Hello I was wondering if anybody had tried the expanding rear pin that is supposed to take up some slack between the AR upper and lower? I see JP enterprises has one in the .250 dia. They sell for around $40 us. Are they worth the money? Any info would be appreciated. Cheers
Rear expanding take down pin.
- Thread starter emmab
- Start date
Works like a charm
Except - you need an allen wrench and a screwdriver for an upper seperation for cleaning.
The accu wedge accomplishes the same thing with standard takedown, You may need to trim the accu wedge with a razor to fit your gun --
Except - you need an allen wrench and a screwdriver for an upper seperation for cleaning.
The accu wedge accomplishes the same thing with standard takedown, You may need to trim the accu wedge with a razor to fit your gun --
Actually no you are wrong, the upper/lower fit has no bearing on accuracy at all, the lower simply holds the firing and recoil management mechanisms. The Accuwedge is a gimmick as are the other tightening devices.
I fired several rifles with the Accuwedge installed and without, absolutely zero difference with the exception that the wedge makes it harder to use the rear take down pin,requiring the use of a tool on a part that was never meant to require one.
I also have seen dozens of lower receivers damaged beyond repair from users using tools to strip their weapons because of the wedge, most often elongating the rear take down pin hole in the rear of the lower by using multitools or similar to pound the pin out..
If crap works - its not crap
A wobble between upper and lower affects the shooter and the accuracy of the gun.
Slight changes in the relationship of upper and lower results in slight changes in body position and trigger squeeze - result - different P.O.I.'s from shot to shot.
Slight changes in the relationship of upper and lower from shot to shot affect the harmonics of the rifle , lock time , hammer strike etc. from shot to shot - result - different P.O.I.'s from shot to shot.
The need for a locking device depends on shooter capability and looseness of the rifle.
Some A.R.'s I've shot were tight enough that that locking the stock into the shoulder locked upper and lower , some were so loose as to be distracting, the last thing I want when I am concentrating.
I enjoy a good crap - if it works for you do it --
A wobble between upper and lower affects the shooter and the accuracy of the gun.
Slight changes in the relationship of upper and lower results in slight changes in body position and trigger squeeze - result - different P.O.I.'s from shot to shot.
Slight changes in the relationship of upper and lower from shot to shot affect the harmonics of the rifle , lock time , hammer strike etc. from shot to shot - result - different P.O.I.'s from shot to shot.
The need for a locking device depends on shooter capability and looseness of the rifle.
Some A.R.'s I've shot were tight enough that that locking the stock into the shoulder locked upper and lower , some were so loose as to be distracting, the last thing I want when I am concentrating.
I enjoy a good crap - if it works for you do it --
Accu wedge
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.
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.
You are describing changes in hold. Obviously, If I hold differently from shot to shot and I'm allowing the upper to just wobble away on the top of the receiver, yeah one would see variation in point of impact.
All things being equal, if you hold the rifle properly, the upper is doing the work. If you put the upper in a vise, and let the lower flop about below it, you would see no change in poi.
Not equal
There would still be a change in P.O.I. with the receiver flopping due to variations in lock time , hammer strike and in rifle harmonics. The greater the flop , the greater the change .
Another example is the P.O.I. changes in Ruger Mini 14's and M14's from using different mags or using no mags which affects lock time , harmonics etc. The mag housing design allows variation of how the mag sits. (Variation also from follower tension changing bolt speed)
U.S Marines in competition had their mags labelled , using the most accurate ones for the longest shooting distances.
Yes , the A.R. flop causes MINOR changes in impact , but for me the flop causes major changes in comfort - like those sliding stocks that wobble !
A 12 buck accu wedge can solve that , or even a 25 cent rubber eraser
There would still be a change in P.O.I. with the receiver flopping due to variations in lock time , hammer strike and in rifle harmonics. The greater the flop , the greater the change .
Another example is the P.O.I. changes in Ruger Mini 14's and M14's from using different mags or using no mags which affects lock time , harmonics etc. The mag housing design allows variation of how the mag sits. (Variation also from follower tension changing bolt speed)
U.S Marines in competition had their mags labelled , using the most accurate ones for the longest shooting distances.
Yes , the A.R. flop causes MINOR changes in impact , but for me the flop causes major changes in comfort - like those sliding stocks that wobble !
A 12 buck accu wedge can solve that , or even a 25 cent rubber eraser
I disagree. Comparing the Mini or M14 to the AR with regard to harmonics isn't logical. The AR-15 system does not have a one piece stock, and the proven practices that make those systems shoot well do not apply.
There are no moving parts in the upper aside from the bolt, and it is mating to the barrel the same shot to shot. With impingement, the only thing that matters is the barrel. The upper receiver does nothing aside from holding the bolt carrier, bolt and the barrel together.
This is the first I have heard of anyone suggesting that the tolerances between receivers could affect lock time or hammer strike.
In any case if you or others want to tighten up the tolerance in your receivers, go for it.
There are no moving parts in the upper aside from the bolt, and it is mating to the barrel the same shot to shot. With impingement, the only thing that matters is the barrel. The upper receiver does nothing aside from holding the bolt carrier, bolt and the barrel together.
This is the first I have heard of anyone suggesting that the tolerances between receivers could affect lock time or hammer strike.
In any case if you or others want to tighten up the tolerance in your receivers, go for it.
Check again
Lock time and harmonics ARE affected - because the hammer is in a different position from shot to shot {its in the lower} and the lower is in different position from shot to shot - {different ping} as M14 and Mini 14 owners know --
I disagree. Comparing the Mini or M14 to the AR with regard to harmonics isn't logical. The AR-15 system does not have a one piece stock, and the proven practices that make those systems shoot well do not apply.
There are no moving parts in the upper aside from the bolt, and it is mating to the barrel the same shot to shot. With impingement, the only thing that matters is the barrel. The upper receiver does nothing aside from holding the bolt carrier, bolt and the barrel together.
This is the first I have heard of anyone suggesting that the tolerances between receivers could affect lock time or hammer strike.
In any case if you or others want to tighten up the tolerance in your receivers, go for it.
Lock time and harmonics ARE affected - because the hammer is in a different position from shot to shot {its in the lower} and the lower is in different position from shot to shot - {different ping} as M14 and Mini 14 owners know --
The hammer isn't in different positions. Of course its in the lower and that lower is held to the upper by two pins. There is not enough varriance in the two halves to affect lock time shot to shot. Again with respect to harmonics - Assuming a floated barrel; there is nothing within the rifle to affect it - its the barrel, bolt and bolt carrier - that is the meat of the system, nothing else matters.Comparing ARs to M14s is like comparing apples to oranges
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
Bottom line: when the bedding in a bolt gun gets soft, the accuracy goes away - this is well-known. The upper/lower fit is the bedding in an AR - same thing. You won't see any difference in a rack-grade 2" gun, but you most certainly will with match components (barrel, trigger, scope, shooter, ammo, etc.) in an AR that will group .4".
ajayofcanada
Regular
It costs 2 bucks and gets rid of the slack, sounds good in my opinion.
and when it breaks down han fun shooting your AR
Asolutely !
Exactly !
All rifles are comparable to each other when it comes to harmonics and lock time. Anything that changes the way the rifle vibrates from shot to shot changes P.O.I.
Bench rest shooters know this well , thats why they rest the forearm in exactly the same place with each shot , to prevent any change in flex and balance which changes harmonics , vibration , barrel whip , recoil movement etc. resulting in P.O.I. shift.
You cant argue with mother nature .
Exactly !
All rifles are comparable to each other when it comes to harmonics and lock time. Anything that changes the way the rifle vibrates from shot to shot changes P.O.I.
Bench rest shooters know this well , thats why they rest the forearm in exactly the same place with each shot , to prevent any change in flex and balance which changes harmonics , vibration , barrel whip , recoil movement etc. resulting in P.O.I. shift.
You cant argue with mother nature .
Exactly !
All rifles are comparable to each other when it comes to harmonics and lock time. Anything that changes the way the rifle vibrates from shot to shot changes P.O.I.
Bench rest shooters know this well , thats why they rest the forearm in exactly the same place with each shot , to prevent any change in flex and balance which changes harmonics , vibration , barrel whip , recoil movement etc. resulting in P.O.I. shift.
You cant argue with mother nature .
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
You'll have no arguement about the bolt gun from me, but comparing ARs to bolt guns isn't the same. Look guys, don't believe me - do some research. The bigest group of shooters that put ARs through their paces are US NRA High Power shooters. They'll tell you the same thing. They have experimented with all of it, and it doesn't make a difference. You only need to fire a couple hundred rounds or so to realize they are right.
When all is said, if putting a wedge or a glop of silicon in your lower makes you feel more secure about the accuracy you are getting from your AR, then by all means, knock yourself out.
