77gr TMKs in a Wylde Chamber?

[AR Shooter]

Anyone shooting Sierra 77 TMKs in a Wylde Chamber in an AR15? Am wondering if I should just stick with mag length ((2.25") OAL or will they shoot better out to 600yd if loaded long.
Would like to hear about your experience.

 

[Park ranger]

When I was chasing points, I had better luck when I seated them long for 600.

 

[thatguyshm]

AR or bolt action? I stick everything I load close to the lands and fiddle with it beyond the 2.260" in my bolt actions. I've always found success with the heavies in 2.350ish and beyond, generally between the lands and probably 50-60 thou off. I'd probably load up close but also send one or two groupings at SAAMI just to see what happens.

If it's for an AR, you have much less wiggle room without magazine mods, I generally will stick to around 2.280" or so, depending on magazine. I prefer metal 20 rounders for my SPR type ARs.

 

[jelenko]

If it's for an AR, you have much less wiggle room without magazine mods, I generally will stick to around 2.280" or so, depending on magazine. I prefer metal 20 rounders for my SPR type ARs.

This.
The 77TMK is too far into the case to load it for AR15 mag length. There are AR mags with a 'window' cut in the front that will take 2.340 COAL - which should work.

That said, they will work fine loaded long and single loaded.

 

[Jeff Porter]

My experience with mag length TMK and AR 15 was the extra cost and work it took to make them shoot was not worth the effort when the non tipped 77’s shot as well or better out to 600 yards.

 

[AR Shooter]

There are AR mags with a 'window' cut in the front that will take 2.340 COAL - which should work.

Do you have a source/link for mags with a front window allowing for a longer COAL?
Thanks.

 

[Twdmar]

Do you have a source/link for mags with a front window allowing for a longer COAL?
Thanks.

You buy them and cut it out with a Dremel.
If you're looking for something for 600, the regular 77s work fine if you want to use one bullet, look at the all-guard team scores.
If youre going to single load longer than mag length, the sierra 80 works very well and takes nothing to tune.

 

[jelenko]

Do you have a source/link for mags with a front window allowing for a longer COAL?
Thanks.

https://www.cavitybackbullets.com/product-p/cb-pri-mod-5.56.htm

Looks like they are out of stock right now. I've seen them go in and out of stock.

 

[Liven The Dream]

Why not just shot 80’s .020 off and Win ?

 

[AR Shooter]

Why not just shot 80’s .020 off and Win ?

I might if I'm forced to single-load. Or go with my bolt-gun. Match is 2min30sec for sighters + 5 shots for record so would prefer to magazine feed. Plus, everyone else is shooting a bolt-gun, so would be nice to shoot with an AR. Is a benchrest silhouette match on 1/3 size animals. 200/300/385/500 meters with 10 animals at each distance. The AR-Tactical match at 600yd is no big deal with plenty of time to single-load.

 

[Twdmar]

I might if I'm forced to single-load. Or go with my bolt-gun. Match is 2min30sec for sighters + 5 shots for record so would prefer to magazine feed. Plus, everyone else is shooting a bolt-gun, so would be nice to shoot with an AR. Is a benchrest silhouette match on 1/3 size animals. 200/300/385/500 meters with 10 animals at each distance. The AR-Tactical match at 600yd is no big deal with plenty of time to single-load.

You can cut a small window in the front of some 10rd magazines or just use normal 77s(they do shoot well at 600).

 

[Bat Rastard]

Has anyone modified any of the Pmag mags? Did it work?
I’m asking because it seems like it would be easier to cut the plastic mags. That, and I have a few spares.

 

[PeteB]

Has anyone modified any of the Pmag mags? Did it work?
I’m asking because it seems like it would be easier to cut the plastic mags. That, and I have a few spares.

Yeah Bat, i have done both but the GI 20 round mag has a marginally longer tip to base than the plastic Pmag, not much. Not sure of exact measurements as i,m not in the shed, around 2.355" and 2.330" for Pmag approx. Check your projectile tips don't foul around the barrel extension area. Never tried TMK 77 but you should be able to get them well out with a modded mag. cheers Pete

 

[AR Shooter]

Yes, the 77SMKs are 0.10" shorter than 77TMKs. Time to give them a try.

 

[AR Shooter]

Loaded up 50, each, of 77 SMKs and 77 TMKs. 25 of each at mag length (2.26") and 25 each at 2.36" to fit the extended length magazine. Got out to test on this beautiful 72F morning..
The bulls are SMKs on the left and TMKs on the right with mag length loads on the bottom bulls.
All at 300yd, I only held center (not caring about windage). All the 'flyers' are yours truly and his shakiness.The wind had picked up by the time I shot the extended length TMKs.
Both the extended length SMKs and TMKs held about 1/2moa at 300yd in my 22" long 1-7" twist Bartlein barreled WOA upper using 24gr of CFE223. I'm pretty pleased with that.

 

[GetReal]

For me, TMKs in in AR mag would put the ogive wwaaaayyy off the lands. Massive jump.... lije 0.120 " or something. Bullet way down in the case, crunching powder.

 

[tommeboy]

Lots of these new bullets are not meant for ar mags in 223. They are meant for the 22arc and Valkyrie. Their case is designed to be able to use them in an ar mag. Hornady has stated this several times about some of their new tipped bullets. So I would guess the tipped MK bullets are the same.

 

[AR Shooter]

For me, TMKs in in AR mag would put the ogive wwaaaayyy off the lands. Massive jump.... lije 0.120 " or something. Bullet way down in the case, crunching powder.

Am guessing that is why both the 77 SMK & TMK shoot much better being set 0.100" further out, which is an ~0.020" jump. Seems to work for me.

 

[GetReal]

Am guessing that is why both the 77 SMK & TMK shoot much better being set 0.100" further out, which is an ~0.020" jump. Seems to work for me.

0.020" off the lands has always been a default starting pt for me.