Rear expanding take down pin.

[acrashb]

gets groups of 2" out of his sloppy AR15 @ 400 m what does that tell you.

If he is really getting repeatable .5MOA five-shot groups, then he has an unusually accurate AR15, and would benefit from getting tighter lockup between the upper and lower halves. Generally, an off-the-shelf AR will not group like this. You need custom components and ammo to do so. He's either got these components, is very lucky, or is not shooting repeatable 5-shot .5MOA groups. Perhaps they are internet groups? http://www.ar15.com/forums/topic.html?b=3&f=118&t=279218

 

[acrashb]

They have experimented with all of it, and it doesn't make a difference.

I'd believe that of the accuwedge - it's flexible, so doesn't really do anything except take the rattle out.

I'll see about some measurements this summer from my JP upper, first on a somewhat loose stag lower and then on a hammer-the-pins-in SOCOM Mfg lower. It won't be scientific - no way to do a double-blind - but might be interesting.

BTW, my "internet groups" comment was directed at the poster of the quote, not at you. I've no doubt you shoot well.

 

[Savage]

If he is really getting repeatable .5MOA five-shot groups, then he has an unusually accurate AR15, and would benefit from getting tighter lockup between the upper and lower halves. Generally, an off-the-shelf AR will not group like this. You need custom components and ammo to do so. He's either got these components, is very lucky, or is not shooting repeatable 5-shot .5MOA groups. Perhaps they are internet groups? http://www.ar15.com/forums/topic.html?b=3&f=118&t=279218

He uses handloads like me as for the tighter lock up between the upper and lower recievers I dont see any gain that would be noticable .As for this lockup BS be my guest and use a product that cures a nonexisistent internet problem if makes you happy so be it Have fun
The only real thing that this product would help is on the FN FAL rifle where the sights are on 2 separate recievers

 

[beltfed]

I'd believe that of the accuwedge - it's flexible, so doesn't really do anything except take the rattle out.

I'll see about some measurements this summer from my JP upper, first on a somewhat loose stag lower and then on a hammer-the-pins-in SOCOM Mfg lower. It won't be scientific - no way to do a double-blind - but might be interesting.

BTW, my "internet groups" comment was directed at the poster of the quote, not at you. I've no doubt you shoot well.

That's ok. Savage is pulling your leg anyhow.
With regard to the accuwedge, that is all you want any of those contraptions to do -take the rattle out. The lower and upper are designed to have a certain amount of 'play' -they are only cases afterall. Total elimination of this tolerance could actually have adverse affect on accuracy - or so I read - I've never bothered to test it, as I trust the sources that claim it - Bill Wylde among them....

 

[Reaper]

I think your post may be referring to the J.P. replacement take down pin which requires tools. An over size screwdriver can damage the hole - {users fault}.

A properly fitted rubber accuwedge has no effect on standard dissassembly unless it is oversize , and requires the use of a punch that can elongate the hole. {users fault}.
If the rubber is swollen it needs to be trimmed to fit.

I used the same accuwedge in a C.A.R. 15 for 30 years and it never swelled - some kind of silicone rubber or something I guess.

No I am talking about the Accuwedge,but thanks anyways.

 

[chopper 1]

Yep yep

Yeah I guess you are right I mean hell Beltfed only gets groups of 2" out of his sloppy AR15 @ 400 m what does that tell you. Hate to break it you guys but the rear pin isn't the problem with the sloopy fit it is the front pin that is the cause

Right on - the front pin causes it - a bit of rubber under the rear pin cures it . But I think the J.P. rear pin does a better job - just a pain for cleaning tho --

 

[chopper 1]

Lock time

LMAO you mean to tell me that an upper that moves 10-20 thou is affecting lock time and barrel harmonics lets get real on this for a second your assuming that the rifle is changing position each time it is fired do you have any proof that this occurs something more than shear speculation

If a hammer is farther away from the firing pin it takes longer to hit the pin - greater lock time.
If the hammer hits the pin from a different angle - different harmonics.
Granted , a small amount of upper lower slop has a small affect, but some rifles have a lot of slop.

 

[beltfed]

If a hammer is farther away from the firing pin it takes longer to hit the pin - greater lock time.
If the hammer hits the pin from a different angle - different harmonics.
Granted , a small amount of upper lower slop has a small affect, but some rifles have a lot of slop.

If you have enough front to back slop in the receivers to change the lock time, you have bigger problems - like feeding and cycling issues. You are only going to encounter this if your pins are oblong - a condition that would render the affected receiver N/S, and one that could be avoided by not using tourist traps like - you guessed it - accuwedges in the first place.

The only way for the hammer to affect harmonics is if it is striking something else in addition to the firing pin, like the bolt carrier, in such a circumstance you most definately have broken parts (likely in the trigger group or the receivers are south) and your gun will be N/S.

I've seen incredible 'slop' between recievers in C7s in the Patricia battle school, and they were still able to print moa, as long as the candidates held on to the bloody things....

 

[emmab]

Thanks guys for starting such a heated conversation. It's probably personal but I don't like the feeling of the two halves wobbling around and psychologically it would throw me off more than the wobble would throw the bullet. I have an acuwedge (that I haven't had to use with my other ARs) and I got the tension pin from a cgn'er which is still in the mail. I can see that it could be a pain to strip the halves, but I usually bring tools with me in case of a jam up, and I can still use a bore snake with the pin in place. I don't usually break the guns down at the range and there is no problems at home, short of buggering up the holes more as stated earlier in the thread. Cheers