Jerry Sharret.......Rail Gun Barrel Block Torque

[jackie schmidt]

You have done quite a bit of testing with torque on barrel block bolts, seeing just how much you can apply before you can feel the ID collapse with a lead lapping plug.

What's your conclusions. This is a typical 6 inch long block, ten 5/16 socket head cap screws, 1.450 barrel, ( turned dead straight to 1.440 in way of block), non metallics bushing, 1/4 wall thickness.

I have taken the effort to actually mount the scope on the action, so if anything could possibly shift, the scope is on the barreled action, just like a regular rifle.

http://benchrest.com/attachment.php?...1&d=1464881593

http://benchrest.com/attachment.php?...1&d=1464881766

[Jerry W]

If we look closely at the picture, the camera isn't focused on the rail gun, it's focused behind it.....on the door.

[.357Mag]

Jerry -

Howdy !

" Apples and ...... "

FWIW -
My barrel " clamp " set-up uses doubled-up " plumbing clamp " plates, w/ 1/4 - 20 carriage bolts & nylon insert " jam nuts ".

I've been running 24 in lb, set / verified using a good quality torque wrench. Clamp location and fastener torque are repeatable.
Have not noted any undue stresses imparted to the barrel.


With regards,
.357Mag

[Dave Tooley]

Jackie,

It shouldn't take much torque on 10-5/16 cap screws to hold the barrel. If you used a polymer or plastic beware of barrel temps and expansion. I used delrin once as bushing material for a 1K BR barrel block. Expansion caused the 12- 5/16 cap screws to pull the threads out of the lower block. I went back with phenolic bushings on each end. No more problems. I'd take my torque wrench to the range and start on the very light side and work up to no more than light to medium torque load and see what shot best.

[Mike Bryant]

I really doubt if a delrin sleeve will cause any problem with a typical short range benchrest rail gun with the temperatures generated by a 6 PPC or .30 BR. Just not the same amount of powder being burned as with one of the large capacity cartridges typically shot in a 1000 yard barrel blocked gun. I use a delrin sleeve in my rail gun and tighten it as tight as I can get it with thumb pressure on the long end of a long allen wrench. Jackie, I think you'll like the delrin sleeve approach better than the full length barrel sleeve you were using previously. Lots easier to make changes, recrowning, rechambering or anything else you might want to do with a barrel mounted in a delrin sleeve opposed to the full length glued in sleeve or cerrosafed sleeve. My Young rail gun is mounted with a delrin sleeve. My old rail gun currently has a barrel that is cerrosafed into a full length aluminum sleeve. Was going to use it at Seymour last time and was going to rechamber it with the current reamer that I had been using. Took one look at the full length aluminum sleeve and left it alone in the vault and shot the Young.

[jackie schmidt]

Mike, Dave, I am using a material called Thorplas. It is a non metallic bearing material that is strong, and very resistant to shrinkage and expansion at different temperatures. We use it a lot in our shop to make steering pin linkage and main rudder tube bushings for Tugboats. It's quite expensive.
http://thordonbearings.com/system/do...pdf?1278591962


I did an experiment. I found a 1.450 diameter 5 inch long drop off of a unlimited barrel, and machined the OD to 1.440, just like my barrel in way of the barrel block. I then took my Deltronic pins and found the one that would slip all the way through, and one that would go through with a little "feel". They happen to be .2369 and .2370.

I then installed this piece in the barrel block with the Thorplas bushing. At 20 inch pounds, no difference. At 40 all the way through 70 inch pounds, no difference. At 90 inch pounds, the .2370 started getting tight, but the .2369 still slipped through easily. At 120 inch pounds, the .2369 started to get a little "feel". At .150. It would not go through easily, but a .2368 would.

So at the range Sunday, I started at 20 inch pounds, using a sequence much like you torque head bolts. and stopped at 65 inch pounds. The gun shot a nice round 10 shot group around at around .170.

This is how I am going to leave it.

Thanks for the replies.

[Mike Bryant]

Mike, Dave, I am using a material called Thorplas. It is a non metallic bearing material that is strong, and very resistant to shrinkage and expansion at different temperatures. We use it a lot in our shop to make steering pin linkage and main rudder tube bushings for Tugboats. It's quite expensive.
http://thordonbearings.com/system/do...pdf?1278591962


I did an experiment. I found a 1.450 diameter 5 inch long drop off of a unlimited barrel, and machined the OD to 1.440, just like my barrel in way of the barrel block. I then took my Deltronic pins and found the one that would slip all the way through, and one that would go through with a little "feel". They happen to be .2369 and .2370.

I then installed this piece in the barrel block with the Thorplas bushing. At 20 inch pounds, no difference. At 40 all the way through 70 inch pounds, no difference. At 90 inch pounds, the .2370 started getting tight, but the .2369 still slipped through easily. At 120 inch pounds, the .2369 started to get a little "feel". At .150. It would not go through easily, but a .2368 would.

So at the range Sunday, I started at 20 inch pounds, using a sequence much like you torque head bolts. and stopped at 65 inch pounds. The gun shot a nice round 10 shot group around at around .170.

This is how I am going to leave it.

Thanks for the replies.

Jackie, sounds like it will work. Certainly easier than the barrel glued into a full length sleeve like you were using previously. It probably be pretty good to torque the screws on my rail gun block. Never have had a torque wrench that would work in the inch pound area. I wouldn't be surprised if my block isn't about as tight as yours. Pretty limiting how much torque you can get on a 6" handle on an allen wrench. It might be less for that matter.

[JerrySharrett]

You have done quite a bit of testing with torque on barrel block bolts, seeing just how much you can apply before you can feel the ID collapse with a lead lapping plug.

What's your conclusions. This is a typical 6 inch long block, ten 5/16 socket head cap screws, 1.450 barrel, ( turned dead straight to 1.440 in way of block), non metallics bushing, 1/4 wall thickness.

I have taken the effort to actually mount the scope on the action, so if anything could possibly shift, the scope is on the barreled action, just like a regular rifle.

http://benchrest.com/attachment.php?...1&d=1464881593

http://benchrest.com/attachment.php?...1&d=1464881766

Jackie, sorry I took so long to answer but I missed this thread. On torque with a 1.45 Hart barrel and a double vee barrel block and 5 bolts/side, anything over 60 in/lb I can feel barrel distortion on a lead slug. That is too much. I've never had a barrel to move at 40 in/lb in firing. I can move it with a Lixie soft tipped hammer though.


.

[jackie schmidt]

Jackie, sorry I took so long to answer but I missed this thread. On torque with a 1.45 Hart barrel and a double vee barrel block and 5 bolts/side, anything over 60 in/lb I can feel barrel distortion on a lead slug. That is too much. I've never had a barrel to move at 40 in/lb in firing. I can move it with a Lixie soft tipped hammer though.


.

Thanks Jerry, that is pretty close to the 65 inch pounds I settled on. The Rifle shoots pretty darned good.

[mrspradlin]

I did an experiment. I found a 1.450 diameter 5 inch long drop off of a unlimited barrel, and machined the OD to 1.440, just like my barrel in way of the barrel block. I then took my Deltronic pins and found the one that would slip all the way through, and one that would go through with a little "feel". They happen to be .2369 and .2370.

I then installed this piece in the barrel block with the Thorplas bushing. At 20 inch pounds, no difference. At 40 all the way through 70 inch pounds, no difference. At 90 inch pounds, the .2370 started getting tight, but the .2369 still slipped through easily. At 120 inch pounds, the .2369 started to get a little "feel". At .150. It would not go through easily, but a .2368 would.

So at the range Sunday, I started at 20 inch pounds, using a sequence much like you torque head bolts. and stopped at 65 inch pounds. The gun shot a nice round 10 shot group around at around .170.

This is how I am going to leave it.

Thanks for the replies.

Jackie,

I was wondering if you had a tuned load before you did your range test

Matt

[JerrySharrett]

Something to factor in, in the relation of linear expansion of materials, steel. When a material expands due to heat it expands in all directions, if it can. So, when a cylinder of barrel steel expands and it is solid, no hole, it expands outward. If it has a hole in the center, barrel bore, it expands inwardly as well as outwardly. If a portion is restricted, barrel block, it can only expand inwardly.

We all have seen hot, thick walled, barrels act strangely when they are hot. I think that is why a material with low linear expansion properties, Delrin etc, help some in causing the barrel remain consistent.


.

[alinwa]

Something to factor in, in the relation of linear expansion of materials, steel. When a material expands due to heat it expands in all directions, if it can. So, when a cylinder of barrel steel expands and it is solid, no hole, it expands outward. If it has a hole in the center, barrel bore, it expands inwardly as well as outwardly. If a portion is restricted, barrel block, it can only expand inwardly.

We all have seen hot, thick walled, barrels act strangely when they are hot. I think that is why a material with low linear expansion properties, Delrin etc, help some in causing the barrel remain consistent.

and

I can move it with a Lixie soft tipped hammer though.

Just......WOW!



These two items just made my day.

Good Stuff

Thanks Jerry

al

[jackie schmidt]

For an update on this, Last weekend I put my standard V Block setup back on the Rail, and lapped the barrel onto the channels before torquing to 60 inch pounds.

I shot some of the best groups that I have shot in a long time, 5 shot "zeros" and 10 shot "ones"

I'm leaving it like this.

http://benchrest.com/attachment.php?...1&d=1467905031

[Dave Tooley]

Jackie

Sometimes we over think things don't we? But that's how we learn.

[Dave Coots]

For an update on this, Last weekend I put my standard V Block setup back on the Rail, and lapped the barrel onto the channels before torquing to 60 inch pounds.

I shot some of the best groups that I have shot in a long time, 5 shot "zeros" and 10 shot "ones"

I'm leaving it like this.

http://benchrest.com/attachment.php?...1&d=1467905031

Sounds like a barrel problem.

Later
Dave