new build questions

gordonm1 · January 18, 2004, 10:06

Just completed installing DSA/FN medium 21" chromed lined barrel with integral muzzle break. I got 100 lbs of torque on barrel after filing shoulder. Type three Imbel gear logo receiver.

Headspace:

closed on 1.630" Forster go gauge.
closed on 1.634" Forster nogo gauge.

will not close on 1.634 gauge with tape apllied to rear of gauge.

I fired the rifle as-headspaced and had accuracy issues. Bullet impact moves up the paper 3-4" at 100 yds from cold barrel to hot (first eight rounds). I installed this new barrel to correct this problem.

What's wrong with my build?

Should I reduce headspace with new locking shoulder?

Is there some fancy way to fit handguards I can read about?

Could receiver be causing POI change? My bet is its all the crap attached to the barrel.

mrbonecrusher · January 18, 2004, 11:12

Are you firing from a rest? If so make absolutely sure to have the handguards contact the rest at the same spot every time, preferably close as you can to the magazine. Check the gas block, sights, etc for looseness. Does the bolt fit snug when in lock up to the receiver? When you checked the headspace did you remove the extractor and clean everything spotless? If yes have you tried different magazines as the FAL is rear of bolt locking rifle this may make a difference. Did you checked the clearance between the extractor and receiver when the rifle was apart? Are the recoil springs new or used, possibly not returning the bolt with the same force as heating begins? Were you able to file the barrel shoulder so that there is an even mating of those surfaces? I would advise getting the headspace pins to do the job with as much precision as possible. Pins=a few $, barrel cost=many $, loss of body parts due to firing weapon improperly headspaced=priceless.

gordonm1 · January 18, 2004, 13:53

Hello and thanks for reply;

The important thing to me on this thread is my new barrel is doing about the same thing the old one did so the barrel may not be part of the problem.
It's possible I could have missed something and both barrels could be contacting/applying forces to the receiver that raise the barrel as it heats up. I could use advice on what to look for here.

My shooting technique could be an issue but I have fired at least a hundred rifles and not seen this much POI shift. Maybe this is extra important on FAL's? I pull the pistol grip into shoulder to stay on target as the +/_ 10 lb trigger breaks.

I have the pin guages and will get a new LS but I wanted to get at/fix the POI shift first. I didn't think large headspace would cause POI to walk up the target.
If noone tells me the barrel is installed with a problem accociated with it I will order a new LS soon expecting to fix things without changing headspace much.

While I wait for new LS I have cheapy set of new Century english handguards to try that have not been modified. They are tighter at receiver than the modified new metric ones I installed already. They need to be squeezed together tighter at the gas block to start the screw. They do look they they are made to avoid contact with the barrel.

gordonm1 · January 18, 2004, 14:10

Mr. Bonecrusher:

After reading your post again
I see I did not check extractor fit and don't really see how to do this.
All I can say is the rifle functioned with old barrel and does so on setting 5 with new barrel and new imbel gas tube.
Also I know barrel is slightly undertimed. Maybe three degrees. I use a scope and hope this will not cause my POI shift. The first barrel used was not undertimed and it did the same thing. The first barrel installed actually
worked loose after gunsmith installation. I got real good toque with a barrel vise installing the new barrel but it the wood blocks and lead shims slip on barrel with 3' cheater bar and about half my 260 lb weight.

gordonm1 · January 18, 2004, 16:59

This afternoon I got out the LS gages and it apears the headspace was about 5 thousandths over .308 minimum.

I had a 0.261 LS on rifle

.266 pin gage closes with pressure on go gage 1.630"
nogo gage backed up go gage .262 gage pin closes on no-go gage 1.634"

I expect I will order a .266 or .265 locking shoulder if I can find one.

Headspace was not too bad to begin with.

I would like to reduce POI change though.

January 18, 2004, 10:06	#1
gordonm1 Registered FALaholic #: 11572 Join Date: Aug 2003 Location: Yakima, WA Posts: 275	new build questions Just completed installing DSA/FN medium 21" chromed lined barrel with integral muzzle break. I got 100 lbs of torque on barrel after filing shoulder. Type three Imbel gear logo receiver. Headspace: closed on 1.630" Forster go gauge. closed on 1.634" Forster nogo gauge. will not close on 1.634 gauge with tape apllied to rear of gauge. I fired the rifle as-headspaced and had accuracy issues. Bullet impact moves up the paper 3-4" at 100 yds from cold barrel to hot (first eight rounds). I installed this new barrel to correct this problem. What's wrong with my build? Should I reduce headspace with new locking shoulder? Is there some fancy way to fit handguards I can read about? Could receiver be causing POI change? My bet is its all the crap attached to the barrel.

January 18, 2004, 11:12	#2
mrbonecrusher Registered FALaholic #: 6604 Join Date: Jun 2002 Location: Pocatello, Idaho Posts: 815	Are you firing from a rest? If so make absolutely sure to have the handguards contact the rest at the same spot every time, preferably close as you can to the magazine. Check the gas block, sights, etc for looseness. Does the bolt fit snug when in lock up to the receiver? When you checked the headspace did you remove the extractor and clean everything spotless? If yes have you tried different magazines as the FAL is rear of bolt locking rifle this may make a difference. Did you checked the clearance between the extractor and receiver when the rifle was apart? Are the recoil springs new or used, possibly not returning the bolt with the same force as heating begins? Were you able to file the barrel shoulder so that there is an even mating of those surfaces? I would advise getting the headspace pins to do the job with as much precision as possible. Pins=a few $, barrel cost=many $, loss of body parts due to firing weapon improperly headspaced=priceless. __________________ Ships boarded, plundered and sunk by appointment only. Custom pirate attacks available.

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January 18, 2004, 13:53	#3
gordonm1 Registered FALaholic #: 11572 Join Date: Aug 2003 Location: Yakima, WA Posts: 275	Hello and thanks for reply; The important thing to me on this thread is my new barrel is doing about the same thing the old one did so the barrel may not be part of the problem. It's possible I could have missed something and both barrels could be contacting/applying forces to the receiver that raise the barrel as it heats up. I could use advice on what to look for here. My shooting technique could be an issue but I have fired at least a hundred rifles and not seen this much POI shift. Maybe this is extra important on FAL's? I pull the pistol grip into shoulder to stay on target as the +/_ 10 lb trigger breaks. I have the pin guages and will get a new LS but I wanted to get at/fix the POI shift first. I didn't think large headspace would cause POI to walk up the target. If noone tells me the barrel is installed with a problem accociated with it I will order a new LS soon expecting to fix things without changing headspace much. While I wait for new LS I have cheapy set of new Century english handguards to try that have not been modified. They are tighter at receiver than the modified new metric ones I installed already. They need to be squeezed together tighter at the gas block to start the screw. They do look they they are made to avoid contact with the barrel.

January 18, 2004, 14:10	#4
gordonm1 Registered FALaholic #: 11572 Join Date: Aug 2003 Location: Yakima, WA Posts: 275	Mr. Bonecrusher: After reading your post again I see I did not check extractor fit and don't really see how to do this. All I can say is the rifle functioned with old barrel and does so on setting 5 with new barrel and new imbel gas tube. Also I know barrel is slightly undertimed. Maybe three degrees. I use a scope and hope this will not cause my POI shift. The first barrel used was not undertimed and it did the same thing. The first barrel installed actually worked loose after gunsmith installation. I got real good toque with a barrel vise installing the new barrel but it the wood blocks and lead shims slip on barrel with 3' cheater bar and about half my 260 lb weight.

January 18, 2004, 16:59	#5
gordonm1 Registered FALaholic #: 11572 Join Date: Aug 2003 Location: Yakima, WA Posts: 275	This afternoon I got out the LS gages and it apears the headspace was about 5 thousandths over .308 minimum. I had a 0.261 LS on rifle .266 pin gage closes with pressure on go gage 1.630" nogo gage backed up go gage .262 gage pin closes on no-go gage 1.634" I expect I will order a .266 or .265 locking shoulder if I can find one. Headspace was not too bad to begin with. I would like to reduce POI change though.