Gunsmithing Thinking the Smith screwed my barrrel

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Minuteman
Oct 5, 2018
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Pondwater Colorado
#1
I acquired a Howa mini 1500 (20" heavy) in 65 Grendel that shot sub .7 @ 100 with my 123 ELD home brew, Moscow Match and Hornady Black 123s.

I had a local Smith thread the barrel for a brake and suppressor.

Started working on load development with RDFs and 130 ELDs and well that sucked. Just could not find anything that worked well or consistent. It occurred to me that the brake I was using was maybe causing a problem so I put on my MPA brake from my PRC. Same crappy results with known good ammo which threw me. Tried running bare barrel and the impact shift @100 was left 8" and 13" low and still shitty groups. WTF???? My Omega 30 does not even cause that much POI shift on my other rifles.

Could simple threading (which are stupid tight) cause this kind of screw up? The crown looks fine, still recessed - 11* I think. I know he turned it in a lathe to cut the threads so I am not quite sure what is going on. No baffle strikes or key holing down range.
 
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#2
Done right, muzzle threads must be coasial with the bore, not the OD. I set up a barrel for muzzle threading just like I do for chambering. I install the brake, then make a cleanup cut on the bore of the brake (or even better buy the brake undersized and bore it after installed). This ensures the bullet exits the center of the brake--it's the last influence on the bullet as it leaves the barrel.

If he just threw it in a 4 jaw and threaded it, the bullet may not be going through the center of the brake. Windage would be much stronger on the closer side and deflect the bullet.

--Jerry
 
#5
"If he just threw it in a 4 jaw and threaded it, the bullet may not be going through the center of the brake. Windage would be much stronger on the closer side and deflect the bullet"

He said it wouldn't shoot with nothing on the barrel.
 
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#6
Button rifled or hammer forged barrel?

If so, find someone (machinist, or your GS if he has them) with gauge pins and see which diameter pin is the largest that will go at least 1" into the muzzle end. If a .258" pin will go into the bore .2-.5" then stick, you have your problem.

If not, could be an entirely wonky crown/thread job. Hard for us to know without being able to indicate the barrel and see what's up.
 
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#7
Anytime you remove enough metal to thread 5/8x24, it causes the muzzle to bell ever so slightly.
There is actually a you tube video showing the phenomenon.
Could it have been caused by the smith? Yes.
Is there a burr on the inside of the muzzle?
 
#8
To be clear, it only happens in barrels that have pent up hoop stress present BEFORE cutting the muzzle. Typically you see it in button rifled barrels that haven't been properly stress relieved. You don't see it in properly stress relieved button barrels (rock creek, benchmark, etc..), nor in cut rifled barrels.

Most factory-grade barrels are button-rifled, however.
 
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#9
The rifling is what ever Howa does on their factory Heavy Barrels.

Same smith did three other actions for me (all 4 of them were cut to 5/8 - 24), and those still shot sub MOA after I got them back. In hindsight, the red flag should have gone up when I had to take them back as none of the three brakes that I had for them would thread more than one rotation before they locked up. I had to bring all three of them back with the brakes for him to "re-do".

If the threads are cut with not enough clearance, or none at all, would mounting said brake compress the muzzle enough to cause distortion?

I brought him the brake with the barrel on this one. I did not want to make a return 75 mile trip again.
 
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#10
Without a muzzle device in hand, many will err on the big side of thread specs, easier to remove than replace material, but the accuracy and POI issues after the work make the work suspect.

Maybe try to find another GS to check it out or see if the original GS will give it a once-over to see if he can fix it.
 
#11
Threading by using the attachment as the gauge is wrong , the threads to be correct either need checked with a thread gauge or precision measuring tools such as a thread micrometer or thread wires .

Best bet is to cut your losses and cut the barrel and start over with someone who has the proper tools .
 
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#13
I have Remington XR100 with a factory barrel that shots .2 easily. I had a machinist/gun smith (he does a lot of work locally and turns out some great shooters) thread the muzzle for a brake/ suppressor adapter. I told him to thread it 5/8-24 but somehow it ended up 5/8-18. So he made a brake, but it was mostly a thread protector and something to cover the sloppy threads.

After it was all said and done the gun shot about .7-.8. I kicked myself but chocked it up to a lesson learned. Later on I sent some stuff to SAC and sent that barreled action and had the proper thread job done by mark and it shoots the same as it did before it was touched. Doesn’t matter if the adapter or suppressor is on, it shoots the same size group now. I was sooo relieved.

I never did see any issue with the crown or any other issue other than sloppy threads to cause it to shoot so drastically different.

Hope you get it sorted!
 
#16
ss go devil said:
Whatever you are threading to the barrel needs to be with the smith to get the best accuracy. Run the accessory half way down the thread and it it wobbles its not a machinists fit.
Click to expand...
This day in age, and especially usage typical with this site, threading to a spec makes much more sense than threading to a single muzzle device. Two weeks from now when the next latest and greatest muzzle brake or suppressor hits the market, you're going to be bummed to find it wont fit your muzzle.
 
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#18
" Machinist fit " translates to too cheap to buy the proper tooling to measure the threads with and too lazy to look up the thread specification in the " machinists " handbook .

There are specifications for different thread types and fits for a reason . The way to check threads is with proper tooling not some mystery flash hider that has been setting on the lathe that is being used in place of calibrated gauges .
 
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#22
ss go devil said:
If your looking for extreme accuracy you need to thread to fit the accessory/action/brake/suppressor.
Click to expand...

If your gunsmith is telling you this inform him that you'll buy him a set of 0-1 PD mics in trade for the next thread job he does for you.


We never thread to fit on muzzles and only under rare cases will do it for actions. Even then I still mic or wire the threads so that we can laser the information on a tracking tag to accompany the receiver in perpetuity. This way the customer can have barrels made without sending the rifle in another time.
 
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#26
I'll usually fluff the end of the qtip out before dragging thru, yes if there is some pickup or a burr it might be accessible enough to remedy fairly quickly. Have had 2+MOA guns go to 1/2MOA after correcting.
 
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