Author Topic: .17?  (Read 972 times)

Prouzy

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.17?
« on: November 30, 2017, 11:51:59 AM »
Bob, have you ever done a .17 build, as in .172 bullet shooter?  I seem to be regressing from my earlier goals in caliber and after working with .224 build (getting there) and also recently shooting 17HMR rimfire, I find myself interested in trying something new.  NOE makes what appears to be a decent weight mold and in length for that caliber, but havent seen anyone do it.  Maybe its for obvious reason that are not so obvious to me  ;D I got a handle on casting the 39gr and 55gr .224, so maybe there is hope for me in casting something even smaller.  Not sure if TJs has such an animal, but I live just south of Green Mountain barrels and they have blanks although the OD would create a challenge on using my go to platform for tinkering.  Just wondered if this had been done and what kind of performance was accomplished.  Chris
« Last Edit: November 30, 2017, 11:55:47 AM by Prouzy »



rsterne

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Re: .17?
« Reply #1 on: November 30, 2017, 03:56:11 PM »
I've never done any .17 cal builds.... You would have to be careful to match the twist rate of the barrel to your longest intended bullet, as always.... The 26 gr. NOE .172 cal bullet is a scaled down NOE 225-55-FN which weighs 58 gr. (RCBS 22-055 FN).... ie identical proportions (shape).... Since required twist rate for a given bullet shape is measured in calibers, in inches the required twist rate can get pretty fast....

I ran the NOE 172-26-FN through the Kolbe twist calculator.... The PB version should be OK in a 9" twist, but the GC version (which without a GC works in theory like a slight boattail) should need an 8" twist.... The TJ's liner, which is 0.168" land and 0.172" groove is a 9" twist (and incidently is only 3/8" OD, although he may be able to do larger OD).... LW don't have anything faster, from what I can see.... I don't know about GM or others....

The SD of the 26 gr. is only 0.126, so you shouldn't have too much problem driving it fast enough without going crazy on pressure or barrel length.... That compares to 0.164 for the 58 gr. in .225 cal.... so the BC should be in that ratio (~76%) by comparision as well....

Bob
« Last Edit: November 30, 2017, 04:03:52 PM by rsterne »
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Prouzy

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Re: .17?
« Reply #2 on: November 30, 2017, 04:32:47 PM »
Thanks Bob.  I looked into and wondered about barrel twist, most are 1:9 (as is my 17HMR which shoots 17gr anyway), however I found one pistol barrel 1:8.  I think that OD in 3/8 could be an issue, I know my .224 was cutting it close for gunsmith to machine it to the breech, and on the flip side, the power burner barrels would require a different set up as well.  I also see many of the powder burner blanks to have a .173 groove and wonder the mold would drop a bit too small.  Have not found other .17 molds, so maybe this project needs to be table for a bit :-)  Thanks!

rsterne

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Re: .17?
« Reply #3 on: November 30, 2017, 04:44:09 PM »
You might be able to find CrMoly tubing to sleeve it with prior to machining.... or CF tube for the same job.... Also, you could ask Mike at TJ's if he can use larger tubing and end up with a larger OD, that may be possible as well.... I think the 9" twist would probably be OK....

Bob
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Prouzy

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Re: .17?
« Reply #4 on: November 30, 2017, 05:58:36 PM »
I should ask Mike, amd maybe that can help make the decision. I have most everything, really just need the barrel so maybe worth a shot for fun!

Monkeydad1969

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Re: .17?
« Reply #5 on: December 06, 2017, 07:55:02 PM »
Hmmm...
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Nvreloader

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Re: .17?
« Reply #6 on: December 25, 2017, 01:34:20 PM »
Joe
FWIW,
I am running a 1x9" twist in my 17 wildcats cases, from 2.5grs to 14grs case capacity,
and all the rifles/pistols I have shoot all bullet weights from 12 thru 25gr, very accurate.

Where you are going the air side, you should be able to find a .172 bbl fairly easy,
look for 17 cal bbls from the Ruger series of PB rifles, will have to remove the RF chamber,
and depending on how the bullet drop from the mold, you can size them to what you need,
using soft pure lead etc.

HTH,

Tia,
Don
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rsterne

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Re: .17?
« Reply #7 on: December 25, 2017, 07:00:18 PM »
Subsonic generally needs a faster twist than Supersonic.... Even if you are shooting bullets Supersonic that drop through Mach 1 from a barrel that is a 9" twist, that does not mean they will be stable if launched under Mach 1.... because their forward velocity slows faster than the RPM.... The only way to find out if a particular twist works in an airgun, if a stability program says if won't work.... is to try it....

Bob
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Monkeydad1969

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Re: .17?
« Reply #8 on: December 28, 2017, 11:05:03 PM »
Hmmm again...
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rsterne

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Re: .17?
« Reply #9 on: December 29, 2017, 09:25:39 AM »
If a stability program says you need an 8" twist, and you have a 9".... I would sure try it....

Bob
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Prouzy

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Re: .17?
« Reply #10 on: December 30, 2017, 03:41:23 AM »
Well, looks like Cedric(Tofazfou) did it! Posted on GTA.

Monkeydad1969

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Re: .17?
« Reply #11 on: January 05, 2018, 10:28:33 AM »
Cedric did a great job on his.  Putting up good numbers and accuracy seems to be there.  I'm pretty sure a YouTube vid is soon to follow.

Joe
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Prouzy

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Re: .17?
« Reply #12 on: January 05, 2018, 05:24:36 PM »
Looks good! Im thinking mine will be off an Airforce platform.