My Keltec RFB (and my shoulder) just survived a runaway bolt.

Discussion in 'Rifle Country' started by Arizona_Mike, Oct 21, 2016.

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  1. Arizona_Mike

    Arizona_Mike Member

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    I was doing some chrony work with 7 gun/upper combinations last evening and a had a catastrophic failure with my RFB. I was running perfectly with 168gr .308 but when I switched to 145gr it was giving me FTEs and mangled case mouths. Apparently the jams had managed to bend back the lips of the ejection chute's spring taps (which prevent ejected rounds from sliding back into the gun) to the point where they were interfering with the dual recoil springs. It looks like on the final shot both the springs were stuck forward (it may have happened one spring at a time over the course of a few jams) and I had an unsprung bolt hit the rear of the gun (called the top cover plate weldment) bulging the steel and knocking the recoil pad back about 1/4". The spot welds all held. Bent metal but I'm OK.

    I will never complain about the weight of the gun again. There is a reason they put a lot of steel in the top cover plate.

    Mike
     
  2. ClickClickD'oh

    ClickClickD'oh Member

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    I've always wanted to get one of these guns, but I'm not going to lie. If it can beat itself into a state where it Kabooms that easily, I'm probably not going to touch one until the redesign that.
     
  3. M1key

    M1key Member

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    Kel-Tec go BOOM. Where have I heard that one before?

    SC
     
    Last edited: Oct 21, 2016
  4. Arizona_Mike

    Arizona_Mike Member

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    Just to be clear it was not a kaboom. There was no premature unlocking and no gas explosion. It was a case of excessive slide velocity due to recoil springs being jammed.
     
    khegglie and M1key like this.
  5. Arizona_Mike

    Arizona_Mike Member

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    This is not my gun but a picture found on the internet showing exactly what happened (on both sides on mine).

    bent.jpg
     
  6. khegglie

    khegglie Member

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    Mike does KelTec give a grain preference for the .308 rounds?
    This was just regular 148 grain stuff right?
    Glad it held up to keep you safe.
     
  7. Arizona_Mike

    Arizona_Mike Member

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    It was 145gr Parvi Partisan (which is about half way in power between M80 7.62 and .308--2720 fps form an 18" barrel). The gun has an 11.25" twist and it tends to prefer bullets in the 150 grain range.

    The RFB will generally run all day when you have the bleed-type gas regulator adjusted right for your ammo but most people find they need a different setting for each weight/brand (you can't run a mixed mag). The finicky gas system is the weak point of the system--the sweet spot even drifts as the gun breaks in. It is a short stroke piston with a very brief impulse (the gas port is close to the muzzle due to the bullpup layout)

    I had the gun tuned for the 145gr load last outing and was pleasantly surprised when the 168s ran flawlessly.

    They offer 4 piston designs with different amount of bypass flow to the bleed screw that they will send to customers who run out of adjustment (plus a 5th suppressor with the entire shaft diameter .2450 to block both the gas port and bypass).

    0 flats: high flow/low bypass,2 flats with smaller shaft med flow/low bypass,4 flats:high flow/high bypass:
    [​IMG]

    And a rare very high-flow/ very high-bypass design:
    [​IMG]

    I was only 3/4 of a turn open on the bleed screw. I have not tried M80 yet but I may have to request a different piston for it--at least until I am broken in.

    Mike
     
  8. khegglie

    khegglie Member

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    You Know your rifle.
    When off to KelTec?
    By the way those are unobtanium in CT.
     
  9. Arizona_Mike

    Arizona_Mike Member

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    They responded to me within hours. I will double check the gun over this weekend for other damage and if there is none, I'll send them the top cover and ejection chute.

    They used to send parts in exchange for a picture. Now they require them sent back above a certain price threshold. They are sending the chute on the honor system but want me to send in my top cover.

    Kel Tec has fantastic customer service. The cynic might say they've had a lot of practice.

    Mine was on back order with Impact Guns out of Utah for >2 years. My credit card number changed 3-4 times in that time period. Sometimes it comes down to luck. Back when the S&W M&P10 was brand and was unobtanium I just happened to walk into a shop when they got one in :D

    Mike
     
    Last edited: Oct 21, 2016
  10. khegglie

    khegglie Member

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    I wish I could shoot one.
    I wonder what the recoil is like with the dual recoil springs.
    I hear the brass doesn't just fly away but can collect a few in the chute and then just fall out in a group!?!

    Just checked the web site... they have great schematics.
     
    Last edited: Oct 21, 2016
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