Thought I would share my latest experience that happened whilst re zeroing my .30-06.

I plodded off with rifles in truck to have a target session and all was going well. then it came to zeroing the 30-06 with its new S5 sound mod on it. At 100m I had to adjust 30 inches up and 16 inches right to get on target and the groups were about 5", not a happy bunny!! The rifle was zeroed without the moddy using the same loads and produces 1" groups no problemo.

Yet if I fit the T8 moderator the re zero only requires about 4" of elevation from the non moderated zero and group size stays the same.

Are we looking at a manufacturing problem here? Your thoughts please.

Have you seen any evidence that the departing bullet has clipped one of the baffles in the mod?

Regards,

Amir

quote:

Have you seen any evidence that the departing bullet has clipped one of the baffles in the mod?

+1!

Something is seriously wrong. You shouldn't require that much POI change.

Take the Moderator "off"; then put "on" three sets of ear protectors and try without!

Did you take a serious or just glancing look at the target? Are the bullet holes oval instead of round? Indications of "Keyholing"?

If the rifle was recently threaded there could be a problem with the "squarness" of the thread to the bore.

Either way I'd get the smith that did the job to look at it and supply some answers.

FB

Have you checked how well the screw thread on the barrel fits the screw thread on the moderator. If its loose, then only when its fully tightened is it bearing anywhere and that is on the tips of the threads and the shoulder of the screwcut barrel end against the shoulder of the moderator.
The T8 (If this is the one which goes back over the barrel) has a bush that should give a second bearing surface and that would make it twitch less when fired giving a better group.

You could try wrapping some plumbers PTFE tape on the screw thread before putting the mod on.
If this improves the group then it suggests that the thread is too loose and that the mod is moving during firing.

The problem for the machinist is that there is a fair amount of tolerance involved when a thread is ordinarily cut on a lathe and whilst it is not particularly skilled, the devil is in the detail. The barrel has to be set up so that it rotates about the centre of the bore which may not be identical to the centre of the barrel.
The thread then has to be cut with a lathe tool as a hand die may not cut quite parallel to the bore.
In order to get a good fit to the female thread on the moderator, in the last stages of cutting the thread, the tailstock has to be moved out, perhaps a dozen times and the moderator offered up, trimming off a few thou until it will just screw on.
This process could take a good machinist several hours and a moments loss of concentration will lead to a cut too far.

I suppose the question in my mind is:
Was your barrel sent off to have a thread cut or was it sent off to have a thread cut and moderator fitted?
If it was just thread cutting then it will be between a range of tolerances,say + or - 5 thou.
The thread on the mod you bought will be made to similar tolerances. Sometimes these tolerances net to zero, sometimes they add up to a lot of slack.

Amir, I can't see any evidence of a bullet clipping baffles but I will go back and check again more thoroughly.

Gerry, without the moddy, accuracy and grouping is fine.

FB, thread was cut by a very experienced tool maker.

Trapper, screw thread seems to be cut to fairly
tight tolerances. The T8 I use floats around its second bush so only has one bearing surface at the threads.

thanks for your thoughts everyone I will keep working on it!!

quote:

Originally posted by Gerry:

quote:

Have you seen any evidence that the departing bullet has clipped one of the baffles in the mod?

+1!

Something is seriously wrong. You shouldn't require that much POI change.

I have never heard of that much elevation and windage being required.
A 5 inch group !Jeez thats awful.Somehow I suspect something is loose or rattling around.

I had the same problem but on a rimfire,it turned out that the crown was damaged, i got it recrowned and its back to shooting like it should.I would give the smith a call and get him to check EVERYTHING for square.If you hand load i would get all your odds and sods and just let rip with them all, then look at the baffles,if the bullet is catching it will be plain to see.

If it were crown damage, I would expect the rifle to shoot poorly with or without the mod fitted..

Is the barrel free floated? If so, is there enough clearance between the barrel and the stock? I'm thinking the extra weight of the mod could be causing the barrel to touch the stock when the shot is taken...

quote:

Originally posted by Gerry Merry:
Thought I would share my latest experience that happened whilst re zeroing my .30-06.

I plodded off with rifles in truck to have a target session and all was going well. then it came to zeroing the 30-06 with its new S5 sound mod on it. At 100m I had to adjust 30 inches up and 16 inches right to get on target and the groups were about 5", not a happy bunny!! The rifle was zeroed without the moddy using the same loads and produces 1" groups no problemo.

Yet if I fit the T8 moderator the re zero only requires about 4" of elevation from the non moderated zero and group size stays the same.

Are we looking at a manufacturing problem here? Your thoughts please.

hav you actually took the mod back to where you got it from and exchaged it
that way you could tell if it is that paticular mod that's at fault
as you say it zero's up and groups with out a mod on and still gives the same grouping with the T8 that you had on it before
take the SS mod back and exchange it that way you hav a chance to eliminate atleast on cause of concern
ATB
Richard

Pete E

That was what i thought,but i was their when the smith recrowned my barrel, so i know he didnt do anything else?I just put it down to things happen.