sound moderator bore vs calibre success

bewsher500

Well-Known Member
not sure if this is the best section but here goes.

I have an overbarrel PES moderator that I purchased at vast expense some years ago for use on a Sako Quad on a variety of rimfire rounds from .17M2 to .22WMR. works like a charm

As I am in the market for a .243 I had the idea in the back of my mind that when I bought it he said it would go up to .2xx calibre but couldn't remember the xx part and assuemed it would be 223/222/22-250 etc!

Quick call to Steve Kershaw who sold it to me and it appears I am in possession of a 7mm (.2755) bored moderator! (quick check with a 7mm drill bit shows that it can be nothing else)
Not only is he very confident that it will work on the .243 it may even work better than the 7.5 or 8mm bored(.30 cal) moderators often used due to the smaller bore!
Apparently .83mm or .0325 clearance is perfectly fine (and have just read about a chap who used an 8mm bored mod with a .308......0.006" clearance!!! bit close for me!)

I need a new delrin spacer for the over barrel part cut to the barrel diameter of 243 and to get it checked over for concentricity / 90 deg shoulders etc but that is pennies compared to a new mod!

Think I have just saved myself £200+

Now I started thinking.
My FAC lists a "small bore" moderator when it appears I have a "full bore" moderator.
apart from the ridiculous situation that allowed me to buy it in the first place I technically have something incorrect on my FAC.

L&B FLO were very helpful and all I have to do is write in and explain what I have and what it should read.
I also will have no restriction to using it solely on the 243 once swapped to FB status.

One size it appears does fit all!!:D
 
Had my wrist slapped recently because in 2007 i bought a .243 rifle and a full bore mod for said rifle. Only when i sold the riflee and mod this year did they tell me i had no rightt to possess a mod up to..30 cal as my ticket said ..243. After explaining that i could not buy a specific .243 mod they said they would let me off this time.

Sorry for speeling and spaces on new touch screeen tablet thing.. lets just say wee dont get on thawt well

Regards pj
 
so....how exactly does one check if the moderator is
a) fitted perfectly parallel to the bore
b) large enough bore to accomodate 90gn of lead and copper at 3000+fps!?

looking down the barrel is pretty tricky to clearly see if there is a less than 5 thousands of an inch obstruction!
its fitted and looks fine to my eye when veiwed from the breech but part of me says there must be more to it than having a good look and putting a round "through" it!

was thinking of having a metal rod of 243 calibre machined, something like brass. if enough was inserted into the muzzle and the rod was true (i.e. perfectly straight) then it would clear the moderator bore equally on all sides if mounted centrally.

any thoughts?
 
so....how exactly does one check if the moderator is
a) fitted perfectly parallel to the bore
b) large enough bore to accomodate 90gn of lead and copper at 3000+fps!?

looking down the barrel is pretty tricky to clearly see if there is a less than 5 thousands of an inch obstruction!
its fitted and looks fine to my eye when veiwed from the breech but part of me says there must be more to it than having a good look and putting a round "through" it!

was thinking of having a metal rod of 243 calibre machined, something like brass. if enough was inserted into the muzzle and the rod was true (i.e. perfectly straight) then it would clear the moderator bore equally on all sides if mounted centrally.

any thoughts?

Clean the bore then look down the barrel you will quickly see if there is a misalignment by a shadow at the muzzle end.
 
I once acquired a .22LR with a moderator (small bore), but had no permission for the mod on the FAC,,nor did I realise I needed permission separately for a mod...RFD sold it no probs...only when it came to sell it again was the issue flagged up with the FLO, who to say the least, was NOT all that pleased. The RFD nearly lost their license...I was ok though, just a misunderstanding of the rules, but they were pretty tough of the RFD who let the mod go, and who didn't point out the rules to me at the point of sale. oops..
 
Clean the bore then look down the barrel you will quickly see if there is a misalignment by a shadow at the muzzle end.

thats my problem, with a 20-22" barrel a wafer thin shadow is (almost) impossible to see but could still be an issue.

I found a long allen key that fit the bore perfectly and follow the rifling and it is closer to one side of the mod bore than the other but then I am not convinced it is not sitting on the land on one side and the true bore on the other side making it squint.
 
it would need to be the correct size of the bore from can muzzle all the way down into the bore to avoid any angles in the rod.

I think I need a 243 sized rod in some material. Delrin would do I reckon
 
it would need to be the correct size of the bore from can muzzle all the way down into the bore to avoid any angles in the rod.

I think I need a 243 sized rod in some material. Delrin would do I reckon
delrin is too flexible
as for the cleanig rod....jeeze!

oh and if your barrel is 'choked'?
 
Last edited:
delrin is too flexible
as for the cleanig rod....jeeze!

oh and if your barrel is 'choked'
?
sorry I dont understand the last two comments.

delrin would work as it would take some of the shape of the lands but would only bend along it axis if being pushed radially by a moderator baffle or moderator muzzle bore.

either way it would have to be cut to the bore at the tops of the lands not the real bore.
 
sorry I dont understand the last two comments.

delrin would work as it would take some of the shape of the lands but would only bend along it axis if being pushed radially by a moderator baffle or moderator muzzle bore.

either way it would have to be cut to the bore at the tops of the lands not the real bore.

Your choice, but if I had to bugger around machining rods and doohdahs to check alignment if I had failed to see a shadow and was somehow still convinced there was still a problem, Delrin would not be high up my list, anyroad while I was standing in front of the lathe it might have occurred to me put the barrel up and clock it.


Ok the cleaning rod comment was aimed at an 'injuneer' that chimed in with usual ** advise.. (either he uses wrong size rods or he really does not see what you attempt to do...)

And 'choked' refers to if your barrel is choked only as an aside. I was thinking about you stuffing rods down the muzzle, if there is a taper there (choked)
your rod will not be much use.
 
I dont have access to a lathe, but could do with out driving 100 miles round trip to get a gunsmith to look at it if at all possible.
doesnt look like I have much option for peace of mind
 
not sure if this is the best section but here goes.

I have an overbarrel PES moderator that I purchased at vast expense some years ago for use on a Sako Quad on a variety of rimfire rounds from .17M2 to .22WMR. works like a charm

As I am in the market for a .243 I had the idea in the back of my mind that when I bought it he said it would go up to .2xx calibre but couldn't remember the xx part and assuemed it would be 223/222/22-250 etc!

Quick call to Steve Kershaw who sold it to me and it appears I am in possession of a 7mm (.2755) bored moderator! (quick check with a 7mm drill bit shows that it can be nothing else)
Not only is he very confident that it will work on the .243 it may even work better than the 7.5 or 8mm bored(.30 cal) moderators often used due to the smaller bore!
Apparently .83mm or .0325 clearance is perfectly fine (and have just read about a chap who used an 8mm bored mod with a .308......0.006" clearance!!! bit close for me!)

I need a new delrin spacer for the over barrel part cut to the barrel diameter of 243 and to get it checked over for concentricity / 90 deg shoulders etc but that is pennies compared to a new mod!

Think I have just saved myself £200+

Now I started thinking.
My FAC lists a "small bore" moderator when it appears I have a "full bore" moderator.
apart from the ridiculous situation that allowed me to buy it in the first place I technically have something incorrect on my FAC.

L&B FLO were very helpful and all I have to do is write in and explain what I have and what it should read.
I also will have no restriction to using it solely on the 243 once swapped to FB status.

One size it appears does fit all!!:D

OK define small bore :doh: in British Militay parlance that is .303. ;) .22" was miniture bore and large bore didn't start until .577". The .45" was a medium bore. Now as that's all written down in history surely even Plod can read it :lol:.

As for clearance well due to a mix up at the shop the .308 Moderator I brought is actually a .243 one. A call to Wildcat settles that's fine to use on the .25" cal (25-06) that it was intended for. I later used it to good effect on the 6.5x55 Swedish Mauser however that was the limit as a .277" dia bullet would not enter the baffles.

It looks like there may be a market for ground "Spuds" to check moderator alignment. Of course due to bore diameter variations it would really require a graduated set just like Parker-Hale and BSA used to make back in teh hey day of service rifle competition at Bisley to check bore errosion and wear.
 
I think there is but it is one of those things that people are probably happier paying £50 in fuel and gunsmith charges to take it somewhere than buy a £20 tool and get it wrong (with the consequences!)

will see what I can come up with as I dont know any smiths around here
 
I wonder how it would have panned out in court. A thing without a barrel cannot have a calibre (diameter of bore before rifling is cut). .243 is a chamber/cartridge not a calibre. Maybe we could club together and buy plod a dictionary and save everyone a lot of grief.
 
I was at an auction in Truro once with a chap who had just got a variation for a .22rf. He thought this meant he could have as many as he wanted and bought three! I don't suppose the auctioneer was too impressed.
 
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