FN SPR A1 (now A5) shoots cold bore into .250MOA at 100yds with boring consistency. I's been bedded with Devcon at the tang and from the front of the recoil lug back to the front of the magwell. No pad is under the chamber. I've been very pleased with this gun's accuracy and the load I've developed for it. I've managed numerous .5-.75MOA 5 shot groups (starting with a cold bore) out to 600yds. While doing 10-shot primer comparisons this past weekend however, I noticed my groups opened up to as much as 2" at 100 by the time I'd fired my 10th shot of a continuous 10 shot string. Conditions were hot. I expect a bit of accuracy degradation but not this much. I would really appreciate some thoughts from those in the know. Thanks!
Gunsmithing It doesn't shoot once it warms up.....
- Thread starter Blackbrush
- Start date
Do you have clearance around the bottom and sides of the recoil lug? on the flat sides of the action? along the flat sides and rear of the tang area?
No
Yes
No
I thought that I would start with the bedding. I know there are a lot of theories about this. I also admit that what I am doing is possibly the cause. I'd like to try to make changes slowly so I nail down the exact culprit(s).
Yes
No
I thought that I would start with the bedding. I know there are a lot of theories about this. I also admit that what I am doing is possibly the cause. I'd like to try to make changes slowly so I nail down the exact culprit(s).
I would go back to the original load/components and see how it shoots before you do anything else.
First thing I would do is clearance the recoil lug
This issue happened with my original load.
I'm thinking I'll start with the bottom of the lug.
I'm thinking I'll start with the bottom of the lug.
Just going by what you wrote. " I've been very pleased with this gun's acurracy and the load I've developed for it ". You started doing primer comparisons and the groups were opening up. Good luck.
Sorry if I wasn't clear. They opened up when I went to 10 shot groups....thereby causing the gun to get hotter. The first shots of each 10 shot group were right in there where they should be. Thanks for chiming in and helping.
I have a Ruger 10/22 barrel from the 1980s that will shoot 3 moa when cold [1.5" @50y] and then after some rapid firing with the long magazines it shoots more like 10 moa [5" at 30y].
If I wait for the barrel to cool down, it is back to the original 3 moa.
I replaced that barrel.
That is part of why I replace all factory barrels, if I can, with custom stress relieved and lapped barrels. Shilen calls them "select match".
I have a select match barrel on a 10/22 that really shoots well when hot [0.6" @50y with hunting ammo].
I have a Lothar Walther 257 barrel that shoots well when it is too hot to touch [0.5" @100y]. LW stress relieving process is more intense than most.
If I wait for the barrel to cool down, it is back to the original 3 moa.
I replaced that barrel.
That is part of why I replace all factory barrels, if I can, with custom stress relieved and lapped barrels. Shilen calls them "select match".
I have a select match barrel on a 10/22 that really shoots well when hot [0.6" @50y with hunting ammo].
I have a Lothar Walther 257 barrel that shoots well when it is too hot to touch [0.5" @100y]. LW stress relieving process is more intense than most.
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Factory barrel or replacement, either way, if during the machining process the barrel was bent slightly, many manufacturers straighten them, as you shoot the barrel tries to get back to the original set. This usualy starts to happen at about 4-6 shots. You said you noticed this when you started to shoot 10 round strings. If you want to narrow this down shoot a ten round string, let the barrel cool overnight then shoot a 3 round group and see if you get .75"
Try redeveloping your load with just a smidge more and less powder, then test it with a warmed up barrel only. Might help.
Fn barrels are known to last and be accurate. I am assuming factory 308 barrel on it. Does it have a pattern when starts to wander or is it just a shotgun blast? How hot is the barrel after 10 shots? Can't see a 308 getting that hot from 10 shots even rapid fire but I can't remember the profile on the factory fn barrels.
Is everything feeling good when shooting the groups? It's tough doing a 10 shot group, that why the writers in the gun mags only do 3 or 5 shot groups.
Have you tried 5 let cool 5 let cool and 5 more into same target? Do you notice shift of impact?
If let it cool down does it shoot groups again?
I would try bedding first as its easy and cheap.
How many rounds through the barrel?
Is everything feeling good when shooting the groups? It's tough doing a 10 shot group, that why the writers in the gun mags only do 3 or 5 shot groups.
Have you tried 5 let cool 5 let cool and 5 more into same target? Do you notice shift of impact?
If let it cool down does it shoot groups again?
I would try bedding first as its easy and cheap.
How many rounds through the barrel?
Thanks for the input folks. I relieved some of the bedding at the recoil lug and got much better results. Both 10 shot groups were much more round in shape and considerably smaller than before. Atmospherics were almost identical to those the first time I tried the experiment.
Thanks again to all. FWIW, 215Ms did not shoot as well as 210Ms with a moderate load of Varget under a 180. SD was much better but the groups were worse.
In reference to the issue with the bedding, relieving the bottom and sides of the recoil lug allowed me to shoot 10 rounds and maintain my shots within the group - that is the group didn't over double in size.
My final accuracy hurdle is that it seems that pressure from the magazine on the bottom of the bolt hampers accuracy. My best groups come when I have no magazine in the well. The gun was an A1 with the only mods being trigger work and the install of an A5 stock, bedding and a CDI bottom - all installed by an amateur - me. I'm on the right track though as it shoots unbelievably well when I get the stars aligned.
In reference to the issue with the bedding, relieving the bottom and sides of the recoil lug allowed me to shoot 10 rounds and maintain my shots within the group - that is the group didn't over double in size.
My final accuracy hurdle is that it seems that pressure from the magazine on the bottom of the bolt hampers accuracy. My best groups come when I have no magazine in the well. The gun was an A1 with the only mods being trigger work and the install of an A5 stock, bedding and a CDI bottom - all installed by an amateur - me. I'm on the right track though as it shoots unbelievably well when I get the stars aligned.
