SOME TIPS AND IDEAS FOUND SO FAR
Buffer tube, buttstock - too long a draw
AR-10 buffer tube and buffer with an EGW stock can get you down to 12.75" LOP for offhand. Another solution arose using a CAR tube and shortened buffer so the bolt clears the bolt lock on compression. Check without spring for sufficient clearance to start.
Buffer spring - too stiff
If not using an x-08 based case, try using an AR15 buffer spring. Some AR-10'ers have had good results with Tubb's CS AR-15 springs.
Gas hole diameter - how big is too big (or small)
Here's some sizes that worked.
.243
4 inches down, .077, AR10 spring, H1000, R-22, IMR&H 4831
1.8 inches down, .067 to .073, AR10 spring, powders between IMR4350 and H1000
6mm 22/250
1.8 inches down, .082 - .089, AR15 spring, powders like Varget
Gas hole timing and barrel length
One case: "barrel lengths were 26" and 27". Either length worked fine and there was no noticeable velocity difference between the two lengths. We even chrono tested one at 27" then cut it off to 26" and there was no change in velocity - which told us that by the time the bullet got through 26" of barrel, it was going about as fast as it was going to go. The 30" bolt gun barrels we chrono tested were also no faster than the 26" AR-10 barrels. As far as gas port location, we settled on 1.8" further forward from the standard location. We tried 4" further and it worked fine (with a larger barrel port size) but in cold weather, and with some powders, there was some minor vapor condensation noticeable around the gas tube inside the receiver. The condensation did not affect anything but we figured some people might not like the way it looked."
Gas Tube - fabrication
Gas tubes have been fabricated from seamless stainless brake line, but
these proved to be soft and corrode. Use a gas tube drawn for an AR15
spacegun from another manufacturer (try Krieger). This will put the hole
1.8 inches farther down the pipe. UPDATE: John Holliger (who else?) supplies
Krieger with 2" over gas tubes. He informs me that 4" over ones will be
available soon, too. Contact him directly at White Oak Precision.
Bolt - don't use SR25
Primer piercings were reported by several shooters using SR25 bolts at modest pressures because of poor primer support on ignition. Problem went away with switch to Armalite bolt.
Magazines - too long for palmrest rule solution
Fabricate short mag from 10 rounder. Fabricate delrin block SLED.
Feeding - so far, no feeding problems are reported with unaltered mags in 6-22/250.
Triggers - Ass'y can't have a wimpy hammer spring
Can't use some aftermarket AR15 match triggers because of weak primer strikes. The AR10 has a coaxial spring to restrain the FP and prevent slam fires (308 OEM buffer spring is a heavyweight!). Try adapting the OEM hammer spring to work with the aftermarket trigger, and if that works, continue to work from there. Check hammer width as some will not fit through the slot in the bolt carrier.
Front Sight bases - which ones
are tall enough?
Texas Tallboy (standard Tall Boy too short)
Sabreco Mfg. Front Sight Base is perfect.
Buttstocks - interferes with charging handle?
EGW version allows use
Medesha version does not - need to fabricate bolt handle for carrier
Ironstone version - can operate charging handle if cheekpiece is rotated
out of the way.
Loads - remember to work up to
these!
For 6mm/22-250 at ~2800 fps,
Pet load - 32 gr Varget, Sierra 107, .005" off lands
For 6mm/22-250, 105-107 grain bullet at about 2750-2850 fps:
IMR 4064 (31-32 grains)
Reloder 15 (31-32 grains)
AA2520 (31-32 grains)
IMR 4895 (30.5-31.5 grains)
H335 (31-32 grains)
IMR 4350 too slow
Contact Info
Did I miss anything? Do you want to see your rifle here? Contact me here.
Contact info for 'Smiths (not just George q;-P) and parts:
Fred Szablewski, Sabreco, (610) 584-8228
George Smith, EGW, Inc, (215) 348-9892 website eMail
John Holliger, White Oak Prec., (309) 376-2056 website eMail
Scott Anzivino
eMail
John Noveske, John Noveske Rifleworks, (541) 479-6117
website eMail
Scott Medesha, Medesha Firearms Ltd., (480) 986-5876
website eMail
Derrick Martin, Accuracy Speaks, (480) 373-9499
website eMail
|
A.K.A., AN AR15 ON STEROIDS,
