Larger Threads At End of Barrel?

[EzGoingKev]

I was looking at some barrels for sale here and am seeing some barrels having 5/8x24 threads which is typically used on .30 caliber barrels.

The reasoning is listed as:

"NOTICE*** THIS BARREL HAS 5/8-24 threads to keep the bore at the muzzle from swelling like most barrels threaded 1/2-28. The tighter bore at the crown gives better accuracy."

I would love to see people who have experience with a barrel configured like this. It would be great if there was some comparison data.

Would I would not love is posts from people with no experience with these barrels, posts from people who had ask where the bullets go, etc.

[tom12.7]

.625" threaded .223/ 5.56 barrels have been known to be better than the .500" threaded ones for a "bell mouthed muzzle" for a long time now. Even before the initial AW ban, this was done by some. Supply and demand really limited this better offering. Even now, there is still little demand.
This is pretty much the reason that KAC uses .750" threads on their SR-25's now and for a while.
The question really is to how this effect compares to other precision or accuracy issues for a lifespan of use?
There's a lot going on in a barrel, look at the "needs" and apply those while reducing negatives. Many guys have been using 7.62 MD's on 5.56 platforms for a potential for some time now.

[Clint]

Theoretically, the crown of a properly stress relieved barrel shouldn't swell due to the smaller muzzle thread.

But from a structural standpoint, our view is that 5/8-24 threads are actually a better match for .750 gas block journals, while 1/2-28 threads are a good match for .625" gas block journals.

Barrel profile continuity can be a key feature and appropriately sized threads contribute toward this goal.

Larger threads are stronger, stiffer and exhibit less flex. Period.


Many muzzle devices are available in either thread pattern, especially as the 300BLK and 6.8SPC variants have grown in popularity.

It seems there is also a trend toward using smaller 30 caliber suppressors to handle anything from 5.56 to 300BLK.

These tend to have 5/8-24 threaded mounts as well.



Our SPR barrels feature the larger threads for all the above reasons.

http://www.blackrivertactical.com/co...tegory=1852006

[EzGoingKev]

This is pretty much the reason that KAC uses .750" threads on their SR-25's now and for a while.

OK so I read that and googled "3/4" thread muzzle break" to see how common they were and to get an idea as to what calibers are normally associated with that thread size. Interestingly enough this was in the results.

http://bulletin.accurateshooter.com/...oo-much-steel/

[Clint]

Great article.

Most barrels do not exhibit the same kind of static bore expansion demonstrated in the videos, but obviously it can and does happen in certain circumstances.


For a little comparison,

5/8" threads on a 22 caliber bore have approximately the same wall thickness as 3/4" threads on a 30 caliber bore.

Both could be considered larger, heavier duty combinations.

The "standard" 1/2" threads on a 22 caliber bore and 5/8" threads on a 30 caliber have roughly 2/3 the wall thickness of the heavy duty versions.

[Junkie]

And if you really want to look at thinner walls, my Keltec Sub2000 has 1/2-28 on 9mm. Then again, a blowback PCC isn't a match grade gun.

I wonder whether anyone profiles the barrels first and then rifles them, it seems like that might be possible too.

[EzGoingKev]

Our SPR barrels feature the larger threads for all the above reasons.

@ Clint, prior to releasing your SPR barrel did you do any testing that compared 1/2" threads vs the 5/8" threads?

[SomeOtherGuy]

I have two of Harrison's 16" 5.56 NATO barrels with 5/8x24 muzzle threads. I have not done any rigorous testing, but they seem to be relatively accurate.

If you can find a muzzle device you like with those threads - and he makes all his options with those threads - then I see no disadvantage. I imagine that the overall weight would be a break-even since the greater mass at the tip of the barrel is offset by less mass in the muzzle device.

[EzGoingKev]

I have two of Harrison's 16" 5.56 NATO barrels with 5/8x24 muzzle threads.

Pardon my ignorance but googling multiple derivatives of harrison ar barrel did not bring anything up. Who is Harrison?

[SomeOtherGuy]

AR15 Performance, the company you posted about, is owned by a man named Harrison Barnes. He posts on here occasionally as Constructor. So when I said "Harrison's barrels" I meant those sold by AR15 Performance.