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Which is the best AR-10 without barrel deflection: the Geissele MRGG or the Seekins SP10M?

sirhrmechanic
Bigjake83 said:
The short and simple answer is Leverage, just the same as using a pry bar.

Yes the barrel is secured into the upper with the barrel nut that holds the barrel extension secured and torqued to the face of the upper receiver threads so now the Barrel Nut and Upper Receiver are ONE.

Now you attach the handguard (PRYBAR) to the outer surface area of the barrel nut and upper, the end of the Handguard where we all attach our mounting attachments for bipod and various other attachments is now the handle of the prybar and now any load/torque applied is now highly amplified by leverage and transferred straight back to the barrel nut and your upper.

Obviously other factors such as handguard length and upper receiver design all come in to effect and can strengthen and reduce the POI shift effect when torque is transferred.

A good example of two Conventional Style Upper Receiver and handguard mounting designs that are easy to conduct a simple side by side POI shift comparison are the Geissele Upper handguard Combo with thier Mil Spec Forged Uppers and the SOLGW Broadsword.

They both attached directly to the Barrel nut but the SOLGW design has a thick walled Upper with tongue and groove style inserts at each corner of the handguard that are press fit firmly into their Milled slots of the upper receiver along with a thick barrel nut which I believe is also longer.

With the SOLGW design the torque that is transferred is equally divided between the barrel nut and the Upper Upper
Receiver where with with the Geissele it's all transferred straight to the barrel nut.

True Free Floating Designs and semi monolithic upper receivers do a fantastic job reducing or removing any and all POI Shift no matter how much load is applied to the end of the handguard.

If this doesn't help you understand then I would suggest you try conducting your own field POI Shift test (Constructivist learning theory )and see for yourself, theoretical speculation will only get you so far no matter how sound your reasoning may seem.
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We're on the same page... when I think of POI shift, I am thinking of something deflecting barrel, changing velocity, etc. etc. And what you are describing is deflecting the barrel by putting pressure on the barrel nut area of the upper. Makes total sense.

Though it does surprise me that there is enough flexibility in an AR-10 upper that pressure on the handguard can 'bend' or flex the upper enough to cause a POI shift. Then again, it doesn't take more than a couple of thousandths of movement to have a significant effect downrange. And light alloys are... light alloys for a reason!

I'll have to bring my AR-10 out to the range next time and see what happens if I 'load' the barrel nut area with predictable/known weights. it'll be a fun experiment to see how much actual deflection there is. And I am sure it will vary by upper-maker, alloy, material, etc.

Interesting thread...

Sirhr
Click to expand...

PortaJohn

Fig
If you think you are a "conservative", or are somehow opposed to communism/socialism/progressivism, and you look around and see that you are vehemently on the same side of an issue as they are, you might want to reexamine your preconceptions and biases to see why this is.

The left is all in with the Islamosatanists because of communist critical theory. The weaker party is always the oppressed and always right no matter what the facts are or how they behave. When you find yourself on their side it is a pretty good indicator that you are not thinking it through and are inventing a bunch of false "facts", and theories that don't add up to arrive at the same place they did.
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Why do people load so hot?

supercorndogs
wvfarrier said:
I am gonna put some of yall into apoplexy.
These two loads are from a 20" 308 win at 150 yards today.
#1- 178 ELD, Alpha SRP brass, cci 450 and Varget. Average 2816fps.

The left hand hole is the cold bore (literally) since there is a 22 degree difference from where the rifle/ammo is to the outside where I shoot.
View attachment 8751749

#2- 178 ELD, Alpha srp brass, cci 450 and Power Pro 2000MR. Average 2749fps.
View attachment 8751742

These pieces of brass have 12 firings on them. All over book max. Still running strong. Annealed after every firing.
Click to expand...
Is the POI that diffrent between the two loads?

I would be interested to see the actual pressure on the varget load. 😳😳 Mine will ejector mark lapau at 43g with the 178 a max at about 2700 in a 23".

I hardly mess with my 308. I need to rebarrel it to a good caliber. It's just not worth 44g of powder to lob potatoes. 🤣🤣🤣
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