).

I load ammo long for my 610 that fits perfectly in my P16 in 40.. and I only use 40 S&W brass to do so..

This only applies to semi-autos as the 610 can fire any length 40 S&W or 10 mm due to it's use of moon clips. But you likely already knew that.
Glad that works for you but it wont for me as I do not reload. Also, if I did I don't think I'd want 2 kinds of .40 rounds floating around as not every gun would handle them and I have more than one .40. Just sounds a tad dangerous to me...
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Old 04-06-2010, 11:46 PM   #8
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If you don't reload then It's likely not for you.

I've a bit of experience in this vein. I use a heavily modified P16 for Action shooting, the only original parts are the barrel, slide, frame, and grips.. everything else has been replaced.. sometimes more than once due to use in a competition environment.

Like I said, the longer length 40's are NOT able to feed in anything other than the P16 or a 610 Revolver.. the shorter length 40's (standard length = 1.135" to 1.140") are only loaded to be safe in the firearms that use them, ie Glock, Sig, S&W, etc. Kind of like using 38's in any 357 but only 357's in guns made for that round.. The 40's made to the 10 mm length will not feed or fit in any magazine of standard length guns. It will however feed and shoot just fine in any 1911 length firearm such as your Para P16 or one of the STI/SVI guns.

Since I reload.. I have different length 40 S&W loads of differing power for specific guns.. I have the Sig length 40's (1.135"), the S&W 610 length 40's (1.175-1.260") and the Para Length 40's (also 1.175 - 1.260").

Bullet profile has an influence as well. The truncated cone style contact the bore sooner and are usually seated under 1.190". I have a long Round Nose that tapers nicely so that the bullet length can be very long (up to 1.260"). Obviously lighter bullets are shorter and can only be loaded so long.. usually in the 1.180" range.

Likely I've given way too much information... but mostly I wanted to show what was possible all loaded into the 40 S&W case..

I've been loading the 40 S&W for over 15 years.. so I've likely experimented a bit more over all those years with many different powders, bullet weights, and lengths.. I still have every 40 I've ever owned.. and none have ever been damaged from using incorrect ammo.

If you want a 10 mm, go ahead and get one.. just hope that you can find ammo Barrel, Recoil spring.. those are the two things you likely need.. the magazines for your gun will already accept the 10 mm ammo as long as it is loaded to standard length.

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Old 04-07-2010, 12:50 PM   #9
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WARNING!!!!

Loading a .40 to 10mm specs may be possible, but this is a VERY specialized endeavor that should not be undertaken by the "average Joe".

One thing you must consider is the length of the throat in the barrel. SOME .40 barrels will allow this. Some will cause the bullet to be jammed into the rifling. Several bad things can happen when this occurs.
1. When removing a chambered round, the rifling can hold the bullet while the extractor removes the case. The resulting stuck bullet will mimic a squib load and bring all the dangers of a bullet lodged in the barrel.
2. The rifling can increase the resistance to loading to the point the bullet is forced into the case causing a compressed load and dangerously incresing pressures.

My STI worked better with long loaded .40's, but I was just loading to IPSC major power factor, not trying to approach 10mm loads. The Nowlin barrel in the pistol had a long throat intended for such loadings.

None of us are "Elmer Keith" and loading Elmer's .44 special to what we now know as .44 Magnum performance is a dicey game. Loading .40 S&W to 10mm performance is pretty much the same thing. If I remember correctly, Mr. Keith destroyed several guns during his experimentation. I would be VERY careful in this modern era of litigation about advocating or attempting such feats.

I have been loading and experimenting for about 35 years and I would not do this. I have a 10mm and a .40. Each has a place.

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Old 04-07-2010, 02:10 PM   #10
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Fair enough.. though you have to admit it is likely more possible today than it was back in Elmer's Day. He was working with the 44 special trying to develop the 44 magnum. He was using N frame Smiths of the time which were not built like they are now with the modern steels and techniques. There were limited availability of powders then that they experimented with, H110, 2400, WC 820 Surplus, Blue Dot, and SR 4756 come to mind. Those were the limits to the powders that they could use to develop magnum ammo.. Now we have many more choices of burn rates.. There is a thread on another forum about swaging your own heavy hollow points from smaller cases.. I am winding up with very long 190-195 gr Hollow points in .40 cal. My test bed is the S&W 610-2 and 610-3. I also used a Para P16 similar to the OP.

Using Longshot, I found that it ran out of steam at a certain point and would not produce any more velocity with increases of powder with those heavyweights even though I had more room in the case.. They were all loaded to 10 mm length.. So you can see where I am at.. I guess sometimes I get excited and like to post what I'm up to without thinking that there is some risk involved.. and I'm willing to take that risk utilizing firearms designed to take some amount of punishment. I did not utilize the P16 beyond the starting load which was already at USPSA Major (about 175 PF). With the 610 I was able to get 1150 fps with a 195 gr HP. I had no pressure signs and the bullets flattened out nicely when hitting a pepper popper

I have personally been loading all kinds of things since approx 1987... the 40 came later since I wasn't into auto-pistols early on. My experience started with the 12 and 20 gauge and extended to 30-30 and 38/357 when I turned 21... I didn't start getting into the 40 until I bought a Sig about 15 years ago.. and now own.. 5 firearms in 40 cal.. 2 in 40, 3 in 10 mm). The 610-2 was heavily used over the years and I wore out about 700 pieces of 10 mm brass.. Since 2004 I've exclusively loaded 40 for the 610 and have likely 100,000 rounds through that specific firearm.. minor, major, and "wow that was intense" loads

To the OP.. take it as you will but since you do not reload, all of this is sort of moot.. It is the internet, and you should not take it all as "gospel". I'm simply posting my experience, but as usual your milage may vary. Back to lurking..

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