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+--- Thread: backup bolt for my grendel....... (/showthread.php?tid=1498)
backup bolt for my grendel....... - usmc1371 - 11-20-2011
i have a liberty barrel. i know that liberty isnt not making barrels for the grendel. how can i get a spare bolt for my stick? how or who makes the bolt? will a 7.62x39 bolt work? i know that the backup bolt will have to headspace with my barrel.will any grendel licensed bolt work?
backup bolt for my grendel....... - LRRPF52 - 11-20-2011
AA sells Grendel bolts for a fair price. 7.62x39 bolts will not work with a chamber cut for a Grendel bolt, as the bolt face depth is different between the two.
backup bolt for my grendel....... - Bill Alexander - 11-20-2011
There is no such thing as differnt 7.62x39 bolt. I studied Colt before drawing my own 12 years ago and have since made more of these things than anyone on the planet including Colt. The Grendel/Beowulf bolt is the industry standard and is in fact a 7.62 x 39 bolt.
The thing referred to as a 7.62x39 bolt is nothing more than a 5.56 opened up. The extractor geometry is wrong, but they proliferate in the internet as they are a cheap way to get something to fit.
backup bolt for my grendel....... - Bill Alexander - 11-20-2011
Sorry missed the OP reply. Measure your case head recess depth if you are at 0.136" I have plenty.
backup bolt for my grendel....... - Armored Transport - 11-20-2011
Is the Beowulf bolt made the same as the Grendel bolt? I know they are the same size but is the Beowulf stronger?
backup bolt for my grendel....... - Bill Alexander - 11-20-2011
Same bolt.
backup bolt for my grendel....... - LRRPF52 - 11-20-2011
Bill, are you saying that the Grendel bolt face depth is the same as a Colt 7.62x39 bolt face? If so, I stand corrected. I thought there was a difference between the two in the depths.
backup bolt for my grendel....... - Bill Alexander - 11-21-2011
The original Beowulf bolts were made from drawings of samples of the Colt bolts. We actually found latter that we did indeed make a slight error in the measurements (difficult to pull dimensions from worn and broken samples) and our bolt is a few thousands out from the old Colt prints but the original Colt was close enough that you would not see a difference. (three depths) Latter Colt rifles reverted to essentially a 5.56 bolt opened out. Interestingly the project for the 7.62x39 was rumored to be a funded work but time, politics and the feed problems canned the work and it was eventually released to general sale as the Sporter. We have some superb reference material in the Colt history. Inconsistencies with accuracy that led to bedding the Grendel rifles were following similarities seen in the Colt rifles. They went as far as to pot the whole barrel extension, barrel nut and receiver threads in high strength epoxy. 5 round mags were common but 10s did exist. I have only ever seen 1 example.
Strangely Colt went as far as to incorporate the dirt groove on the exterior circumference of the bolt recess even when they changed to the 5.56 modified bolt, This feature has origins only in Soviet designs and not a natural inclusion in the AR bolt as it degraded life of the part.
The engineering effort and background to this weapon is astounding. I have upper prints that show redrafting errors that even now are still in the finished item.
backup bolt for my grendel....... - LR1955 - 11-21-2011
LRRPF52 Wrote:Bill, are you saying that the Grendel bolt face depth is the same as a Colt 7.62x39 bolt face? If so, I stand corrected. I thought there was a difference between the two in the depths.
LR52:
I have used three 7.62 X 39 Colt made bolts in Grendel uppers. The bolt face of a Grendel bolt is deeper than the Colt 7.62 X 39 bolt face.
LR55
backup bolt for my grendel....... - PaulB84 - 02-03-2012
sorry to bring back an old thread but I have exactly the same situation and I didnt see just bolts for sale on AA's website.......Liberty barrel and bolt, and I would like to get a spare bolt for when I shear a lug (bound to happen)
Can any competent gunsmith headspace the new bolt to my barrel?
thanks
edit. never mind. found the bolts on AA's website. my bad. still curious how I get it fit to my rifle
backup bolt for my grendel....... - Schwag173 - 02-03-2012
Correct me if I'm wrong, guys (because I need to know this also), but GO/NO-GO gauges will verify headspace. In other words, anybody can simply replace the old bolt with a new one then check with the GO/NO-GO gauges. If it's good, no problem. But if it's not good then the headspace will require adjustment and that will require an AR gunsmith. Do I have it right or am I all fouled up?
backup bolt for my grendel....... - Variable - 02-03-2012
Correct. Proper headspace is set when the barrel extension is installed on the barrel. A proper bolt should fit a proper barrel extension period with no adjustments to be made.
backup bolt for my grendel....... - smoke13 - 02-03-2012
Bill, is it correct that the Alexander Arms bolts are different (face cut deeper) than the regular 7.62x39mm bolts which have a .454 bolt face ID (inside diameter) and a .136 bolt face (depth), and that the standard 7.63x39 bolts will not headspace with an AA barrel, and that the inverse is also true, that the AA bolts won't work with non-AA barrels (unless cut that way)?
backup bolt for my grendel....... - bwaites - 02-03-2012
As I understand it, the ORIGINAL Colt 7.62 bolts and the Grendel are very similar in dimensions. Those sold now have generally have a different face depth than the Grendel bolt. Those sold now are essentially a 5.56 bolt opened up with a similar face depth to the 5.56 bolts. The Grendel bolt is about .011 deeper in the face, to allow an appropriate amount of metal on the end of the extractor to stand up to wear and tear of the thicker Grendel rim.
backup bolt for my grendel....... - jkingrph - 02-04-2012
I have not measured bolt face depth or diameter, nor rim thickness of various brass, but have been using a lot of IMI 7.62x39 brass to fireform to 6.5 Grendel. I got it a few years back when Grendel brass was very expensive and hard to find and have not had any trouble with it feeding, chambering or extracting. No signs of any headspace problems.
I have a feeling that every thing is so close that it all fits within a spec range.
backup bolt for my grendel....... - OLd Man - 04-16-2012
If you have an AA gun and it came properly headspaced then a replacement AA bolt would also be properly headspaced? The headspace adjustment is in the barrel extention. I,m new to the AR help me out here.
backup bolt for my grendel....... - LRRPF52 - 04-17-2012
Yes, an AA bolt should headspace in an AA barrel just fine. After re-reading this, I understand that Colt's original 7.62x39 bolts were the basis for the Beowulf then Grendel bolts, and other manufacturer's 7.62x39 bolts are merely 5.56 bolts opened up with a 5.56 bolt face depth.
backup bolt for my grendel....... - Dflores22 - 04-22-2012
I have a Sabre Defence barrel and want to get a new bolt, would a AA bolt work or no?
backup bolt for my grendel....... - Variable - 04-22-2012
Dflores22 Wrote:I have a Sabre Defence barrel and want to get a new bolt, would a AA bolt work or no?
Yes. Someone can correct me if I'm wrong, but I'm pretty sure Sabre always used an AA bolt (they made barrels for AA until the ATF hammer descended on them for other stuff...).