BULLPUP FORUM

Bullpup Rifles (Auto & Semi-Auto Centerfire) => Kel-Tec RFB, RDB, M-43 => Topic started by: HBeretta on December 06, 2016, 09:35:45 PM



Title: RDB Accuracy Thread
Post by: HBeretta on December 06, 2016, 09:35:45 PM
Wanted to do this sooner - see below for results.  I went to Walmart and bought pretty much all they offer in 223 Rem which is Federal 55gr Value pack 100 rnds and Federal American Eagle 55gr.  I'm running a Vortex Strike Eagle 1-6x and bore-sighted it for 50yds.  So after getting on paper and adjusting, I starting firing 4-5 shots groups.  Did shoot a 7 shot group as well.  I went about all this casually...didn't want to spend all day trying for the best groups or using a secure rest fine tuning etc...  So with some lazy shooting and a quick zero at 100 yds I'm happy to say the gun is pretty damn accurate.  Also, the 'X' shots are from just getting on paper at 100yds to zero and another from a shooter just a lane over to my right.  Results below equate to 1.7" moa average from 100yds for this session.  Now I'm anxious to test match grade ammo.  

Ammo Used
(http://i56.photobucket.com/albums/g166/HannibalBeretta/42bef186-f839-4326-b2f3-68373279d4d0_1.f13208d1c0ae46bc140d22013f1ed601_zpskzgwajte.jpeg)
(http://i56.photobucket.com/albums/g166/HannibalBeretta/11953_zpsecxdh0kw.jpeg)

Rest Used
(http://i56.photobucket.com/albums/g166/HannibalBeretta/20161206_153000_zpsde4psy8d.jpg)

Group 1 - American Eagle ∙ 5 shot ∙ 1.875" moa
(http://i56.photobucket.com/albums/g166/HannibalBeretta/20161206_154028_zpsgzhfccfg.jpg)

Group 2 - Amercian Eagle ∙ 7 shot ∙ 2" moa
(http://i56.photobucket.com/albums/g166/HannibalBeretta/20161206_152757_zpsctqfyqpc.jpg)

Group 3 - American Eagle ∙ 4 shot ∙ .75" moa
(http://i56.photobucket.com/albums/g166/HannibalBeretta/20161206_152749_zps5u89ofxj.jpg)

Group 4
- Federal ∙ 5 shot ∙ 1.5" moa
(http://i56.photobucket.com/albums/g166/HannibalBeretta/20161206_152720_zpsc7cpuyrf.jpg)

Group 5 - Federal ∙ 5 shot ∙ 2.375" moa
(http://i56.photobucket.com/albums/g166/HannibalBeretta/20161206_152806_zpsyvyuefkf.jpg)





Title: Re: RDB Accuracy Thread
Post by: Frostburg on December 07, 2016, 04:19:30 PM
I have also gotten accurate groupings with mine.  :)


Title: Re: RDB Accuracy Thread
Post by: Tj7 on December 11, 2016, 10:31:37 PM
Some very impressive groups with just 55gr! I would wonder how much match ammo would improve the groups. I can't wait to pick one up and do some testing with it, I am still waiting for OD.


Title: Re: RDB Accuracy Thread
Post by: Frostburg on December 11, 2016, 11:11:50 PM
Some very impressive groups with just 55gr! I would wonder how much match ammo would improve the groups. I can't wait to pick one up and do some testing with it, I am still waiting for OD.

You still don't have one yet??    :-\


Title: Re: RDB Accuracy Thread
Post by: Frostburg on December 11, 2016, 11:13:00 PM
I love mine. I am also planning on buying a 20" barrel one once they come out.


Title: Re: RDB Accuracy Thread
Post by: HBeretta on December 12, 2016, 01:23:16 PM
I love mine. I am also planning on buying a 20" barrel one once they come out.

same i'm becoming more impresssed with the gun and haven't had any issues aside from the fluke firing pin, BUT...must admit now...likely user error on my behalf.  when disassembling the bolt and removing the firing pin retainer pin it went flying onto my ceramic tile in the kitchen.  at that point i didn't really look for damage and the malfunction did occur on the next range session after inspecting/tinkering with the bolt assembly.  regardless, it's been smooth shooting with a variety of mags and tends to stay pretty clean between range sessions; cleaner than my fs2000.  it's light, has the best stock bullpup trigger and is very accurate...tough to beat considering competing bullpups run $700-1000+ more.    


Title: Re: RDB Accuracy Thread
Post by: BullpupT on December 12, 2016, 01:37:33 PM
Great groups! I wish I had a 100 yard indoor range. JEALOUS ;D


Title: Re: RDB Accuracy Thread
Post by: HBeretta on December 12, 2016, 04:42:40 PM
Thanks man!  I'm hoping others follow suit with posting results.  i've got a utg riser on the way for my fs2000 (optic ver) with the plan to mount the vortex 1-6x on it to compare groups.  then down the road...the tavor or x95 is next.  i still can't accept the accuracy issue with the x95; want one to shoot for myself to believe it.  well i want the x95 period.


Title: Re: RDB Accuracy Thread
Post by: HBeretta on January 24, 2017, 01:42:37 AM
Tj7 posted an article on the RFB and RDB by American Rifleman (link below) that got me thinking about the accuracy of the RDB.  I realize each gun is unique but more or less consistent to a certain level of accuracy.  Obviously, accuracy issues are sussed out in no time when a new product hits the market.  An example of this is the x95.  But, that's not to say all x95s suffer from accuracy problems as many report fairly good accuracy on a consistent basis.  Point is, I'm always intrigued by various end user results with regard to accuracy on a given platform or in particular a specific product.  Speaking to the bullpup platform, it appears 3 MOA is the expected standard.  I'll admit, I became anxious when I got to the accuracy portion of this article - always do with regard to accuracy.

The first time I decided to document my RDB accuracy (posted on this forum) I was quite surprised to average 1.7 MOA from 100 yds.  That hasn't been the case on subsequent range trips, but of course there have been variables to go along with that.  I've averaged closer to 3 MOA recently and started to wonder if the first time out was a fluke.  The variables that I speak of are not cleaning the bore on one occasion and extremely cold on another occasion (indoor range cycling in outside air - felt like 30-40 degrees).  Along with this, I made more of an effort to try to be accurate on subsequent efforts versus the initial carefree laxed approach which in retrospect may of been why i shot better groups.  Anyway, I do plan on setting up on a secure rest and giving my gun more of proper accuracy test when the weather improves as my indoor range simply doesn't have the bench space.

Likewise, even with various loads, Jeff Johnston from AR averaged 2.88 MOA from 100 yds.  Surprisingly there wasn't much of a difference with match and standard AE 55 grain.  I've stuck to AE 55 grain on my accuracy tests.  I've read other users averaging 2.5-3 MOA with the RDB as well.  I still feel compelled to test my gun further to see if that first outing of testing and sub MOA group i hit wasn't the fluke that it likely was.  Anyway, anyone else out here pretty much getting the same with their RDB?  

(http://i56.photobucket.com/albums/g166/HannibalBeretta/kelt3_zpscisttskd.jpg)  

https://www.americanrifleman.org/articles/2017/1/23/tested-kel-tec-rfb-rdb-bullpups/# (https://www.americanrifleman.org/articles/2017/1/23/tested-kel-tec-rfb-rdb-bullpups/#)


Title: Re: RDB Accuracy Thread
Post by: Potss on February 04, 2017, 01:06:26 AM
The results with the RDB are promising.

What we really need is someone who reloads to test the accuracy with high quality components after doing a ladder to find their barrels node.  Then locking it down for the test.  That would be the best approximation of absolute mechanical accuracy.

The more expensive version of the test is to just try out different types of match ammo till you find one your barre likes best.  I ended up doing that for my SPR, and the differences were pretty staggering and unexpected.  Black Hills 60gr Vmax and 77gr TMKs would barely do an inch, while HSM 55gr Bergers would do .62moa (all 5x5) for my Lothar Walther barrel.  Likewise Nosler Varmageddon's group in the .7s but Sierra Blitzkings (from Gorilla) I cannot get under 1in.  I'd recommend trying this for your RDB if you don't reload.  At 100y flat base bullets have an advantage over the higher BC boat tails all else being equal.  Here is a list of my results and Molon's results so far, might be a place to start:

.223- GECO 55gr Target 1.2" $.35/r.

5.56- Mk. 262 Mod 1 1.1" $1.06/r.

.223- Federal Fusion 62gr 1.004" $.862/r Gold dots almost as good (including 64 & 75gr $.75/r), Fed Tactical bonded better $1.50/r.

5.56- Black Hills New 75gr Match 1" $.92/r.

.223- Fiocchi 77gr Exacta .995" $.78/r

.223- Nosler Custom Competition 77gr OTM .98" $.964/r.

5.56- IMI razercore 77gr otm .95" $.747/r.

.223- Hornady 75gr Steel Match .95" $.44/r (55gr not much worse 1.3" $.34/r) Will not cut barrel life.

.223- Prvi partizan 75gr Match .91" $.525/r.

.223- Cor-bon 69gr Match .88" $1.10/r.

.223- Austrilian Outback 69gr SMK .86" $.65/r.

.223- Hornady American Gunner 55gr HP .85" $.55/r.

.223 Noveske 55gr Nosler Varmagedon .82" $1.10/r

5.56- Barnes Precision Match 85gr OTM .81" $1.24/r

.223- Stillwood Ammo 77gr Sierra TMK .8" $.86/r.

.223- Hornady 53gr Superformane Varmit Vmax .70" $.799/r

.223- Federal Gold Medal Match 69gr .67" $1/r (2590fps avg), 77gr also recommended $1.10/r

.223- HSM 55gr Berger Match Flat Base .64" $1.47/r.

Ammo that hasn't been tested but might be decent:

Lapua 55gr and 69gr.

Prime Ammo 55gr and 77gr Match+

Monolithic Munitions 40gr and 60gr Gold.

Atlanta Arms 77gr TMK.

Copper Creek 77gr loads.


Title: Re: RDB Accuracy Thread
Post by: HBeretta on February 04, 2017, 02:24:48 AM
very nice.  what was your test environment?


Title: Re: RDB Accuracy Thread
Post by: Potss on February 24, 2017, 11:00:30 PM
Mine is an open 200y range with berms in a small valley, so low wind.  Molon's is an even more enclosed 100y range, he has pics up if you want to see it.


Title: Re: RDB Accuracy Thread
Post by: BrianK on May 11, 2017, 12:02:39 PM
I'd been having accuracy problems with the RDB and it was suggested that I check the rail. So the other day I had time to check it. It was good except for the last screw closest to the breech. Today I fired it.

Previously it was all over the paper, disappointingly so. Today it was much better.
Here's the group I shot with Federal FC 262 77grOTM: https://www.dropbox.com/s/1rdwlxr5vza79am/5_11_17%20RDB%20group_FedFC262%2077grOTM%20100yds.jpg?dl=0 (https://www.dropbox.com/s/1rdwlxr5vza79am/5_11_17%20RDB%20group_FedFC262%2077grOTM%20100yds.jpg?dl=0)

Conditions were 50F and gusty wind. The range was 100 yards and it was shot from the bench.

It measures just a hair under 1" center to center. That's the limit of my eyes and the 4x scope.

But I put the can on it and I'm not even on the paper at 100 yards. So I backed up to 40 yards and the group was 6" high. I need to decide if I'm going to shoot it suppressed all the time or unsuppressed. I'm leaning toward unsuppressed. Or maybe I'll contact KT and get another barrel assembly and stress that the threads must be concentric to the bore.  Comments?

I'm happy with the way it's shooting, just not with the POI shift suppressed.


Title: Re: RDB Accuracy Thread
Post by: Laserbait on May 12, 2017, 10:18:43 PM
Brain, what kind of suppressor do you have?  My Omega 7.62 does not shift my POI that I have noticed.


Title: Re: RDB Accuracy Thread
Post by: BrianK on May 12, 2017, 11:21:19 PM
A Surefire FA556k. It is noted for not shifting impact, and doesn't on any of my other guns. I'm thinking that the threads on the RDB aren't aligned with the bore, and with my Gisselle gauge it looks OK. I'm not getting baffel strikes.

I took the adapter off and have the OEM flash hider on it at this time. I gave up on suppressing it for now. I'll wait for the MDR to come in and my bets are on it. It's 2 strikes against the RDB at this time.


Title: Re: RDB Accuracy Thread
Post by: Laserbait on May 13, 2017, 01:49:27 PM
A buddy of mine was having a similar issue with a suppressor of his (I think it was a Griffen, or Dead Air, can't remember).  Anyway, it turned out to be his QD muzzle device was the problem.  Something was "off" with it.  He swapped it for another one from a different rifle, and the POI shift went away.


Title: Re: RDB Accuracy Thread
Post by: BrianK on May 13, 2017, 07:03:56 PM
I'll try that. Thanks.


Title: Re: RDB Accuracy Thread
Post by: Potss on May 16, 2017, 03:06:03 AM
I'm still looking forward to folks trying out 5x5 or 3x10 with some premium match ammo like the stuff mentioned above :).


Title: Re: RDB Accuracy Thread
Post by: HBeretta on May 18, 2017, 04:37:49 PM

Previously it was all over the paper, disappointingly so. Today it was much better.
Here's the group I shot with Federal FC 262 77grOTM: https://www.dropbox.com/s/1rdwlxr5vza79am/5_11_17%20RDB%20group_FedFC262%2077grOTM%20100yds.jpg?dl=0 (https://www.dropbox.com/s/1rdwlxr5vza79am/5_11_17%20RDB%20group_FedFC262%2077grOTM%20100yds.jpg?dl=0)

Conditions were 50F and gusty wind. The range was 100 yards and it was shot from the bench.

It measures just a hair under 1" center to center. That's the limit of my eyes and the 4x scope.


i went to my indoor range today.  i have a lot of bulk 55gr ammo that i'm going through; xmas gift.  i keep telling myself i'm going to take photos but seem to be lazy about it.  after checking my zero and adjusting i shot 5 shot groups at 100 yds the entire session.  i realize to get a general idea of where your shots are hitting a 3 shot group works just fine, but prefer 5 shot groups or more to get a better idea of accuracy.  many times i found myself hovering around an inch or slightly more 3 shots in, but the 4th and 5th shots opened up my groups to about 2" average for the session.  i did have two 3-3.5" groups, but more often than not i was hovering around 2" groups.

my rdb seems to be a 2-2.5" 100yd gun for me which is entirely subjective obviously.  the next guy could come in shooting 1" groups regularly, but i'm the one shooting the gun.  i've hit below 2" for a session but on average i seem to hover right around 2".  i don't like shooting from a sled because i don't feel it's practical.  i try to get away with as good as i can get with as little as possible.  today i was basically resting the gun on my magazine pouch with the empty mags as the stool and table height required just a little for me.  otherwise, for comfort i'll setup with bag and rest.  

i went in today with the intent to post feedback here with photos, but that didn't happen.  lol...i did manage to snap a quick photo of the lane and text to my brother just to give him crap while he's slaving at work while i'm enjoying the next two days off...go figure.      

  


Title: Re: RDB Accuracy Thread
Post by: BrianK on May 18, 2017, 05:17:24 PM
HB' do you have any heavy bulletted loads? I don't remember the twist on the RDB (1:7 or 1:8), but I remember thinking to myself that it favors heavier bullets. Mine certainly appears to reflect that.


Title: Re: RDB Accuracy Thread
Post by: HBeretta on May 18, 2017, 06:46:23 PM
HB' do you have any heavy bulletted loads? I don't remember the twist on the RDB (1:7 or 1:8), but I remember thinking to myself that it favors heavier bullets. Mine certainly appears to reflect that.

not currently but have put 69 & 77gr through.  i predominantly shoot indoors, but the best i've done with my RDB was with black hills 77gr OTM shooting outdoors.  well i should say 77gr only once on the mentioned outdoor occasion.  that stuff is too expensive at just over a $1 per round.  i was hitting under 2" groups and several 1" or a tad above.  i didn't see noticeable results with 69gr, but then again i'm not as consistent as i'd like to be; depends on how much coffee i've had that morning  8).  outdoors for me is much better as everything is bright and clear.  problem is my indoor range is so much closer.  

kel-tec website has it listed as 1:7 twist although not indicated on the barrel.  i believe the pre-production guns were 1:9.

i'm going to push for more outdoor shooting with 55gr and push a little more for accurate groups.  i tend to be lazy and casual about it even when curiosity has me going through the motions.    


Title: Re: RDB Accuracy Thread
Post by: Potss on May 18, 2017, 11:39:46 PM
Just so folks are away, twist has basically no effect on accuracy.  The bullet either stabilizes or it doesn't.

And if you are shooting groups at 100y, it is actually better to use high quality lighter flat based bullets all else being equal.  They are easier to QC so they will generally form a more even seal when leaving the barrel unlike the heavier rounds which all have boat tails to boost BC.  Inside 100y, the low BC of flat base match bullets doesn't matter, it is too short a range.  That is why you see Berger 55gr match bullets with a flat base, and not coincidentally they are the most accurate load I've found yet...at 100y.  Push it to 300y and the TMK will reign supreme (until I get the 70gr RDFs shooting).  But if you are testing for mechanical accuracy of a gun at 100y the best rounds to use are stuff like the Lapua 55gr, Prime Match+ 55gr, and HSM Berger match 55gr.  Although I will say in this case the difference between flat base and non-flat base is probably outdone by simply finding factory ammo that best fits your rifle's nodes if you aren't a handloader.  FGMM is certainly worth trying for that alone.


Title: Re: RDB Accuracy Thread
Post by: BrianK on May 19, 2017, 01:02:48 AM
Potss your assertion flies in the face of the history of bullet stabilization garnered by many thousands of people and tests over decades. An over stabilized bullet or understabilized bullet might not be stabilized, or it could be. That's basically what you wrote (That's an assumption I make since you used the word "away" and not "aware").  A statement of that sort really nails it down! (If it's stabilized it's stabilized. [basically])

The fact is that longer bullets require faster twist rates to get the spin they require to stabilize, and shorter bullets generally respond better to slower twist rates. If you don't understand that you need to go back to Ballistics 101. Any experimenter can prove that to themselves by playing with longer bullets stabilized at high twist rates and at high velocities and then lowering the velocity (spin rate) and watch the keyholes on the paper. It's pretty basic stuff. It's the reason the industry went from 1:10 or 1:12 for 55 grain bullets for normal velocity .223 or 5.56mm to 1:7 twist on the M-16 when they changed bullet weight to the SS-109 load with the 62 grain bullet. This is kindergarten basic ballistic knowledge. Yeah, I know knowledge has been lost today, we now have the internet and BS knowledge. So very much is being lost merely by folks not proving things for themselves and repeating garbage knowledge. By repeating BS many times it doesn't make it true.


Title: Re: RDB Accuracy Thread
Post by: patrick711 on May 19, 2017, 07:10:00 AM
Potss, I thought you were being sarcastic at first. OMG


Title: Re: RDB Accuracy Thread
Post by: HBeretta on May 19, 2017, 12:51:46 PM
It's pretty basic stuff. It's the reason the industry went from 1:10 or 1:12 for 55 grain bullets for normal velocity .223 or 5.56mm to 1:7 twist on the M-16 when they changed bullet weight to the SS-109 load with the 62 grain bullet.

potss...lol...you lost me man.  going into my RDB purchase there was debate on whether or not the production guns were 1:7 or 1:9 twist as it's not indicated on the barrel.  i hadn't read anywhere either of someone figuring this out for themselves.  even going into my rdb purchase with the notion of getting either twist i was contemplating bullet weights if i was going to shoot for accuracy.  i can't speak for other RDB owners out there but i went the old school route in figuring out my twist rate with a cleaning rod, painters tape, sharpie and tape measure.  it appears what kel-tec has listed on their website is accurate - my rdb has a 1:7 twist rate. then again, with the subtle changes such as the new bolt and so on, that isn't announced by kel-tec, i wouldn't be surprised if the early production RDBs were 1:9 twist; up to each owner to measure their twist rate.

my worst groups and outings have been with 55gr.  with 69gr and up, with 77gr being the best i've shot, i've never walked away going damn i really sucked today, but have on several occasions with 55gr.  the RDB has a 17.3" barrel, so i had the notion going into my purchase with the assumption i'd be getting a 1:7 twist that i'd be shooting more accurately with heavier bullets rather than stretching it with a 1:9 twist.  basically i figured the RDB wouldn't shoot 55gr worth a damn which really hasn't been the case.  i've shot pretty damn good groups, but with greater deviation than the heavier loads like 69-77gr as expected though.

with regard to twist rates, i figured it was common knowledge the progression to faster twist rates to help stabilize along with evolving to the heavier bullet trends.  this and the military adopting for 62gr back in the 80s along with the purpose to stabilize the longer tracer rounds.  that and the 1:7 being ideal for 10.5" SBRs with regard to 55-77gr loads that a slower twist rate wouldn't be able to handle.  well basically getting away from the slower twist rates period, that won't stabilize the heavier loads - like the 1:14/1:12 twists.  

    


Title: Re: RDB Accuracy Thread
Post by: Potss on May 19, 2017, 03:44:08 PM
Ok, a lot of misunderstands to clear up here.

1.) @ BrianK, you don't seem to have understood my post.  A bullet that is under or over stabilized by definition isn't stabilized.  Perhaps if I restate my initial statement this way it will make more sense to you: once a bullet is stabilized properly, twist rate does not effect accuracy.  In other words, a 1:7 will stabilize a 55gr, as will a 1:9, and all else being equal they will exhibit the exact same level of accuracy since the round is stabilized. Do you understand what I'm saying now?  Of course bullet stabilization depends upon twist rate and bullet characteristics (although there is a little more to it than that, JBM does a good job here: http://www.jbmballistics.com/cgi-bin/jbmdrag-5.1.cgi), and if you'd read my prior posts here you'd know that I have made very specific posts on this subject. Perhaps instead of going on a tirade about insanely obvious s***, you should have stopped making assumptions and asked what I meant (which I thought was blindingly obvious).  Also it should have been obvious by the second part of my post what I was referring to.

2.) @ HBeretta, you realize you quoted BrianK and not me right?  And you realize BrianK is talking about the M16-->M16A2 progression, not the RDB right?  Also please re-read my OP more carefully.  I am stating that flat base bullets specifically have an advantage over boat tail bullets at 100y all else being equal, which is true.  For 5.56/.223, there are actually surprisingly few flat base match grade bullets available, all three of the best of which I mentioned in my post.  The vast majority of 40-55gr ammo is not flat base, they have small boat tails and this includes the M193-style 55gr bullets used in the loads you have been shooting.  I am NOT stating that 55gr loads are inherently more accurate at 100y.  Just that a high quality match FLAT BASE bullet will be more accurate than a boat tail bullet at 100y, all else being equal.  Additionally, A 1:7 twist will stabilize basically all 55gr bullets, and some of the longer 50gr and 45gr bullets.  Once a bullet is stabilized properly (not under or over) twist rate does not effect accuracy, so the RDB will be just as accurate with a 55gr bullet as it will with a 77gr bullet, all else being equal (again if the 55gr has a flat base, it will be slightly better at 100y).

Hope that clears everything up for both of you.  I guess I wasn't clear enough in my OP on a topic I thought was very obvious.


Furthermore I would just like to add that high quality match ammo will be massively more accurate than normal use stuff in almost all cases.  But you must find the load that matches your rifle barrel's node to really take advantage of the massively increased consistency of match ammo.  This requires testing a lot of match loads in your gun unless you reload.  What I posted on the prior page was the data I had from my precision AR + Molons, and that should give you an idea of the number of loads that need consistent testing to find the true mechanical accuracy limit of the rifle (again if you don't precision handload, if you do you can just do a ladder test and refine your load from there).


Title: Re: RDB Accuracy Thread
Post by: HBeretta on May 19, 2017, 05:12:01 PM
Ok, a lot of misunderstands to clear up here.

2.) @ HBeretta, you realize you quoted BrianK and not me right?  And you realize BrianK is talking about the M16-->M16A2 progression, not the RDB right?  Also please re-read my OP more carefully.  I am stating that flat base bullets specifically have an advantage over boat tail bullets at 100y all else being equal, which is true.  For 5.56/.223, there are actually surprisingly few flat base match grade bullets available, all three of the best of which I mentioned in my post.  The vast majority of 40-55gr ammo is not flat base, they have small boat tails and this includes the M193-style 55gr bullets used in the loads you have been shooting.  I am NOT stating that 55gr loads are inherently more accurate at 100y.  Just that a high quality match FLAT BASE bullet will be more accurate than a boat tail bullet at 100y, all else being equal.  Additionally, A 1:7 twist will stabilize basically all 55gr bullets, and some of the longer 50gr and 45gr bullets.  Once a bullet is stabilized properly (not under or over) twist rate does not effect accuracy, so the RDB will be just as accurate with a 55gr bullet as it will with a 77gr bullet, all else being equal (again if the 55gr has a flat base, it will be slightly better at 100y).

Hope that clears everything up for both of you.  I guess I wasn't clear enough in my OP on a topic I thought was very obvious.


potss...yes i'm well aware that i quoted Brian - running with the progression of faster twist rates to accommodate heavier bullets going back to the 60s.  RDB or not - it's a 1:7 twist 17" barrel.  

now i get what you're getting at now that you've clarified 'once a bullet is stabilized properly'.  but to imply twist doesn't affect accuracy doesn't hold for me.  you can't go shooting 77gr through 1:14, 1:12...hell even 1:9 and not see accuracy issues in the form of bullet yaw/keyholing etc...the decreased twist rate will certainly result in a dramatic decrease in accuracy.  and yes i'm aware of flats vs boats.  BUT, again, you did clarify once stabilized.

and i'm not disagreeing with this notion of 55gr bullets.  i realize we could go in circles all day about why some guns shoot better with bullets of one weight versus others.  how heavier bullets will not remain stable over longer distances if they don't have enough velocity and so on.  i mean we could throw everything out the window and say barrel length, twist rate and a lot of other factors determine accuracy.  do i think bullet weight matters?  yes!  do i think it's the only reliable indicator for accuracy?  no, as i feel twist rate, velocity and barrel length plays into this.  

that or i could just throw semantics aside and go out and keep shooting various ammo types to get a better feel for what my RDB prefers.

i assumed my RDB would handle the heavier loads better and it has but like i mentioned hasn't been drastic and in fact some might consider negligible, but i'm the shooter...so subtleties are noticed.

i'm open to different perspectives and until you clarified, with you apparently dismissing twist rate altogether initially or so it seemed, i was definitely questioning your approach.  i'm still not on board with your statement about twist rate, but will look to your ammo recommendations to see what performance i get.  again, i'm not entirely convinced my RDB favors the heavier bullets, but like i mentioned previously - have noticed less deviation with them and best groups on those occasions.

in fairness, InRangeTV didn't really see much difference with their RDB going from 55gr to 69gr but then again they were shooting a pre-production 1:9 twist rifle.


Title: Re: RDB Accuracy Thread
Post by: Potss on May 19, 2017, 08:10:44 PM
I'm glad my updated post was more clear, but I can see it still wasn't entirely clear.  When I say "properly stabilized" I mean specifically the bullet is not under or over stabilized.  In other words, I don't mean a 77gr out of a 1:12 or a 40gr out of a 1:7, those are not stabilized properly.  Here is conclusive evidence that as long as you are in the stabilization range, twist does not effect accuracy: https://www.ar15.com/forums/t_3_16/687746_55_Grain_Bullets_Fired_From_AR_15s_with_1_7_Twist_Barrels.html  Better yet it is specific to 1:7 vs 1:9 and 55gr.

I am glad you are going to be testing more ammo types in your RDB, and I look forward to the results  :)


Title: Re: RDB Accuracy Thread
Post by: gunn on July 15, 2017, 11:37:56 PM
Mine shoots 55 and 62 gr equally well.