• The AGN App is ready! Search "Airgun Nation" in your App store. To compliment this new tech we've assigned the "Threads" Feed & "Dark" Mode. To revert back click HERE.

TJ barrels for Impact - I Placed the order - more about grinding

Jump to latest Follow Reply
Azycray

Azycray

Member
Oct 19, 2016
241
40
Virginia, United States
I would like to try a TJ barrel for my Impact but have not had any success reaching them. I've searched and cannot find a web site. I've called and left a message because they don't answer the phone, but no return call. How does someone figure out what they need and what it will cost? I thought they made barrel liners, do they also make aftermarket barrels for air guns? How long of a barrel can you get? Do they fit it or do I have to send it to a gunsmith after I receive the barrel? Thanks for any help you can provide, RJ
 
I got a response from Mike at TJ's liners ( [email protected] ) he said:

"I have a .250 groove with a 1 - 14 twist. That should be what you need to shoot slugs with. I can get it close in the O/D with that being .560 (9/16) . Cost runs $4.95 per inch in any length. Also this is keep in stock for fast shipping. S/H charges run $15.50."



Now all I have to do is find someone who can precision grind a hundredth off of about 12" that fits inside the receiver. Anybody know someone who can do that?
 
Upvote 0
I got a response from Mike at TJ's liners ( [email protected] ) he said:

"I have a .250 groove with a 1 - 14 twist. That should be what you need to shoot slugs with. I can get it close in the O/D with that being .560 (9/16) . Cost runs $4.95 per inch in any length. Also this is keep in stock for fast shipping. S/H charges run $15.50."



Now all I have to do is find someone who can precision grind a hundredth off of about 12" that fits inside the receiver. Anybody know someone who can do that?
Click to expand...

I bet most machine shops could do that if you shop around.
 
Upvote 0
I ordered a barrel from TJ's but I have a question I asked them twice and it seemed like when I asked it, I was completely ignored. So the next time all I asked about was how to pay. When I got a response from Todd I responded back with the question again which is, are the barrels lapped or do you even offer that service? Again, I was ignored. I went ahead and sent them money via PayPal and placed the order but it seemed to me like a very legitimate and common question considering the business they are in. Does anyone know if their barrels are hand lapped when they ship?

When it comes to grinding this is what I found out. Your average run of the mill machine shop most likely will not be able to do it. When you are looking for someone to do a precision grind on a barrel you have to search for "Centerless Grinding". With centerless grinding they do not grind concentric to the bore, they match what is already there. So if your bore is concentric when they start, it will remain so. Most custom barrel makers use pretty tight spec's when it comes to bore concentricity so this is not an issue. If you wanted the grinding to be be done concentric with the bore the cost would be much much more. I spoke to one centered grinding guy who explained all this to me and said the setup cost to do one barrel would be around $1,000, for just the setup. He would have to make a mandrel for the bore and grind around it. Anyway, there are plenty of centerless grinders around the country, I spoke with 4 and they all had a minimun between $75-$90 which would cover it. With shipping about $100. Not exorbitant but adds to the cost of a custom barrel when you can't get the right O.D. to start with, which is most of the time it seems to me. At least when it comes to the Impact. The important information to take from this is that with the thin walled barrels that are common to air guns, the use of a lathe to cut down to size is not the right way to do it. You might not be able to see anything wrong with the naked eye but the chance of ruining accuracy is a very likely possibility.

Update: I just got a response from Todd at TJ's, he said:

" We clean the barrels up but do not hand lap them. Generally speaking lapping is not necessary with barrels that are hammer forged. They come out very smooth."


 
Upvote 0
Okie dokie, let me clarify a few things about the machine work that was mentioned above. I was an aerospace machinist for 15 years and still do a lot of machining for personal projects. Airguns are similar to firearms when it comes to barrel work. It’s not magic, just precision machining. For centerfire rifles, namely bolt action rifles, when we do any sort of machining on the barrel that creates a bearing surface, threads, anything at all used to locate the barrel within the action, you ALWAYS use bore centric machining. It’s nothing special and I’ve never heard of anyone grind these surfaces, they are always machines. These operations are all done in a lathe by a properly set up gunsmith. Any legitimate Smith should have a set of spider jaws in their lathe or something similar that lets them hold the work piece in the machine and get it perfectly centered in relation to the bore. We use a product called a Grizzly Rod which is a precision rod with bushings sold in .0002” increments. The smith sizes the appropriate bushing to snugly fit the bore then uses a dial indicator on the lathe along with the spider jaws to perfectly center the barrel. After that the machine work is relatively simple and fast. The set up is where the work is. It can go quick some days and take 15 minutes and other days you can struggle and take 2 hours. Either way that is how barrels are machined and that is how I would have my barrel done. Anyother way is wrong in my opinion, it I come from a precision rifle background so there is only one way to do these things.

Back to the question at hand... No, your average machine shop would not have the tooling to do this correctly and easily. Your average gunsmith on the other hand should have the tools, specifically a smith who is into barreling rifles. 

I hope that makes sense, there are some great YouTube videos on the process I mentioned above. Contrary to popular belief, most barrel makers could care less about how concentric the bore is to the OD of the barrel and most of the time it’s not concentric at all. If you machine to the outside diameter you run the risk of having a barrel that essentially points the wrong way and you could run into a myriad of problems. Do it the way mentioned above and everything will line up correctly. 

Cheers mates. 
 
  • Like
Reactions: Smitty911
Upvote 0
The information given above is specific to air gun barrels, not powder burners that have barrels much heavier. This information was given to me by Steve at Pomona Air Guns and confirmed by another respected builder right here on this forum. When you have a barrel as an example, that has an O.D. of .590-.560 with a .250 bore and you need to remove material from more than a few inches you are going to get "chatter" using a lathe. I'll let the knowledgeable airgun smiths among us chime in further if so inclined. I'm just reporting what I learned from experienced people with air gun barrels.
 
Upvote 0
I’ll say this, centerless cutting is the cheap and easy way to do it. People get away with it on sporting airguns but that would never fly if you were truly building something you wanted to be accurate and correct in my opinion. I’ve been doing this for a long, long time...

The only reason you would have chatter on a lathe is if you were an inexperienced machinist or had improper set up and tooling. Tubing much, much, much thinner walled than an airgun barrel is cut every day around this world on lathes without issue. It’s all in the set up. 



Also, why do you need to turn the whole length of the barrel down, wouldn’t the first couple inches that contacts the breech be sufficient like most airguns???
 
Upvote 0
Try motorhead on GTA

a hundredth? every machinist in the shop I worked for would say 10 thou (0.010)

and they would want to know your tolerance plus how many thou and minus how many thou.

example +0.000 , -0.002"

the only time I ever saw them use a grinder on the lathe was to grind a ceramic coating that was sprayed on with a torch setup then ground back to the required dimension

and they only would do it on one lathe. in the shop. it is not good for the ways, and a lot of cleaning afterward.

and a GOOD machinist will not have chatter problems. All machinists are not created equal
 
Upvote 0
Try motorhead on GTA
Click to expand...

I contacted Motorhead and this was the response I got from him:

" .003 to .005" of material removal and doing so concentric to bore is a tough one, doable but takes some set up to get it right.
IMO any small machine shop with manual machines should be able to do this IMO ... tho finding a shop with shafting grinder would be best.

Sadly my machine ( Lathe ) is just not precision enough for such work starting out with a diameter so close to finished specs required. "

I don't want to get into a debate about how best to get a barrel fit for my Impact. All I wanted to do was share some of the info I gathered while trying to get it done. All I can do is take the info I get from experienced people and base my decision on that. If someone has an option I haven't heard yet I'm all ears. If I misrepresented a professional opinion somehow, I apologize but since I have not been able to locate someone able to do the job on a lathe I took the advice to have it precision ground and centerless was the only viable option I found without spending more than the $500 it will cost me when all is said and done. I welcome supportive suggestions but am not in the mood to be criticized for doing the best I can based on many hours of research and advice from expert sources. I thought about giving my resume like some others here but it really doesn't matter. The only thing that matters is a better solution to my task. Unless someone steps up and says they can turn my barrel on a lathe, and why after learning the challenges, I'll be sending it to a precision/centerless grinder.
 
Upvote 0
i see u want to try the 1.14 twist.that is for slugs.just to let u know..they will ask u chovked or non.find out.alex
Click to expand...


Thanks for trying to help Alex. Yes it is for slugs and I do not want it choked but Mike made the recommendation for shooting slugs so I doubt he would choke it without asking. But Just on the outside chance they might, I'll shoot them an e-mail to make sure they don't. 
 
Upvote 0
I can think of a couple ways to do it using a spider jaw and live center. If I had access to an impact I would volunteer to cut the barrel for you. I would want the rifle to take my own measurements off. I absolutely love little projects like that. Plus TJ barrels are great ( bughole shooters in my WAR Flex) and I would love to see one on an Impact. 
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu