Snapper314 Wrote:Would a barrel from JP Rifles be considered among these 1/2 MOA brands?

grayfox Wrote:As a "what-if" to all you engineers out there...
I think the gas velocity until the bullet exits is roughly equal to bullet velocity, during acceleration which would put it all at up to about 2500-3000 ft/sec, and all roughly in the same ballpark.
Until bullet exit, then due to venting of the remaining pressure it escapes at 2-3x initial bullet MV, for that brief time. Wouldn't most of the erosion therefore happen after bullet exit, during that high-pressure vent? If so then gas volume/temperature and pressure at time of exit would relate to erosion. For a 243 compared to smaller diameter/case volume/barrel volumes such erosion would be high: high volume through a narrow pipe... grendels, with less case volume and typically shorter barrels as well as lower final exit gas pressure, would tend to make it low, or lower. A theory anyway.
As to temperatures, I would guess that particle velocity has more to do with erosion that particle/gas temperature. Temperature would mostly affect pressure... thus velocity. But velocity would rule.

bamban Wrote:I chamber my own barrels and I support the TX JRs High Power Team by spinning their barrels from Shilen donated Select Match blanks. I also do barrel work supporting my brother's benchrest shooting.

I was schooled by a retired benchrest gunsmith, so I treat all barrels as though they go to a benchrest rifle. I give him a one day service. Must have chambered a 30BR for him from every barrel manufacturer out there.

I never owned a Grendel till a local gunsmith friend gave me a take off bolt gun barrel that I repurposed it into an AR Grendel. I cut off the old 6.5x47 chamber, turned the fat section into an AR dimension and chambered it.

Here is one check I do on the chamber. This one is checking the area ahead of the leade angle, the most important part of the chamber to make sure the bullet goes in straight.
https://youtu.be/EWS7StHQ80c

I also check the rest of the chamber for runout.
Watch "12 Aug 2020 Chamber Runout To The Neck" on YouTube
https://youtu.be/3XZvLCJZ-lQ

As you might notice the tenon does not a have the threads, I do that last after I set headapace by adjusting the shoulder on the chamber that purposely cut about 0.010 deeper. Easier to adjust chamber by cutting the shoulder instead of running the reamer to final headspace

FYI, for the bolt I just chucked up couple of old GI M16 bolts and machined the face for the Grendel dimension, and bought a Grendel extractor.

On the Grendel barrel I never had the time to do load development, I just threw the load and on brass I processed from somebody's absoleted Lee die set. He upgraded to fancy match set. I sent the target that I shot at 200 yards when I was zeroing the scope to a friend. He ran his target calculating app on the groups. Those rounds were the only ones I shot through the barrel since. I only have a little over a box of once fired brass.

The 2000MR load looks very promising. Once I get more brass I will start tweaking the load. I believe I can tweak this to agg nicely at around half minute. My only limitation for running heavier/longer bullets is the barrel, it is only a 10 twist. I may look for some 100 grains hunting bullets if I can find any 120s.

FYI, I am not in the business, just a hobbyist.

lazyengineer Wrote:You're going to love it. I would suggest taking a look at the TEAM Grendel bolt sold here by BFT. Of all things Grendel, the bolt system is its biggest Beowulf. Those lugs are weaker and strained to the limit. When made right, that limit still works, but the margin of error is low, unlike with .223. It won't kaboom, but lugs and extractors break in Grendels more than typical - especially if not new and to spec. The BFT group buy Grendle bolts aren't that expensive, and have relief cuts on every lug, that I like.

I haven't broken a Grendel bolt yet, but I've broken at least 3 extractors so far. I'm starting to lose count. (But not BFT'S Team Extractor yet!)

bamban Wrote:Thank you for the bolt suggestion, I will definitely get one.

Do these bolts require a compatible barrel extension? For high power competition application we use these barrel extensions (BE). I used the same one my Grendel. Though these are longer by 0.300, and the threads are 20 TPI, instead of 16, they are still compatible with M16 GI bolt dimensions.

https://www.whiteoakarmament.com/competition-barrel-extension-m4.html

These bolts are ever so slightly larger in OD compared to the original ones. When coupled to a Bravo Company upper, I have to heat up the receiver face to slide the extension in, thus providing a tight fit without any heroics like Locktite to fill the slop in the BE to upper fit.

bamban Wrote:Thank you for the bolt suggestion, I will definitely get one.

Do these bolts require a compatible barrel extension? For high power competition application we use these barrel extensions (BE). I used the same one my Grendel. Though these are longer by 0.300, and the threads are 20 TPI, instead of 16, they are still compatible with M16 GI bolt dimensions.

https://www.whiteoakarmament.com/competition-barrel-extension-m4.html

These bolts are ever so slightly larger in OD compared to the original ones. When coupled to a Bravo Company upper, I have to heat up the receiver face to slide the extension in, thus providing a tight fit without any heroics like Locktite to fill the slop in the BE to upper fit.

grayfox Wrote:In lots of forum experience, bam uppers are tight and need to heat them up. As to bolts, the standard bolt face depth is 0.136, I think the 556 bolts are 0.125. So chambers will have to handle the one or the other. Bft’s bolts are the std depth. So you want to make sure you stay with those dimensions. A 0.125 bolt face depth and chamber will work but I’d think you want to go with the 0.136 depth.