Author Topic: Knurled bbt 51g (Read 10622 times))

oneshot61 · « **on:** December 31, 2016, 05:13:37 PM »

I read about doing this somewhere on a forum, just cant remember where. I tried it today, and it definitely tightened my group. For me, if I can shoot an inch at 100 yards with an air rifle, I'm a happy man. I shot several groups today and when I got back home, for the life of me I cannot find the target in my truck. So mandatory pictures will have to wait till next weekend. But here is what it looks like after rolling between two medium files.

Edit: Moderators, meant to post this in pcp gate. Please move?

rsterne · « **Reply #1 on:** December 31, 2016, 05:36:19 PM »

Interesting way to do the knurling.... It was BillG here on the GTA that knurls his swaged slugs....

Bob

oneshot61 · « **Reply #2 on:** December 31, 2016, 05:51:54 PM »

Yes sir, you are correct. I just did a search here and its one of the post I read. It works.

Habanero69er · « **Reply #3 on:** December 31, 2016, 05:52:42 PM »

John Cripe (Johninthecamper) knurled some .22s for me. They weren't BBTs, but the knurling had the same effect.

oneshot61 · « **Reply #4 on:** December 31, 2016, 06:03:27 PM »

Good to know. I've not shot any of his, (Johns) but know him by reputation. Lot of great minds here doing a lot of great things for the air gun world. I'm just getting to reap the benefits of their knowledge. Love the bbt's and the knurling seems to take out some of the variations that cause fliers at longer ranges. Chasing that perfect bullet, barrel, pressure setup.

Prouzy · « **Reply #5 on:** December 31, 2016, 07:10:38 PM »

What effect does it have, easier grooving, less friction, etc? Interesting, had not seen that.

oneshot61 · « **Reply #6 on:** December 31, 2016, 08:02:46 PM »

Someone with more experience can chime in but for me it equalizes any imperfections in the casting and I'm seeing more consistent groups. Seems to stand up micro pieces of the bullet to fill the groves more evenly. ( that's my newby explanation)

rsterne · « **Reply #7 on:** December 31, 2016, 08:22:03 PM »

They will chamber easier.... That may be most of the key, allowing the bullet to "self-align" with the rifling due to a lower force required.... My concern would be with the method used (rubbed between two files) not producing a uniform "knurl".... If that happens, the bullet could chamber off-center....

Bob

rifle50 · « **Reply #8 on:** December 31, 2016, 09:12:55 PM »

Quote from: rsterne on December 31, 2016, 08:22:03 PM

My concern would be with the method used (rubbed between two files) not producing a uniform "knurl".... If that happens, the bullet could chamber off-center....

Bob

DUH-YA THINK?? Rubbing/rolling free hand between 2 files ISN'T going to produce a more concentric bullet than one out of a premium cut mold......If it helps accuracy, they aren't size correctly to start with, or something else was not at it's best..........

oneshot61 · « **Reply #9 on:** December 31, 2016, 10:21:04 PM »

Maybe so. I tried .251,.252,.253,.254. After cleaning the barrel, 1,2,3 shot good with .251 shooting the best. But I kept getting out lying shots. After doing this today, I got 3 groups of 6 at 1 inch @ 100 yards. ( measured with a tape) I have a six shot revolver mag. Then refill after 6 shots. Not sure why it's working, but it is at this point. I'll get a shooting vice to remove my shaky hand input and a more true test of the bullet itself. I'm resting on my range bag at the moment. If it reduces my group size to do this, might be worth it.

rsterne · « **Reply #10 on:** December 31, 2016, 11:20:32 PM »

I have a creedo that says "never argue with success".... I was merely pointing out a possible source of inconsistency with this method of knurling.... However, if it works for you, and you can repeat the process from day to day and month to month.... then more power to you.... ANYTHING that allows you to increase accuracy and repeatability is worth doing, regardless of what the theory says....

Bob

K.O. · « **Reply #11 on:** January 01, 2017, 12:18:23 AM »

In one of my post I mentioned making a jig for repeat-ability with the file method, simple U shape...but it was one of the things I was going to try if necessary to get the BBT 40g thru the choke. Take a look at a chamberd round knurled and not knurled any finning on the back of the drive band..? If so the knurling can reduce it depending on how knurled it is... heaivly knurled and it gives the lead some where to get displaced to other than the back of the band...

you can also build something like the Korbin knurler... http://www.bulletswage.com/hct-2.htm

K.O. · « **Reply #12 on:** January 01, 2017, 12:23:35 AM »

What Barrel? speed? or speeds?

oneshot61 · « **Reply #13 on:** January 01, 2017, 01:06:47 AM »

I agree it's probably not the most consistent manner and actually was looking tonight at the Corbin unit. I believe the barrel is 1-18 twist and shooting a high of 955 with an average of 905? Over 20 shots.

Tofazfou · « **Reply #14 on:** January 01, 2017, 01:01:15 PM »

Those are great results despite the "HAND" method while knurling.

What happened to Bill G with the whole KNURLING thing anyways? I was anxiously awaiting those after he announced them.......

shorty · « **Reply #15 on:** January 01, 2017, 01:57:28 PM »

I have been interested in the knurled bullet too.

Doesn't knurling increase the diameter of the bullet. I know when turn parts on the lathe and then knurl, the part always increases in diameter slightly. Do you think it would be advisable to re-size after the bullet is knurled or does that defeat the idea?

Tofazfou · « **Reply #16 on:** January 01, 2017, 02:35:30 PM »

Quote from: shorty on January 01, 2017, 01:57:28 PM

I have been interested in the knurled bullet too.

Doesn't knurling increase the diameter of the bullet. I know when turn parts on the lathe and then knurl, the part always increases in diameter slightly. Do you think it would be advisable to re-size after the bullet is knurled or does that defeat the idea?

Sizing after knurling would defeat the idea:
NON AIRGUN RELATED-"knurling" bullets is simply to keep lube on the bullet. The old 38 special 158 gr Keith SWC's from SPEER were always knurled and they were awesome target rounds.

AIRGUN RELATED-"knurling" is new grounds no one has ever covered. So we don't really need lubed bullets. We will see what advantages Knurling offers for us.

rsterne · « **Reply #17 on:** January 01, 2017, 03:53:16 PM »

Bill G was starting with a swaged bullet between the land and groove diameter, and knurling it to make it seal while being easy to chamber.... He could then swage at a single, common size, and knurl to make the OD whatever he needed for the barrel.... His knurling tool was adjustable for finished diameter (with a stop), and the consistency was incredible....

I think he was simply overlooked at the time as a gimmick, which is a pity if that was the case.... I think he's still around, I PM'd him.... It was his hope, and intention, to sell swaged, knurled bullets in all the common calibers.... I know because I worked with him on the basic designs quite a bit....

Bob

K.O. · « **Reply #18 on:** January 01, 2017, 05:55:41 PM »

I feel each barrel needs evaluated )If you are sending realy heavy stuff with shallow rifling and the fps is getting up there... it may promote stripping and of course that will show up as leading...

I think the op is using an ace precision apex 330 .25 caliber and all I know is the barrel is part of the upper double air res... are the choke for pellets what sort of rifling

what I do not know is what type of leade it has... the leade on Cabbie (stock Syrod from Cabela's) is causing fliers with the BBT 40g... where as Norm for some reason is getting less fliers (stock power plant wood stocked Syrod from Norm)... from how they seat I am pretty sure the leades are hard edged like disco barrels

knurled also might tend to lead up a choke... maybe not... If so then lube might help...

I do think my 1322 that is sending 30g BBT out at about 550 fps thru a 22" disco barrel can/may benefit from reduced friction maybe... It was Loonie accurate at 40 yards first outing with the 220/222 that dropped way small but fit the disco barrel well... quick pine tree rested about 2 moa (a Loonie is just about 1" diam) at 40-50 yards first quick and dirty testing... I certainly will do the experiment... the development process is half the fun... especially when you get things working well..

I do think I will get close to moa at 50 yards(@550 fps

)with more work

but yep I can see probs and benafits from knurled BBT and some other rounds...

But the BBTs are charmed an elf told me they are the work of Santa's cousin... By the way when I asked him about designing the lights I did not know about the family connection... guess I am going to have to work on staying a good boy... the charm might go the other way for those that shout, cry and pout..

Tofazfou · « **Reply #19 on:** January 01, 2017, 06:13:34 PM »

Quote from: rsterne on January 01, 2017, 03:53:16 PM

Bill G was starting with a swaged bullet between the land and groove diameter, and knurling it to make it seal while being easy to chamber.... He could then swage at a single, common size, and knurl to make the OD whatever he needed for the barrel.... His knurling tool was adjustable for finished diameter (with a stop), and the consistency was incredible....

I think he was simply overlooked at the time as a gimmick, which is a pity if that was the case.... I think he's still around, I PM'd him.... It was his hope, and intention, to sell swaged, knurled bullets in all the common calibers.... I know because I worked with him on the basic designs quite a bit....

Bob

Good on ya Bob. Tell him that I said i want him moving fast forward on this. I always thought BG had great ideas and they are ideas that need pursuit. He knows that he has me as a loyal and dedicated tester for him and I will always give him my honest opinion. I want him back..............

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Knurled bbt 51g

Author Topic: Knurled bbt 51g (Read 10622 times))