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Gunsmithing Accuracy Troubleshooting Steps?

PLeighton

Sergeant
Full Member
Minuteman
May 25, 2007
492
6
49
NE North Carolina
www.l8ntactical.com
Ok, first a little background on the rifle and the situation.

I have an FN A5-M that all of a sudden is no longer able to hold a group.
This happened while in the final stages of load development.
After becoming frustrated with not being able to get any of my newly developed loads to hold a group under 1 & 1/2 inches at 100 yards,
I tested it with known good factory ammunition (GMM) with the same result.

My next step was to use some Boretech Eliminator to completely remove any copper fouling that may be present.
(I normally only use Hoppes #9 and let it ride.)
I also used my Seekonic torque wrench on the action and rings to ensure they were not loose.
After that, I scheduled a range session with my shooting partner for another round of testing.
This time I had my partner shoot all of the test shots so that my shooting could be ruled out as a cause.
The test was a round robin test on 8 targets using 4 different factory loads and 4 different hand loads.
Best group was 1 inch at 100 yards and it was with one of my hand loads.
All velocities were logged and the ES of the four hand loads was no greater than 1 fps for each loading respectively.

For anyone that may not know the history of the FN SPR and their issues:
FN uses a hammer forged chrome lined barrel in their SPR line of rifles.
When they announced that they were closing the Winchester plant in Conn,
mysterious problems began to manifest themselves in the chrome lining of these rifles.

My rifle was identified as having a defective bore and was replaced by FN.
As compensation for my troubles, FN handpicked a new rifle out of their warehouse with the best test target.
This rifle was then sent to GAP to be bedded in the same fashion as their A3G rifles.
When the rifle was returned from GAP to FN, the rifle was retested and shot a test group of .260 inches at 100 yards.

I have been able to replicate these results regularly with factory ammo and was getting even better results with my initial hand loads.
There have been reports that around the 800 round mark, some of the FN SPR chrome lined barrels begin to have additional problems with the chrome.
My round count is 760 and this makes me fearful that I may be having problems with the bore.

The reason for this post is to try and confirm my thought process as well as to solicit any additional advice & theories from the community.
My next steps will be thoroughly clean the bore and check out a bore scope from work to see if I can see anything.
In addition to that, I will remove the action from the stock to check for any deris.
Then I'll remove the scope from the base so I can re-torque it.
I have another optic that I will throw on there so I can rule that out too.
If it still can't hold a better group after all that, I'm afraid that I will have to bite the bullet and send her off to GAP to be re-barreled.

Any suggestions are greatly appreciated.

Cheers!
 
Re: Accuracy Troubleshooting Steps?

+1 on the scope. Also the chrome lining might have flaked off in some parts of the barrel and could be causing the accuracy issues you are having.
 
Re: Accuracy Troubleshooting Steps?

Phil-

I spent months chasing my tail with an FN that formerly shot tiny little groups. What you have described is EXACTLY what happened with mine, and it turned out to be a bad barrel.

This is the reason I sold my replacement SPR the day I received it--without ever removing it from the box.

Once the scope proves to be a non issue, slap on a real barrel!!!
 
Re: Accuracy Troubleshooting Steps?

Had a Leupold 6.5x20 mk4 go bad on me after I had my SPR bedded. It would no longer shoot those majic groups, I blamed the bedding(it wasn't broke and I had it fixed)I almost had it rebarreled. But changing scopes proved to cure the problem. It is still one of my favriot rifles. 2K plus rds and still going strong. I really cant say bedding helped anything.
 
Re: Accuracy Troubleshooting Steps?

hgr2,

Thanks for a glimmer of hope.
I currently have a Mark 4 8.5x25 FFP sitting on this rifle.
Hopefully it will be the culprit.
I will try to do a re-shoot tonight.

JLM,

I don't think that the PBRs have the same issue.
That product line was introduced almost a year after the Winchester plant was closed.
(I'm not 100% on that though.)
 
Re: Accuracy Troubleshooting Steps?

If you want to diagnose the problem, you've got some additional steps you can take:

- Untorque the action and set the gun upright. Place finger at gap between stock and barrel at foreend. Snug the rear tang screw. Now repeatedly tighten and loosen the front action screw. Feel for barrel movement at the foreend. If more than ~ 10 thou, might be your bedding.

- Melt some lead and make a lap, melted around your wrap jag. Feel the bore. If you feel tight spots other than near/at the muzzle, it might be a bad bore. If you DO feel tight spots other than the muzzle, get some valve lapping compound (~ 200 grit) and get to lapping.

-Cerrosafe cast the chamber and first inch of the bore. Is the chamber square with the bore? Can you see indications of unbalanced rifling on the cast? If so, then likely poor chambering.

- I'd say that if the rifle DID shoot, and now does not: Check the scope and bases first, then bedding, then slug that bore, then cerrosafe cast the chamber. If it's still bad I'll make an offer for that non-shooter.
 
Re: Accuracy Troubleshooting Steps?

Thanks for the extra info & ideas.
I can't stand it and will be taking off at lunch today to run home.
I'll throw a different optic on, check the base & action, then shoot some test targets.
If I still have the issue, I'll take the borescope home tonight and post some pics of the bore on this thread.

At this point in time, I'm actually hoping that it's the Mark 4.
That way I can send it to Leupold and hopefully have it back in time for the ASC "308 Only" match in September.

I'm keeping my fingers crossed...
 
Re: Accuracy Troubleshooting Steps?

The wind is the biggest factor in accuracy for me.

I monitor the wind speed and direction at the range with Accuweather.com hourly updates and hourly predictions.

I should have gone today.
 
Re: Accuracy Troubleshooting Steps?

Well....

I did some additional testing yesterday.
Scope base was good to go, so was the action & bedding.
Put a POS Simmons 3x12 on and headed out for some shooting.

After zeroing, I shot three groups that all measured well under 1/2 inch @ 100 yards.
Looks like I get to see how quick Leupold customer service is today.

Thanks for all the posts.
Since I went through all the trouble of getting a property pass for the video borescope from work, I'll still scope and record what the bore looks like after I clean it this weekend.
I'll post some pics & or video of it on this thread.

Cheers!

Phil
 
Re: Accuracy Troubleshooting Steps?

Leupold was very apologetic and they should have my Mark 4 in their hands today.
I will post up with my account of their customer service performance.

Bore scoped the rifle last night and here is the video for anyone who was curious.
I didn't realize that this scope also recorded audio,
so please disregard the faint conversation my wife was having with her sister in the background.

(Please be advised that it is about 2 & 1/2 minutes long.)
FN A5-M SPR Bore Video

I feel like a real idiot, because I don't really know what I'm looking at.
All I could identify were tool marks on the lands and the occasional piece of stray lint from my patches.
I was not able to see any evidence of any cracks or voids in the chrome.
For all of you pros out there, please give me some professional opinions on the images.

Thanks again for everyone's input thus far.
 
Re: Accuracy Troubleshooting Steps?

Just got off the phone with Leupold and they told me that they replaced the erector spring and that my Mark 4 was sitting on my porch.
smile.gif


Pretty good turn around time.
My tracking number says that they recieved it on Tuesday!

Now, to mount it up and see if it is indeed repaired.

Will post up after testing.