HMR Moderator accuracy issues

[spanner]

Got a lovely Cooper HMR recently and had it chopped to 18 inches and rethreaded. Trying to zero it today and the group sizes were 4 inches at best! Took the Mod off and the difference was amazing you could cover a 3 shot group with a penny piece with ease. Moderator is a Wildcat Whisper 22 flavour. If I look down the barrel with the Mod on things look fine and I took it apart and there is no sign of the bullets clipping anything. Will it need cutting again perfectly concentric with the bore although it appears to be with a visual inspection down the barrel. I didn't shoot the rifle before I had it cut, it was done whilst my variation was in. Will try a SAK which has quite a bigger bore than the Wildcat but am very interested to hear if anyone else has had a similar experience?

[fizzbangwhallop]

I don't know what weight of barrel your Cooper has but I tried 3 makes of moderator on my .22 Finnfire 21" standard barrel and the Sirocco SM11 gave the best groups against a good old Parker Hale and the Ase Utra from my 17HMR (on an 18" CZ452). Think I even had an SAK to try looking back through the old posts.

 

The Sirocco is easily the lightest of the 3 but I don't know if, perhaps, it has nylon or plastic baffles and not be recommended for a 17?

 

Don't think any of the groups were 4" though, more like 2" on the biggest spread.

 

atb

 

Fizz

[gbal]

Got a lovely Cooper HMR recently and had it chopped to 18 inches and rethreaded. Trying to zero it today and the group sizes were 4 inches at best! Took the Mod off and the difference was amazing you could cover a 3 shot group with a penny piece with ease. Moderator is a Wildcat Whisper 22 flavour. If I look down the barrel with the Mod on things look fine and I took it apart and there is no sign of the bullets clipping anything. Will it need cutting again perfectly concentric with the bore although it appears to be with a visual inspection down the barrel. I didn't shoot the rifle before I had it cut, it was done whilst my variation was in. Will try a SAK which has quite a bigger bore than the Wildcat but am very interested to hear if anyone else has had a similar experience?

Moderators are a bit cheaper than Coopers.The rifle can clearly shoot,despite no before/after data.I would try a few more mods before you alter the barrel-or threading-as you are intending to do but it might be the threading that is not true,in which case the cutter may be able to fox it- ..I doubt that you will see much by looking..if it sn't clipping ...

g

[spanner]

Thanks gents I actually got a Cailper out today and measured the 3 groups I shot from the target I kept.

 

2 3/4 inches with the Mod on 4 shots which was better than my orginal efforts, the original targets I didn't keep whilst setting zero.

 

The groups without Mod one a 3 shot group of 1/4 inch and a 4 shot of just over 1/2 with 3 shots nearly touching and one opening the group. Will try a SAK and a Sirocco if that doesn't work,

 

The barrel is a heavier profile than my Finfire Hunter but not as heavy as a Varmint, it is a truly nice rifle.

[onehole]

I dont have a .17HMR any more,,,,have had three,,,,ammo is main problem let alone any other issues.Bye Bye 17HMR,,,,,,,,,,,There are other ways of doing it better but not necesssarily any easier or cheaper unfortunately.Personally I would jump from 22lr to small 22 CF,,reload and be done with it. Accuracy and range all extended and improved way beyond 17HMR performance.

[spanner]

Ammo has never been an issue for me with the HMR, my last slab of Blue Tips has neen very good. I have a Sako A1 in 17FB and it is superb but it is not a volume Rabbit tool like the HMR and the HMR is a better tool than a 22lr in some situations. Plus I love Coopers having had a Model 21 in 223 and at £500 it was a bargain and not having to reload for volume shooting is a real bonus and probably a must with FB brass availability.

[baldie]

Is the barrel still clear of the stock channel with the moderator fitted ?

Try a business card around the barrel.

[kent]

Is the barrel still clear of the stock channel with the moderator fitted ?

Try a business card around the barrel.

Interesting, do you feel free float so important to ruin accuracy so bad in a heavy tubed HMR?

[baldie]

If the stock is touching the barrel slightly at a high point it doesn,t matter what the calibre is, or how fat the barrel is , it will throw shots. The simple addition of a few ounces of moderator can do it, if the clearance was borderline in the first place.

Check the simple things first.

[kent]

If the stock is touching the barrel slightly at a high point it doesn,t matter what the calibre is, or how fat the barrel is , it will throw shots. The simple addition of a few ounces of moderator can do it, if the clearance was borderline in the first place.

Check the simple things first.

could you explain the dovetailed Lug on the CZ varmint then? surely this should totally wreck accuracy? At the extreme are you saying if someone chambered a HMR in a Douglas taper tube it still need good free float?

[baldie]

Right.

 

Barrel harmonics go west when a barrel touches the stock now and again, or intermittently. The shot fired, when touching will have a different POA.

 

A dovetail lug half way up a barrel like on a cz 550 will have a completely different effect if its done up tight.It effectively makes the barrel free floating from that point forwards.

 

Barrels either have to be completely free floating , fixed mid point, or fully bedded from front to back, otherwise you get harmonic problems. Some manufacturers rather than going to the expense of completely free floating a barrel , will put a couple of pressure pads near the front tip of a stock. When the action screws are tight, it effectivley makes the barrel and stock completely solid. As opposed to completely free floated.

 

Pick up a tuning fork, tap it and listen for a minute.

 

Tap it again and touch it.

[spanner]

Thanks Dave it is floated I can get a piece of paper down between stock and barrel but it is not a slack fit. I think you may have hit the nail on the head because the threading job looks fine and I see no shadow at all when I look down the barrel with the Mod on and it is not clipping the Mod. It is floated down to about an inch in front of the recoil lug where it is bedded. I will open it up from there forwards and try it again. I must admit to being amazed that the weight of the Mod could cause the barrel to no longer float. What would you suggest to seal the wood? Thanks for the advice.

[kent]

Right.

 

Barrel harmonics go west when a barrel touches the stock now and again, or intermittently. The shot fired, when touching will have a different POA.

 

A dovetail lug half way up a barrel like on a cz 550 will have a completely different effect if its done up tight.It effectively makes the barrel free floating from that point forwards.

 

Barrels either have to be completely free floating , fixed mid point, or fully bedded from front to back, otherwise you get harmonic problems. Some manufacturers rather than going to the expense of completely free floating a barrel , will put a couple of pressure pads near the front tip of a stock. When the action screws are tight, it effectivley makes the barrel and stock completely solid. As opposed to completely free floated.

 

Pick up a tuning fork, tap it and listen for a minute.

 

Tap it again and touch it.

Ok I get it now, I have become sort of split minded of late about so many accuracy related musts. The full stocks and the old trend of full bedding on the barrel and pressure on the tip of the forearm, dovetail lugs all seemed to fly in the face of Free Float. in deed I know of a Ruger that took a heck of a lot of work to get shooting again when the pressure at the tip was relieved. Is free float requirement not related to barrel stiffness though as in a silly thick Douglas allied to a tiny little HMR ?

[spanner]

Well it is now certainly floated with plenty of meat left in the stock, I can get a business card down the channel easily right up to the bedding, will have another go at zerioing and feed back. Thanks all!

[gbal]

Ok I get it now, I have become sort of split minded of late about so many accuracy related musts. The full stocks and the old trend of full bedding on the barrel and pressure on the tip of the forearm, dovetail lugs all seemed to fly in the face of Free Float. in deed I know of a Ruger that took a heck of a lot of work to get shooting again when the pressure at the tip was relieved. Is free float requirement not related to barrel stiffness though as in a silly thick Douglas allied to a tiny little HMR ?

I have had 'mannlicher' full stock types with the barrel effectively screwed into the stock near the muzzle.Fine.And of course plenty 'free float'-the barrel just never touches the stock wood ahead of some point,where it is effectively and deliberately bedded/'anchored'.What I thought was not good ,is the intermittent touching of barrel/stock,because this is an inconsistency,that sometimes(when they touch) disrupts the barrel vibration harmonics,and throws the bullet relative to the shots where the barrel does not touch (or is firmly located,as in the full stock' design.I suppose free float is just easier/cheaper to achieve,so is popular,and won't go wrong,unless there is wood warping and/or barrel movement-which a mod might just induce,in a marginal clearance barrel?

Maybe it's more complex,but essentially you want complete consistency shot to shot-.free float does that and you can have a generous clearance,to allow for minor changes,but not extreme ones-the old bank note/cigarette packet test-while any system of resticting the barrel is potentially more vulnerable to changes in the pressures so induced? And sometimes a bit tricky to get set again-I didn't like removing the 'mannlicher' full stocks.

Is this about what you are saying,Dave,based on a lot more experience?

 

 

george

[baldie]

Yes, George, you have hit the nail on the head.

Inconsistency is the accuracy killer.

Looking at a barrel face on, imagine a shot being fired. The barrel will oscillate round and round, much like the fingers going round a clock face.
Say its fully floated. As it oscillates, the shot may exit the bore at 3 o clock every time, and shoot real nice. Get that wood stock wet, and you may JUST have a little high spot, that JUST touches, when you lean on the bipod, 3 shots out of 5. It will cause 2 shots to exit at 3 o clock normally, but the other 3 shots could exit at 9 o clock...with the resulting poi shift.

A weight like a mod can do this.
A good tale [and true] was a US marine doubting his gunny when told the same. The gunny told him to fire a group on the target at 1000 yards, which he did with good success.
The gunny then took out a handkerchief, and draped it over his barrel and told him to fire 5 rounds again.
Not one hit the target.

On a wood stock, you want at least a business card thickness floating, and seal the stock again with tru-oil, linseed, or varnish.

Fibreglass stocks can run slightly tighter, but the card is a good rule of thumb. On a stalking rifle, keep an eye out for seeds, and grass getting caught in there. Biggest cause of a rifle going "off song" there is.

[spanner]

Yes, George, you have hit the nail on the head.

 

Inconsistency is the accuracy killer.

 

Looking at a barrel face on, imagine a shot being fired. The barrel will oscillate round and round, much like the fingers going round a clock face.

Say its fully floated. As it oscillates, the shot may exit the bore at 3 o clock every time, and shoot real nice. Get that wood stock wet, and you may JUST have a little high spot, that JUST touches, when you lean on the bipod, 3 shots out of 5. It will cause 2 shots to exit at 3 o clock normally, but the other 3 shots could exit at 9 o clock...with the resulting poi shift.

 

A weight like a mod can do this.

A good tale [and true] was a US marine doubting his gunny when told the same. The gunny told him to fire a group on the target at 1000 yards, which he did with good success.

The gunny then took out a handkerchief, and draped it over his barrel and told him to fire 5 rounds again.

Not one hit the target.

 

On a wood stock, you want at least a business card thickness floating, and seal the stock again with tru-oil, linseed, or varnish.

 

Fibreglass stocks can run slightly tighter, but the card is a good rule of thumb. On a stalking rifle, keep an eye out for seeds, and grass getting caught in there. Biggest cause of a rifle going "off song" there is.

Dave top adice and many thanks, that Hanky story is quite amazing and here was me thinking a Mod wouldn't be heavy enough!

[gbal]

Dave top adice and many thanks, that Hanky story is quite amazing and here was me thinking a Mod wouldn't be heavy enough!

 

Be sure not to sneeze anywhere near the mod either.

 

Dave,does it work the other way-if you are missing at 1000,will a hanky over the barrel get you back on?

 

george

[spanner]

Just an update, went today for another play with it. Gave it a clean and started to shoot and certainly better for being floated further but not what i would have expected. Six x 4 shot groups and none consistent so tried again with the Mod off and after 1 flier 3 shots virtually touching WTF!! Anyway Mod back on and the next 3 x 4 shot groups were what I would have expected so as well as needing a bigger float it also likes to be dirty, the difference in consistency after half a box was suprising to say the least.