New member hello and question about cocking ramp

Howdy,
I've been a lurker for some months reading and learning. It's a great site w lots of good personalities and posts. I appreciate the help I've already gotten as a lurker! Anyhow, I'm shooting a couple Savages:

---Staggerfeed 270 110 w a walnut stock from Ebay, a SAV2 trigger, Deadnutz mount, Vari-X III 3.5x10x40, Kiff bolt body, Stockade handle, homemade bolt lift bearing, and a lot of other bolt mods.

---Centerfeed Stevens 200 308 w the factory camo tuperware, 3 screw trigger tuned to 3lbs, all the same bolt mods, another Vari-X III, and the same mount. I filled the entire buttstock w epoxy and I filled the forestock w epoxy and #8 shot mixed. I'm not worried about flex too much on it. I shoot of a pretty wide front bag.

I handload for both. 150gr SGKs over RL22 or H4831SC in Win brass for the 270. And 165gr SGKs over H4895 in Win brass for the 308. Right now, the 270 puts 2 touching and a third flier at about 1 MOA. I don't know if it's the rifle, me, or the load. The 308 only has 12 rounds thru the tube and it pulls of 3/4MOA w no issues. I love both rifles.

On to my first question. I know that SSS recuts the cocking ramp for decreased bolt lift, less wasted movement, and a shorter pin fall. I'm not interested in the full time and true. I talked to them and they won't recut the ramp w/o doing the whole job. That's understandable I suppose. I haven't talked to Kevin at Stockade, but I plan on it. I figure he'll have the same answer though. That just leaves me w a couple options. Ideally, this would be easiest achieved on CNC lathe w live tooling. I have access to many shops w that capability, but like any machine shop they tend to screw up the first piece doing setup and programming! It's an option though I reckon. My other thought is this. The cocking ramp could be shortened. Instead of doing a new helix or ramp angle (which requires the CNC), one could just cut the ramp short. The cocking pin would ride up part of the ramp, then move horizontally to its detent position. It wouldn't decrease bolt lift effort up the ramp initially, but it would decrease the amount of the lifting stroke that utilizes that much effort. And the material would still be there if you ever wanted to change the ramp angle. The advantage to this is that it could be done on a Bridgeport w a rotating vise and an endmill. What's yall's thoughts on both options?

"You're gonna shoot your eye out." ;D

http://4.bp.blogspot.com/_4pmUNQE7ll...tmas+Story.jpg

I know, I know. I'm looking forward to TBS's 24hrs of that! I can see the lamp now...

You can see that lamp now....

[img width=600 height=400]http://www.flicklives.com/Glossary/leg_lamp/major_award_4.jpg[/img]

Seems to me the cocking ramp really doesn't need to truly helical. The lift is so short that a straight cut would likely feel the same. A mirror polish on the ramp face would seem to be a good idea. I did some rough measurements sometime ago and as I recall the ramp on a Target Action can be shortened no more than about .090" and still leave a little overcocking for sure functioning. What do you say?

In the old days, custom gunsmiths routinely speed-locked P-17 Enfields and Mausers by shortening the firing-pin fall by at least 50% and sometimes adding a heavier firing pin spring. They recut the cocking ramps by hand with a pencil grinder as there were certainly no CNC machine tools around.

RWO

Tis true, but I was looking for a better fit and finish than what they were probably after. The more helical, the better---the Savage cut is helical. It would allow the full width of the cocking pin's bearing surface to follow the face of the cut; just more surface to bear the force. The finish would be critical just as you said. The measurement is mucho appreciated!

I got to thinking about this pretty hard tonight, and I need somebody to follow thru my logic if he/she has some time and is curious. Has anyone experimented w lightening the firing pin spring? To reduce the force to pull the cocking button back, you can only do a few things: reduce the spring rate, reduce the compression distance, or reduce the preload (assuming it's a linear, massless spring---a common assumption that you have to make). All three are directly related to the cocking force (F=kx---force equals the spring constant or rate times the compression distance). In either case you will get decreased pin strike energy, but by how much... We know that less energy still lights the fire as evidenced by the many successful T&T jobs. It's late, and I could just be barking up the wrong tree, but what are yall's thoughts on the ramp vs spring thing?

bump

Thought about it a little more. W shortening the ramp, you eliminate a completely wasted overcompression of the spring (overcocking). So, there's another benefit to changing the ramp.

You should probably get a copy of Stuart Otteson's book, "The Bolt Action". In the appendix he covers in detail the entire design process balancing spring constant, firing pin mass, firing pin travel, locktime, etc. He also has charts showing striking energy, locktime, inertia constants, etc for all the common bolt actions. The Savage 110 has a good bit of excess of energy in comparison with the Remington 700, Win 70, etc. It looks like you could reduce the spring constant somewhat and get away with it.

Each bolt action( including the 110) is covered in the book in detail with the ignition characteristics listed: firing pin travel, locktime, impulse, energy, and velocity. It should be fairly easy to compare the 110 with several other different actions and make an educated guess for a first shot.

RWO

If I had a half dozen spare bolt bodies and springs, the machinery, tooling, fixturing, and time to do the work, plus the mechanisms and supplies to test the results, I would consider fooling around with the experiment.

For me its simpler to have Fred do a T&T job

Please let us know what you learn

Quote:

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Originally Posted by RWO

They recut the cocking ramps by hand with a pencil grinder as there were certainly no CNC machine tools around.

RWO

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I bet they used an end mill - those have been around for a LONG time. I have several M1917 and P-14 sporters as you describe and they look to have been milled (or had the parts replaced with new manufacture parts - several methods were used).

I do believe the best solution is to pony up the bucks to SSS - a complete package where all the mods work together.

Changing the cocking ramp angle is only one part of the big picture. With out the other procedures it will make it very hard to close the bolt. Changing the ramp angle also changes the sear timing.
I can reduce the firing pin retraction and get more travel and at the same time maintain correct timing and use less spring force. It only took me about 3 years to figure it all out, and then another year to figure out a formula with parameters.
You are correct about the spring. Less spring and more travel is better than more spring and less travel.

RWO, that is much appreciated info! I will do my best to get my hands on that book.

I do understand that it is an excellent option to just have SSS do the job, since they've put in the calculations, work, and trials to do the job right the first time. I just figured I do some good learning for the winter since there's more indoors time. I guess it's the combination of curiosity, my hobby, and some idle time! I strive for the satisfaction of doing something myself.

SharpShooter, again, much appreciated insight. And, I just want to make sure I don't come across as someone probing for trade secrets that vendors/sponsors have figured out. That's not what I'm after. I'm after exactly what you and RWO have said here; just guidance and insight.

I can't say enough about the site. Yall are a big help for a noob w a technical question right out of the gate. I'm proud to not be a lurker anymore!

I almost forgot to mention this. In various experiments w the bolt in varying degrees of the complete assembly, I inserted it into the action and did my best to better understand the amount of overcocking. I put some sharpie on the cocking ramp and worked the bolt several times w the pin cocked. I reasoned that the cocking pin would wipe the sharpie off the portion of the ramp that was 'overcock'. To my surprise in stock trim, I didn't find much overcocking. What I did decide to do was take some hones and knock down the detent bump quite a bit. I'm not sure how much I took off, but there's no more than .005" bump left. That made a slightly noticeable difference right at the top of the bolt lift. It's really not noticeable w a dropped firing pin though, like after you've fired a round and are recocking the pin. I used a couple hones from McMaster Carr that I really like and use for lots of machine parts polishing tasks:
600 grit 47465A54
400 grit 47465A52
220 grit 47465A49
They're all about $3-$4 and are 6"x1/2"x1/8". There's oodles of other sizes and grits. They break down kinda quick on a sharp spot like that detent bump, but they're cheap and there's lots of surface there to work with.

The cock detent has nothing to do with overcocking, it is simply there to retain the cocking piece from uncocking when it is out of the gun.
To figure out how much over-cocking you have, you must measure the firing pin travel.

Sharpshooter, I realize that. I just polished off the transition of the detent. It was pretty sharp/rough on the newest action I have. A little wear would have probably cured it anyhow.

PaHog, it would be wise not to doubt the abilities of whom you're speaking to, before you speak, without knowing anything about him, IMHO of course. Pretty quick judge of character/abilities since I've only posted about 8 posts.

One thing I do not enjoy about this site is the incessant, obvious wallet padding of the sponsors. If you got a great product from there, awesome. I have as well and will continue to do so, but not a T&T job right now, as I clearly stated in my original post. There's far too many that just take the easy way out, plop the money down, and move on. That's great. That's keeps a few people in a job. I find as far as hobbies go, those are the people that typically abandon the hobby in a few years and move on to the next.

For a fella like me, who doesn't want to go thru recutting the ramp at a local machine shop, just lightening the spring to get the energy level where it's at on comparable bolt actions seems like the way to go right now. It would reduce cocking effort. I won't know what rate I need though, until my book that was recommended gets here... Does anyone happen to know the factory spring rate? That would save me some work.

You can change the angle of the lower sear tab to would academically fix an overcocking or undercocking issue. But in the case of overcocking, if you fixed it by changing the lower sear tab angle, you haven't changed the amount of force required to open the bolt any at all. The cocking pin still rides up the same ramp to the same detent; it just doesn't drop down as far to the upper sear tab. If you did this to correct undercocking it would sure enough help out on the amount of force required to close the bolt. Both of mine overcock, but the Stevens only slightly; just enough for functionality. I haven't checked the Savage to see by how much it overcocks.

I'm not doubting your abilities, I was mearly saying that for me a "Normal Joe Schmo" the $125.00-150.00 for a T&T is well worth it and safer than messing with it ourselfs. I'll retract my previous post don't want to affend anyone was not the point Sorry.

Wonderful analysis and explanation Smokepole. Like you I have been very intrigued with this bolt lift issue. Also, it is a hobby for me and refuse to send it in for Fred's artwork. Would take the fun out of it for me.

Myself, I decided to just take a couple of coils off of the firing pin spring. I also did the washer/ball bearing thing. The lightening of the firing pin spring did the most for helping the bolt lift on mine.

If the cocking ramp gets re cut, I would presume it is necessary to re harden the metal. That is something I want to avoid as well (unless able to do it myself, LOL).

Also, I am curious about a cocking ramp profile that would be more aggressive at the begginning of the lift (lower spring compression forces) with a taper (less aggressive) profile at the top of the lift where the spring is getting more compressed. That would allow compressing the spring sufficiently while avoiding the sticky tendency towards the top of the lift.

Now that's an idea right there. A progressive curve. Initially, I would think that curve would be parabolic since the spring is linear. You and I are in the same boat on the hobby business. It's all a learning experience, particularly in the winter when I don't want to be outside! I have received the text mentioned above, and it indeed has oodles of good info. There's plenty of good formulas for energy, lock time, etc., as well as measured values. At any rate, it looks like, qualitatively, anything we do w/o modifying the travel or ramp will probably cost us in lock time and of course energy (both of which the Savage has plenty extra). I'm just trying to find out what mod will affect it the least, and by how much. If the lock time only goes up to that of a competitor's action, I'm willing to sacrifice that much for easier bolt operation. Basically, the only variables to mess w w/o changing the ramp are, spring rate and preload. I'll post back when I figure something out.

Just so you know Smokepole, I am tagging you with being responsible for pulling me out of the lurking mode. Should be able to kill the hole winter on this one.

I have some more thoughts on the issue.

1st - one of the reasons I just took a couple coils of the firing spring to lighten the force on the cocking pin. I feel the small radius is more susceptible to wearing down fast (it did on my MKII 22). Also, this small radius would seem to be partly responsible for the hard bolt lift issue, especially being sticky if the bolt is opened slowly. Thus, for now there will be less wear and tear on the cocking pin with a lighter pressure on it. It surely cost some in lock time. But it seems on par with my Marlin now. Might need to see about gaining the ability to measure it. Does anyone know of any tools/equipment available to do this?

2nd - I am thinking it may be possible to kill 2 birds with one stone on this one. How about a cocking pin with a larger radius. Of course there would have to be other modifications to accommodate it. The larger radius on the cocking pin would allow some machining on the cocking ramp to maintain that same fixed in space position when cocked. Thus, allowing the removal of material at both the top and bottom of the cocking ramp to accomplish a more parabolic curve.

3rd - I replaced the sear torsion spring with a lighter one from McMaster Carr. Also, took a couple coils off the main trigger spring and got that all adjusted. My thinking is this results in less back pressure forces on the firing pins release from the sear return spring. Thus, the firing pin has less force fighting is forward acceleration since the sear falls out easier. It ended up giving me a very nice trigger to boot. Another factor that makes up for a little loss of lock time.

So, on the issue of re profiling the ramp. I would think a person could use an economic milling machine from Grizzlys to machine the bolt, do some manual honing, re harden it, then do some touch up honing. Certainly the profile wouldn't end up having a perfect parabolic curve. However, I would bet one could get it pretty good. Good enough to make for a nice bolt lift, reduced cocking pin wear, and maintain good lock time without changing layout geometry.

That's OK, I've been credited w much worse! I've spent the better part of the day looking thru McMaster's extensive list of springs to find a suitable replacement w no luck so far. But, the best I can tell the stock spring is 3" relaxed and has a rate of about 16.5lbs/in measured rather crudely by me. By Otteson's formulas (that I checked), that spring yields an energy level about 12% more than what Otteson states is the norm for the 110. I guess that could be attributed to friction and vibrational losses (which Otteson clearly states as well). But, the task is finding one off the shelf that takes less cocking effort but provides the 75oz-in of energy he states is necessary to pop a LR primer consistently (that was determined by SAAMI and the military I do believe and it does have a fair amount of safety factor in it---temp sensitivities, pin eccentricity, excessive headspace, etc.). I've spent hours today hunting. The nature of the formulas requires one to do the calculation for each spring. There's not a real good way to just 'look' at the spring's parameters and 'know' if it's better or not. But suffice to say, McMaster doesn't offer anything useful. Other actual spring manufacturers do, but the least min order I've found is $25. I guess that's acceptable to try out.

Update on my cocking ramp profiling. I decided to cut down the top of the ramp .020" and blend to the bottom or beginning part of the ramp. Thus, I approximated a parabolic curve and will need to re harden the metal for permanent use. However, it worked great for alleviating the stickiness at the top of the bolt lift which annoyed me highly on mine. I would bet SSS's mod which probably is just a shorter lift with a straight helical cut works even better. I found on mine now the top of the lift is easier than the beginning after my mod. Thus the straight helical cut with a more gentle slope is probably the best way to go now that I have tried the curve idea. I love learning though.

Another simple mod is to just put the bigger bolt handle on it. It helps greatly, I just wanted to try and stick with the small bolt handle.

Lastly, There is no doubt about the value of SSS's service for those who don't have the "must do it myself" disease. This stuff is definitely a bunch of monkeying around (kind of the whole point anyway), but what a learning experience for myself so far, with much thanks to all those contributing here BTW.

Smokepole

You getting any further along on this quest?
I have been watching with interest your posts about this particular mod. If you feel so inclined, I would like to stay in the loop, and maybe share anything that I can come up with. I have done a few things myself to reduce bolt lift.

Thanks
Tony

Yes, I swapped to a lighter weight firing pin spring. I won't come out and say the part number because I don't want anybody blaming any ignition problems on me! But they came from MSC and were cheap. Have to buy a pack of several though. And, I highly recommend Otteson's book. It can be had on Ebay for about $18 plus shipping. The formulas in there will lead you in the right direction. It's a little aggravating because the search is iterative. For the short action, the spring I'm using is a little smaller wire and about 30% lighter rate w the same relaxed length and the factory dimensional preloads (due to geometry of assembly). For the long action, Savage uses a longer spring, 4". But, I'm going to use the same aftermarket spring w a 1" spacer to keep the preloads right. That spacer won't move, so the actual firing pin mass in motion is the same.