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Help to improve accuracy in a heavy 7mm08 rifle

01 Jun 2015
@ 06:17 pm (GMT)

[email protected]

Greetings,

I already asked this question on a Danish discussion board, but I was suggested by another member to ask a the question here also. Let's try!

So I have this Howa 1500 rifle i bought for building a long range capable rifle.. I will try to make my story short at to the point.

First I bedded this stock hunting rifle using the principles of stress free pillar bedding:



I only shot few rounds, however, accuracy was definitely submoa with 308w Norma factory ammunition.

Then I build my own AICS style chassis, and I bedded the rifle like this:





Only places of contact between chassis and action are in the spherical front of the recoil lug, the vertical plane in the back for the recoil lug and the horizontal plane at the rear action bolt. First I tighten the bolt in the recoil lug to wedge the recoil lug in the bedded cavity. Afterwards I tighten the rear action bolt gently.

Knowing that I wanted to get a new barrel chambered in a new caliber better suited for LR, I only shot a few rounds with the stock barrel and factory ammunition (still Norma Golden Target 308w). Accuracy was now 1/2 moa or better and that was even shooting the chassis raw without skins to grip.

Now I have got the barrel changed to a 23" Lothar Walther heavy barrel chambered in 7mm-08 with 1-9 twist and completed the rest of the rifle in a new and better home made chassis. Unfortunately the accuracy has disappeard for a while. I'm reloading my own rounds now and therefore there are several new factors in the equation.

I load 162gr Hornady A-max in necked down 308w Norma brass with Reload Swiss 60 powder. I'm very thorough and pernickety when reloading, and having read lots of great stuff abouts 162gr A-max in 7mm-08 I had great expectations.

First I have tried 6 different powder loads from 42 to 45,5 with the same COAL on 72,5mm. All of them grouped between 50 and 30mm. I now measure max COAL to 75,2mm and therefore made the next test loads with variable COAL and two different charges for each COAL. All of them grouped between 30mm and 50mm.

Now I ask the question of what you would do next in the pursuit for accuracy. I build the rifle to go below ½ moa, but there are some road left.

Would you continue with different ammunition (different powders and bullets) or do you see any red flags regarding my chassis/bedding/barrel setup? You can see more photos of my rifle project on this page:

http://nordisk-forum.dk/viewtopic.php?f=49&t=53710

Thanks in advance!

Søren from DK

Replies

01 Jun 2015
@ 08:01 pm (GMT)

Nathan Foster

Re: Help to improve accuracy in a heavy 7mm08 rifle
Hi Soren, thanks for the detailed description of bedding, that helps a great deal.

I have been experimenting with bedding techniques and the design of bedding compound for many years, the result being our Matchgrade products along with website and intensive book instructions. As best as I can tell, you have pretty much performed the opposite of what constitutes a good bedding job.

The two problems you face are that on the one hand, you have minimal action / bedding contact while at the same time, the contact you have in the area of the recoil lug is creating pinch points because THE FRONT of the lug is not properly relieved. I am guessing you have not relieved the sides of the lug either. This means that your action may not be able to return to battery after each shot.

Have a good read of the bedding instructions on the site or better still, look into the book series to gain a deeper understanding of the factors involved.

These issues will need to be addressed before you can look at the bore as a variable.

Hope that helps.
01 Jun 2015
@ 08:47 pm (GMT)

Nathan Foster

Re: Help to improve accuracy in a heavy 7mm08 rifle
I should have mentioned, the first stock and bedding job appears to be much more acceptable.
02 Jun 2015
@ 12:23 am (GMT)

Martin Taylor

Re: Help to improve accuracy in a heavy 7mm08 rifle
Soren,
have a look through some other posts and you will see what Nathan is saying!
Get the books to gain a better understanding of bedding principles and rework the bedding. You are only wasting your reloads and getting false results!
Money well invested to develop your knowledge.
02 Jun 2015
@ 08:26 am (GMT)

Ben Law

Re: Help to improve accuracy in a heavy 7mm08 rifle
neat looking bedding job on the timber stock.

as you have re-barrelled, you could try sanding down the bedding a touch at the 'knox' on the timber stock so the barrel is completely free floating and try a few groups.
or re-bed the chassis after some more reading.
02 Jun 2015
@ 03:36 pm (GMT)

[email protected]

Re: Help to improve accuracy in a heavy 7mm08 rifle
Thank you all for fast replies! :)

I will try to look into what has been written about best practice bedding on this site before doing anything else. I had the sense that something might be off with the rifle since all my test loads all performed equally bad.

The thought behind my bedding job was to eliminate any kind of tension in the action while having it totally fixed to the chassis. That is was what I thought was the goal by bedding?

If any of you guys already can see now how the Howa action should be bedded in a AICS style chassis, please let me know :) I am a bit under time pressure, the rifle must be shooting accurate in 1 month from now and work is busy..

@Ben Law: The new barrel is way to thick to fit the old wood stock, so that won't be an option unfortunately.
02 Jun 2015
@ 03:38 pm (GMT)

[email protected]

Re: Help to improve accuracy in a heavy 7mm08 rifle
BTW this is how the current chassis looks like without bedding compound. I'm using Devcon.[b]
02 Jun 2015
@ 03:39 pm (GMT)

[email protected]

Re: Help to improve accuracy in a heavy 7mm08 rifle
Forgot the picture :)

Isn't it possible to edit a post?

02 Jun 2015
@ 06:26 pm (GMT)

Thomas Kitchen

Re: Help to improve accuracy in a heavy 7mm08 rifle
hi soren
i suggest you get straight into ordering some bedding kits from nathan if your on short time frame, i think his books getting printed in different countries depending on where you are so thats might save some time if you order them.
i have never come across a chassis like that before look well made but i think it will take some damming when bedding as it seems to be very shallow. is there a chance you can open up the barrel channel on your wood stock for new barrel? re bed that so you have a better understanding of bedding then move on to your chassis?

also check out http://www.ballisticstudies.com/Resources/Discussion+Forums/x_forum/17/thread/6584.html martin has done a beautiful job bedding a howa with plenty of pictures and info to help all of us out. best of luck and please keep updates coming its very interesting
02 Jun 2015
@ 06:58 pm (GMT)

[email protected]

Re: Help to improve accuracy in a heavy 7mm08 rifle
Quote:
hi soren
i suggest you get straight into ordering some bedding kits from nathan if your on short time frame, i think his books getting printed in different countries depending on where you are so thats might save some time if you order them.
i have never come across a chassis like that before look well made but i think it will take some damming when bedding as it seems to be very shallow. is there a chance you can open up the barrel channel on your wood stock for new barrel? re bed that so you have a better understanding of bedding then move on to your chassis?

also check out http://www.ballisticstudies.com/Resources/Discussion+Forums/x_forum/17/thread/6584.html martin has done a beautiful job bedding a howa with plenty of pictures and info to help all of us out. best of luck and please keep updates coming its very interesting


Isn't the Devcon plastic steel putty i already paid for good enough? Buying goods from NZ will end up being extremely expensive.. I would rather donate the same amount to this site and get advice on how to proceed with the alu chassis instead. The chassis is homemade and that's why you haven't seen anything like that before ;)

Remember I can mill the chassis anyway I like to make it more bedding friendly..


02 Jun 2015
@ 07:42 pm (GMT)

[email protected]

Re: Help to improve accuracy in a heavy 7mm08 rifle
I have just purchased the skills bundle and look forward to read it, especially the parts about bedding. Too bad it is already time for bed in DK now. I also just took a few close up pictures of the chassis seen from the top:




I have marked where you could remove some material to make place for bedding compound similar to the many pictures I have seen on this site.

02 Jun 2015
@ 11:14 pm (GMT)

Martin Taylor

Re: Help to improve accuracy in a heavy 7mm08 rifle
I'm a little baffled by your chassis design Soren and have never worked on anything like that but the bedding principles will still be the same. Fore end control will be interesting.

With this application Devcon will work well, it's just that we like to support Nathan by using his product because it is superior when bedding a traditional design. TB's kits also have instructions and personal support from Nathan & Steph which is a stand-alone difference to any other product you can buy. Proven bedding techniques.

Have a look over my Howa post Thomas has listed, it is not intended to be a tutorial but Ideas to get you thinking. Nathan's YouTube bedding tutorials and the books (maybe ebooks for time saving!) will be your best resource by far, failing this email Nathan directly and pay for his time then you will have personal, understandable and professional advice!

Marty
03 Jun 2015
@ 08:25 pm (GMT)

Nathan Foster

Re: Help to improve accuracy in a heavy 7mm08 rifle
Hi Soren, thanks for the book purchase, much appreciated. By now you will have been able to gleen rigid versus return to battery bedding.

The suggested cuts in the chassis should work well.

You mentioned that the barrel is ultra heavy. More support in the area of the action will help with this though it is a pity that the barrel has to be fully free floated with this type of chassis design. While it is common to fully free float an F-class rig, on very heavy barrels, a degree of barrel sag and potential action stress needs to be taken into consideration if the barrel is very long.
05 Jun 2015
@ 11:32 am (GMT)

[email protected]

Re: Help to improve accuracy in a heavy 7mm08 rifle
Hello Nathan and Martin,

I have now read selected parts of the accurizing book and understand that I at some point have to make a choice of whether to glue/screw to action to the chassis or to make return to battery bedding. Right now my barreled action is not fixed to the stock free of stress nor able to return to battery due to pinching the recoil lug.

Preliminary question:

How do I know that my action is not as fixed to the chassis to the same high degree as using the glue/screw principle? Having the bottom face of the recoil lug relieved and thereby wedge fitting the lug in the chassis by tightening the bolt makes an really strong connection. The frictional force in the contact surface between chassis and recoil lug goes toward infinite when tightening the bolt due to the narrow angel on the front spherical surface of the recoil lug.

Glue/screw aspects that comes to my mind:

I need to 100% complete the chassis before gluing the parts together. I still need to mill some visual details and paint the chassis, which I cannot do after glueing.

How do I avoid tension in the action when thightening the bolts while the epoxy is starting to cure? Perhaps the same questions is if there should be contact between chassis and action in the botton face of the recoil lug prior to guleing to support the point of pulled force by tightening til bolt.

Return to battery bedding:

With the limitations created by my chassis layout, will this solution never be as optimal as glueing?

Btw, my barrel is not ultra ultra heavy, its 23" and 22mm and the tip, so just moderate heavy :)

Btw btw Nathan I have lived in NZ for half a year in 2012 and I look so much forward to come back for some long range hunting :)
05 Jun 2015
@ 08:35 pm (GMT)

Nathan Foster

Re: Help to improve accuracy in a heavy 7mm08 rifle
Answered privately.
 

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