View Full Version : measuring 5 groove bbl.
porthos
03-02-2021, 05:07 PM
have taken pound cast's of 2 enfields. i think that there is a "trick" to measuring the groves of the 5 groove bbls. can someone refresh my memory??
para45lda
03-02-2021, 05:27 PM
Not sure if you've searched here yet but I know I saw it a few years ago.
http://castboolits.gunloads.com/showthread.php?149803-Actual-barrel-dimension-of-bullet-size-for-the-Lee-Enfield
#1- A dial caliper I would call close, a real mic better choice. Find a soda can and cut off top and bottom with scissors, cut side to create a sheet. Cut strips the width required for your given area of intent. Measure strip thickness, = (x), I wrap boolit and light pinch off backside with hemostats, measure total and then subtract the thickness of can x 2 = your slug. Works good enough for me. There is a fancy drawing requiring process of a triangulation method, but-----
Nobade
03-03-2021, 07:00 AM
I use a V anvil mic designed for measuring 5 flute objects. Got it for measuring throating reamers and such.
midnight
03-03-2021, 09:25 AM
I use two v-anvil micrometers, one for three fluted objects & one for 5 fluted objects. A machinist with a lot of tooling should have one & may measure for you. I have also seen the dimensions of a v-block used to do this. I have it around here someware. Using the search function should find it. I decided v-anvil micrometer was the best solutiom.
Bob
Goofy
03-03-2021, 11:12 AM
A more detailed examination with measuring a wrap around with pics:
http://www.texas-mac.com/Measuring_Groove_Diameters_of_Odd_Groove_Bores.htm l
The above answers are good, and I can only add what works for me. Life long machinist/mechanic with a good feel for micrometers here. I can slowly spin a cast bullet in my mikes as I slowly close the spindle and "feel" a good measurement. I have checked my method against the "wrapping" method and get accurate measurements with my method...
oley55
03-03-2021, 01:57 PM
A more detailed examination with measuring a wrap around with pics:
http://www.texas-mac.com/Measuring_Groove_Diameters_of_Odd_Groove_Bores.htm l
I prowley won't be trying to use the Powley formula. Just saying...
An aside, soda cans are not perfectly uniform top to bottom (+/- .0005"), which only makes sense when considering the pressing/forming process. To eliminate this tiny variable, cutting your strips following the radius of the can will be more consistent.
vagrantviking
03-03-2021, 03:01 PM
The above answers are good, and I can only add what works for me. Life long machinist/mechanic with a good feel for micrometers here. I can slowly spin a cast bullet in my mikes as I slowly close the spindle and "feel" a good measurement. I have checked my method against the "wrapping" method and get accurate measurements with my method...
This is what I do. The high points on the corners come very close. Plenty close enough to get a starting point for 2 to 3 thousandths over size.
oley55
03-03-2021, 03:20 PM
This is what I do. The high points on the corners come very close. Plenty close enough to get a starting point for 2 to 3 thousandths over size.
yes and no. Take my Ruger Speed-Six which always seemed to be trying to lead, but never severely. Using the shim wrap method I confirmed my cylinder throats were only .0008"-.001" over groove. A 2-3 thou guesstimate would be/was meaningless in this situation. After nearly four hours of slowly honing my throats yesterday, I now have a sweet .002" throat over groove diameter and can't wait to see how she performs.
Bad Ass Wallace
03-03-2021, 08:40 PM
https://i.imgur.com/KU0yt5k.jpg
The most accurate way!
oldhenry
03-03-2021, 09:04 PM
I wrap a .002 feeler gauge around the slug, measure with my Mitutoyo. I deduct .004 & have the answer.
Alstep
03-04-2021, 02:24 PM
The above answers are good, and I can only add what works for me. Life long machinist/mechanic with a good feel for micrometers here. I can slowly spin a cast bullet in my mikes as I slowly close the spindle and "feel" a good measurement. I have checked my method against the "wrapping" method and get accurate measurements with my method...
This method works well for me too. The "feel" is skill only acquired with time & experience in the shop.
alfadan
03-04-2021, 05:36 PM
Just for kicks you can use a ground v-block and a height gauge calibrated with a pin gauge. :groner:
W.R.Buchanan
03-04-2021, 05:44 PM
Measure the actual bore dia with a gage pin. .303 ? Measure groves with caliper, you will be in one grove and one land. .308= grooves are .005 deep. so .308+.005 = .313 which is exactly what mine is.
Randy
GregLaROCHE
03-04-2021, 09:35 PM
I have a NOE boolit sizer and a range of inserts. I try the slug in the smaller size working my way up until the boolit passes through. It works like a go, no go gauge.
M-Tecs
03-04-2021, 10:50 PM
Just for kicks you can use a ground v-block and a height gauge calibrated with a pin gauge. :groner:
You have a 108 degree v-block? That's rarer than 108 v-mics.
Good discussion here http://www.texas-mac.com/Measuring_Groove_Diameters_of_Odd_Groove_Bores.htm l
alfadan
03-05-2021, 11:00 PM
You have a 108 degree v-block? That's rarer than 108 v-mics.
Good discussion here http://www.texas-mac.com/Measuring_Groove_Diameters_of_Odd_Groove_Bores.htm l
I thought a 90* v block would work. May not be groove center-to-center but the depth of the grooves would "practically" be equal across the width of the groove. Good enough for what we're doing I suppose but I'm not a professional machinist, or even a good one lol.
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