HKPRO Forums banner
1 - 20 of 33 Posts

·
Vendor
Joined
·
8,218 Posts
Discussion Starter · #1 · (Edited)
While working tonight (morning) at the shop, it hit me... HK "swags" the barrels on the HK41x and I believe as well on the MR-series firearms. For those of you who do not know, "swag" is the term HK uses to refer to the bore tapering towards the muzzle.

My understanding is that the bore is slightly oversize at the chamber and several thousandths undersized at the muzzle. This "swag" is what HK attributes the ability to get better accuracy with shorter barrels.

What I do not know is if the degree of "swag" is constant with all barrel blanks or if it is based on barrel length. If based on barrel length, you could be ruining your MR-series barrels by cutting them down.

Since the specifics are R&D information from Germany, I doubt I will have any luck finding answers as the folk down in Columbus probably will not know either, but I will put a call in and see if someone can find out.

UPDATE:

Straight from the US/German Operations coordinator...

"Important dimension are the diameter at the beginning of the rifling and the diameter at the muzzle. Therefore the angle of the "swage" varies between the different barrel lengths. At HKO every barrel length is forged differently.

Cutting a barrel to e.g. a length of 14.5" - instead of using a "real" 14.5" barrel - will have a negative effect on performance of the rifle and is not recommended."

So take it for what you will as the type of shooting you do may not matter the loss in accuracy, however when I asked about the warranty the US Technical Liason answered...

"Absolutely voids any warranty."
 

·
Premium Member
Joined
·
1,736 Posts
Joe, I think you meant swage, but thats good info to have that H&K is tapering their barrels.

This is one of the pluses of hammer forging; you can make a barrel with a taper.

I would imagine this is much harder, if not impossible to do this with button/cut rifling without changing the depth of the rifling.
 

·
Registered
Joined
·
202 Posts
FN also does this with the SCAR. I know over a dozen of people personally who bought SCAR-16S rifles and cut them down with no appreciable loss in accuracy, knowing beforehand that this was a design feature of the SCAR barrel. I know 4 people whose MR556 barrels have been chopped as well with no real loss. Maybe if we bench rested them with a high magnification scope and match ammo there might be a slight fall...maybe..., but not enough to make a difference or notice in any other type of shooting. I wouldn't sweat it too much.

ETA: just got off phone with Larry Vickers about this...when asked if it would make a measurable difference to cut it down, assuming it was done properly/professionally with no workmanship issues at the crown or with the gas system, "My guess is no, it won't matter"
 

·
Registered
Joined
·
263 Posts
Wow!!...This discussion came up yesterday at my LGS regarding my MR556. He was suggesting/throwing out and idea of cutting the bbl down and that they've done this w/ very good results but on other makes of AR platform rifles but did reiterate that they haven't done it yet w/ an HK. Thx for this topic, good timing Chopstix! :wink:
 

·
Vendor
Joined
·
8,218 Posts
Discussion Starter · #6 ·
Joe, I think you meant swage, but thats good info to have that H&K is tapering their barrels.

This is one of the pluses of hammer forging; you can make a barrel with a taper.

I would imagine this is much harder, if not impossible to do this with button/cut rifling without changing the depth of the rifling.
Lol, I was going by how they were pronouncing it, no idea how it was spelled. Thanks!

As for the other comments, I kinda figured it might not be an issue as well but better safe than sorry. Worse case it may void your warranty. I'll get as much info from HK as I can. Thanks for the feedback.
 

·
Registered
Joined
·
3,466 Posts
I think, from what I saw in MRs with cut barrels, that cutting MR barrel for eg to 14.5 may reduce barrel accuracy but it will still outshoot most other 14.5 barrels, bare custom ones.

There are already several people here, who shortened MR barrel, so they can chime in with accuracy reports.
 

·
Premium Member
Joined
·
3,930 Posts
In theory, I think you may lose some accuracy just by cutting a 16.5 inch barrel down to 14.5 inches, and even more cutting it down to 10.5 inches, swaged or not. Personally, I don't see that cutting it down to 14.5 is going to make a measurable difference in accuracy beyond what you'd see from shortening any barrel of similar profile by 2 inches.
 

·
Vendor
Joined
·
8,218 Posts
Discussion Starter · #9 · (Edited)
Ok, that was quick! Straight from the US/German Operations coordinator...

"Important dimension are the diameter at the beginning of the rifling and the diameter at the muzzle. Therefore the angle of the "swage" varies between the different barrel lengths. At HKO every barrel length is forged differently.

Cutting a barrel to e.g. a length of 14.5" - instead of using a "real" 14.5" barrel - will have a negative effect on performance of the rifle and is not recommended."

So take it for what you will as the type of shooting you do may not matter the loss in accuracy, however when I asked about the warranty the US Technical Liason answered...

"Absolutely voids any warranty."
 

·
Registered
Joined
·
518 Posts
I was going to mention what M4guru said...FN SCAR barrels are swaged as well, and while not based off a large sample...I've seen several people mention that their SCAR's shot just as accurate, if not a little more so after cutting their 16" barrels down to 10" Of course this is a different rifle and different barrel, so the results may not be the same.

Anyhow, great information Chopstix, and thank you for sharing your correspondence with Hk!
 

·
Registered
Joined
·
263 Posts
Ok, that was quick! Straight from the US/German Operations coordinator...

"Important dimension are the diameter at the beginning of the rifling and the diameter at the muzzle. Therefore the angle of the "swage" varies between the different barrel lengths. At HKO every barrel length is forged differently.

Cutting a barrel to e.g. a length of 14.5" - instead of using a "real" 14.5" barrel - will have a negative effect on performance of the rifle and is not recommended."

So take it for what you will as the type of shooting you do may not matter the loss in accuracy, however when I asked about the warranty the US Technical Liason answered...

"Absolutely voids any warranty."
Well...that answers that! Looks like I'll just try and find an OEM shorty upper from somewhere and fork over my wallet and keys to the truck.
Thx for the info Chopstix
 

·
Banned
Joined
·
879 Posts
I'm pretty sure that any change in performance won't be noticed by the average shooter, much less the more proficient shooters.

Cutting the barrel certianly doesn't "ruin" it by any stretch of the imagination.

As I said, i've managed to pull out at least one 1 1/4 inch group at 100 yards with a magnified RDS, so I'm not too terribly worried about it.

Accuracy testing as well as DI parts interchangeability testing to be done this weekend.
 

·
Vendor
Joined
·
8,218 Posts
Discussion Starter · #14 ·
I do not know if the swage on the SCAR is constant or if it is specific to barrel length as with the 41x/MR-series. Just passing along info and as with anything, do with it as you will.

But please keep in mind that it does void the warranty on the entire firearm. I know in the past some firearms have still been warranteed despite modifications, however I am under the impression that a barrel cut will indeed void ALL warranteed repairs on the MR-series.
 

·
Registered
Joined
·
269 Posts
I do not know if the swage on the SCAR is constant or if it is specific to barrel length as with the 41x/MR-series. Just passing along info and as with anything, do with it as you will.

But please keep in mind that it does void the warranty on the entire firearm. I know in the past some firearms have still been warranteed despite modifications, however I am under the impression that a barrel cut will indeed void ALL warranteed repairs on the MR-series.
Can you buy a barrel from HK in the 10.39"? If you can how easy is it to change the barrel? Can you send an upper to HK and have them do it?
 

·
Registered
Joined
·
1,690 Posts
Chop - to make sure I get what you're saying - because the barrels **inner** diameter (where the bullet passes through) is wider at the chamber end and smaller at the muzzle essentially making it a tighter hole for the bullet to pass through when fired, cutting the barrel shorter means the new muzzle end wont be as tight at 14.5 than the factory 16?

What I'm getting from this is that its more than the age-old issue of a shorter barrel = less accurate because of velocity, but because the muzzle hole is wider at 14.5 than 16 - yes?
 

·
Registered
Joined
·
765 Posts
This is one of the pluses of hammer forging; you can make a barrel with a taper.
Possibly even actually required in hammer forging, in order to be able to remove the mandrel. I've never done the process, but I could imagine that a perfectly straight mandrel would be significantly more difficult to remove than a tapered one.
 
1 - 20 of 33 Posts
Top