View Full Version : Tough one to figure out
belizejet
09-12-2015, 08:11
I have a BHW 18" barrel in 6mmx45. Last year I had it built up on an upper and loaded a ton of different ammo with it. I did a lot of testing. I was getting near MOA groups with 70grn nosler BT varmint loads behind H-335. I loaded about 100 of them and was preparing to use it for varmint hunting. I then decided that I wanted to get the barrel threaded because it was just target crowned. I took the upper apart and sent in the barrel and a silencerco QD muzzle break so I could use my suppressor on it. Got it back and it looked great. Built the upper back again and took it to the range to sight it back in with the can on it. I decided to use the same ammo that was giving me pretty good result from before. This was from the same batch I had loaded before about a year ago. I couldn't get the thing to hit paper at 50 yards after bore sighting. I finally moved up to 25 yards. The bullets were hitting the paper sideways!!! I took the can off thinking that we effecting it. With just the brake on it it was still tumbling bullets at 25 yards!! Same rounds I was getting 2.5 in groups with 200 yards was now not even MOA at 5 yards. I checked the brake and it seems aligned. I'm stumped. Next step is to take off the brake and shoot it without. I ran out of time before I could do that. I'm guessing either I built the upper up wrong or the barrel got screwed up at the smith who threaded it. Any thoughts? I've built a bunch of uppers (10 or 11) and never have seen this before.
Great-Kazoo
09-12-2015, 09:39
Possibly the crown. OR................ the brake is just tight enough (diameter wise) it's throwing your shots off. Have you measured the clearance? I had a similar issue with YHM brake. Threw it on the lathe, opened it up to the next size and no problems.
BPTactical
09-12-2015, 13:59
I would check the threads for concentricity and the brake for same. Pull the brake and check for any evidence of strikes.
Unless you have a well practiced eyeball for anomalies such as this your eye won't tell you much.
A suppressor alignment rod or range rod would be a more accurate method.
I can check it if you like.
Nothing you did as far as a build would cause keyholes to the best of my knowledge.
I would say you sent the barrel to the wrong Smith.
I would say you sent the barrel to the wrong Smith.
I agree.
belizejet
09-13-2015, 20:08
It could be the brake being too close in tolerance. It's a .223 brake from silencerco which is measured at .25. I was shooting 6mm (.243) through it. Not strikes on the brake so maybe it just needs a few more thousandths.
Only time I've had that happen is with a poorly threaded barrel that caused hits to the end of my brake, 3" from the end of the barrel.
I opened up the brake and it shoots fine. Can't ever put a suppressor on it though.
Since it's an 18" barrel, you can have it cut back and re-threaded - by a different gunsmith.
eneranch
09-14-2015, 08:36
It could be the brake being too close in tolerance. It's a .223 brake from silencerco which is measured at .25. I was shooting 6mm (.243) through it. Not strikes on the brake so maybe it just needs a few more thousandths.
Probably should have led with that.
One would think a qualified gunsmith should have caught this.
belizejet
09-15-2015, 06:10
Really? I thought it would perfectly. Live and learn I guess.
eneranch
09-15-2015, 06:24
Once you get it fixed, let me know how it shoots.
You changed the barrel harmonics. That means you need to develop a new load.
Nor saying anything said above is inaccurate, just saying you need to do load development whenever you change the size, weight, characteristics of the barrel.
You changed the barrel harmonics. That means you need to develop a new load.
Nor saying anything said above is inaccurate, just saying you need to do load development whenever you change the size, weight, characteristics of the barrel.
Not that this is bad advice but barrel harmonics aren't going to cause rifle bullets to keyhole at 25 yards.
Running a 223 brake on a 243 is definitely a no-no and I'd be willing to bet a dollar that's the whole problem.
Great-Kazoo
09-15-2015, 10:23
Not that this is bad advice but barrel harmonics aren't going to cause rifle bullets to keyhole at 25 yards.
Running a 223 brake on a 243 is definitely a no-no and I'd be willing to bet a dollar that's the whole problem.
That's the 1st thing the OP (or anyone) should check. Especially when using a m/brake or flash hider that's not for that specific caliber.
belizejet
09-15-2015, 19:18
It's actually .255. Plenty of room for .243.
belizejet
09-15-2015, 19:19
Silencerco oversizes muzzle brakes. The .30 cal is .34
belizejet
09-15-2015, 19:21
Probably why the brakes don't work that well. They have lots of room. I'm still confused as to why this would cause problems. You seem to act as if it's a no brainer but I'm perplexed. Never come across this before.
Everything seems like a no brainer once you already know the answer.
XC700116
09-15-2015, 20:15
As info, a properly sized bore for any brake is at least .020" over bore diameter, so that's .263 for a 6mm, I'm not saying that's definitely the cause, but you're cutting it pretty close.
It has to do with how the bullet and the gasses pushing it leave the barrel. It's why sometimes a ding in the crown of a barrel can make it shoot less than the barrel is otherwise capable of.
belizejet
09-15-2015, 20:29
Thanks for the help. I'm going to shoot it with the muzzle brake off and if it works then I guess I get the brake bored out a bit.
AAC M4-2000 - 0.275" blast baffle bore, 0.300" end cap bore. 0.275 - 0.223 = 0.052
YHM Phantom - 0.241" blast baffle bore, 0.296" end cap bore. 0.241 - 0.223 = 0.018
Yours - 0.255 - 0.243 = 0.012
Your bullets are grazing the muzzle brake because the hole be too small.
belizejet
09-15-2015, 21:01
No marks on it. I looked. I figure the gas discharge is making the bullets fly different.
Your best bet would be to take the rifle along with a 25 yard target with the key holes to the guy that did your work and ask him "WTF?"
belizejet
09-27-2015, 23:48
Ok guys. I just couldn't believe that they did that bad of a threading job but when I looked closer, I did see some evidence of strikes on the brake. I re measured the inner diameter and it was actually closer to .260 with my calipers. If I look hard I can actually see the offset of the threading. I'm pissed. I have to confront the smith and see what they will do before I publicly bad mouth his work by name. He does a lot of work maybe a new worker did it or something.
dustdevil
09-28-2015, 14:25
Mod edit
A gentleman does not have drinks before dinner...
Ok guys. I just couldn't believe that they did that bad of a threading job but when I looked closer, I did see some evidence of strikes on the brake. I re measured the inner diameter and it was actually closer to .260 with my calipers. If I look hard I can actually see the offset of the threading. I'm pissed. I have to confront the smith and see what they will do before I publicly bad mouth his work by name. He does a lot of work maybe a new worker did it or something.
Glad you found the culprit.
Hope they make it right for you.
If this guy doesn't make things right with you, post up who they are so you may save someone else from a bad decision.
belizejet
09-28-2015, 22:58
I never saw dust devils response until now. Such a positive person. Thanks for the insults and lack of help. Way to make a guy feel better that has the same common interests and beliefs about protecting our freedoms. For some reason I always thought these forums were for helping and unifying us. Btw, you have no idea about me, what I do, and my little brain and i'd just as soon keep it that way. I guess a gunsmith that can't measure .027 is a good one in your book.
BPTactical
09-29-2015, 06:09
Belizejet- if your "Smith" won't do you right come see me.
I'll fix it, and it won't cost you much more than gas for the drive.
Stories like this are why it is critical to know at least a bit of the process that is involved when you are requesting work to be done. You need to ask the right questions.
Does the "Smith" reference the centerline of the bore? What does he do to ensure concentricty AND axial alignment.
Does he use a 3 jaw, 4 jaw or collet to hold the barrel?(hint- only one answer is correct.)
Hope your guy does you right, if not holler.
Trick question. Everyone knows you only use a 13 jaw, obviouslly.
Great-Kazoo
09-29-2015, 08:10
Trick question. Everyone knows you only use a 13 jaw, obviouslly.
There was no slack jaw in that poll.
Trick question. Everyone knows you only use a 13 jaw, obviouslly.
It was a trick question. The answer is "none of the above". We all know Bert uses a hacksaw, a dull file, and a set of dies from Harbor Freight.
[Coffee]
I am only kidding of course. Bert is one of the few people I trust to work on my stuff. If he can find a way to do something beyond perfect he will.
The answer is "freaking lasers"...
Powered by vBulletin® Version 4.2.3 Copyright © 2025 vBulletin Solutions, Inc. All rights reserved.