First Build Help - DM Hardware

Yes, it can be legal to make a silencer. For everything Form-1, from silencer designs that are easily made, to filing forms with the BATF, to 3D modeling. Remember, you must have an approved BATF Form-1 to make a silencer. All NFA laws apply.

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d-fi
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First Build Help - DM Hardware

Post by d-fi » Fri Dec 02, 2016 12:11 am

I am finally getting around to getting my first form 1 build going, and I am running into some issues. I am using endcaps and tube from Diversified Machine, with the YHM QD adapter. I am having some significant concentricity issues, and something is not correct in either the tube or the endcap. My suspicion is either the tube or the YHM endcap adapter. I have tried two different YHM QD mounts on three different host barrels, and get similar results - when checking with an alignment rod, I am way off center. The endcaps and baffles are rubbing and visibly off center, especially when getting to the end of the tube.

With the endcap off, I took some measurements, and its bad. These are from the inside of the tube to the edge of the alignment rod:

Left = 0.632
Right = 0.660
Top = 0.662
Bottom = 0.667

The rod is too far up and left from the perspective of center.

Also, I have been emailing Chris from DM a few times since November 20th, and got no response. I had also ordered some other gear for another build from the web site over 10 days ago (in stock parts) and no response from that either.

Thoughts / advise / help?

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Bah21963
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Re: First Build Help - DM Hardware

Post by Bah21963 » Fri Dec 02, 2016 1:00 am

Hsve you checked the muzzle device with the alignment rod. Do you have another suppressor with the yhm adapter you can check on the host with problems. Another thought did you use a crush washer. If so take off the crush washer. Have you tried using some precision washers between the barrel and muzzle device. One last thought try a precision nut on the barrel without locking again't the barrel shoulder.

I have many tubes from DM and have not had a problem. You could also use the contact form on his website. DM is a member of the form1suppressor.boards.net and is on line almost daily. You could head over there and send him a pm. His user name is DM.

cdakers
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Re: First Build Help - DM Hardware

Post by cdakers » Sat Dec 03, 2016 2:46 am

I assume you have checked to make sure your alignment rod is straight? Just a thought.

Historian
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Re: First Build Help - DM Hardware

Post by Historian » Sat Dec 03, 2016 8:39 am

Might be just the way your camera was positioned but it
seems that the front hole is off center.

Take a caliper and measure some of the distances between the
outer edge of the inner hole and the outer circumference.
If they vary then the hole is off center.

Do the same thing with the baffles.

Did you get a good price on them?

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cdrissel
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Re: First Build Help - DM Hardware

Post by cdrissel » Sat Dec 03, 2016 11:01 am

Check your rod. Is it from CNC Warriors?

One of theirs was bent when I got it - I contacted them and the sent me a new one.

If your rod is straight I would check your bore to barrel threads for concentricy. Also check if the tread shoulder is perpendicular to the bore. If it's not that can cause the muzzle device to be out of alignment.

I've had no issues with DM's parts. Only with bore to thread issues.

vaeevictiss
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Re: First Build Help - DM Hardware

Post by vaeevictiss » Sat Dec 03, 2016 9:02 pm

If it is their stuff im sure they will make right. They are top notch just SUPER busy.

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d-fi
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Re: First Build Help - DM Hardware

Post by d-fi » Wed Dec 07, 2016 9:11 pm

So, I had a thought today - it could be that the YHM QD mount needs to also index inside the can. I believe that this is how the YHM cans are built. I think they use the acme threads and spring to lock to the QD mount, but also have an internal ring that indexes to the end of the mount. Having a second index point would definitely align everything vs. depending on the large acme threads and spring to hold everything true.

Any thoughts and experiences on using a YHM QD on a form 1 can are appreciated. Should have some time to make something on the lathe to accomplish this in the next week or so and I will report back.

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yondering
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Re: First Build Help - DM Hardware

Post by yondering » Fri Dec 09, 2016 3:30 am

You are certainly not the first I've heard of to have alignment issues when using YHM mounts. I don't know if it's the mount in your case, but it seems to be a common factor.

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John A.
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Re: First Build Help - DM Hardware

Post by John A. » Fri Dec 09, 2016 1:31 pm

Another question besides the rod being straight, have you tried to use shims between the barrel shoulder and the muzzle device? I don't mean a crush washer, I mean actual shims.

You can often reduce or eliminate concentricity problems from doing that. It's a $5 option to try and what do you really have to lose in trying it?

gemtech makes a really good set of shims just for that very reason.
I don't care what your chart says

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d-fi
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Re: First Build Help - DM Hardware

Post by d-fi » Fri Dec 09, 2016 3:36 pm

So, I spent about two hours checking the alignment on four different barrels (YHM, LBE, RRA, and CMMG), using two different muzzle devices (YHM QD brake and YHM QD flash suppressor), and flipping the tube around as well. Total configs to measure was 16. I used shims from a Precision Armament Accu-Washer kit to time the muzzle devices to maintain the correct orientation when measuring.

Conclusion? All configs were approximately off by the same amount and direction. Yes, there were variances between the barrels, but for all configs, the alignment rod was closer to the right side of the tube than the left side, but approximately .040. The rod is also off from the vertical position, but only by .010 to .015.

Also, it is a Geissele alignment rod that I am using to true up everything.

I am going to turn a tube insert to index the can to the brake inside the suppressor and see how that helps. I did get a chance to speak with Chris at DM and he stated that a lot of customers have issues getting good alignment with the YHM QD on Form 1 cans. He offered to make another QD end cap if needed, so A+ there. I will just see how it goes after I try turning the new part.

speed6
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Re: First Build Help - DM Hardware

Post by speed6 » Fri Dec 09, 2016 4:17 pm

This has inspired me to get a griffin adapter instead of the YHM mount. I have several approved form 1s and need a multi-caliber can ASAP. By the way, DM got my griffin mount shipped out 3 hours after I ordered it :shock: .

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