RMH
Member
For recoil management you might look into gas shocks. You can get them in a variety of mount configurations, length of stroke, and pounds of compression.
I needed a large mass at one time for a different project and after trying to figure out how to manage 500 pounds, I decided to use the 2" receiver hitch of my truck. And you'll have the added advantage of detracting tailgaters.Then test fire just with the weight of 100 lb table/platform and add weight to lower bench shelf as necessary to reduce movement.
Yes, that's exactly what I am trying to do with the prototype build, a machine rest that "hard mounts" pistols and carbines yet allows recoil with precise return to zero for higher consistent repeatability.
Yes, I have studied the difference in designs and how they "evolved" to handle recoil vs return zero.One interesting note in variation between Bart’s linked photos and most “unlimited” benchrest rifles are the angled front runners. That said IIRC it was made 60 years or so ago, may be a better way to skin the cat today but you always learn something from the past.
That's very good point. I was thinking of using friction between bottom of platform and top of table to manage recoil force but may need to rethink that.I think it’s not only the impulse even static loads. If you can’t touch the bench without changing the POA, it likely won’t take the “hammer” of a shot. The slicker you make free recoil the better off you are in the latter case, less energy transfer from one to another.
I am still thinking hard mounting barrel in the way of attaching free-float/handguard is better over "nesting" carbine/rifle in a cradle as there are many points of play that could "stack".Makes the recoil run the muzzle up, just like a bag would let the stock down (muzzle up) with a regular rifle stock. If you needed more food for thought. Also note the attachment points of the rifle above, not just “sitting” in the mount.
That's where I was going with the prototype machine rest build.Unlimited br rifles these days are very linear and very “free”.
The video obviously gave me something to chew on but I need to build a "universal" machine rest. The rifle in the video is purpose built and I doubt I can repeat what's shown in the video with an average quad rail/free-float AR.I don’t think you have to have “hard mount” to have consistent repeatability. The machines that make the guns and optics we use on them, transverse some amount of distance. The rifles can too and be fairly repeatable.
Something more for me to chew on. You are expanding "working" regions of my brain. (Wife and daughter are increasingly claiming I have many "dead" regions of brain )If we took a rifle that was 48” from the butt plate to the barrel, using a target that is 100 yards away .001” of movement (of only one end) moves impact point .075”. .003” of one end would be .225” and .013” would be almost an inch.
The longer you make the fixture, assuming the rifle does not move in it, the better things get, the closer together contact points get (shorter fixture) the more precise they need to be to be able to achieve the same accuracy.
The rifle in the video is purpose built and I doubt I can repeat what's shown in the video with an average quad rail/free-float AR.
There are also linear bearings such as these:This is the bearing (From fidget spinners) I was talking about. I was planning to use them for "low friction" recoil set up and also to limit X/Y axis movement using adjustable or tensioned brackets.
Now you understand why it took me so long to research prototyping a "portable" machine rest. My poor brain ... what little neurons still firing ... doing their best ...I don't see how a machine rest will be useful unless it is anchored on an un-moveable mount/table
We will find out on our initial test firing. You will get front row seat of groups prototype produces.The tolerances required to replicate the aim point seem too small to allow a moveable set-up. However, I would like to be proven wrong!
Me too. If not, I am sure jmorris and THR peanut gallery will provide plenty of suggestions.I hope you are successful!
If proof of concept can be repeated with pistols at 25 yards, I will be testing carbines at 50 yards and then rifles at longer distances.I know the current project is not for precision long range shooting
OMG, that's a great idea.You guys are smarter with more skills than I, but there are also linear magnetic dampeners (i like the fact that it is a finite, unchangeable force in relation to the object it is opposing. That may be something to look into.
Yes, I did look at them but decided on fidget spinner bearings because I plan to use adjustable/tensioned brackets.There are also linear bearings
ATV strut would be overkill. I would only need hatch strut/strong arms but even those would be too much.To manage the recoil energy have you considered something like an ATV strut?
May even test 9mm Major loads pushing 124 gr bullets to 1400-1450 fps using 40-9 conversion barrels with thicker chamber/barrel walls.