Anyone Here Have a Go-Gauge for 223 Ackley Improved Willing to Loan?

[HollowPoint]

I'll be happy to pay shipping to and from with insurance if need be. I'm getting ready to rebarrel my Tikka Lite with a shorter barrel and I thought I'd make up the slight difference in velocity by converting it to an Ackley Improved.

If not, no problem. I just thought I'd ask. A new one costs somewhere in the fifty-dollar range plus shipping. I can rent one but that cost about 35 bucks and shipping. This is another budget rebarrel project I'm gathering parts for. I won't actually need the Go-Gauge for another couple of weeks. I'm just trying to get all my ducks in a row. I just have a hard time buying something outright that I'll only use once and then have it collect dust on a shelf.

My last Tikka rebarreling project turned out better than I'd hoped so now that I'm on a roll I thought I'd do the 223 as well. Nothing wrong with what I got now. It's just that I'm wanting something a bit more compact and maneuverable without sacrificing the out of the box accuracy.

HollowPoint

[M-Tecs]

http://pacifictoolandgauge.com/cross-compatible-headspace-gauges/11615--aaa-223-remington-556-x-45-mm-ackley-improved-headspace-gauges.html

$37.00

[5Shot]

You don't really need one...just use a 223 Go Gauge and use it as a No Go. Should be like 0.008"-0.010" short on a 223 Go Gauge. That gives you a bit of crush on a standard 223 during fire forming.

[joatmon]

I thought you could use a no/go 223 as a go 223 in an Ackley chamber? Did I miss it some how?
Aaron

[5Shot]

I thought you could use a no/go 223 as a go 223 in an Ackley chamber? Did I miss it some how?
Aaron

You have it backwards. If you use a No Go as the GO you will have a huge headspace issue. The AI chamber is slightly shorter than the parent cartridge.

[joatmon]

You have it backwards. If you use a No Go as the GO you will have a huge headspace issue. The AI chamber is slightly shorter than the parent cartridge.

Thanks! Glad I didn't use that method?
Aaron

[HollowPoint]

Thanks for the comments gentlemen. I did plenty of research about the .223 AI before deciding on this change. This includes checking the different prices from online vendors. During that research I also came across most of the information that has been posted here. My main reason for posting this inquiry was to try to get away from having to buy a Go-Gauge that I'll only be using once. If I ever did need one more than once, I could rely on my notes of these measurements in the future.

I do have a work around for this but since it's the first time I'm dealing with an Ackley Improved chambering I thought I would at least try to find an alternative to buying. I plan to fire form my cases using cast lead bullets and pistol powder. The same way many of us do when shooting our cast bullets. By seating my bullets out far enough to touch the lands I can seat the bullet in the chamber at the exact OAL it needs to be for the fire forming process and in theory, get a nicely formed bunch of brass.

The actual head-spacing on a typical rifle cartridge is fairly simple when using the "Savage-Barrel-Nut" system of replacing the barrel. I'm using the barrel nut method so I'm relatively sure I can work with what I got. It would be nice to have the formal Go-Gauge to work with though. The method of head spacing I'm referring to involves the use of the actual cartridge brass I'll be shooting. I found out about this method back when I was shooting Savage rifles when I was member of the Savage forums.

HollowPoint

[Wayne Smith]

Hollowpoint be aware Ackley says no - use a full power load to make your brass or you risk shortening the brass and creating headspace issues.

[HollowPoint]

Since Mr. Ackely's passing several different ways of fire forming AI shell casings have been devised. Including the way that Mr. Ackley himself utilized, (full power loads) there is the "Cream of Wheat method, the inert packing method, the hydraulic die set method and the method I mentioned above; and possibly more. Not being patronizing; I will take your suggestion under advisement. I know it's important to be safe.

The need for any gauges is still a couple of weeks away so, I'm holding out hope that something will turn up by then.

HollowPoint

[5Shot]

There's an AI Group on FB (barf)...might be worth a try.

[Texas by God]

I thought that the Ackley improved cartridges headspace the same as the parent case. I mean that can't a regular .223 gauge be used?

Sent from my SAMSUNG-SM-G930A using Tapatalk

[5Shot]

I thought that the Ackley improved cartridges headspace the same as the parent case. I mean that can't a regular .223 gauge be used?

Sent from my SAMSUNG-SM-G930A using Tapatalk

Yes, but you must use it as a NO GO gauge. There needs to be 0.008-0.010 crush on the parent case. This is why you can't just run the reamer in and call it good when re-chambering. You have to set the barrel back one thread then finish ream.

[HollowPoint]

Yes, but you must use it as a NO GO gauge. There needs to be 0.008-0.010 crush on the parent case. This is why you can't just run the reamer in and call it good when re-chambering. You have to set the barrel back one thread then finish ream.

I think the confusion here is due to me not being clear on my rechambering to the AI chamber. All that has been posted in replies to this thread are essentially true. This applies when you are rechambering by reaming out an existing .223 Rem chamber. What I'm doing is chamber reaming a new barrel. As such, I'm fairly certain that I can simply ream the new 223 AI chamber just deep enough to create the needed head space.

I mentioned before that my need for a 223 AI go gauge is still a couple of weeks away. This hasn't changed. In the mean time I'm still doing alot of informal research into this. I'm finding similarities in this project with what I encountered when I set out to rebarrel and rechamber my K31 Swiss rifle. Lots of knowledgeable folks repeating stuff they've read but not coming from a position of having actually done the work themselves. I hope that doesn't sound to smart-alecky cause I've never done an Ackley Improved chambering either and I really do appreciate you guys taking the time to post any useful info; hence the research and hence the search for a loaner Go-Gauge. For my first go around, I figured I should do what I can to go by the book; but that "Book" can get rather obfuscated by the different points of view when sharing the information.

I'm still going through with this project. I'll let you all know how it worked out. If things go south on me, perhaps you can come visit me in the hospital. HA!

HollowPoint

[M-Tecs]

Simple rechambering will not give you a "true" Ackley chamber. The correct Ackley improved chambers have a crush fit on factory unfired cases. To achieve this the barrel needs to be set back or the headspace will be long. This can be worked around by creating a false shoulder or jamming the bullet into the lands for fire forming. After fire forming set your sizing die for .002 shoulder set back.

Good overview here:

https://ackleyimproved.com/headspace-and-ackley-improved-cartridges/

[HollowPoint]

Simple rechambering will not give you a "true" Ackley chamber. The correct Ackley improved chambers have a crush fit on factory unfired cases. To achieve this the barrel needs to be set back or the headspace will be long. This can be worked around by creating a false shoulder or jamming the bullet into the lands for fire forming. After fire forming set your sizing die for .002 shoulder set back.

Good overview here:

https://ackleyimproved.com/headspace-and-ackley-improved-cartridges/

I'm going to have to learn how to write more clearly. I thought I had mentioned that I'm not reaming out an existing 223 chamber to 223AI, I'm chambering a new barrel blank. "Setting Back The Shoulder" will not be necessary in this case, unless one considers facing off the barrel blank to get a true perpendicular chamber face to be the same thing as setting it back.

On an existing barrel that has the tenon already threaded and already has the chamber cut for the parent cartridge case, then you do the setting back thing. In my mind, and in theory, I should be able to ream my 223AI chamber just deep enough so the factory-spec 223 Remington brass will go in just deep enough so that the only contact point of that factory spec case will be right at the junction of the neck and shoulder of the case.

The tenon of a Tikka barrel is set up so that there is no extraction groove. It's just a flat face. With the cartridge or empty case inserted into the chamber, it sticks out of the chamber end about .10" if I remember correctly; I'll have to re-measure to be sure but, anyway, I think I now have a clear picture in my mind on how the head spacing works on AI chambers. Now I'm just waiting on my barrel blank to arrive.

I hope to be able to flute my barrel this time around so right now, as I await the arrival of my barrel, I'm trying to learn how to set it up on the 4th axis of my mill to be able to flute it. This too requires some research.

HollowPoint

[5Shot]

You still need the crush, even on a brand new chamber, or it isn't technically an AI. Somewhere down the road, if someone shoots a 223 in it there could be a case separation and possible disaster. Both of my AIs were made that way from the start (not rechambered), and both are a crush fit on factory brass.

You can certainly do it the way you are thinking (where a 223 fits with 0.000 crush), but I personally wouldn't.

[5Shot]

Here is what PTG says about their Go-Gauge for the AI. Most I have talked to think that more than 0.004 is required. If you do get the AI gauge, you will have a minimal crush.


From PTG:

Thus, the GO gauge for Ackley Improved cartridges is .004" shorter than the GO gauge for the parent case, and this GO gauge isn't compatible with any other chambering. However, the standard GO gauge for the parent case, being .004" longer than the Ackley version, CAN be used as a NO-GO gauge for the Ackley Improved version of the cartridge. The shoulder angle doesn't matter, because the headspace contact is on the neck-shoulder corner, not on the shoulder as such

[Wolfer]

I don’t have any AI gauges. I do have standard 223 go/ no go if they would be any help to you.

[HollowPoint]

I don’t have any AI gauges. I do have standard 223 go/ no go if they would be any help to you.

Thank you Wolfer; I appreciate that. I'll keep you in mind should it turn out that I do need the use of either of your 223 gauges. In the past, when re-chambering conventional factory chambers I've used the actual brass that I planned on shooting out of my gun to do my head spacing and they've all turned out very well for me. This includes the 6.5x55 Swede Tikka Hunter rifle I recently rebarreled. The fact that I use the "Barrel-Nut" method of rebarreling tends to make head spacing particularly simple for me. I believe the same will hold true with the AI chambering.

In the case of the conventional rimless chamberings I've done, for a No-Go-Gauge I simply stuck a piece of Scotch-Tape to the base of my brass which added an additional .002-.003" of an inch to the length of the brass; depending on the brand of Scotch-Tape. I try to aim for a bit tighter head space that many "Experts" state one should strive for.

By removing .002-.003" from the base of my brass, it essentially achieves the same result when using this to dictate the depth of my chamber. I hope that makes sense to you all. It makes sense to me.

I'm going in to have my taxes done the week after next. Who knows; I may get a tax refund to cover the cost of the gauges I need. I'm not stressing out of this project, I'm just wanting to get all my ducks in a row so that it goes as smoothly as possible. Thanks again to everyone who has taken the time to post comments. I'll keep checking back here for any new post with information that I haven't already come across during my own research efforts.

HollowPoint

[M-Tecs]

I try to aim for a bit tighter head space that many "Experts" state one should strive for.



Headspace is not a recommendation from "Experts". It is simply SAAMI standard to ensure safety and interchangeability for a standardized product.

https://www.brownells.com/aspx/learn/learndetail.aspx?lid=12555

http://bulletin.accurateshooter.com/2019/02/gun-info-101-headspace-defined-and-illustrated/

AI chambers are ideal for setting up without a headspace gauge when using a barrel nut system since the intent is to have a slight crush fit with factory ammo. Remove the cocking piece and ejector and set the barrel so you feel a slight resistance when you close the bolt and you are done.

[HollowPoint]

I thought I'd have this project done this weekend but now it looks like my budget rebarreling project will drag out as long as it takes to receive the cheap Chinese 4-jaw chuck I had to order. It's scheduled to arrive between April 11th-the 22nd. It's coming from China. I could have bought a cheap one from some vendor within the US but, bare in mind that this is a budget project. My 4th-Axis CNC setup is presently wearing a small 3-Jaw chuck that I cannot get to center perfectly on my milling table. In the past this wasn't an issue cause I never had any real need for absolute precision but, with this particular rebarreling job I thought I'd go all out and try some spiral-fluting on the barrel itself. Not just for aesthetic reasons but to try to bring the weight down on the barrel blank.

The 22" long pencil thin factory barrel weighs about 2.75 pounds. (weight has been corrected since I originally posted this) The 17" barrel blank I'm working with weighed 4 pounds out of the box. In order to get the balance of the rifle as close to the center of the rifle (or right at the front of the magazine well) I put it on the lathe and turned a straight taper with the muzzle ending up at .875" and the chamber end retaining it's 1.063" diameter. After threading the muzzle and the tang end, as well as reaming out the chamber I was able to get the weight down to just a tad over three pounds. I'm thinking that with the fluting it will get my weight down to just a little above two-and-a-half pounds. With the scope mounted it should bring the balance point about to where it should be.

My CNC mill only has a 14" X-Axis work envelope so I had to lay out my spiral flutes so that I have a section of flutes fore and aft of center. In the center of the barrel in between the two separate sections of spiral flutes I also have some flutes drawn up but those particular flutes are short and straight front-to-back about 1 1/8" long. I'll have to machine one set of flutes along with the straight center flutes and then turn the barrel around and machine the spiral flutes at the opposite end of the barrel.

I did the headspacing after finishing up the lathe work so that I could index the barrel on my receiver. That indexing gave me the top-dead-center position of my barrel when correctly head-spaced so this will allow me to index the barrel blank in the 4th-Axis of the mill and in theory when the flutes have been cut I should be able to install the barrel on the receiver and end up with all my flutes perfectly positioned within the stock. I've been taking photos as I've gone along. I'll post those after I get it all done.

After doing some more research into the "Go-No-Go" gauges I was able to figure out what was needed to safely head-space this re-chambered 223. It turns out that it wasn't as complicated as all of the online pontificators and experienced alike had shared. To avoid a potential fire-storm of opinions and experienced hands-on-input-folks from going at one another about this 223 Ackley Improved head-spacing issue, I will just state that I was able to figure it out thanks to some of you guys here and others in a couple of the other forum venues I visited.

Because of the short barrel blank I'm working with I did have to fabricate some additional items in order to index it on the lathe for threading and chambering. The length of the head-stock bore on my lathe was longer than the 17" barrel so I had to cut, bore and thread-internally an extension so that my outboard spider could secure the muzzle end of the barrel blank. The small work envelope of my hobby mill meant that I also had to fabricate a type of steady-rest that I could use on my mill table to support that barrel blank at the center of it's length to avoid potential chatter from my end mill as it cut the flutes. Also; I want to first make a test run of my tool paths to make sure that those tool-paths will cut the spiral flute patterns I have laid out. To this end I cobbled together a home made spring-loaded felt-marker that I could chuck up on my mill so as to run my tool paths with the felt-marker to see if I got it right before doing any actual cutting. I may not be making any sense at this point so I'll have to wait till I post those pics I mentioned in order to clarify. I'll be back after my 4-jaw chuck arrives.

HollowPoint

[HollowPoint]

Here are a couple of photos that may explain some of my ramblings in the previous post. This is still a work in progress. In the mean time, while I'm waiting for my small 4-jaw chuck to arrive I've been busy trying to draw up a CAD model of what I hope will be a 3D printable extended magazine for this same Tikka rifle. The factory extended magazines are outrageously expensive.

[HollowPoint]

I'm still waiting on my 4-Jaw chuck to arrive before I can go any further with this re-barreling project. I've mentioned before that I'm replacing the factory 22" barrel with a 17" barrel.

It's all ready to be fluted and I've already done all my lathe work including the muzzle. I also mentioned that I was re-chambering to 223 AI to compensate for some of the loss of velocity from the shorter barrel.

I've already made up my new thread protector and it blends in quite smoothly so the seam between the barrel and the thread protector is barely visible. Here's my question:

Generally speaking; the longer the barrel the higher the velocity of the projectile. If I make a new thread protector that's an inch or two longer than the end of the actual muzzle of the barrel, with the bore hole cut so that my bullets clear as it passes through that one or two inch length of thread-protector-bore, can or will this act as additional barrel length and increase the velocity by any amount?

I have it on good authority that "There Is Nothing New Under The Sun" so I'm relatively sure someone has tried this at some time before. I'm wondering if any of you guys have ever tried this and if you have, what were the results? Did you get any quantifiable change in velocity?

HollowPoint

[M-Tecs]

If I make a new thread protector that's an inch or two longer than the end of the actual muzzle of the barrel, with the bore hole cut so that my bullets clear as it passes through that one or two inch length of thread-protector-bore, can or will this act as additional barrel length and increase the velocity by any amount?

I have it on good authority that "There Is Nothing New Under The Sun" so I'm relatively sure someone has tried this at some time before. I'm wondering if any of you guys have ever tried this and if you have, what were the results? Did you get any quantifiable change in velocity?

HollowPoint

Never tried that but I have used or built rifles with bloop tubes https://www.accurateshooter.com/gear-reviews/bloop-tubes-from-norm-houle/

Velocity was not effected but the ID would be either .750" or .812"

[HollowPoint]

Never heard of "Bloop Tubes". I'll have to look into it. With that large of the thru-hole it's understandable that velocity would not be effected.

What I was thinking was cutting or boring a thru-hole just large enough for my bullets to safely clear while still keeping any hot gas expansion from taking place or mitigating the amount of gas-cutting that might occur due to my bullets not keeping the gas in check.

I was just hoping that one of the guys here had already tried something like this. This may be one of those cases where I'll just have to try it to see if it works.

One of the driving factors that got me thinking about this was that again, generally speaking, whenever I've mounted my suppressor on my rifles, the added length always seems to increase my velocities. It's not a big increase and the amount depends on the bullet weights I'm shooting but on average it equated to having an additional one or two inches of barrel length. In some cases I could swear it also increased the accuracy but that could just be a type of placebo effect of not having to deal with the loud report of the shot.

HollowPoint

[Willbird]

After some thought I say just make one :-). You have a barrel to use as a jig to measure things. Put your normal "go " gauge in there, measure from the case head to the end of the barrel. Say the measurement is .107", write that down.

Then take a cartridge case, new will look prettier but fired will work too, start trying to bump the shoulder back, your die and shellholder combination might not allow bumping the shoulder, but first try adjusting the die until it makes FIRM contact with the shell holder, and full length resize the case. Drop it in the chamber, if you get .103 than do a little happy dance :-). if not ..say you get .106"...put .003 shim on the back of the case and size it again, then remove the shim stock and measure...now you have .103, and you are almost done with your gauge.

Now cut the neck completely off with a case trimmer...this will ensure you are only measuring headspace with it not some other feature of the chamber by accident.

They work pretty good really, I made one for something or other, and have just made headspace gauges on the lathe too. Making them in the lathe one can just turn them straight, and wrap black tape around them mid body so they center up in the chamber better.

Bill

[HollowPoint]

Greetings Willbird:

The headspacing issue I originally inquired about in this thread has been solved. Right now I'm just passing the time as I wait for an incoming 4-jaw chuck by throwing out questions on things I'm wondering about; like, that extended thread protector and by making up a 3D printed extended magazine.

HollowPoint

[Willbird]

Never heard of "Bloop Tubes". I'll have to look into it. With that large of the thru-hole it's understandable that velocity would not be effected.

What I was thinking was cutting or boring a thru-hole just large enough for my bullets to safely clear while still keeping any hot gas expansion from taking place or mitigating the amount of gas-cutting that might occur due to my bullets not keeping the gas in check.

I was just hoping that one of the guys here had already tried something like this. This may be one of those cases where I'll just have to try it to see if it works.

One of the driving factors that got me thinking about this was that again, generally speaking, whenever I've mounted my suppressor on my rifles, the added length always seems to increase my velocities. It's not a big increase and the amount depends on the bullet weights I'm shooting but on average it equated to having an additional one or two inches of barrel length. In some cases I could swear it also increased the accuracy but that could just be a type of placebo effect of not having to deal with the loud report of the shot.

HollowPoint

The old school term for that kind of device in artillery might be "chase tube" ?? Some supressor baffle designs made for subsonic ammunition (K baffles ?) can cause a supersonic bullet to become unstable and tumble IN the supressor even :-).

I seem to recall something in Rifle Accuracy Facts by Dr. Harold Vaughn dealing with this subject, he saw some issues with partially unburnt powder granules in the ejecta behind the bullet. Dr. Vaughn did a lot of work on detailing what goes on when a bullet leaves the rifle muzzle. Within the barrel it is forced to rotate around it's geometric center. At some point forward of the muzzle it starts to rotate around it's center of gravity.

Dr. Vaughn was working with a large capacity 270 cartridge of his own design. He was firing the rifle over a tall field of grass, under conditions of no wind he noticed that the muzzle blast wave across the grass was inconsistent shot to shot...he traced this back to to bullet making that adjustment to free flight. He worked on several ideas to bleed off gas pressure before bullet exit, one was ports drilled into the rifling grooves...actually cut in a more precise way than drilling. Another thing he tried if I am remembering right was counter boring the muzzle to achieve what you would end up with.

Here is the lead in to the ideas.


More than thirty years ago a friend of mine (Ed Cave) and I were camped
in a mountain meadow covered with tall green grass. Green grass is
pretty unusual in this part of the world (New Mexico). I decided to shoot at
a target on a distant mountain side, so I sat down and fired several rounds
over the grass. My friend was standing behind me, and when I had finished
shooting he said, “Something funny is going on — sometimes I don’t see the
muzzle blast on the grass and at other times it appears off to the left or to the
right and sometimes right in front of you.” Well normally I would have an-
swered “Uh huh” and gone on shooting, but I knew this guy was an accurate
observer. So, I asked him to fire a few rounds so that I could watch, and sure
enough he was right. It was pretty clear that the direction of the muzzle blast
varied a lot from shot to shot. Well, that experience has bothered me for
years, so I decided to find out just what the heck was happening. The first
thing to do was to repeat the “grass” experiment in a more professional man-
ner, and try to get some presentable data.

[Willbird]

Never heard of "Bloop Tubes". I'll have to look into it. With that large of the thru-hole it's understandable that velocity would not be effected.

What I was thinking was cutting or boring a thru-hole just large enough for my bullets to safely clear while still keeping any hot gas expansion from taking place or mitigating the amount of gas-cutting that might occur due to my bullets not keeping the gas in check.

I was just hoping that one of the guys here had already tried something like this. This may be one of those cases where I'll just have to try it to see if it works.

One of the driving factors that got me thinking about this was that again, generally speaking, whenever I've mounted my suppressor on my rifles, the added length always seems to increase my velocities. It's not a big increase and the amount depends on the bullet weights I'm shooting but on average it equated to having an additional one or two inches of barrel length. In some cases I could swear it also increased the accuracy but that could just be a type of placebo effect of not having to deal with the loud report of the shot.

HollowPoint

The old school term for that kind of device in artillery might be "chase tube" ?? Some supressor baffle designs made for subsonic ammunition (K baffles ?) can cause a supersonic bullet to become unstable and tumble IN the supressor even :-).

I seem to recall something in Rifle Accuracy Facts by Dr. Harold Vaughn dealing with this subject, he saw some issues with partially unburnt powder granules in the ejecta behind the bullet. Dr. Vaughn did a lot of work on detailing what goes on when a bullet leaves the rifle muzzle. Within the barrel it is forced to rotate around it's geometric center. At some point forward of the muzzle it starts to rotate around it's center of gravity.

Dr. Vaughn was working with a large capacity 270 cartridge of his own design. He was firing the rifle over a tall field of grass, under conditions of no wind he noticed that the muzzle blast wave across the grass was inconsistent shot to shot...he traced this back to to bullet making that adjustment to free flight. He worked on several ideas to bleed off gas pressure before bullet exit, one was ports drilled into the rifling grooves...actually cut in a more precise way than drilling. Another thing he tried if I am remembering right was counter boring the muzzle to achieve what you would end up with.

Here is the lead in to the ideas.


More than thirty years ago a friend of mine (Ed Cave) and I were camped
in a mountain meadow covered with tall green grass. Green grass is
pretty unusual in this part of the world (New Mexico). I decided to shoot at
a target on a distant mountain side, so I sat down and fired several rounds
over the grass. My friend was standing behind me, and when I had finished
shooting he said, “Something funny is going on — sometimes I don’t see the
muzzle blast on the grass and at other times it appears off to the left or to the
right and sometimes right in front of you.” Well normally I would have an-
swered “Uh huh” and gone on shooting, but I knew this guy was an accurate
observer. So, I asked him to fire a few rounds so that I could watch, and sure
enough he was right. It was pretty clear that the direction of the muzzle blast
varied a lot from shot to shot. Well, that experience has bothered me for
years, so I decided to find out just what the heck was happening. The first
thing to do was to repeat the “grass” experiment in a more professional man-
ner, and try to get some presentable data.

I either mis remembered about the chase tube in Dr. Vaughns book or it is in a different section than I thought.


https://archive.org/stream/RifleAccuracyFactsFullV1.0FirstFullScan/Rifle%20Accuracy%20Facts%20Full%20v1.0%20%28First% 20Full%20Scan%29_djvu.txt


Bill

[Willbird]

HA :-). I found it :-). We could guess that his one attempt that did not work was something like what is being discussed. This text covers that change in the bulllet being controlled to the bullet being a free flying object.


Bullet Balance Compensator

The trick to solving the bullet imbalance problem would be to allow the bul-
let to spin about its centroidal axis before leaving the barrel. The centroidal
axis passes through the CG and is parallel to the geometric axis. If this could
be done, the barrel would decrease the lateral drift velocity and decrease the
effect of bullet imbalance. I tried three approaches to making a compensator
and all three attempts failed.

The first approach was to counterbore the muzzle for a distance of three inches.
For this to work the radial clearance between the bullet and bore must be
small (less than 3mils). The reason for this small clearance is that the


176


Chapter 9: Bullet Imbalance


corrective effect depends on viscous interaction between the bullet and the
barrel. I tried this starting with a 1 mil radial clearance and the groups were
enormous. I gradually increased the clearance and at about a 10 mil radial
clearance the gun shot about as well as it did before modification. After
doing the muzzle blast shadowgraph tests and seeing the small partially burned
powder granules traveling along with the bullet, I have doubts about this
method ever working. Also, after testing I sectioned the barrel and found that
the counterbore was off center. So that may have doomed the test from the
start. If anyone wants to try this, I suggest making piloted reamers in 1 mil
increments. According to computer calculations it should work, but I may
have missed something in the physical model.

Another way to compensate for CG offset would be to allow the barrel to
move about the bullet CG before the bullet exits the muzzle. I tried two
different approaches and neither one worked. One of them appeared to be
trying to work but it drew straight lines of bullet holes as a result of thermal
distortion. I tested the barrel on the bench and found that the muzzle warped
enough with a modest change in temperature to explain the drift.

While I haven’t given up on this problem I decided to go ahead and publish
this book because it is a difficult problem that may not be solvable. Mean-
while all you can do is buy the best bullets that you can find. It also should be
pointed out that bullet manufacturers are continually trying to improve the
quality of their bullets and since this data was taken some time ago the situ-
ation may have changed by now.

[HollowPoint]

A few days back I spent the morning cutting air as a test of my tool paths with this fluted barrel project. My home made spring loaded felt marker confirmed that all my tool paths were good but I ran into a problem with the thread protector on the muzzle end of my barrel blank.

It seems that my 4th-Axis unit worked well enough but when the tool path called for a clock-wise rotation it tended to just unscrew the thread protector from the barrel blank so I had to fabricate another type of thread protector with a slit cut along one side so as to allow the jaws of my vice to clamp down on the muzzle threads without damaging them and securely keeping the barrel from rotating during machining.

I made a similar thread protector for the chamber end cause I knew if the muzzle end was unscrewing during certain milling operations the chamber end would most likely do the same.

After running those air cutting tests with my felt marker I determined that I had crisscrossing flutes that were spaced to far apart so that it really didn't look balanced out so I went back to the CAD software and added another flute. Now with the crisscrossing flutes it looked like I had to many flutes and it still looked out of balance so, I decided to run all my flutes in the right hand direction and call that good. They looked evenly spaced and overall they looked well balanced for a short barrel blank like this.

This morning I bit the bullet and decided to cut the flutes. My plan was to mill the flutes on the muzzle end of the barrel blank and while I had the barrel already indexed in the 4th-Axis I'd go ahead and do the short center flutes as well. The first three muzzled end flutes went off without a hitch so I loaded the G-Code for the center flutes and it was going just as well as the muzzle end flutes. The feeds and speeds seemed to be spot on. You should have seen the $#it-Eating-Grin I was sporting as I stood their watching my end mill do it's magic. Until, it got to the second to the last little flute.

I don't know what the heck happened. At first I thought that my newly made muzzle thread protector had slipped and the barrel wasn't turning in step with the 4th-Axis. Like an idiot I let it keep running and it did the same darn thing. For some reason my end mill did a left hand turn and started cutting toward the last flute to be cut. By then the end mill had already cut down to about the .1" depth of a .128" deep flute and I really expected for that little 1/4" two-flute end mill to just snap and put me out of my misery. It was at that point that I regained the sense to hit the "E" stop. That little end mill didn't snap. It hung in their.

The barrel isn't ruined by a long shot and it's not a loss of any kind. It's just a real head scratcher cause I checked to see if my muzzle thread protector had slipped and it was still synched down super tight. My computer simulations showed my tool paths working flawlessly but in doing the actual milling operation it went completely off the expected tool path on that second to the last flute. (enter foul language here)

Tomorrow or the next day I'll be cutting more air. This time I'll be testing the tool paths on the chamber end of my barrel blank. If I can get them to come out like the muzzle end flutes I'll be a happy camper with a semi-nicely spiral fluted barrel. I'll then have to go in and doctor up the bad cuts made when my end mill veered off course. If I take my time I'm pretty sure I can make it look like I meant for it to be this way all along but, it sucks that everything is going beautifully and then something like this happens.

At the time I thought to myself, "Oh well, if the bad cut is on the under side of the barrel blank as it sits in the stock it won't be that big of a deal, but as it happens, my tool paths started with the initial little flute being the one on the underside of the barrel blank. The tool path went off the rails as it was cutting the second to the last flute which sits to the right of the top-dead-center flute that I had pre-indexed when I mounted and head-spaced the barrel in the receiver. ****! I guess it could have turned out far worse. I did take some pics that I'll be posting a little later. I have to shrink them down so that I can upload them to the various online forums that are following this project.

Just to let you know; my barrel blank is a $39.00 barrel blank I bought from Green Mountain Barrels so it's not like I'd be out alot of money if I had managed to destroy my barrel blank. Now that I've learned a few things the hard way I may just buy another of these barrel blanks and do it all over again with a little more confidence.

I'll be back with those photos later. I'll be back when time permits. Pray for me brethren; and don't act like nothing like this as ever happened to you either. If it hasn't, just give it some time and I'll be able to empathize with you; or maybe commiserate.

HollowPoint

[Willbird]

I spent a few years running a fadal 4 axis cnc, and another couple running a 3 axis. One thing I have seen them do is wander off toolpath...the one thing consistent in every time it happened was in the "following" portion of the screen.

Those numbers for each axis show the deviation from the programmed toolpath ...there is always a small following error, not sure if the number is in .0001" or what the units really are. But the mill would wander inches from programmed tool path...and the following error instead of being say 10-25 was way up at 400 or 500.

That said on 4 and 5 axis work I have seen really weird things when something runs into a chuck jaw...could be tool holder or part of the milling machine head will bump into a chuck jaw during the cut....in the one case I was milling 4 rectangular windows into a steel tube, two windows were correct and the other two windows one corner of the window was messed up, exactly the same issue on both windows.

Turns out that something was colliding with the jaws of the 6 jaw chuck. The FIRST window had no issue and that is the one you really watch when test running the program, the second window it hit, the third was ok, and the fourth hit again. It was also different depending on Z position so if I had dry run 1" above the part, or even just scratching the surface it would have been fine, but with the cutter 1/4" deeper Z- it caused the issue :-).

Bill

[HollowPoint]

I spent a few years running a fadal 4 axis cnc, and another couple running a 3 axis. One thing I have seen them do is wander off toolpath...the one thing consistent in every time it happened was in the "following" portion of the screen.

Those numbers for each axis show the deviation from the programmed toolpath ...there is always a small following error, not sure if the number is in .0001" or what the units really are. But the mill would wander inches from programmed tool path...and the following error instead of being say 10-25 was way up at 400 or 500.

That said on 4 and 5 axis work I have seen really weird things when something runs into a chuck jaw...could be tool holder or part of the milling machine head will bump into a chuck jaw during the cut....in the one case I was milling 4 rectangular windows into a steel tube, two windows were correct and the other two windows one corner of the window was messed up, exactly the same issue on both windows.

Turns out that something was colliding with the jaws of the 6 jaw chuck. The FIRST window had no issue and that is the one you really watch when test running the program, the second window it hit, the third was ok, and the fourth hit again. It was also different depending on Z position so if I had dry run 1" above the part, or even just scratching the surface it would have been fine, but with the cutter 1/4" deeper Z- it caused the issue :-).

Bill

I still have this particular operation saved in my CAM software so after I get the rest of it done I'll be going back and looking at my G-Code line by line in the area where I experienced the tool path error. I want to see if the numbers are in sharp contrast to those of the previous four little center flutes the end mill had already cut perfectly before that second to the last one when it decided to go off the rails.

This is the first time I'd experienced a problem like this. I suspect that in the end the fault will lay in me ASSUMING to much. Like I mentioned; I went back and added a flute and subtracted some flutes from my model. I then cut air to test those tool paths on the spiral fluted sections of this project but I didn't do any air-cutting tests on these small center flutes. I just ASSUMED that if the spiral flutes turned out good then those short smaller flutes would also turn out just as good; and they did, UNTIL I got to that second to that last flute. OH WELL; live and learn.

HollowPoint

[HollowPoint]

I tried to get a close up of my damage done by my wondering end mill. I wish the accompanying photo had come out clearer but it does give you an idea of what I was shooting for.

All that's left for this project now is to repair the bad cut, finish milling that second to the last short center flute to the correct depth, then I can move on to inletting the stock to accept the fatter bull barrel.

In the photos I mistakenly wrote that this is a Tikka T3 Hunter. That was my previous Tikka rebarreling project. This one is just a Tikka Lite in factory stainless guise with a black synthetic stock. Sorry about that. I'm always in to much of a hurry and this and other errors seems to be the results.

HollowPoint

[HollowPoint]

I finally got it all put back together again and properly head-spaced. Now I have to find some more free time to get to the range for some fire forming followed by some load work up.

I loaded about fifty rounds a couple of days ago so I'm ready for the next phase of this project. It's taken me so long to get this far because I've had a few emergency incidents that came up that out of necessity diverted my attention and resources to get those taken care of.

Right now my assembled rifle is wearing all of the cheapest peripherals money can buy. I won't be investing any more money into it until I find out if she's going to shoot good for me or not. At any rate, I learned alot while doing this project and if or when I do it again I know that I'll go into such a project with a whole lot more confidence.

HollowPoint

[Texas by God]

I bet it will shoot fine but I wouldn't lay money on it outshooting the Tikka barrel[emoji16]
Your snafu only made it unique! Be sure to try some 52gr match bullets, the quick twist will shoot them well in my experience.

Sent from my SAMSUNG-SM-G930A using Tapatalk

[HollowPoint]

I'll be working my way though some of the left over bullets I have on the shelf. I'm starting out with 60 grain and 55 grain soft points. The next batch will be made up of some 55 grain Dog-Town bulk bullets then I'll move onto the lighter bullet weights.

Since this is intended as a varmint rig I'm looking for something that will get me and keep me within the 3000 FPS range. For fire forming I'll just stick to bullets in the 55 grain weight since I have a bunch of those on hand.

HollowPoint

[Texas by God]

Those Dogtown bullets are good ones. You should reach your velocity goal easily at mild pressure with the AI case.

Sent from my SAMSUNG-SM-G930A using Tapatalk

[HollowPoint]

Those Dogtown bullets are good ones. You should reach your velocity goal easily at mild pressure with the AI case.

Sent from my SAMSUNG-SM-G930A using Tapatalk

I've had pretty good luck with them as well. The 60 grain and 50 grain soft points have been in my storage room for so long I can't remember the last time I loaded any of them. I bought the dog-town bullets a couple of years back and I still have a half a box left. I had my sights set on the 50 pills for this project gun when I first decided to go through with it.

They should be able to deliver good velocity and energy levels on coyotes out to three hundred yards at least. I've never shot a coyote out that far but if I'm right in my assumption, it should give me a good safety margin with respect to wounding as opposed to killing coyotes at that distance. Of course all of this hinges on being able to hit what I'm aiming at.

HollowPoint

[HollowPoint]

I dug around in my storage room searching for a scope I could use when I got to the range to fire form the fifty cartridges I had loaded up. I swapped scopes between the Tikka Hunter rifle I had rebarreled previously and this latest rebarreling of my Tikka Lite from 223 to 223 AI.

Why swap scopes? I was still working up loads with 6.5x55 Tikka hunter and my last trip to the range was showing some screwy looking groups shooting the 129 grain SST bullets. I expected far better than that since my 100 grain accuracy testing was giving me some sub-MOA groups right out of the gate. These 129 grain bullets looked like they wanted to group well but something just wasn't right so I thought I'd try a scope change to confirm that it wasn't the scope that was the problem.

I think I was right cause this last time out with the Tikka hunter I was getting tighter groups and my scope was tracking reliably. The groups I shot using these heavier bullets still weren't as tight as I'd like but at least now I think I had a handle on the cause of my shot-groups. That last time out to the range I was testing OALs to see if this would tighten up my groups shooting the 6.5x55 rounds. I found that with the 129s my rifle tended to shoot better with the bullets seated deeper than I had previously seated them. I'll be going out as many times as it takes to find the sweet spots. I'm thinking it may take a bit more bullet-jump to get this Tikka back to sub MOA groups. I've never owned a Tikka that didn't shoot good with the bullets seated more than one or two thousands off the lands. This could be a first.

At the same time I took out the Tikka Hunter I also brought along my newly rebarreled Tikka light in order to fire form brass; the Tikka with the Spiral Fluted shorter bull barrel. I never fired a shot with that rifle cause I couldn't get the bolt to go into battery. After a few choice cuss words I discovered that when I mounted my scope mounts, the front-most screw for the front mount extended just a fraction to far down into the reciever so that one of the bolt-lugs was making contact with the very tip of that scope mount screw. It was frustrating as heck when you consider that a round trip to the shooting range is about fifty miles.

For an instant when I experienced that bolt not wanting to go all the way into battery I thought I might have fouled something up with my head-spacing. Thank God it was just an overly long scope mount screw. I really didn't want to take that rifle back apart to fiddle with the Head-spacing again.

I'm seeing the light at the end of the tunnel for this latest Tikka Lite rebarreling project. I won't be able to get to the range till next week some time so it will be that long till I can post some pics of my accuracy testing results. After that I'll call this particular project done and I won't use up any more perfectly good internet band-width on this project thread. I shall return.

HollowPoint