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Thread: Need a gunsmith recommendation for drilling a barrel and gas block.

  1. #1
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    Need a gunsmith recommendation for drilling a barrel and gas block.

    I have an SLR GB-7 low-pro gas block and a Daniel Defense barrel that DD no longer sells (16" mid-length S2W). The gas block comes with a roll pin, but I'd like to use a taper pin instead. Is there a go-to gunsmith that the M4C hive mind recommends? Need the barrel drilled for both the set screw and the pin, and the gas block has a starter hole where the roll pin goes but needs to be drilled as well (which is why I'm assuming I can convert this to a taper pin).

    Thanks.

    (Also, if I'm wrong about preferring a taper pin please educate me.)

  2. #2
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    Quote Originally Posted by Bryson View Post
    I have an SLR GB-7 low-pro gas block and a Daniel Defense barrel that DD no longer sells (16" mid-length S2W). The gas block comes with a roll pin, but I'd like to use a taper pin instead. Is there a go-to gunsmith that the M4C hive mind recommends? Need the barrel drilled for both the set screw and the pin, and the gas block has a starter hole where the roll pin goes but needs to be drilled as well (which is why I'm assuming I can convert this to a taper pin).

    Thanks.

    (Also, if I'm wrong about preferring a taper pin please educate me.)
    IMO... I would be comfortable with just the set screw. There are no forces trying to rotate the GB. To me the adjustable GB is more of a liability than the set screw mount. I am assuming the barrel is new and not drilled.

  3. #3
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    I’m on the other side of the fence. I have set screw GB’s but prefer pinned.
    Contact Marvin Pitts. He pins GB’s for $45. It sure if your requirements would impact that or not. He’s an awesome barrel guy. He’s an awesome guy.

    nefariousarms@live.com

    You can also reach him on Facebook. “Nefarious Arms”
    Last edited by RobertTheTexan; 06-06-18 at 20:00.
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    John Thomas is the man. Great work and turn around time. Fair pricing. Much preferred to anyone else I have used
    http://www.retroarmsworks.com/

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    If you email him he will get back to you shortly. Was very responsive when I contacted him

  6. #6
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    Quote Originally Posted by Bryson View Post
    I have an SLR GB-7 low-pro gas block and a Daniel Defense barrel that DD no longer sells (16" mid-length S2W). The gas block comes with a roll pin, but I'd like to use a taper pin instead. Is there a go-to gunsmith that the M4C hive mind recommends? Need the barrel drilled for both the set screw and the pin, and the gas block has a starter hole where the roll pin goes but needs to be drilled as well (which is why I'm assuming I can convert this to a taper pin).

    Thanks.

    (Also, if I'm wrong about preferring a taper pin please educate me.)
    My correspondence with Criterion Barrels Tech Support told me that they do not recommend using taper or roll pins, just set screws, and the taper pins displace barrel material and both can affect harmonics. Here is a quote from them...

    "From: CBI Customer Service
    Sent: Monday, May 14, 2018 1:10 PM
    To: 'John'
    Subject: RE: Enquiry John

    John,

    I think that you would be very well pleased with one of our chrome lined barrels. In my opinion they are the finest chrome lined barrels available anywhere and our record speaks for itself. We hold numerous National Match titles and world records that were shot with our chrome lined barrels. Head-spacing is essential to obtain optimal timing, function, and performance. An improperly head-spaced barrel/bolt combination results in inconsistent chamber pressures which leads to premature wear on internal components like the extractor and the chamber walls. Inconsistent chamber pressures result in accuracy issues. Head-spacing directly relates to consistent seating depths which aids in accuracy and consistency. Lastly, I do not recommend pinning of the gas block, ever... When you drill a hole through the barrel and the gas block and then drive a taper pin through it, material is displaced. This frequently causes crimping of the bore, harmonics issues, etc. Although this practice has been used by the military for decades, it is something that they are moving away from in order to improve upon their 4 MOA accuracy requirements. As an example here is a recent article about a contract put out by the Marine Corps. Take note of the fourth bullet point under "Required Characteristics", it specifically stated that gas blocks are not to be pinned.

    http://www.thefirearmblog.com/blog/2...kly+Newsletter

    Working with a number of firearms manufacturers, I have seen issues occur time and time again as a result of this process. I recommend installing your low profile gas blocks with a small amount of thread locker in conjunction with our set screw dimple. If you snug the screws down (being careful not to over torque) to the barrel your gas block will not move until you want to remove it. I have tested this method under sustained full auto fire and have never had a gas block walk off on me... the only thing separating a hobbyist and a professional is knowledge, skill, and experience (something I work on obtaining every day). Let me know if you have any other questions.

    Sincerely,

    Michael Ross
    CBI Technical Support

    W172 N13050 Division Rd.
    Germantown, WI 53022
    Phone: (262) 628-8749
    Office Fax: (262) 677-2554"
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  7. #7
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    I think gas blocks should be pinned rather than relying just on a set screw and some glue (LocTite). It's cheap and easy, even if you don't do it yourself. I've had gas blocks pinned at Ranier, ADCO, from a local gunsmith, and I did one myself with my good old Sears drill press, all with excellent results. It's a very straightforward process and doesn't require much in the way of sophisticated tooling.

  8. #8
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    Quote Originally Posted by everready73 View Post
    John Thomas is the man. Great work and turn around time. Fair pricing. Much preferred to anyone else I have used
    http://www.retroarmsworks.com/
    Agreed. OP, I have post on him from a few months ago with some details about my very positive transaction with Retro Arms.
    Sic semper tyrannis.

  9. #9
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    In terms of absolute strength and clamping force, a taper pin is stronger.

    But all that force may be too much of a good thing, as mentioned before.

    You'll notice the RFI wording.

    Quote Originally Posted by USMC RFI
    – Barrel may include low profile gas block but may not use taper pin
    No taper pins allowed, but does not say anything about pins in general.


    A Coil Pin is a good option here, as the low forces eliminate concerns around bore deflection while offering good security for a low pro gas block.

    Last edited by Clint; 06-07-18 at 07:13.
    Black River Tactical
    BRT OPTIMUM Barrels - 16" BRT EXT Gas System
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  10. #10
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    OP,
    I had that same barrel pinned by ADCO a few years back. I had two smiths turn down the job. They said the barrel was too hard. I don’t know how true that is, ADCO had no problem with it

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