Heat on the upper Fore Stock

[JohnEd]

Citizen Pete was trying to eliminate some heat from the Piston area.  He was trying to plug the Piston relief holes in the underside of the Gas Block with aluminum foil I seem to recall.  DAN said the original Gas Blocks were of such varied dimensions and spec that he wouldn't use those surplus GBs on the DTech guns.  The drilled gas port on my Dtech was a #28 bit EXACTLY with a slug forced in and the slug drilled to a #32 bit.  The 32 chokes down the "over-gassing" that a gas port of the #28 dimension would provide.  I now have SIX front GBs and even the latest from Numrich has the #28 bit hole clear through to the barrel.  I have fired one of my guns with that #28 hole and it kicks like a Mosin Nagant MULE and there is painful "cheek-slap".  Little wonder that there are many opinions on muzzle brakes functionality.  So that is one variation on the GBs spec...gassing.

Now for another:  Those relief holes in the underside of the GB in some cases are drilled into thicker casting between sample GBs.  A couple of mine actually look to be almost/sorta really short tubes while the rest are drilled through thin metal that is the Piston "cylinder" if you will.  The steel casting is very different.  That is of no consequence that I can determine except to add to the opinion that the GBs are not identical.  Now, those two holes dump the gas from the piston after it has traveled as far as it should to get the cycling complete.  Problem I OBSERVE is that those holes are not drilled in the same location  between GBs.  One of my GBs will have the gas dumped before the piston gets to the end of the GBs cylinder.  All the rest vary in that one will not dump the gas till the piston gets all the way clear of the GB cylinder in the area where the upper hand guard retains the piston in the GB and that is way to far but the piston doesn't jam on that gun.  The remaining 5 GBs all vary in how much of the hole is uncovered when the piston comes to the end of the cylinder.

I guess the gist of this is that some guns will heat up faster than others due to excessive gassing causing gasses that pass the piston to be dumped under the hand-guard.

[RSR]

This is very interesting actually.  And very surprising...

Would be very interested in pics.

On a side note, I have seen your gas block PMs, I just haven't had the time at home to dive in.  Sorry -- will get to them eventually.  On my list.

[JohnEd]

This is very interesting actually.  And very surprising...

Would be very interested in pics.

On a side note, I have seen your gas block PMs, I just haven't had the time at home to dive in.  Sorry -- will get to them eventually.  On my list.

What is "SURPRISING"?  I am interested in your opinions on this.  For me it is a slam dunk as I have taken a viscous recoiling 58 and, with an Allen wrench, made it the softest recoiling imaginable.  I can get it so soft it actually "fails to eject" 2 out of five shots.   Of course, that is corrected with a 1/4 turn of the Allen screw.  No disassembly to adjust is a good bonus.

My observation is that the "designer", in order to get reliable gassing, designed the gassing to work on the "softest" ammo the gun might encounter.  That leaves the gun OVER-GASSED to one extent or another for ALL OTHER ammo we use.  Compromise!  I don't think that all slightly over-gassed guns operating with most of the ammo we use is in any real danger of damaging itself with Dust Cover strikes.  BUT I want the gun's moving parts moving the least distance possible with no impacts.  With my "adjuster" mod I can reset the Gassing Force to the ammo I will be then currently using.

Another "ANGLE", if you will, is that the more gas you employ to cycle the action, the more hot gas you will inject under the Beaver Barf stock.  While that isn't an issue with me there seem to be many that are drilling vent holes in the fore-stock and installing "heat shields" to make the gun more comfortable.  Eliminating the excess gas used to cycle the action might relieve this heating problem for many and possibly eliminate it entirely.

RSR, my advice is, and bear me out on this, all should insert a #28 drill bit into the gas port and verify that they have a drilled slug in the gas port.  That I received so many Gas Blocks without any restricting slug tells me that there must be many out there with a problem brewing.  Both of my KITS contained wide open Gas Blocks and just how many here have 58s that they made from a kit? A survey would bear that out.  Counter point is that I contacted a friend with 5 guns and all of his had the #32 bit restrictor plug installed.  Humm?

[JohnEd]

This is very interesting actually.  And very surprising...

Would be very interested in pics.

On a side note, I have seen your gas block PMs, I just haven't had the time at home to dive in.  Sorry -- will get to them eventually.  On my list.

RSR,

Your opinion really matters to me....and others i am sure.  What was it that surprised you? 

I won't have all the GBs I mentioned as I have drilled and tapped one and sent it off to a friend with this problem.  I noted the different location of the vent holes that exhaust the gas from the piston cylinder.  I don't think this variance will affect the operation and cycling as that piston is traveling as fast as it ever will by the time it gets anywhere near that pair of holes.  Further back puts the holes closer to the front stock but the culprit is the amount of gas being vented.

I'll try again with the pictures.

Thanks,

John

[RSR]

Two counts:

The drilled gas port on my Dtech was a #28 bit EXACTLY with a slug forced in and the slug drilled to a #32 bit.  The 32 chokes down the "over-gassing" that a gas port of the #28 dimension would provide.  I now have SIX front GBs and even the latest from Numrich has the #28 bit hole clear through to the barrel.  I have fired one of my guns with that #28 hole and it kicks like a Mosin Nagant MULE and there is painful "cheek-slap".  Little wonder that there are many opinions on muzzle brakes functionality.  So that is one variation on the GBs spec...gassing.

AND

Problem I OBSERVE is that those holes are not drilled in the same location  between GBs.  One of my GBs will have the gas dumped before the piston gets to the end of the GBs cylinder.  All the rest vary in that one will not dump the gas till the piston gets all the way clear of the GB cylinder in the area where the upper hand guard retains the piston in the GB and that is way to far but the piston doesn't jam on that gun.  The remaining 5 GBs all vary in how much of the hole is uncovered when the piston comes to the end of the cylinder.

[RSR]

So basically from this chart, if a 1/8" bit fits, then it's overgassed?

If it doesn't then it's good to go?



And any chance you can provide pics of gas blocks w/ and w/o the slugs?

[JohnEd]

Two counts:

The drilled gas port on my Dtech was a #28 bit EXACTLY with a slug forced in and the slug drilled to a #32 bit.  The 32 chokes down the "over-gassing" that a gas port of the #28 dimension would provide.  I now have SIX front GBs and even the latest from Numrich has the #28 bit hole clear through to the barrel.  I have fired one of my guns with that #28 hole and it kicks like a Mosin Nagant MULE and there is painful "cheek-slap".  Little wonder that there are many opinions on muzzle brakes functionality.  So that is one variation on the GBs spec...gassing.

This is refering to two different "holes".  There is a pair of holes on the underside that exhaust gas from the piston/cylinder when the piston is at the rearmost of its travel.  The stuff about a 32 and 28 is pertaining to the gas port that is drilled through the GB and then through the barrel to inlet the gas to the piston.

AND

Problem I OBSERVE is that those holes are not drilled in the same location  between GBs.  One of my GBs will have the gas dumped before the piston gets to the end of the GBs cylinder.  All the rest vary in that one will not dump the gas till the piston gets all the way clear of the GB cylinder in the area where the upper hand guard retains the piston in the GB and that is way to far but the piston doesn't jam on that gun.  The remaining 5 GBs all vary in how much of the hole is uncovered when the piston comes to the end of the cylinder.

[RSR]

This is refering to two different "holes".  There is a pair of holes on the underside that exhaust gas from the piston/cylinder when the piston is at the rearmost of its travel.  The stuff about a 32 and 28 is pertaining to the gas port that is drilled through the GB and then through the barrel to inlet the gas to the piston.

Yes, I understood that this was the gas port hole in the gas block.  Was my understanding on that correct?  Didn't really get when you mentioned this an earlier thread until re-reading it here...

Regarding the gas port holes on underside of the gas block, those will affect the speed/force of/on piston.  Though should cause less variance than the gas port size itself.  I will have to compare rifles side by side more closely.

But for the gas port slug, that's something that might be worth looking into buying new or having a gunsmith correct posthaste on current guns if/where an issue. 

[JohnEd]

RSR,

Of the five GBs I had only two had the drilled slug in the barrel port.  I lost the initial papers I had written the hole size down on.  I called Morgan and he had a few on his bench and he measured the holes.  #28 for the big hole and #32 for the drilled hole in the slug and I am sure of those numbers but I don't speak for Morgan.

The GBs I had were all of different dimensions except for the #28 hole.  My holes through the slugs were somewhat smaller than what Morgan measured but he said he was measuring 5 different GBs.  The GBs I had I had to use for drill guides/fixtures to drill the barrel.  Each GB had to match up to a barrel and each GB was different so i paired GBs to particular barrels  and drilled the barrel THROUGH the GB's port.  Consequently, I have no GB with and intact slug that can be inspected.

I installed a set screw into the GB body that intersected the internal gas port connercting the barrel port to the piston.  I used a regular tap but I repeatedly ground off the point till I had a perfectly flat bottomed "BOTTOM TAP".  The hole for the set screw has a concave bottom that mirrors the end of the bit I used to drill the hole.  The set screw has a cone shaped bottom that closely matches the driled hole bottom and the threads go completely to the bottom of the tapped hole.  In short, when bottomed, there is precious little space for gas to flow around that set screw.  In spite of that the gun cycles perfectly 3 times out of 5 with two "Fails To Eject" out of 5.  This indicates to me that i need very little dimension on that hole in the slug to get the gun to cycle properly and reliably.  What I do have is a gun that is powder puff soft on recoil.  With the hole wide open and using the same ammo the Butt slaps me almost silly with each shot.  The gas flow must be METERED or the gun is uncomfortable at best and self destructing at worst.

Pics are a ways off and I will show that hole and the two methods of dealing/metering the gas flow.

[JohnEd]

This is refering to two different "holes".  There is a pair of holes on the underside that exhaust gas from the piston/cylinder when the piston is at the rearmost of its travel.  The stuff about a 32 and 28 is pertaining to the gas port that is drilled through the GB and then through the barrel to inlet the gas to the piston.

Yes, I understood that this was the gas port hole in the gas block.  Was my understanding on that correct?  Didn't really get when you mentioned this an earlier thread until re-reading it here...

Regarding the gas port holes on underside of the gas block, those will affect the speed/force of/on piston.  Though should cause less variance than the gas port size itself.  I will have to compare rifles side by side more closely.

But for the gas port slug, that's something that might be worth looking into buying new or having a gunsmith correct posthaste on current guns if/where an issue.

[JohnEd]

This is refering to two different "holes".  There is a pair of holes on the underside that exhaust gas from the piston/cylinder when the piston is at the rearmost of its travel.  The stuff about a 32 and 28 is pertaining to the gas port that is drilled through the GB and then through the barrel to inlet the gas to the piston.

Yes, I understood that this was the gas port hole in the gas block.  Was my understanding on that correct?  Didn't really get when you mentioned this an earlier thread until re-reading it here...

Regarding the gas port holes on underside of the gas block, those will affect the speed/force of/on piston.  Though should cause less variance than the gas port size itself.  I will have to compare rifles side by side more closely.

But for the gas port slug, that's something that might be worth looking into buying new or having a gunsmith correct posthaste on current guns if/where an issue.

Not often I get even a scintilla of variance with your posts but this is one.  minor though it be.  Those pair of holes vent the gas pressure and while the piston may travel past them it is no longer accelerating.  Some of mine are completely past the end of the piston and the gas would be completely vented by the piston exposing the cylinder section.  Most have the holes positioned well inside the cylinder and they would surely vent some gas towards the stocks.

Your understanding is correct.  We are talking about two different holes in one post.  The "pair" is under the rear of the GB and vents the piston.  The 28 and 32 are referring to drill bit sizes for the holes in the GB port to the Barrel.

R, I think many have this condition and are not aware.  You repeatedly hear what a mild recoil this gun has yet all three of my kits had GBs that were open to #28 and would certainly have abusive recoil had I not discovered this.  I think I will be able to get video of the gun adjusted for max to min recoil with and without my Slovak brake.

Good talking to you and thanks for your concern .

John