Problem with moderator!

[Graham M]

Took the .243 out yesterday for a bit of target practice. I set up my target at @ 175yds in the private woods on my farm and set about playing.

Now this is the first time I have used the rifle with the moderator on for playing with, apart from zeroing it after first fitting the mod. At that time I fired one shot and then waited for the moderator to cool before firing a second……and so on until I had zeroed it, so nothing seemed untoward.

Yesterday I didn’t wait between shots and was amazed to find that the first two shots were within 1 inch of each other……….but the third shot was 1 inch low and 4 inches to the right. At first I thought that I had hit something along the way so I allowed the rifle to cool down and then set about firing another three shots……with exactly the same result. :o

Set up a new target and had a rest whilst allowing the rifle to go as cold as it was before firing…..and again two shots together and one 1 inch low and 4 inches right. :o

It has to be something to do with the moderator because it never used to do this prior to fitting one.

Has anyone else had a problem along these lines.

G.M.

[ronttuk]

im sure when u either add or remove a moderator you need to zero the rifle in again as ive only ever used mine with a moderator this would need to be confirmed by someone who does switch moderators around.

[Graham M]

Yes I know, and that is why I re-zeroed it after fitting it.

The trouble starts when I try to fire a string of shots with the mod’ fitted. The first two shots are together, but then, as if something has warmed up and moved, the third shot goes 1 inch low and 4 inches to the right.

G.M.

[dunganick]

sounds odd to me.

 

another confusing problem which comes about through the mind boggleing world of barrel harmonics.

 

What mod? is this the T8 you had proofed as 243mag?

 

is it a poorly fitting bushing on the T8?

 

what weight barrel?

 

Floated? (was on a T3 if i remember correctly, so it should be)

 

I dont know why i am bothering to write this, i know you will have gone through all these lines of thought already

 

best of luck any how

[kip270]

The two Forest ranger's i shoot with have had problem's with their rifle's and POA moving.

Without a mod the rilfe reacts the way it was built to with recoil, but when a mod is fitted the recoil changes and the rifle is pushed back, which in turn can affect the scope. They have both had to re-zero their rifle's after a few shots. One using a .243 & the other a .270........

They had a big disscussion with Callum (precision rifle's) and he has had several customers with blown scopes (the cross-hairs blown out!!!) And he has studied this and it is because of the change in recoil to the scope.

 

I have a .222 & .270 and swop my T8 between them, and so far i have not had any problems.

It may be worth putting a small drop of paint on your scope mounts to see if the mounts are moving back or the scope in the mounts, because of the change in recoil.

[dunganick]

The two Forest ranger's i shoot with have had problem's with their rifle's and POA moving.

Without a mod the rilfe reacts the way it was built to with recoil, but when a mod is fitted the recoil changes and the rifle is pushed back, which in turn can affect the scope. They have both had to re-zero their rifle's after a few shots. One using a .243 & the other a .270........

They had a big disscussion with Callum (precision rifle's) and he has had several customers with blown scopes (the cross-hairs blown out!!!) And he has studied this and it is because of the change in recoil to the scope.

 

I have a .222 & .270 and swop my T8 between them, and so far i have not had any problems.

It may be worth putting a small drop of paint on your scope mounts to see if the mounts are moving back or the scope in the mounts, because of the change in recoil.

 

But its repeatable, so i doubt the scope is moving. If he can shoot 2 shots same hole and then 3rd shot always exactly the same distance out. then the gun is accurate and consistant its just not shooting to POA on the 3rd shot.

 

My guess would be changed barrel harmonics due to the heat in the barrel. But my problem with this theory is that none of the T8's i have come across suffer with this problem. Hense i would assume a poor fitting bush? But then again its repeatable, i would not expect this with a poor fitting bush.

[markbivvy]

would like to know the outcome of this. as my mate has the exact same problem with his 223, and t8 mod.

[Graham M]

The scope certainly isn’t moving and if it were then the POI would be moving all the time. And let’s face it there is very little recoil to start with using a .243, and even this is REDUCED by the fitting of a moderator which acts like a muzzle brake.

The bush theory sounds very near to the mark as it isn’t a tight fit when the barrel is cold, but fits nice and snug when the barrel gets hot. Noticed this when I removed the mod’ and saw that the bush had marked the barrel slightly as it turned, something it has never done before whilst cold.

It seems that the bush is not tight onto the barrel during the first two shots, and then when the third shot is taken the barrel has expanded enough to grip the bush and push it minutely to the side, which in turn causes the escaping pressure/gasses to push the bullet off course.

Trouble is I was always under the impression that the bush should only be a loose fit without actually gripping the barrel, but if this isn’t true then it would seem to me that I need to get this bush looked at and if necessary replaced.

Having said that, I only need to be sure of the first two shots in reality, because let’s face it how often do you get three consecutive shots at a fox/deer.

How tight are your bushes on your barrels?

G.M.

[markbivvy]

I only need to be sure of the first two shots in reality, because let’s face it how often do you get three consecutive shots at a fox/deer.

 

my mate says the same thing. will have a look at his bush tomorrow

[miffy]

let’s face it how often do you get three consecutive shots at a fox/deer.

 

 

Done it many times Graham....Fox and Deer

[Graham M]

In which case I think it needs to be sorted

G.M.

[Browning]

How tight are your bushes on your barrels?

G.M.

 

Graham,

 

Just checked the T8 mods on my .243 and .270 (both Tikka T3), both bushes are a snug fit when cold, and I've

never had the problems that you are experiencing.

[Sussexboy]

my mate says the same thing. will have a look at his bush tomorrow

 

I didn't realise it was that sort of forum!!!

 

Sorry, couldn't resist

[DaveK]

Graham,

 

I was led to believe that the bush is only there to hold the mod. Have a look at the floating of your barrel. Maybe the extra weight of the mod has it touching the stock somewhere.

 

Dave

[hill billy]

i no one common fault with mods is that if they are slightly off centre it clips the side of the bullet but you are getting to much of a consistant result for this to be the case, are touching the barrel on any thing because this will change the harmonics and move the poi and if all else fails try bench resting the gun and fireing it that way it maybe you because i no a few people who had the same problem when they added a mod because they were expecting a large a mount of recoil they flinch or compensate for the recoil sub conchesly

[Graham M]

Graham,

 

I was led to believe that the bush is only there to hold the mod. Have a look at the floating of your barrel. Maybe the extra weight of the mod has it touching the stock somewhere.

 

Dave

First thing I looked at Dave

[deadeye ive]

.

How tight are your bushes on your barrels?

G.M.

Graham

 

My bush on the T8 is actually removing the blueing on the barrel when fitted from cold .........This needs to be as tight a fit as possible ........Not long ago my T8 had vibrated loose when zeroing ...........It was only slight (fraction of a turn )but the end result was 6" out at 175yds and I have the hole in my target holder to prove it .

 

From what I've read about this consistant 4" out on your third shot indicates the barrel warming up and interacting with the poor fitting rear bush causing a change in the harmonics

[Graham M]

Thought so. I will have to get a new bush and get it fitted. The so-called “Gunsmith†who fitted this also fitted my friends moderator, and that is an even sloppier fit than mine. I also had to re-crown my .17hmr after he had shortened and re-threaded it because it was out of kilter.

I will certainly not be using his services again even if he is a little cheaper than my local dealer.

G.M.

[dunganick]

snug fit here too mate

[varget]

I asked my wife to see if i could have a look at her bush. she said i could of yesterday but not today coz she's shaven

marvellous

 

i've a wilcat on my rifles and the bush is tight tight even when cold.

[markbivvy]

the bush is tight tight even when cold

 

you lucky ******.

[DaveK]

may I just point out ............. for my safety amongst other things that: -

 

 

 

 

I HAVE NOTHING TO SAY ABOUT LORRAINES BUSH

 

 

 

 

I thank you

dave

[markbivvy]

evening Dave, see your not in the garden in the dog house thingy.

and on the PC, you must have been behaving.

[DaveK]

evening Dave, see your not in the garden in the dog house thingy.

and on the PC, you must have been behaving.

 

 

Hi Mark,

 

Dog house thingy nearly blew away the other day

 

 

..... and I was sat inside it

 

 

..........for four hours

 

 

.......waiting for pigeons

 

 

......that never came near me.

 

 

...... *********

 

Dave

[Paul223]

Thought so. I will have to get a new bush and get it fitted. The so-called “Gunsmith” who fitted this also fitted my friends moderator, and that is an even sloppier fit than mine. I also had to re-crown my .17hmr after he had shortened and re-threaded it because it was out of kilter.

I will certainly not be using his services again even if he is a little cheaper than my local dealer.

G.M.

 

I was under the impression that the correct way to measure the bush size is ; screw the mod on the barrel, mark off the length of mod ( to where the rear of the bush sits), remove mod and work out where the CENTER of the bush would sit and cut the bush hole to suit that size, then when the bush is fitted and the mod screwed on, the bush will grip the barrel for a mill or so ( cause the barrel is tapered ) and the bush should be plastic and will deform to suit

 

and yes my mod leaves marks on the barrel to!