Ar10-T throat length

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14 years 6 months ago - 14 years 6 months ago #4416 by skogm
Ar10-T throat length was created by skogm
Hi, new AR10T owner. Factory upper. home built Armalite lower. I measured, using a Stoney Point OAL gauge with a Sierra 168gr match bullet, the rifling at 2.880 Ogive. I can seat mag length at around 2.820 leaving a .060 (corrected)jump to the rifling. So far, I've been averaging .7 with FGMM and about.6 - .7 with a home load of 44gr Varget with a 168 gr Sierra match seated to 2.820 Ogive. Pretty good for a semi I think but I can't help but wonder if the throat is too long or if maybe I should be trying a different bullet? Any ideas? My TBA .308 is .020 off the lands at 2.810 Ogive with the same load. I know that some bullets like a longer throat but I don't think the Sierra 168 is one of them.

-Mike
Last edit: 14 years 6 months ago by skogm.

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14 years 6 months ago - 14 years 6 months ago #4420 by The Duck of Death
Replied by The Duck of Death on topic Re:Ar10-T throat length
.6 inches OFF THE LANDS!!! I'll assume yo meant .06


The Sierras are not that finicky about jump as other bullets like the VLDs. You are good to go. Try loading a dozen kissing, just off (.003 to .01) and than .02 off the lands and see if you notice any difference.

I did notice a negative affect too close with the MKs.
Last edit: 14 years 6 months ago by The Duck of Death.

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14 years 6 months ago #4436 by skogm
Replied by skogm on topic Re:Ar10-T throat length
Yes, I meant .060...wow..what a jump .6 would be...I would send that back to the armory! Today, I'm trying the SMK 168gr loaded to 2.840 to the ogive. This puts me longer than mag length but .040 off the lands. I'll continue to load closer checking accuracy. -Mike

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14 years 6 months ago #4442 by skogm
Replied by skogm on topic Re:Ar10-T throat length
Update. ok, it must be me. I need to settle down behind the rifle and get used to the trigger etc. (the nut behind the butt) Today, I shot 2 sub .5 groups with 168gr FGMM and my hand load of 44gr Varget under a 168gr SMK at 2.820 ogive. I can't wait to measure them tonight because I think they are in the high .3's or low .4's. The rest of the groups (I'm still breaking in) were .7 or so and I knew that the ones that I shot sub .5 were spot on before they went downrange. So..this is one capable rifle! Pretty amazing. I have two issues so far. One, the new Winchester brass I used seems softer than even FGMM and shows a nicely pronounced dent in the body of the case. I know it's a semi but...the FGGM has a slight dent and the Military match brass from '68 shows nothing. I've always used Winchester brass but maybe I need something harder for the AR10? Second, the charging handle is developing some jaggies on the edges and it has worn away the charging handle finish and is very rough to the touch. This causes it to stick a little. I think the charging handle alloy is weak or maybe the upper CH guides need to be lapped? Maybe this is normal and will go away but it's never happened on any of my .223 AR's.

-Mike

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14 years 6 months ago #4446 by skogm
Replied by skogm on topic Re:Ar10-T throat length
Wow, .234, .314 and .460. 44 grs varget under 168SMK 2.820 ogive, FGMM and 44 grs varget under 168SMK 2.810 ogive...I'm shocked...these targets looked like my TBA M40A1. This stick can shoot as long as I do my part!

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14 years 6 months ago #4465 by lotoofla
Replied by lotoofla on topic Re:Ar10-T throat length
The reason your MilSpec brass does'nt have any dings is tha it's heavyer for the ejector to throw (differant ejection pattern). The dings you see in your Winchester brass are "soft" and really don't affect the reliablity. I have a friend who shoots an M1A1 and the brass it spits out looks awful!! If you buy an RCBS Precision Mic you may find out that the throat is longer than you think. I have an AR10-A2,AR10(T), and a cheapo Remington Mod 700 all in 308 Win bought new that have a .090-.095" bullet jump from a 175gr. Sierra MK with a OAL of 2.830" MAX OAL for the M852,and M118(LR). The Remington is a tack driver, with a 1x12" twist.
Tom

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14 years 6 months ago #4469 by skogm
Replied by skogm on topic Re:Ar10-T throat length
The Stoney point that I have is somewhat subjective in that you can push the bullet into the lands with it. I take about 10 readings and go with the most consistent. It's quite possible the throat is a bit longer. I had a Remy 700 PSS with a long throat that still shot .5 - .6. However, when I seated them .020 off the lands...whoa...it went sub .5. Lot's of guys get their barrels set back because of this. I don't understand the long throat mentality in the industry. I'm not going to shoot 220 gr bullets out of my AR10! -Mike

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