What's the benefit of fitting aftermarket drop in barrels in a P320?

[RoverSig]

I recently bought an aftermarket "drop-in" barrel for building a P320 3.9" pistol with a new slide and a used FCU (like new).

 

The barrel came from a well-know company (not Bar-Sto or KKM). 

 

Well, the pistol shot a 6" group at 7 yards, compared to a typical 3" group at 7 yards with my other P320 3.9" pistol.  And examining the slide and the new drop-in barrel, after 150 rounds the barrel hood is beat up on the top corner, and the abutment on the edge of the breech (which was new) has been beat up in one spot along the side of it.  When in battery, the top of the barrel hood where it meets the top of the breech face has a bigger space on one side compared to the other. 

 

So what was the benefit of buying an aftermarket "drop in" barrel?  At least it was on sale ($135).  More to the point, what would be the benefit of buying a KKM or Bar-Sto aftermarket barrel that needs fitting and getting the barrel fit to my P320?  Granted, the barrel is not the only factor in my accuracy (trigger, sighting, grip, etc., all have effects) but in this case the new "drop in barrel" from Brand-X doesn't appear to be doing much good. 

 

This is not really a cost-benefit question, that's a separate issue, this is more of a "what is the degree of benefit, if any" question.

 

Thanks.     

[RangerTrace]

None if it's drop in.

[Boomstick303]

2 hours ago, RangerTrace said:

None if it's drop in.

 

While I agree if you are going to spend money on a barrel replacement that it should be fitted in the P320 to see true benefits of a barrel swap, Bar-sto and KKM chamber are different than the stock Sig barrels which have unsupported chambers.  In my eyes that is an added benefit, but not enough to justify the cost.

 

What I did find is that the Bar-sto barrel I installed on my P320 was not as finicky when it came to ammo.  Meaning, I did not get a huge shift in Point Of Impact when switching from ammo to ammo.  That barrel has made my P320 more accurate and more consistent which is worth the cost.  This was using Gun Smith fitted barrels though.  

 

For the OP, I would ask what ammo was used?   Not all ammo performs the same out of a given barrel.  Stock P320 barrels hate slow ammo.  People generalize this by saying that P320 barrels hate 147 gr bullets which is not necessarily true.  I got 147 gr bullets to group fine out of the stock barrel by speeding the bullet up.  But that kind of defeats the purpose of using a heavier bullet for USPSA use when we are trying to dial in a specific Power Factor.  In those barrels faster is better in regards to grouping, so it makes sense to use a lighter bullet.   

 

 

[RoverSig]

I am shooting 115 grain 9mm running around 1145 fps - S&B, Magtech, Blazer Brass - relatively inexpensive ammo available from various internet sellers at around $239-$269 per 1000.

 

Ammo type and brand might be a factor; perhaps Brand-X doesn't like this stuff.  (My self-defense ammo, and occasional range ammo, is 124 grain).

 

My first P320, actually a M18, does fine with this stuff and gives me good groups.  The Brand-X barrel I bought expanded that to 6" groups at 7 yards.  I ordered a KKM barrel that may require a little fitting and will see what it likes; I can fit the barrel hood anyway if needed.   The standard twist rate for Sig barrels in the P320 is 1:10; for the Brand-X barrel, also 1:10; for KKM, the standard twist rate is 1:16.  We'll see if that has any practical effect on how the pistol shoots.

 

I'd like to send three P320 family pistols out to Bar-Sto or KKM to have them fit a barrel; maybe I can do that later.  We'll see how the KKM drop-in barrel works.   I'd watch out for Brand-X -- not a great product and not "drop-in" in the English language sense of the words. 

 

 

[RangerTrace]

My answer was a little too short.  A drop in might have some benefits over OEM, but a fit barrel will give you the best accuracy improvement.  I've tried all the Glock barrels and KKM gave me the best accuracy.  I fit a semi-fit Barsto barrel to my GGI 3.9" gun, but the chamber was too tight.  Barsto fixed it, but now its pretty sloppy.  I haven't had time to shoot any groups with it, but it feeds everything.  

[RoverSig]

Reviewing the Bar-Sto and KKM web pages, it reads like a fitted aftermarket barrel can achieve very good accuracy (1.5 to 2 inches at 25 yards from a rest). 

 

It is my guess that a semi-fitted or drop-in barrel can achieve good accuracy if it matches up with the particular slide with which it will be used (presuming it is of good manufacture, rifled properly, accurate in its own right, etc.).  The problem with the first drop-in barrel I bought, which opened up my groups at 7 yards by 100% spread over the ones I shoot with a stock P320, may be its level of happiness with the particular ammo I am using, or that the particular barrel doesn't fit well with that particular slide.   A gunsmith might fit it a bit better and get better results if it is the latter problem.

 

I would like to send a pistol to Bar-Sto or KKM for them to fit a barrel -- and may do that with the M17 that sits in the safe next to the two P320 Carry models...  

[RJH]

I'd say probably the biggest advantage to aftermarket barrels is that your gun doesn't blow the ejector out

[HOGRIDER]

5 hours ago, RoverSig said:

Reviewing the Bar-Sto and KKM web pages, it reads like a fitted aftermarket barrel can achieve very good accuracy (1.5 to 2 inches at 25 yards from a rest). 

 

It is my guess that a semi-fitted or drop-in barrel can achieve good accuracy if it matches up with the particular slide with which it will be used (presuming it is of good manufacture, rifled properly, accurate in its own right, etc.).  The problem with the first drop-in barrel I bought, which opened up my groups at 7 yards by 100% spread over the ones I shoot with a stock P320, may be its level of happiness with the particular ammo I am using, or that the particular barrel doesn't fit well with that particular slide.   A gunsmith might fit it a bit better and get better results if it is the latter problem.

 

I would like to send a pistol to Bar-Sto or KKM for them to fit a barrel -- and may do that with the M17 that sits in the safe next to the two P320 Carry models...  

Having sent my MAXX to Robert Burke for his competition action job and custom barrel, I would highly recommend you talk to him about doing the install/fitting!  Highly recommended!  And he'll take time to discuss your needs and his recommendations over the phone!

 

https://www.thesigarmorer.com/#home-1

[RoverSig]

I sent a contact email to the Sigarmorer to ask about fitting a 4.7" Bar-Sto or KKM barrel my M17.  

 

For the P320 Carry build, since this is a build with a new FCU ($219) from a M17 that was stripped for parts, a left-over WC Carry II grip module, and a new slide I purchased from Sig -- I needed a barrel.  There was no "factory barrel" in the first place, so now I am going to see how the KKM "drop-in" barrel works.  The other P320 Carry (well, really a M18) I've had seems to work pretty well with the Sig factory barrel so expensive improvements on that can wait.  

[RoverSig]

I ordered a KKM drop-in barrel from MGW for the P320 Carry and am very impressed by how accurately it shot today.  The next step is to consider having Sigarmorer fit a 4.7 Bar-Sto barrel (with the LCI) to the M17.   

 

So not all problems are the gun, some are the shooter; but having a barrel I know is accurate (e.g., in this case, the KKM 3.9" drop-in) takes away worrying about the gun and allows me to concentrate on my shooting - grip, sight picture, trigger press, etc. 

Edited November 29, 2023 by RoverSig

[LMS]

I think it also may be kind of a crap shoot as well.   After shooting my X5 Legion for a while I started chasing more accuracy.   I sent the gun to Barsto for a fitted barrel.    I got more accuracy with it but also got some ammo fussiness.  

 

Then I read enough here and other places to be convinced it's not the barrel that's the problem, accuracy-wise, it's the slide.   So bought a Gray guns classic slide set up, which came with a Sig barrel.   Better accuracy than the Barsto setup, so I was convinced about the slide theory.

 

Then when the "my sig just blew up" issues started popping up, and it looked like part of the problem might be the depth of seating of the round in the Sig barrels, I bought a KKM drop in barrel.    I put the KKM in a stock slide, and damned if it's not just as accurate as the Grey slide with Sig barrel.

 

I've heard that Gray now ships their slides with a Faxon barrel, but I've thrown enough money at this as it is.