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One of Us |
Does anyone have a shop drawing for the LR Mauser bolt lapping tool, similar to the one Brownells sells? (part#: 080-097-198)? Many thanks. -- ale | ||
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It's so simple you don't even need them. But send me your email or address and I'll get you out a set of blueprints. -Don | |||
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I have to agree with Don, further, whenever I see someone working on their (hopefully not someone else's) gun ask a question like this, I wonder what they are doing working on guns. | |||
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Don you are a nice guy, thanks for helping out opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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Thanks, Don, but I think I'll pass. It appears some people already think I'm a bubba. I was more curious about the spring tension than a cross-sectional view. Thanks, guys. | |||
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spring tension is not very critical. I cut up Mauser firing pin spirngs for mine. Just do that because I have a box full of them and they are cheap. I can post a pic of what a complete and torn down one looks like if you want me to. Won't be any problem (just need to snap a pic), so let me know if it would help you | |||
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Here it's for both lugs and torque shoulders. -Don  | |||
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I don't use a spring in my lapping jigs any more. Instead, I use a setscrew with a lock nut and keep adjusting it a little at a time. This keeps from lapping a helix into the lugs. With a spring, the longer you lap it the more helix you get. I never had any problems with rifles I built using a spring loaded lapping tool. I just saw an extreme example when an action was left on an automatic lapping machine too long and put a severe helix in the lug face, bolt & action. The action had to be set up and machined square again. | |||
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Can you give some more details on this? Sounds interesting. -Don | |||
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If you look through the front of an action when rocking the bolt like you were lapping it, the leading edge of the bolt lug and action lug recess get the most contact time. So, these parts get more material removed. When the bolt is closed the leading edge of the lug is not in contact with the leading edge of the recess. Parts that have the most lapping time line up with the part that has the least lapping time. This eventually grinds a helix on both if they are held together with spring pressure. If you replace spring pressure with a fixed distance then there is less chance of grinding a helix. | |||
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I made mine from the stub of a military barrel, with the chamber enlarged with a shoulder drill. Mandrel shaft is the size of the drilled out chamber (.500")for the first step, and .375" for the drilled out barrel portion. I pointed up the threads turning it between centers on the mandrel to square everything and make it easier to turn on by hand. Not fancy, but it works well. | |||
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Thanks, now it makes sense! -Don | |||
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Jim - Gunmaker, I don't understand. A helix? isn't a helix a spring shaped spiral as in a double helix is two intertwined springs like a DNA strand? I don't understand what you mean by you will grind a helix? Mike Legistine actu quod scripsi? Never under estimate the internet community's ability to reply to your post with their personal rant about their tangentially related, single occurrence issue.  What I have learned on AR, since 2001: 1. The proper answer to: Where is the best place in town to get a steak dinner? is…You should go to Mel's Diner and get the fried chicken. 2. Big game animals can tell the difference between .015 of an inch in diameter, 15 grains of bullet weight, and 150 fps. 3. There is a difference in the performance of two identical projectiles launched at the same velocity if they came from different cartridges. 4. While a double rifle is the perfect DGR, every 375HH bolt gun needs to be modified to carry at least 5 down. 5. While a floor plate and detachable box magazine both use a mechanical latch, only the floor plate latch is reliable. Disregard the fact that every modern military rifle uses a detachable box magazine. 6. The Remington 700 is unreliable regardless of the fact it is the basis of the USMC M40 sniper rifle for 40+ years with no changes to the receiver or extractor and is the choice of more military and law enforcement sniper units than any other rifle. 7. PF actions are not suitable for a DGR and it is irrelevant that the M1, M14, M16, & AK47 which were designed for hunting men that can shoot back are all PF actions. 8. 95 deg F in Africa is different than 95 deg F in TX or CA and that is why you must worry about ammunition temperature in Africa (even though most safaris take place in winter) but not in TX or in CA. 9. The size of a ding in a gun's finish doesn't matter, what matters is whether it’s a safe ding or not. 10. 1 in a row is a trend, 2 in a row is statistically significant, and 3 in a row is an irrefutable fact. 11. Never buy a WSM or RCM cartridge for a safari rifle or your go to rifle in the USA because if they lose your ammo you can't find replacement ammo but don't worry 280 Rem, 338-06, 35 Whelen, and all Weatherby cartridges abound in Africa and back country stores. 12. A well hit animal can run 75 yds. in the open and suddenly drop with no initial blood trail, but the one I shot from 200 yds. away that ran 10 yds. and disappeared into a thicket and was not found was lost because the bullet penciled thru. I am 100% certain of this even though I have no physical evidence. 13. A 300 Win Mag is a 500 yard elk cartridge but a 308 Win is not a 300 yard elk cartridge even though the same bullet is travelling at the same velocity at those respective distances. | |||
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Mike It's not a steep helix, but the more you close the bolt after the lugs clear the closing cams, the farther the bolt moves forward. You can measure it with a depth mike on receivers that have been lapped too much. If you put dykem on the lug recess after lapping and rock the bolt a few times and look in the receiver from the front you will see the blue is rubbed off just some of the way around. It may be wiped off completely on the bolt lugs, but looking at the missing blue may not be telling you the true story. You really need to look in the front of the receiver and think about it while rocking the bolt. the last few degrees of bolt rotation only get a few degrees of lapping time. If you could cut off the bolt handle and spin it round and round in the receiver that would lap things perfectly flat. I don't think this would be a big problem on bolts that you hand lap for a limited time. The one I remember was left on a lapping machine over lunch or something and it had to be machined back. The next time the bolts were run there was a special one with more meat left on the back of the lugs to match the re machined action. | |||
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I'm not sure that's a helix. Perhaps an angle as in what you'd see in a ramp. Isn't the cocking notch a true helix versus what you are talking about? | |||
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 A machinist understanding and explaination | |||
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Bill Calfee has an interesting article on Locking lugs and lapping. I think that he is saying about the same thing as Gunmaker. This is in this months Precision Shooting. Butch | |||
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Butch, You referring to the guy that has all those "Friends"; "your friend..." Jim Kobe 10841 Oxborough Ave So Bloomington MN 55437 952.884.6031 Professional member American Custom Gunmakers Guild | |||
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gunmaker -- Thanks for the great suggestion. The locknut and set screw idea sounds a lot like my reloading dies. Between Don's photo and your description, I think I've got a handle on it. Many thanks. For the sake of discussion...wouldn't limiting the rocking of the bolt handle from 45- to 15-degrees, or even 5-degrees, prevent the uneven wear that you describe in the spring loaded lapping tool? | |||
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Brian, You really need to read my "friends" article in PS. It will make you think a little bit about cutting and or lapping lugs. Butch | |||
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I'm going to the book store this morning <g>. | |||
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That's pretty much what I do now. Less rotation theoretically would cause less helix. The reloading die is a good example. I use a bolt face sized brass pin between the bolt face and the set screw. I still lap things in, but the more I do the more I believe less is more. If the lugs are that far off then they should be machined square first and not over lapped out. There's still the cocking piece pushing the back of the bolt up when the rifle is in battery. This puts the bolt in a different attitude then when there is pressure on the bolt face during lapping. When you pull the trigger the back of the bolt drops and changes attitude again. The top lug doesn't bear all the time and the bottom lug acts like a pivot. I wonder if a benchrest action would be better served with the lugs locking up at 3 and 9 o'clock instead of 12 and 6?  | |||
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It would be much better at 9 and 3. Butch | |||
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There are some benchrest actions that have three locking lugs up front. Seems like a good idea to me. The only easy day is yesterday! | |||
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