Sig Rifle caliber pistols

J

jwalker497

New member
I noticed Sig has several of these style guns but I cannot tell the difference between them. Their site has the following options...

PM400, available in 5.56, Elite version avail in 300 blackout
P556xi, available in 5.56, 300 blackout, 7.62x39
P516, available in 5.56
P716, available in 7.62x51

I have 2 questions

1) Can anyone tell me what the basic differences are aside from calibers?

2) What would be the difference in ballistic energy difference between them. I assume the 5.56 is the weakest followed by 300BO, then 7.62x39, then 7.62x51?
 
The PM400 is an AR platform as it is a direct impingement system.

The P516 is a short-stroke piston drive version of the AR platform. It uses a standard AR pistol buffer tube assembly and from what I understand (I have not tried on mine) will accept a standard AR upper. This of course is taking into consideration the minor pattern differences of the AR that do not allow complete interchangeability.

P716 is the big brother to the 516. Think piston drive AR10.

The 556xi is a different beast. It is the third gen of the 556 line which was based on the Swiss army's 550 assault rifle. The original 556 had a gen 2 version, making this one the the 3rd. It is not an AR platform although it accepts AR style mags. The 556 does not have a buffer tube as it has a full stoke piston drive system. In the rifle version it is able to have a folding stock due to the lack of buffer. It has an ambidextrous, reciprocating charging handle.

Edited to add
The ballistics performance can be addressed by people here that are much better experts than I on this but my understanding is that the 300BO is really designed for the shorter barrels and doesn't loose as much performance from them.

As an example Federal 193 out of my 556xi clocks at 2850fps and out of my 10.5" 516 clocks 2500fps.
 
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2) What would be the difference in ballistic energy difference between them. I assume the 5.56 is the weakest followed by 300BO, then 7.62x39, then 7.62x51?
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This kinda of question is a classic flamefest bait question. I would recommend simply going to an easy on-line calculator (like Hornady's) and finding out for yourself rather than trying to make sense out of a 20-page on-line apples to oranges debate. : )
 
So looking at the 556xi in 300BO or 7.62x39mmm.

  1. What are the ballistic differences in a short barrel like this?
  2. Is there any advantage of the 7.62 over the 300BO in a short barrel?
  3. How about accuracy, the compaint of the 7.62 is that its not an accurate round?
  4. If one doesnt plan on getting it supressed is there any reason to go with the 300BO?
 
Looking at those 2 choices I would be inclined to go 300. I had a 556xiR and sold it after I got it broken in. I got it to run steel cased ammo through but didn't find much good ammo for it.

I have no information on the Xi in 300 but I understand that round to be capable 250-300 yards out of a top end AR pistol upper.
 
In defense of the 7.62X39;

It is very cheap (I just picked up 80 rounds at Wal-mart today for $19.86 plus tax)
It retains energy fairly well out of a shorter barrel (don't know how it stacks up against .300 blackout)
Accuracy with the cheapest ammo is not great but I have never struggled hitting a 6-8" plate at 100 yards (do you plan on doing more than that with your pistol?) and there are some decent rounds available including Hornady SST

7.62X51... well, while I've always wanted a short barreled G3/FAL rifle or pistol, I can't say I can see much practical use for one. Shooting even on the bay next to a .308 with a barrel as short as 10" is incredibly unpleasant. There's a lot of unburnt powder and that equals muzzle flash and concussion

5.56 does lose a lot of muzzle velocity and energy in short barrels and also suffers from muzzle bang but this inefficiency can be combated somewhat by going with heavier grain ammo.
 
Best all around choice in a 10.5" AR Pistol? 5.56.

It's been used in that capacity since the adoption of the XM177 in the 1960's. Ammo is cheap and good ammo is available. Down range ballistics aren't that compromised, 5.56 is still going as much as 2,700 fps with some loads from that 10.5" barrel.

Yes, please DO look up ballistics calculators and push the buttons. What some have picked up on is the use of MILITARY ammo and it's lack of ability to expand or fragment when shot from the shorter pistol barrels. The DOD doesn't prescribe it for that use - they prefer MK262 70 gr OTM ammo for superior performance. .300BO in a hunting load would do the same supersonic, it's forte is subsonic with really big bullets and a suppressor. 7.62x39 can be as cheap or cheaper than 5.56 but when you move to a hunting around with expanding tip ammo you are going commercial and that plants your right back in the $1 a round ammo. There's no getting around it - quality ammo for live target use ( I hunt deer with my AR pistol) isn't cheap and never will be. But surplus ammo is. There is no cheap .300BO surplus and likely never will be.

Economy of ammo is part of the all around best choice and it's the ones who ignore it who post later about how the alternate new cartridges are so "pricey." Of course - they aren't taxpayer subsidized with surplus to sell off.

Since the application for a short barreled rifle cartridge based firearm is less than 125 m then take with a grain of a salt discussion about how well one cartridge does over another. Most are repeating the supersonic long distance concept of what the ammo does, not the short range expected performance of how the gun will be used. Goes for claims that they are much louder - of course they are and nobody should be using them with no ear protection, same as a 9mm handgun. Especially indoors, where they are all LOUD.

SIG makes nice guns but it is good to keep in mind these are proprietary designs with single source parts - unlike AR pistols. And when you might need to buy box of ammo it does become a problem if it's a proprietary round, not issue. The Army has done just fine with 5.56 for nearly 50 years in a short barreled rifle cartridge firearm and there's no reason to discount that just because it's not the Bullet of the Month on the market.
 
Since the application for a short barreled rifle cartridge based firearm is less than 125 m then take with a grain of a salt discussion about how well one cartridge does over another. Most are repeating the supersonic long distance concept of what the ammo does, not the short range expected performance of how the gun will be used. Goes for claims that they are much louder - of course they are and nobody should be using them with no ear protection, same as a 9mm handgun. Especially indoors, where they are all LOUD.
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Of all the choices mentioned, only the 300 BO was specifically designed from the ground up as a short-barreled multi-velocity application cartridge. Pretty much end of discussion as far as I'm concerned.:)
 
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