Kel-Tec’s RDB

Home Defender - - Contents - By Richard Schutz

Some are call­ing Kel-Tec’s RDB rev­o­lu­tion­ary. Our au­thor calls it a very wor­thy home de­fense weapon.

Is a Wor­thy Home De­fense Weapon

Kel-Tec’s mid­dle name is in­no­va­tion. The Co­coa, Florid­abased com­pany has long been known for in­no­va­tive poly­mer firearms. From the P3AT and PF9 pis­tols, SU-16 ri­fle, SUB2000 car­bine, KSG shot­gun, RFB and RDB bullpups to the up­com­ing KSG-25 shot­gun and RDB Sur­vival bullpup, Kel-Tec has al­ways thought out­side the box.

The RDB (Ri­fle, Down­ward-eject­ing, Bullpup) in 5.56x45 NATO came on the heels of the RFB (Ri­fle, For­warde­ject­ing, Bullpup) in 7.62x51 NATO, in 2015. They started with the de­sign of the RFB and made it less com­pli­cated, with the same re­sult, the empty cas­ing ends up at your feet.

One of the draw­backs of a tra­di­tional bullpup de­sign has al­ways been that if you shoot it weak side, the brass will eject in front of, or into your face. That is not the case with the RDB. The RDB is a poly­mer-frame, semi­au­to­matic, mag­a­zine-fed, bullpup­style ri­fle cham­bered for the 5.56x45 NATO round. Its rev­o­lu­tion­ary de­sign ejects spent cas­ings out of the bot­tom of the re­ceiver, onto the ground at your feet. It is light, ma­neu­ver­able and well-bal­anced, with its cen­ter of grav­ity over the pis­tol grip. Con­trols are am­bidex­trous and well-laid-out. Other than a some­what long take-up, the trig­ger is quite good. Gas si­phoned off the bar­rel, as the bul­let passes the gas port in the bar­rel, op­er­ates a short-stroke pis­ton, that in turn, forces the bolt car­rier to the rear. This ac­tion causes the bolt, which looks sim­i­lar to that in an AR-15, to ro­tate and un­lock from the lugs in the bar­rel ex­ten­sion. The spent car­tridge is ex­tracted from the cham­ber by the ex­trac­tor, which is in the 6-o’clock po­si­tion on the bolt face. With the cas­ing an­gled down­ward due to the po­si­tion of the ex­trac­tor, dual plunger ejec­tors (at the 2- and 10-o’clock po­si­tions) ex­ert pres­sure on the cas­ing as it moves rear­ward un­til it clears the mag­a­zine and is forced out from un­der the ex­trac­tor claw and down the ejec­tion chute. Dur­ing its rear­ward move­ment, the bolt car­rier also cocks the ham­mer.

The bolt car­rier rides along the ac­tion spring rod, com­press­ing the ac­tion spring as it moves to the rear. Once rear­ward travel is com­plete, the ac­tion spring causes the bolt car­rier as­sem­bly to move for­ward, strip­ping a round from the mag­a­zine and push­ing the bolt into bat­tery, cham­ber­ing the


The po­si­tions of the ex­trac­tor and the ejec­tor plungers, and strength

of the plunger springs, are the keys to the down­ward ejec­tion of the spent cas­ing. This sys­tem must also be strong enough to eject a loaded round that is much heav­ier than an empty cas­ing. There is noth­ing else to as­sist the cas­ing on its trip along the ejec­tion chute.

A for­ward mounted, non-re­cip­ro­cat­ing charg­ing han­dle is lo­cated above the hand­guard. The spring-loaded lever folds for­ward along the up­per re­ceiver when not in use. This lever can be eas­ily moved from one side to the other to ac­com­mo­date both right- and left-handed shoot­ers. Like an HK MP-5, when the cock­ing lever is pulled to the rear, it can be ro­tated about 35 de­grees up to lock it into place. Once a loaded mag­a­zine is in­serted, the lever can be slapped down and a round will be cham­bered. There is also a bolt re­lease on each side of the ri­fle, above and to the rear of the mag­a­zine well, so that the bolt can be re­leased quickly with ei­ther hand dur­ing a mag­a­zine change.

An am­bidex­trous mag­a­zine re­lease is lo­cated be­hind the pis­tol grip and in front of the mag­a­zine well. It is pushed to the rear to op­er­ate. This po­si­tion al­lows it to be op­er­ated by the in­dex fin­ger (mak­ing the mag­a­zine change) or by the base of the thumb of your trig­ger fin­ger hand. If the op­er­a­tor has large hands, it may be pos­si­ble to in­ad­ver­tently hit the lever and drop the mag­a­zine. This was not a prob­lem for me. By Mur­phy’s Law, this is bound to hap­pen at the most in­op­por­tune time!

The am­bidex­trous safety is lo­cated above the pis­tol grip, slightly far­ther to the rear than on an AR-15. It op­er­ates in a short, ap­prox­i­mately 45-de­gree arc rather than the 90-de­gree arc found on most AR-15s. It is eas­ily op­er­ated by ei­ther the thumb or the trig­ger fin­ger.

Kel-Tec rec­om­mends ad­just­ing the gas reg­u­la­tor for the par­tic­u­lar am­mu­ni­tion that you are us­ing, then con­tin­u­ing to use the same type of am­mu­ni­tion. The ri­fle is ad­justed at the fac­tory to func­tion prop­erly with M193-type am­mu­ni­tion. When ad­just­ing the gas reg­u­la­tor, in­crease the amount of gas by turn­ing the reg­u­la­tor coun­ter­clock­wise (look­ing from the rear of the gun) un­til it cy­cles prop­erly. Then, for re­li­a­bil­ity and vari­a­tions in bar­rel gas pres­sure, in­crease the gas by one more click.

Un­like other bullpup-style ri­fles that I have shot, the stock trig­ger in the RDB was quite good. There was an ap­prox­i­mate 0.085-inch take-up, but there was no slop­pi­ness in the link­age and no de­tectable over-travel. The trig­ger broke at an av­er­age of 5 pounds, 9


ounces for 11 con­sec­u­tive pulls, us­ing a Ly­man dig­i­tal trig­ger scale. At the time this ar­ti­cle was writ­ten, the RDB was the only model that was read­ily avail­able. An RDB Sur­vival model was shown at the NRA show and should fol­low soon. The RDB-C (Cal­i­for­nia com­pli­ant) ver­sion will fol­low the Sur­vival model. Fi­nally, an RDB cham­bered in 6.5 Gren­del has gone through engi­neer­ing but has not yet been green-lighted for pro­duc­tion.

Ac­ces­sories, sights and scopes that will fit on a Mil-Std 1913 rail will be right at home on ei­ther the milled top rail on the re­ceiver or the molded rail on the bot­tom of the hand­guard. Typ­i­cal AR-15-style trig­gers, stocks and hand­guards will not fit the RDB. Kel-Tec re­quires the use of NATO (5.56x45) or SAAMI (.223 Rem.) spec­i­fi­ca­tion am­mu­ni­tion. They also rec­om­mend try­ing var­i­ous types of am­mu­ni­tion to see which one per­forms the best, then stick­ing with it. The use of reloaded, re­man­u­fac­tured or for­eign or mil­i­tary sur­plus am­mu­ni­tion of un­known or ques­tion­able qual­ity is not rec­om­mended. The use of such am­mu­ni­tion will void the war­ranty.

Dur­ing range eval­u­a­tion, I used am­mu­ni­tion pro­duced by var­i­ous man­u­fac­tur­ers in full metal-jacket, hol­low-point and boat­tail hol­low-point con­fig­u­ra­tions. Bul­let weights ranged from 43 to 77 grains. All the am­mu­ni­tion used func­tioned flaw­lessly and ejected cleanly. Over 350 rounds were fired dur­ing this por­tion of the re­view. Var­i­ous brands, types and ca­pac­ity mag­a­zines were used dur­ing test­ing. These in­cluded Mag­pul PMAG Gen M3, C-Prod­ucts De­fense, Daniel De­fense 32-round, alu­minum GI 20-round and 60-round Sure­fire mag­a­zines. All func-

tioned prop­erly and all but the C-Prod­ucts De­fense and Sure­fire mag­a­zines dropped free at the touch of the mag­a­zine re­lease. When per­form­ing a tac­ti­cal reload on a closed bolt, make sure to firmly seat the mag­a­zine. Some mag­a­zines seemed to be more finicky than oth­ers dur­ing this ma­neu­ver. For ac­cu­racy test­ing, I in­stalled a Night­force SHV 4-14x50 F1 ri­fle­scope, us­ing Night­force’s 30mm Ul­tralite Un­i­mount 20 MOA rail mount with a bub­ble-level

top ring half. This setup worked well.

I mounted an EOTech model 553 holo­graphic sight on the top rail for CQB work. If you mount a red dot or holo­graphic sight on the RDB, make sure that it is high enough to see through com­fort­ably. With the straight stock of the RDB, it is dif­fi­cult to get your eye low enough to see through low-mounted sights or op­tics. The RDB is sim­ple to field strip, cer­tainly no more dif­fi­cult than a pis­ton-op­er­ated AR-15, once you have done it a cou­ple of times. Prior to field strip­ping the RBD, make sure that it is un­loaded, the mag­a­zine is re­moved and that there is no am­mu­ni­tion in the area. Fol­low the in­struc­tions in the “Safety, In­struc­tion and Parts Man­ual” for de­tailed dis­as­sem­ble and as­sem­bly in­struc­tions.

Two semi-cap­tive pins pretty much hold the RDB to­gether. Be care­ful with the pins. The man­ual says that they are cap­tive, but they will come out. The only re­motely dif­fi­cult part of dis­as­sem­bly/as­sem­bly is align­ing the three pieces when you in­sert the pins dur­ing as­sem­bly.

I cleaned the RDB thor­oughly prior to any shots be­ing fired. Dur­ing the ac­cu­racy and ve­loc­ity eval­u­a­tion, the ri­fle bore was cleaned ev­ery 45-50 shots. The RDB was a plea­sure to shoot. It han­dled flu­idly, and re­coil was negli-



gible. Even after shoot­ing an AR-15 for 20 plus years, I found the con­trols of the RDB easy to adapt to and op­er­ate. The only thing that took a lit­tle get­ting used to was the for­ward charg­ing han­dle. I kept reach­ing to the rear look­ing for my BCM charg­ing han­dle.

Ac­cu­racy and ve­loc­ity eval­u­a­tion was per­formed by fir­ing three strings of five shots each, at 100 yards for each type of am­mu­ni­tion used. The av­er­age for three five-shot groups for each of eight dif­fer­ent fac­tory loads were within 0.31 inches of each other. Hor­nady’s 8026 75-grain Match BTHP had the small­est av­er­age for three five-shot groups at 2.27 inches. It also had the sec­ond small­est sin­gle group at 1.48 inches. In sec­ond place was the Fed­eral Pre­mium 223R 43-grain Speer TNT Green load at 2.36 inches. Fioc­chi’s 223MKC 69-grain MatchKing tied for sec­ond place. The IMI 5.56x45 77-grain OTM, LR Mod. 1 load had the small­est sin­gle group at 1.42 inches. The RDB isn’t a tack-driver, but then, it isn’t de­signed to be one. What it is, how­ever, is con­sis­tent. It is a close-quar­ter bat­tle ri­fle and does a good job of it.

To de­ter­mine how well the ejec­tion sys­tem worked, I fired the RDB in var­i­ous po­si­tions, in­clud­ing up­side down, left-side down and right-side down. It kicked the spent cas­ings out smartly in all po­si­tions. There were no feed­ing or ejec­tion prob­lems en­coun­tered at any time dur­ing the eval­u­a­tion. When fir­ing in the nor­mal, up­right po­si­tion, it was nice to have the brass land at your feet and not have to go look­ing for it across the range when it came time to clean-up.

When mov­ing while shoot­ing both strong and weak side, the ri­fle han­dled well. When shoot­ing weak side, it was nice not to have brass ejected in front of my face. The trig­ger wasn’t a Geis­sele, but it was still very good for this type of ri­fle.

One safety is­sue must be men­tioned. When check­ing to make sure that the ri­fle’s cham­ber is empty, it is not re­ally easy. The only way to see the cham­ber is to re­move the mag­a­zine (which you should do any­way), in­vert the ri­fle while keep­ing it pointed in a safe di­rec­tion and look up through the mag­a­zine well. Even then, you must have di­rect sun­light or a flash­light to il­lu­mi­nate the mag­well and cham­ber. I re­gret that I was up against a dead­line and was un­able to run the shoot house with the RDB. That would have been fun, and I’m sure that the RDB would have per­formed well. This is a well-bal­anced and easy-to-ma­nip­u­late ri­fle. A loaded mag­a­zine coun­ter­bal­ances the heavy bar­rel, mak­ing it han­dle well. The RDB cer­tainly has ad­e­quate ac­cu­racy for dis­tances en-

coun­tered in and around your home. There are many opin­ions re­gard­ing what makes a good home de­fense weapon. The two most im­por­tant fac­tors are re­li­a­bil­ity and fa­mil­iar­ity. When things go bump in the night, you need to know how to op­er­ate your weapon with­out think­ing about it and you need to know that it will fire, eject and feed ev­ery time you pull the trig­ger. An­other con­sid­er­a­tion is tac­tics when search­ing for an in­truder in your house. The short length of the bullpup de­sign will help you with proper tac­tics when “pieing” a corner, go­ing through door­ways, and so on.

The bullpup de­sign ri­fle cer­tainly isn’t the only op­tion for home de­fense, but it is one worth con­sid­er­ing. Look at all op­tions and choose what works best for you. If you de­cide on a bullpup in 5.56 NATO, take a close look at the Kel-Tec RDB. HD

Top: The hand­guard has a molded-in Mil-Std 1913 bot­tom rail and a sling clip at­tach­ment hook in the top-front po­si­tion. The hand­guard can be de­tached by re­mov­ing a sin­gle pin lo­cated to­ward the front of the hand­guard.

The for­ward open­ing is the mag­a­zine well where the closed bolt can be seen. The rear­ward open­ing is the lined ejec­tion chute. The rear of the ac­tion spring rod can be seen at the top of the chute.

The mag­a­zine re­lease is in front of the mag­a­zine well. The bolt re­lease is a small tab the pro­trudes from the re­ceiver above the mag­a­zine well. The right-side safety lever is lo­cated above the pis­tol grip.

The left side of the RDB shows the sling at­tach­ment points, the am­bidex­trous con­trols and up­per and lower Mil-Std 1913 rails.

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