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Post by magnumwheelman on Jul 22, 2021 10:19:43 GMT -5
Just bought a new Leupold Mark 4 20 MOA base... interestingly, it comes with both #6 & #8 screws... 8-40 screws to be exact... my Browning A Bolt I'm mounting a new scope to, is tapped for #6's... I bought a long range 3-30 power, 1st focal plane, lit reticle, Osprey & it's a biggun... the new mount says use the 8-40's for "today's larger scopes" my local tool & fastener place had to special order me the 8-40 tap, apparently they are not common beyond gunsmith work ... again, assuming on a 338 Win Mag, that the #8 screws are substantially stronger than the #6's & it's worth while drilling out the threaded #6 holes & tapping for the #8's???
... & that I should go ahead & drill & tap the holes in my receiver to 8-40... no negatives... right???
( the older Leupold base I had on the rifle, only used 3 of the 4 #6 screw holes in the receiver, I never had problems with the larger Burris scope that was on it for years... it just didn't have rings available for the 35 mm scope tube ) maybe 4 - #6's are plenty for a big scope??? this Osprey is the largest, heaviest scope I now own, & thinking the #8's on the 338 Win Mag is cheap insurance...
also on another note, I recently bought an unfired older BFR in 45-70... total intention was to mount a Leupold red dot tube sight like I have on my 500 JRH BFR... this older gun, ( has the "fits Ruger" rubber grip, Ruger logo rear sight, & stainless Super Blackhawk hammer, includes the factory mount, as it should, but the screws are all standard straight slot screwdriver style, rather than Torx screws like I think came with the newer manufactured 500 JRH BFR... before I Locktite the straight slot screws in, I'm thinking I should switch them out for Torx ( I should have some that fit in my screw kit... would there be any reason I should keep & use the straight slot screws??? can imagine they would be much more difficult to remove down the road after Locktite, than the Torx
Thanks
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Post by bradshaw on Jul 22, 2021 16:51:26 GMT -5
Just bought a new Leupold Mark 4 20 MOA base... interestingly, it comes with both #6 & #8 screws... 8-40 screws to be exact... my Browning A Bolt I'm mounting a new scope to, is tapped for #6's... I bought a long range 3-30 power, 1st focal plane, lit reticle, Osprey & it's a biggun... the new mount says use the 8-40's for "today's larger scopes" my local tool & fastener place had to special order me the 8-40 tap, apparently they are not common beyond gunsmith work ... again, assuming on a 338 Win Mag, that the #8 screws are substantially stronger than the #6's & it's worth while drilling out the threaded #6 holes & tapping for the #8's??? ... & that I should go ahead & drill & tap the holes in my receiver to 8-40... no negatives... right??? ( the older Leupold base I had on the rifle, only used 3 of the 4 #6 screw holes in the receiver, I never had problems with the larger Burris scope that was on it for years... it just didn't have rings available for the 35 mm scope tube ) maybe 4 - #6's are plenty for a big scope??? this Osprey is the largest, heaviest scope I now own, & thinking the #8's on the 338 Win Mag is cheap insurance... also on another note, I recently bought an unfired older BFR in 45-70... total intention was to mount a Leupold red dot tube sight like I have on my 500 JRH BFR... this older gun, ( has the "fits Ruger" rubber grip, Ruger logo rear sight, & stainless Super Blackhawk hammer, includes the factory mount, as it should, but the screws are all standard straight slot screwdriver style, rather than Torx screws like I think came with the newer manufactured 500 JRH BFR... before I Locktite the straight slot screws in, I'm thinking I should switch them out for Torx ( I should have some that fit in my screw kit... would there be any reason I should keep & use the straight slot screws??? can imagine they would be much more difficult to remove down the road after Locktite, than the Torx Thanks ***** The heavier a scope, the greater its inertia as the rifle recoils. The higher a scope the the greater its leverage. I would try the #6 screws as is, clean threads and mount surfaces with acetone. Apply Loctite 380 or Loctite Red to mating surfaces. Paint fingernail polish in threaded holes and on screws. Tighten. Torq are a good idea but do not negate need at disassembly for HEAT to weaken Loctite. I would not try to loosen Loctite 380 or Red without heat. The .338 Winchester Magnum is a powerhouse without shame, possessed meanwhile of a bit of recoil. David Bradshaw |
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Post by potatojudge on Jul 22, 2021 18:44:43 GMT -5
Maybe not helpful, but I'd reconsider the Osprey scope. I mounted a 34mm illuminated Meopta scope for a friend recently and it felt like strapping a brick to the top of the gun at I think around 40 ounces.
Similar specs with a solid reputation is the Sightron SIII and it's a relative lightweight with good glass and turrets, FFP, all that in a Japanese IIRC made scope that weighs 22 ounces or so. They have a good reputation with precision rifle guys and specialty pistol shooters.
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Post by bigbrowndog on Jul 22, 2021 19:22:20 GMT -5
The only scope I’ve ever had come flying off was a relatively lightweight Leupold 4x compact, mounted on a 416 rem mag, the 4 #6 screws sheared off and sent the scope into my forehead. Luckily during a range session. I do not recall my mounting regimen at the time, but retapping the receiver for #8 screws and loctite everything down solved the issue. It would suck to have a catastrophic failure while on a hunt or In the field.
David is correct in that weight and height of the optic and mounting system, along with recoil speed of the gun will affect whether or not screws will hold. Personally I’d go with the #8’s if they recommend them.
Trapr
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Post by magnumwheelman on Jul 22, 2021 19:52:58 GMT -5
Well on the BFR, the base has bigger holes ( the slot screw heads are bigger diameter ) I have Allen and Torx screws, but they have smaller diameter heads… so I’m keeping the slot screws for now
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Post by leftysixgun on Jul 23, 2021 16:06:08 GMT -5
Ill add this also, make sure you seat the base against any recoil lug the base and rifle have to offer. That helps any “whiplash” (likely not correct term) issue.
Granted they are only .223 rifles, but my Seekins base has a recoil lug that seats against an edge of the receiver. Actually the forward top edge of the ejection port.
Proper screw torque goes a long ways too!
Bottom line....Under recoil, everything has to move in unison.
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Post by Sawfish on Jul 27, 2021 12:20:27 GMT -5
I have replaced all of the mounting screws om my heavy kickers with 8:40 screws. Brownells has the screws as well as the taps.
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WARDOG
.30 Stingray
Retired.....mostly.
Posts: 199
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Post by WARDOG on Aug 10, 2021 20:58:35 GMT -5
Interesting...I posted some advice / how to on this thread and my post is now gone. Posted July 22 I believe.  Here it is: Y ou're asking about negatives and screw strength?
The difference between a #6 and #8 is about .027" o.d. which doesn't sound like much, but it is. I'm surprised to learn that the Browning only uses #6's.
For a heavy Osprey on the magnum the #8 screws will be advantageous. However, do you have the proper equipment to enlarge the holes? A good vise to hold the action, a way of center finding the action so the new holes will be centered? Do you have a solid drill press or milling machine? Don't try to do the hole by eye with a Makita. Personally I would use a reamer to ream out the old threads. Drill bits can bite at the thread entrance and start a new hole off center. If you choose to use a drill bit, you will need the correct size. Don't round up or down to make the hardware store bit work. With 8-40 screws the threads are very fine so they will need a close tolerance hole. Hopefully the holes are through holes and not blind. If you tap the through hole be sure to deburr the inside of the hole before you reinsert the bolt. A poor quality 8-40 tap can easily break in the hole so use lube, take your time, don't force the tap and back off every 180* or less to break the thread chip before advancing.
There is a lot to know just to enlarge some simple holes. If you are not prepared, you will be happy you sought out a gunsmith or machinist to do the work. |
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Post by magnumwheelman on Aug 11, 2021 7:51:28 GMT -5
thanks for reposting... I did see your original post...
I have a #29 Drill bit which should be the correct size for the #8 tap... which the 8-40 tap took almost a month to get ( dang shortages of everything right now )
I think I'm going to try it myself... I'll pull the barreled action out of the stock, & remove as many parts as possible... I have a vice for my drill press, & all the holes go through the receiver... not sure the best way to deburr in the bolt tunnel after drilling & tapping ( maybe a rat tail file carefully )
my fabricator buddy could get me out of trouble, as long as I don't go too far ( he has proper drill bits & taps ) but is extremely busy right now... & if he has any free time, I'm hoping he can cut down the 10" barrel on my newest BFR, rather than helping me with what should be a pretty easy redrill & tap???
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Post by magnumwheelman on Nov 2, 2021 11:51:14 GMT -5
so a follow up on this project... the Browning A-Bolt does not have a flat side, it would take a lot of verifying ( probably screw some long screw stock into the existing holes to verify they are true ) before locking things down & drilling new hole diameters... So... I have a machinist / fabricator buddy that has been wanting to start working on guns... he bought all my retired tool & die buddies equipment ( most of it was old school, but now has most of the tooling needed for his newer equipment ) he just got done cutting down the barrel, on a long barrel BFR for me including drilling & tapping a true hole for the front sight... I decided to let him do the drilling & tapping on my rifle... he's been charging me about half what I'd expect to pay, & if something is questionable, we talk about it, & or he can still call my retired tool & die buddy for suggestions... so this project moves forward... which is a good thing, since it's been torn apart on my work bench for a couple months, while I tried to talk myself into doing it  |
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Post by zeus on Nov 2, 2021 12:39:42 GMT -5
“Apply Loctite 380 or Loctite Red to mating surfaces”
A riflesmiths nightmare when it’s found. I get pics from smiths all the time when a gun comes in like that 🤣🤣 I guess it works but what a mess!
Glad to hear you’re getting some help. Some receivers just aren’t easy to hold at all. Last thing you want is it coming loose when the drill is going!
On a side note, we use 8-40 on almost everything. Most custom actions come that way as well these days. As far as loc tite goes, we use it on nothing. Torque your screws right and if you want to, have your smith pin that receiver and your base as an “anti shear” method. Any resistance helps with inertia. I just finished a build for my son in 300 Win Mag with a titanium receiver and carbon barrel and it has a big scope for his hunt he was on. But the gun is light and the scope is heavy. That action I think uses two pins, front and rear portions of the reciever. Blind bottom in receiver and matched to rail. Super simple way to getting that support.
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Post by magnumwheelman on Nov 2, 2021 12:59:18 GMT -5
This one has the BOSS system... so with the longer barrel, weight on the end, & ports... I always thought it kicked like a 30-06... so I should be good... I'm hoping to build a trailer with jacks on the corners for stabilization, my 1/4 mile long driveway runs beside & behind my 300 yard rifle range... I'm hoping if I go about 300 yards down the driveway & plant the trailer, that when the crops are out, or in the spring, when the corn is shorter, that I can get about 600 yards shooting over to my backstop... thought this would be a good rifle for me to play with at 600 ish yards... |
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Post by zeus on Nov 2, 2021 13:24:40 GMT -5
Should be fun!
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Post by bushog on Nov 2, 2021 17:37:24 GMT -5
This one has the BOSS system... so with the longer barrel, weight on the end, & ports... I always thought it kicked like a 30-06... so I should be good... I'm hoping to build a trailer with jacks on the corners for stabilization, my 1/4 mile long driveway runs beside & behind my 300 yard rifle range... I'm hoping if I go about 300 yards down the driveway & plant the trailer, that when the crops are out, or in the spring, when the corn is shorter, that I can get about 600 yards shooting over to my backstop... thought this would be a good rifle for me to play with at 600 ish yards... You can tune those BOSS systems to change the resonance in the barrel. Can be VERY accurate rifles. |
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Post by magnumwheelman on Nov 3, 2021 13:21:08 GMT -5
Buddy turned around the rifle in 1 day... so looks like I get to clean it up & put it together tonight... hoping I can find all the parts ( it's been apart for almost 2 months  ) Speaking of tuning the BOSS, I should look for my tuning paperwork... I think the rifle came with suggested BOSS adjustments, based on bullet weights... found this on line... www.browning.com/support/faq/boss-sweet-spot.htmlIn excel, I made up a chart, spaced out the bullet weights over an entire sheet, just for the 338, so there are lots of spaces for handloads, across the bullet weights... assuming both velocity & bullet weights greatly affect the harmonics of the barrel... in the past I just bought factory, & set to the averages posted on the sheets... hoping over the next year, to reload a bunch, & shoot, tune, & record my results out to 600 yards with this rifle... anyone else with a BOSS played around with lots of reloads & documented your results???  |
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