TUNNEL REPORT Thur 11-30-08

G

Gene Beggs

Active member
TUNNEL REPORT Thur 10-30-08

Testing of the barrel indexing system continues.

The barrel I'm presently working with has one specific position in which it shoots best. The day before yesterday it was shooting well but I was getting a stiffer bolt lift than I like and there was definitely a 'click at the top' in spite of full-length sizing and bumping the shoulder .001. I figured, 'Well, these cases are just getting old and work hardened; I guess it's time for a new set.' (That wasn't the problem at all :eek: more later.)

Twenty new cases were turned to .0120 and fireformed in the usual manner, i.e., 20 grains of H4198 with the cases lubricated with Imperial sizing die wax which insures they do not stretch during the initial firing.

The second firing was with 22 grains; cases were then ready to accept a full charge of 26.5 grains of H4198 behind a 68 grain bullet which in my rifle produces around 3350 fps. The rifle was cleaned, and seating depth established at .015 off 'JAM.'

A fouling shot and a couple of sighters were fired. The group showed about one bullet hole of vertical. I gave the tuner a quarter turn and the next two bullets went into the same hole so I figured, "Perfect." (Wrong!) :eek:

Sadly, I was a little premature in declaring the rifle in tune and the first group on the record target showed two bullet holes of vertical. A classic key hole group. :mad:

What happened? :mad: Then I remembered :eek: I did exactly the same thing at the Nationals in Phoenix. :mad:

What happened was the barrel had not settled in after cleaning. Adjusting the tuner so soon was futile until velocity stabilized which in this case took about seven or eight shots. After shooting the group with two bullet holes of vertical, I gave the tuner a half turn and the following group was a small dot. :) Subsequent groups were also in the mid to low ones.

This was not the first time this had happened to me. I knew better, but in my haste to get on with it, I went to the record before the barrel was ready. Hopefully, I will never make that mistake again.

When shooting in a match, I begin a five match agg with a clean barrel and do not clean until the agg is finished. This way, I do not have to waste five or six shots every time I go to the line getting the rifle settled in. Also, if a condition is right when the range officer says, "Commence Firing" I can go right to the record and rattle off five shots before the condition goes away. :D

Onward thru the fog.

Accuracy continued to be excellent but I was surprised to feel a noticeable 'click at the top' even on the third firing with the new cases! :eek: What is going on?:mad: Same action, same load I have been using. The action has always opened like it was on ball bearings with not a hint of 'click at the top.' Then it dawned on me; this was exactly what an experienced friend said was likely to happen with small diameter tenons. :eek:

The thinner chamber wall thickness of the .800 tenon was swelling more upon firing, stretching the cases more than when the tenon was a full 1.0625. :eek: Remember; this was the third and smallest diameter tenon used with the barrel indexing bushing. The first tenon was .900, the second, .875 and this one was only .800 before threading.

The experienced friend who told me what was likely to happen was none other than Stuart Harvey!

Stu, I hope you don't mind me relating this story and mentioning your name. I just wanted everyone to know how wise you are in such matters. :) Is there ANYTHING you don't know about this stuff? :)

Stu told me about a rifle he owned that had an unusually small tenon diameter and would not accept the loads he normally uses in other rifles with the same cartridge. He further stated regarding my .800 dia., tenon,

"You will probably be okay with that .800 tenon, it's not going to blow up on you or anything like that but you are likely to experience tight cases prematurely because of the thinner chamber walls." And boy,, was he ever right!! Thank you Stu! I'm a wiser man because of you. :)

Tommorow, I will remove the barrel with the .800 tenon and declare it scrap. Yep, back to the .875 tenon for use with the index bushing. We will see if that cures the tight case problem, and I think it will. If not, we may have to wait until one of the action makers sees fit to build us an action with a 1.125 diameter thread specifically for use with the barrel indexing system. That would be the cat's meow. :)

Later,

Gene Beggs
 
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Gene,
Thanks for sharing. If Savage can enlarge an action thread without increasing the diameter of an action, why couldn't one do the same with a steel bodied Benchrest action by setting it up like like one does when single pointing threads in a factory action? BTW were there any problems with the .900 tenon setup?
Boyd
 
Gene,

What is the largest tennon dia. that can be cut while using a differential threaded insert in your 1.062 action?

How much torque does it take to hold the insert in place, without moving, while tightening a barrel to the action?

If you are still having additional inserts made for the .800 dia. tennon, may be time to revise their specs. or delay the order until this tight case problem is sorted out..........Don
 
Boyd Allen said:
Gene,
Thanks for sharing. If Savage can enlarge an action thread without increasing the diameter of an action, why couldn't one do the same with a steel bodied Benchrest action by setting it up like like one does when single pointing threads in a factory action? BTW were there any problems with the .900 tenon setup?
Boyd
Click to expand...


Boyd, the .900 tenon setup worked perfect.

Gene Beggs
 
Gene

While following this thread I knew you would run into this problem at some point. Myself and several other smiths have had problems with 1.00" diameter tenons and cases the diameter of the Winchester WSM's. The receiver ring expands, the barrel tenon expands and the brass expands. The problem is the brass has expanded past it's yield point. As they say,You can't fool Mother Nature.


Dave
 
Don said:
Gene,

What is the largest tennon dia. that can be cut while using a differential threaded insert in your 1.062 action?

How much torque does it take to hold the insert in place, without moving, while tightening a barrel to the action?

If you are still having additional inserts made for the .800 dia. tennon, may be time to revise their specs. or delay the order until this tight case problem is sorted out..........Don
Click to expand...


Don, in my opinion, the largest tenon diameter that could be used is .900 and that's pushing the limits with 1.062 threads.

Once the barrel is placed in the desired position minus an allowance for tightening, and the bushing is snugged up with the rear entry tool, the bushing does not move as the barrel is tightened. I attribute this to the fact that the ID threads of the bushing are finer than the OD. Also, I do not lube the OD of the bushing; there is no need because the only time these threads move is while the barrel is loose.

A small number of bushings are being made for the .875 tenon diameter. I believe that will be the best compromise.

Later,

Gene Beggs
 
Actually, what I meant to say is that I believe that an action that is the same diameter as a Savage or Remington (1.360?) can accommodate the larger threads. For instance, some of the Savage actions have a 1.120 thread diameter, I believe.
 
B.Johnson

What would this do, to bring back the .222 as a 100 yrd. rifle?
 
I wish Gene would tell us who won the election. Seeing as how he lives in a time machine Thur 11-30-08.
 
Big Al said:
I wish Gene would tell us who won the election. Seeing as how he lives in a time machine Thur 11-30-08.
Click to expand...


Al, you have a sharp eye. Thanks for pointing out my error. :eek: If a man doesn't even know what month it is, how can you believe anything he says; huh? :rolleyes:

Thanks for the good laugh, I needed that. :D :D

Later,

Gene Beggs
 
If you make the action tenon

much bigger, you will start running into trouble with not enough shoulder on 1.2 to 1.25 barrels.
 
stiller said:
much bigger, you will start running into trouble with not enough shoulder on 1.2 to 1.25 barrels.
Click to expand...


Jerry, what we really need is an action designed specifically with barrel indexing in mind. It must not be heavy and/or complicated. Adjustments must be simple, easy and quick. I know that's a tall order but that's what we need. The more I work with barrel indexing, the more convinced I am that this is something that has great potential.

Have you looked at the barrel/receiver joint designed by Harold Vaughn? It may be the answer and can be found on page 119 of "Rifle Accuracy Facts." The barrel tenon is not threaded and the way it tightens up would make it infinitely adjustable. Do you think something like that might be better than the differential bushing idea?

Gene Beggs
 
Chisolm said:
Someone always has to be the voice of reason, don't they.;)
You could however also add a Savage type barrel nut.:D

James
Click to expand...


James, the Savage barrel nut has always intrigued me. It's a good idea and I wish there was some way to use it with the barrel indexing system.

Gene Beggs
 
Gene Beggs said:
James, the Savage barrel nut has always intrigued me. It's a good idea and I wish there was some way to use it with the barrel indexing system.

Gene Beggs
Click to expand...

Gene I was only pointing out the barrel nut system as a way to get around the issue that Stiller brought up.


James
 
Jerry,
Since the tenon would be say .9, and the action 1.360,something like a Remington recoil lug, only round and a hair less than action diameter, should bridge from the ample barrel shoulder to the face of the action. It could be round, ground parallel, 1/4" or so thick, 1.350 OD, and a hair over.900 (or more) ID. Problem solved..
One question, if the outside bushing thread is 18 TPI, and the inside 26, what is the minimum bushing thickness before threading, assuming that the tops of the threads come flush with the original OD and ID? If we start from a bored out 1.120 action thread, subtract twice this thickness, and add twice the depth of the 26 TPI thread we should arrive at the maximum tenon diameter.
 
B.Johnson

Just for the purpose of testing, both tenon size, and indexing for accuracy, why not use the smaller dia. .222? For now, would'nt that tell you want you want to know.
 
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