Smith Sumo II and your thoughts on BR design......

C

csdilligaf

New member
I have been working on a new Sumo II design and nearly have the first one done for testing. I have made some design changes that I thought it needed. I have redid the entire Hammer so it it very light and short stroke for quick lock time. The action is now lower with the barrel clamps going vertical and the rail much closer to the barrel. It will have a balanced valve set up to allow the lighter hammer to open it easy. All this should mean less impact and vibration. The picatinny rail will be at 25 moa but will be in two pieces to allow more loading room. Also I have put a bleed off port in the side of the action to aid in de-gassing. This will allow removing the tube to work on the gun or the reg without having to mess with useing a hammer spring spacer to bleed down the presure. I have some more contour shaping on the side lever but that is just for looks.
So as for input from shooters, Would BR shooters mind the bolt and the cocking being two separate levers or movement? The Sumo II is still a single cocking and loading operation but I have found some advantages to makeing them separate. One being that I could use a stronger hammer spring with no preload and still make the cocking effort even lighter.
 

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2 separate actions to achieve ready to fire could be a problem for some when trying to run a condition. Not that a person could not overcome it with practice. Some might be a bit pick-itish on this. Only have 20 minutes to out guess Mother Nature 25 times.
 
I would have preferred an integrated scope rail ... just one less thing to go wrong ....

For the rest .... looking good .....

From the photo one cannot see ..... but do you still use the 3 x stack in the front .... bottom = cylinder, middle = valve, top = barrel ??

I was thinking if one move the barrel and valve slightly further apart then you could get away with only 2 x ..... top = barrel, bottom = valve + Cylinder behind it .... This could bring the centre of gravity down on the whole action ..... might even help with less air going around corners changing direction etc ......
 
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I have 8-10 Sumo II in the works right now. Two of them being 6AL-4V Titanium. They will be built like the prototype in the picture. This Dual lever thought just comes from wanting to make the cocking so easy and smooth it will not upset the gun in the bags. It would be basically no effort. But it would require like the poster above says, another motion that will need to be done and that is exactly why I am reluctant. For a hunting rifle it is ideal, Have a pellet in the chamber ready to go and when Rocky J Squirrel comes along you just cock the hammers side lever and shoot. But that is not the case in a 20 minute match.
 
Looks really good Chip!! I would also lean away from the two operations during firing for the bench gun. You are right about it being fine for hunters however. Could you PM with what something like this would cost?
 
Got some work done on the Hammer. This is a Dan Brown recomendation that I try teflon o-rings for low friction. Works pretty slick all right.
 

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Trying to get as much time on this as I can. I work 12 hrs a day on real work and then change over to hobby work after dinner. Tonight I got the bolt finished, Re-profiled the side lever and made the 6 barrel clamps. Trigger is done and is sweet. Once I have it all done an proven with good results the rest of the run will go faster. The barrel in the pic is a .30 cal that was laying around . Looks like most guys want to go with a one piece rail at 25 moa. This side lever is so nice to move. Nice clean tucked in linkage. Since I redesigned the hammer I have had to make some big changes with the cocking dog and trigger and taken more time than I wanted but its moving along now.
 

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Chip,

Your best work ever. Say the word and I can send a couple of barrels for you to play with.
 
No matter how many Revisions I make it seems like I always have things in my mind about how to do things different the next revision. Here is two changes that I wanted to implement. The barrel now protrudes 1/8" out to ease pellet insertion. I had to recess the bolt face the equal amount. Then the transfer port insert was something that I wanted to work on. Now I have the transfer port the same size as the oring and the oring groove is a full radius but leaves .010" of the oring above the surface for compression. That way it stays put when reloading. I can change transfer port sizes from .09" to .187" with ease and will have to change the design a little for the big bore guns. There is another oring for sealing around the neck of the barrel and you can feel the compression.
I can put a pellet in very easy. It does take both hands from each side to do it gracefully and even. This barrel is a Mark Chanlynn, Rocky Mountain Rifle Works barrel. I love the material he used. It is magnetic but cuts like stainless steel, very good finish. Inside is nice and shiney and the pellet just slide through with the slightest amount of tension, never loose. It is not choked and I will try it to see how it does and then choke it and try again.
 

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Thank you, Lets hope it shoots as good as it looks. I think if you take everything to a high quality level of fit and finish and try to keep pushing with new idea's and test them that the end result will be better. I was born to machine things.
 
csdilligaf said:
Thank you, Lets hope it shoots as good as it looks. I think if you take everything to a high quality level of fit and finish and try to keep pushing with new idea's and test them that the end result will be better. I was born to machine things.
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Glad somebody is. I was born to throw away my attempts at machining.LOL I have always appreciated people who are masters at machining, which you are. Anyone who thinks it's easy need to try and do a project like your and they will find out quick enough. That's why I can appreciate what you do.
Pat
 
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