Mmmm i wonder??????

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sussex lad

Active Member
In trying to save myself a few quid i have come up with this brianwave...
For my new 6.5X55 i will need a new mod (T8 ).

So i looked it up on Jacksons rifles web site to check which one i would need, and noticed that the difference in hole size is only 1mm!!
Also that the largest Caliber for the T8 i have on my .223(7.5mm hole) is the .243 and that the smallest caliber for the one i would need is the 6.5(8.5mm hole).
If you covert .243 to metric it comes out at 6.172 not to far different from the 6.5.
Plus it states as a rule of thumb take the caliber add 1mm minimum gap to get the correct aperture size..
So 6.5mm+1mm=7.5mm so my mod would maybe be ok??
Just to check i used asked the guy in the machine shop next door to work to check the size with his long nosed internal mic thing and the smallest apertuer was 7.82.

So what i am asking is will my mod be safe to use on the 6.5 or would it be best to get a new one for it and use it on the .223 also. Then sell the .223 mod to get some pennies back?



Below is the copied text from Jackson web site...
Baffle hole diameter

Standard baffle apertures are 7.5 mm , 8,5 mm, 10,5 mm and 13.0 mm. As a rule, the bullet caliber (bullet actual diameter ) plus at least one millimetre gives the exit aperture diameter.


7.5 mm hole takes 222, 223, 22-250, 6mm, 243, etc.

8.5 mm hole takes 6.5mm 270, 7mm, 308 , 30-06 etc.

10.5 mm hole takes 9.3mm, 338 etc.

13 mm hole takes 45-70 etc

The smaller the baffle hole diameter the better the sound suppression, but the difference between each of the above hole size increments is only 1 or 2 dB. In general, it is better to reduce the sound by adding more baffles than risk making the baffle holes too small.


Well-Known Member
I have used a T8 for the last eleven years and as long as the bullet will clear the hole it is safe to use on allsorts of calibres.
I have used my T8, which was originally bought for a .308, on my .222 - .243 - 22-250 and my .308 all I did was get extra delrin bushes for the relevent barrel profiles.
Once I had a T4 specifically for my .222 but fancied using it on my .308 so got a mate to run a drill bit tho it and it was fine. I think the drill bit he used was an 8mm bit, I dropped a bullet down it before using it to make sure it would clear the moderator and it did so I went ahead and used it.
Just as a matter for the record, I am now using a Wilcat Predator 8 and using the same principles for varying calibres.


Site Staff
I use the same T8 on my 6.5 X 55, 243 and 222 as EMcC states all you need is a separate delrin bush for each one.

I got the T8 for 6.5 originally then thought, like you, I could save myself some money and just got the bushes, problem solved



Well-Known Member
The Problem you may find using a mod with the minimum clearance particularly with long bullets (common in 6.5) is that you will get occasional 'flyers' this is due the bullet grazing the baffles as it yaws when exiting the muzzle. If the crown is perfectly square with the bore and the mod is absolutely concentric with the bore you may get away with it. The mod will be less effective on the smaller calibre’s than a calibre specific one.

You pay your money and take your choice!


Well-Known Member

I do the saem thing with T8,

Same mod on 22-250 and 308 with different bushes. Makes sense,

Try it, I dont like humping moderators around for a1 shot but if you have to have them have 1.

Try it what do you have to lose?


Well-Known Member
When I spoke to Jackson's after I sent my first one back due to a manufacturing fault, they did mention that the smaller one might not be suitable for heavier grain bullets due to their lenght. It may be worth a call as they were very helpful on the phone with me.



Well-Known Member

Get it wrong and couple it with the slightest bullet yaw and you will/may have a very interesting scenario on your hands :!:
It may be ok for many rounds, then one day ..........................
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