Jeffrthehunter
Well-Known Member
Thanks for the info, I have decided to shorten the throat a little. I double checked magazine and load lengths on 175 and 180 and should be good to go. BTW, great looking rifle, laminated stock looks good.
Custom reamer for 7 Rem Mag and 195 Berger, any thoughts? 5/28 Chamber drawing added
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Jeffrthehunter
Well-Known Member
Thank you very much for the write up! The amount of info on this website is amazing. I have made some notes below in regards to your thoughts. I am just an amateur gun builder that likes to tinker, this build is more of lets see what I can do for a long range mountain rifle.
[QUOTE="keithcandler, post: 1914975,
Things to remember on reamer design:
A. neck clearance, take into account the skim cut on the neck if you want to clean it up. You want a minimum of .004 clearance in the neck of a loaded round. (my hand loads are .313" with Lapua brass so .316" cut size should be good, I do not want to turn necks)
B. .240 Freebore is very, very long. There is also another .015 at least that comes off the case mouth on that 45* angle you see. I would not go longer than .190. Stuff the bullet down in the case, and monitor for doughnuts. (based on yours and a few others feedback I have shortened the throat. I will have plenty of clearance in my magazine and still have full case capacity. 175 ABLR and the 180 VLD can be loaded to the lands if I wanted, for hunting rounds I have always had at least .020" jump)
C. you say you have .030 Cartridge base to ogive on a new barrel, Length of the cartridge for magazine use. Few hundred rounds and your have zero clearance in your mag box...plan for success, give yourself more clearance. Planning on .030 clearance on a new barrel, is in deed planned failure. (should not have many rounds through this barrel, it is a hunting gun)
D. .514 dia in front of the Web. Get samples of the brass you plan on using and mic it with a good micrometer, not calipers. Give yourself .003 at a bare minimum, and you may want to buy the set of dies you are planning to use in advance, size some fired brass, and see what dimension the dies size to taking into account the spring back.
E. I like #5 contour barrels, and Brux is at the top of my list. If I were hiking in the Utah mountains, I would either have the #5 fluted or go #4 contour. The less machining on my barrel, the better I like it, chambering and threading the muzzle is all I will tolerate. I expect a custom hunting barrel to shoot at least in the very low 3's, preferably better. 1/2 MOA is border line for me, 1/4-1/3 MOA is acceptable to an old benchrest shooter/hunter, and 5/8 MOA is time to set a barrel back or put on a new tube. ( 1/2 moa is the best I can shoot on good days, old nerves and old eyes)
F. 7 Mags have some recoil, you need some weight for controlling recoil. (agree, this gun will be at least 10lbs)
G. Alex Wheeler on accurateshooter is a darn smart cookie when it comes to building long range deer and elk rifles. He knows his way around long range rifles, and will steer a guy in the right direction, first time! ( I agree, seems like a great guy)
H. Magazine box OAL will eventually have something to do with your barrel life, so change your expectations, and plan on eventually shooting a single shot. (should be good with shorter throat)
I. if you want to use the magazine box for all hunting applications, then plan on 600 and MAYBE 800 rounds of useful barrel life. This short barrel life, does not leave much room for load development, thus the shorter freebore becomes more attractive.
In the past, I have gone much tighter dimensions than the ones above, and experience has a $ cost to the learning curve. For instance, .002 clearance on the .514 web dimension...really bad thinking as this was what Target shooters use. I did not check the dimension against the web of the brass nor the dimensions that the brass was sized to. I had to have RCBS make me a small base sizer, and RCBS does not offer this service anymore. Often, the most accurate load that is shooting 1/4 MOA is on the ragged edge of high pressure, plan on success giving yourself some breathing room in the web.
ON a more positive side, I have gone .110 FB using 168g Bergers with no problems, Remington & Win brass, R#22 and R#26, and Retumbo at 3100 in a 26" and one 28" that was 3200.
Two things, I don't like the cost of a carbon fiber barrel, and I do not like the way a reamer pilot rides the tops of the lands of 7mm 5 R rifling. If/when the reamer pilot falls down in the trough between the land tops, this creates reamer chatter. There are ways to "hide" & clean up chatter. Tight fitting reamer pilots can stop this problem, but they also may cause other problems. Many gunsmiths will not chamber a 5 R barrel for this reason....many. This 5R issue is controversial I know, but I don't take a chance. Give me a good 4 or 6 groove barrel any day, personal preference.
Shoot for accuracy in the extreme, don't cut corners, and GRAND success is sure to follow.
[/QUOTE]
[QUOTE="keithcandler, post: 1914975,
Things to remember on reamer design:
A. neck clearance, take into account the skim cut on the neck if you want to clean it up. You want a minimum of .004 clearance in the neck of a loaded round. (my hand loads are .313" with Lapua brass so .316" cut size should be good, I do not want to turn necks)
B. .240 Freebore is very, very long. There is also another .015 at least that comes off the case mouth on that 45* angle you see. I would not go longer than .190. Stuff the bullet down in the case, and monitor for doughnuts. (based on yours and a few others feedback I have shortened the throat. I will have plenty of clearance in my magazine and still have full case capacity. 175 ABLR and the 180 VLD can be loaded to the lands if I wanted, for hunting rounds I have always had at least .020" jump)
C. you say you have .030 Cartridge base to ogive on a new barrel, Length of the cartridge for magazine use. Few hundred rounds and your have zero clearance in your mag box...plan for success, give yourself more clearance. Planning on .030 clearance on a new barrel, is in deed planned failure. (should not have many rounds through this barrel, it is a hunting gun)
D. .514 dia in front of the Web. Get samples of the brass you plan on using and mic it with a good micrometer, not calipers. Give yourself .003 at a bare minimum, and you may want to buy the set of dies you are planning to use in advance, size some fired brass, and see what dimension the dies size to taking into account the spring back.
E. I like #5 contour barrels, and Brux is at the top of my list. If I were hiking in the Utah mountains, I would either have the #5 fluted or go #4 contour. The less machining on my barrel, the better I like it, chambering and threading the muzzle is all I will tolerate. I expect a custom hunting barrel to shoot at least in the very low 3's, preferably better. 1/2 MOA is border line for me, 1/4-1/3 MOA is acceptable to an old benchrest shooter/hunter, and 5/8 MOA is time to set a barrel back or put on a new tube. ( 1/2 moa is the best I can shoot on good days, old nerves and old eyes)
F. 7 Mags have some recoil, you need some weight for controlling recoil. (agree, this gun will be at least 10lbs)
G. Alex Wheeler on accurateshooter is a darn smart cookie when it comes to building long range deer and elk rifles. He knows his way around long range rifles, and will steer a guy in the right direction, first time! ( I agree, seems like a great guy)
H. Magazine box OAL will eventually have something to do with your barrel life, so change your expectations, and plan on eventually shooting a single shot. (should be good with shorter throat)
I. if you want to use the magazine box for all hunting applications, then plan on 600 and MAYBE 800 rounds of useful barrel life. This short barrel life, does not leave much room for load development, thus the shorter freebore becomes more attractive.
In the past, I have gone much tighter dimensions than the ones above, and experience has a $ cost to the learning curve. For instance, .002 clearance on the .514 web dimension...really bad thinking as this was what Target shooters use. I did not check the dimension against the web of the brass nor the dimensions that the brass was sized to. I had to have RCBS make me a small base sizer, and RCBS does not offer this service anymore. Often, the most accurate load that is shooting 1/4 MOA is on the ragged edge of high pressure, plan on success giving yourself some breathing room in the web.
ON a more positive side, I have gone .110 FB using 168g Bergers with no problems, Remington & Win brass, R#22 and R#26, and Retumbo at 3100 in a 26" and one 28" that was 3200.
Two things, I don't like the cost of a carbon fiber barrel, and I do not like the way a reamer pilot rides the tops of the lands of 7mm 5 R rifling. If/when the reamer pilot falls down in the trough between the land tops, this creates reamer chatter. There are ways to "hide" & clean up chatter. Tight fitting reamer pilots can stop this problem, but they also may cause other problems. Many gunsmiths will not chamber a 5 R barrel for this reason....many. This 5R issue is controversial I know, but I don't take a chance. Give me a good 4 or 6 groove barrel any day, personal preference.
Shoot for accuracy in the extreme, don't cut corners, and GRAND success is sure to follow.
[/QUOTE]
Last edited:
Alex Wheeler
Well-Known Member
See the scuff marks left on the neck from your neck bushing? See where they stop? Below that is unsized neck. The junction of the shank of the bullet and the boat tail is where the pressure ring forms on a bullet. Its usually a few ten thousandths larger than the rest of the shank. It acts like and expander mandrel when you seat a bullet. If you push it through the sized part of the neck, you loose control of neck tension. That doesnt mean it wont shoot. But, ideally if its possible, I like to keep the pressure ring in the sized part of the neck at the farthest jump you may use. Keep in mind different bullets have very different bearing surface lengths, for example a 175 lrab needs .050" more freebore than a 180 hybrid. Its hard to get a reamer to do it all, thats why I end up with so many.
Jeffrthehunter
Well-Known Member
Thanks for those thoughts Alex, it is so tough for me to learn and put my best foot forward when many of the experts disagree. With that said I went to a .220 free bore with the VLD180 in mind. This should allow me to do as you described and I am sure it will shoot good. 195 is what I want to shoot but I was afraid to commit my chamber to that round. Hopefully I can shoot half MOA with everything!
Jeff
My 7 stw has .219 freebore for 180s. It shoots great. One of my 7mm rem mags only has a Sammi throat and it shoots great with 180s but I can't get the velocity that the fellows with .220 freebore get. If you can get a 180 to 3050 with .220 freebore in the 7mm rem mag, and I think you can, it will be very hard to beat ballistically, terminal wise, recoil tolerability, and very economical as far as brass is concerned. What's not to like about that. Good luck.Thanks for those thoughts Alex, it is so tough for me to learn and put my best foot forward when many of the experts disagree. With that said I went to a .220 free bore with the VLD180 in mind. This should allow me to do as you described and I am sure it will shoot good. 195 is what I want to shoot but I was afraid to commit my chamber to that round. Hopefully I can shoot half MOA with everything!
Jeff
Alex Wheeler
Well-Known Member
.220 is a bit short for a 180 vld if your jumping, but if you pay attention to the doughnut you will be ok. Ream it out if it starts touching the bullet. For 1/2 moa you'll be just fine. Unless you know the bullet well, dont guess. Send a dummy in and have it measured, thats the only way you will get what you want.
