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Bolt weights Cont. pt2

13K views 57 replies 13 participants last post by  colonelhogan44 
#1 · (Edited)
This will be the THIRD time this data is posted, I don't give a whoot about the politics of the thing....this data should be publicly posted for the community!
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Starting from scratch AGAIN so fellow tinker-ers don't have to wade through the same mud we've been neck deep in...

What we Know

-The bolt was oversped by design to accomodate full auto fire (Atchison/Ceiner patent *Link needed*)
-A ball detent can be used to delay blowback and de-bounce the bolt, it is succesful but never took a foothold (lots of info on other forums)
-In a straight blowback gun the spring contributes nothing ("The machine gun" Chinn vol-4 pg. 15)
-Bolt speed should be <10m/s (Chinn again)
-Matching the 10/22 bolt weight is a good jumping off point (anecdotal knowledge)
-A buffer ALONE is a patch not a solution (catching skydiver in swimming pool)
-magnets are seldom the answer (outlined in another thread)
-A true conversion behaves different than a dedicated .22 upper (2 impulses, detonation&gas tube return pulse) but can be tamed in much the same way.
-43g is sort of a one size fits all number but errs on the low end to keep the gun reliable
-49g will get us reliable cycling with ammo from 40gr@1060 all the way up to the SSS with all its peculiarities.
-A TRUE Dynamic ABW (ricochets around) can be too heavy/light, or too long/short and the tuning parameters make it tricky to pin down a good match for each of our rifles (running with the 5 gal bucket of water vs a cup)

Colhogan was nice enough to do a heap of testing with his weight system and post all the results in m/s so we're all on the same unit measurement
(but you'll have to convert oz to grams for the weights.....Why? because all science is metric! HERE is a handy conversion tool)



Some of those numbers look slow at first glance but aguila's more exotic products use a slower burning powder that would seem to benefit from more time in the chamber (this is evidenced in the following test series videos)

(The blue gun is a .223 white oaks match upper 26" barrel.With a Cmmg "India" evo kit)
Initial tests 40gr@1060 and SSS with and without a 48gr weight


Followup tests 2x 40gr@1060 & 2x 40gr@1250 with the weights outlined in title


All details outlined in video


So now we have strong jumping off point on a variety of cartridges with a variety of weights.

Armed with this data and access to the weights you should be able to start to tune your specific setup for max performance. As you do, Post it all so we can build a database of what works best! Like the 50@200 thread over in the longrange forum we'll assemble a definitive data set that can act as a resource for all the newcomers.

+Hopefully the 10/22 benchrest guys are on to something and slowing the bolt down adds accuracy!?

Keep it civil, keep it on subject, post your experiences.

Be sure to include your setup, ammo used and the weight (in grams) added to the bolt.

(MODS,
IF THIS THREAD IS DELETED, I WOULD LIKE A REASON!!!
LeShaghal)
 
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#7 ·
What we Know
...
-A buffer is a patch not a solution (catching skydiver in swimming pool)
...
-A TRUE Dynamic ABW (ricochets around) can be too heavy/light, or too long/short and the tuning parameters make it tricky to pin down a good match for each of our rifles (running with the 5 gal bucket of water vs a cup)
A buffer is an element of several semi-auto designs, and can solve problems that are otherwise left unsolved.

For use with your 43gr weight, I installed a quarter inch hard polymer buffer at the back of the bolt frame. As the bolt travels rearward, the back of the weight hits the polymer and stops both the weight and the bolt. Consequently, the spring shroud isn't what stops the weight from travelling backward and wear on the spring shroud and weight should be reduced.

While I am happy to be corrected if wrong, I believe your weight does function as an ABW. I can hear it click back and forth in the BCG and you can observe in your video that a small gap between the weight and bolt closes when the bolt stops. A large gap won't work for an ABW because the ABW won't be were it needs to be to stop the bounce when the bolt lands on the barrel.
 
#9 · (Edited)
Yup

Zuke, I cede to your wisdom!
You are correct. A buffer has it's place. I will edit my post to say

"A buffer alone is a patch"

Our skydiver can happily parachute into said swimming pool and it will indeed be easier on his joints!

The red urethane buffers I tinkered with were too thin to hit the 43g weight, only the spring guide. With the speed reduced by the weight it worked well. worked even with the CMMG fwd assist. With all that extra surface area the pressure density falls meaning: softer quieter materials can be used without getting squished to death. If you're touching the weight you could be using something pretty soft and still get some life out or it. If you use a weight with a solid back you can use some Really soft stuff back there!

I always worked from the assumption:

-A buffer is an Elastic material. Some of the energy it absorbs it gives back (like a bouncy-ball)
Or so physics would tell us, BUT I've tried to capture the bolt "trampolining" off various durometer buffers and never saw any quantifiable amount of that energy returned/reflected into the forward stroke.

While I am happy to be corrected if wrong, I believe your weight does function as an ABW. I can hear it click back and forth in the BCG and you can observe in your video that a small gap between the weight and bolt closes when the bolt stops. A large gap won't work for an ABW because the ABW won't be were it needs to be to stop the bounce when the bolt lands on the barrel.
Yes it does!

-The 43g weight is a loose fit. yes! it is a drop in piece (49g is the same fit)

-It rattles back and forth during the recoil cycle. correct again

-it acts as a dynamic ABW. Yup...

Any weight that isn't welded is going to move. The gap is too small to significantly alter the timing of the recoil impulse. We're talking like .010" or less. The bolt collects it almost immediately. As the two parts reverse direction and head forward, the "overlap" isn't large enough to delay the bolt's forward motion but is large enough to get a de-bounce on closing that a welded weight wouldn't provide

There are 2 sweetspots;
-High-weight:small-gap
-Low-weight:big-gap

Tuning that weight:gap ratio to get constructive interference with a light weight was always beyond my math capabilities to estimate. The 40g@ .160" long was a shot in the dark and a total miss. I've tried it many times since and the action is always erratic at best.

The Ceiner ABW used a slot in the weight's upper web to make the timing asymmetrical....little gap traveling backward, BIG gap on the return stroke. This leaves the weight at the rear, while the bolt gets a head start, and as its collected it slows the bolt down just as it closes. The light weight then runs into the back of the bolt body to prevent a bounce. This was/is done so the bolt had/has sufficient fwd velocity to trip the auto sear without affecting the cycle. (This is like the HALO jump of bolt travel, they open the chute at the last moment)

In all these ABW systems,
The trade-off to all this bouncing around is the weight is always hammering on itself under the spring guide's tail again pressure density. I used 416L Stainless and tested my weights 10k rounds to make sure they didn't hammer themselves "out of time" and negate the de-bounce effect. If you made a weight out of lead it would hammer itself out of time in a few mags. I was afraid the ends would peen up over time and everything would wedge up rigid.
 
#10 ·
LeShaghal In all these ABW systems said:
again pressure density[/U]. I used 416L Stainless and tested my weights 10k rounds to make sure they didn't hammer themselves "out of time" and negate the de-bounce effect. If you made a weight out of lead it would hammer itself out of time in a few mags. I was afraid the ends would peen up over time and everything would wedge up rigid.
This statement by LS caught my attention. I noted that ColH is offering his weight system with a weight made of what appears to be brass. Stainless is offered as well. I was wondering if the BRASS weight tends to "hammer" (wear) noticeably compared to the stainless weight? So I guess this question should be directed to ColH and MikeAK-- Approximately how many rounds (LS indicated he fired 10K rounds during testing) have been fired in testing on both weight materials, and is there any significant hammering noted on the weights under the spring guide's tail? Just curious in any differences between the two. Sorry MikeAK, I'm still talking I guess:D
 
#11 ·
This statement by LS caught my attention. I noted that ColH is offering his weight system with a weight made of what appears to be brass. Stainless is offered as well. I was wondering if the BRASS weight tends to "hammer" (wear) noticeably compared to the stainless weight?
Given Col. H's offer to replace failing brass parts with SS, it seems safe to assume that these brass weights will wear more quickly.

I am not very concerned about 1) losing the anti-bounce quality that a bit of wiggle room causes, or 2) wear of or damage to the weight. I am more concerned about wear to the $160 BCG.

I am contemplating using JB Weld to glue/shim it to the bolt so that there is no part of the cycle in which either part is accelerating toward any other part. The bolt speed reduction (with less force applied to the bolt stop) should still suffice. (I suppose I could melt some plastic or use some kind of glue, but I already have JB Weld and it seems pretty incompressible when cured.)
 
#29 ·
I'm not at all confident that the weight contributed to this episode....
you've also a second and third variable with which I've not dealt
As someone who deals almost exclusively in those variables. Believe me, in all confidence, the weight contributes

If the as system hadn't spewed junk onto the BCG, do you think this would have been a problem? If you were using any other round, do you think this would have been a problem?
No and NO

It's a Gas System, SSS, 26" Barrel, 49g weight, No Buffer specific problem.
Which is why I posted my setup.

Let me Reiterate....
I'm not saying these are unsafe, or flawed!
The SSS is a special case and I'm using a conversion not a dedicated .22lr upper.
What I'm saying is;
Remember we're still in pretty uncharted waters here, so proceed with caution!
 
#31 ·
reasons 4

LS - I'm just curious why you are shooting the conversion through your 26" WOA match setup? Is it just to get extra trigger time with your match rifle? As you are obviously aware, there are so many excellent options for dedicated 22LR barrels.
Reasons:

1. I already had it and it already has $$$ worth of sights on top...its not the extra upper, its the $900 in sights that burns me.

2.Silhouette shooting: @ 300 yrds its hard to knock over a .22bpcr ram with 40gr subsonics. The SSS stabilizes in the 1:8 twist and shoots <2moa with my 49g weight. Hits like a sledgehammer when I do my job.

3.M261 I bought a compass lake .22 match upper, and its great. BUT I only have one GI mag and it is soooo frustrating to shoot 3 and pump 7 live ones on the ground. (I started a thread about this and talylorkh got me pointed in the right direction. )

4.My .22 spacegun isn't yet complete new thread on that when the time comes. It's pretty action packed
here's a Preview:


yeah that's a 34" barrel
 
#34 ·
How does the CMMG anti-bounce weight compare to the BB weight kit? I understand it only weighs 3/4 oz. Does it take any bounce out? I haven't seen any high speed video of the ABW kit but was wondering, send it has more dead blow movement than the BB weight. Thanks

Sent from my Pixel 3 XL using Tapatalk
 
#35 ·
I carved out a bit of the work day to make it to the range and function test both the Leshaghal (LS) and BoreBuddy (BB) weights.

Summary: they're great. The LS on my scale comes in at 44 grams. I don't recall if the BB was 44 or 47 grams.

The LS was in a bolt with a cut recoil spring, and I cut it so short that it barely has an oomph left at the end of the bolt travel. The bolt failed to go all the way into battery only once. This is a spring problem. I has some indication of excellent accuracy with Aguila HV. I used a hard polymer spacer at the back of the BCG.

The BB was in a BCG with a normal spring. Function was perfect. The buffer for the BB weight was just a silicone dot from Home Depot

Thunderbolt was tested in both because it can cause the bolt to beat the BHO to the punch. That never happened with either weight.

Though the recoil forces are modest, the added reciprocating mass was noticeable.
 
#36 ·
Though the recoil forces are modest, the added reciprocating mass was noticeable.
My buddy was actually able to bump fire the AR22 with the 2.8oz weight installed and stingers last range trip with his Geissele single stage trigger with the heavy spring. He's going to try the light trigger spring next range trip to see if he can empty a whole 25rd mag. I personally find the added recoil useful for training purposes.

:Blasting_
 
#39 ·
Without sounding like an uneducated boob, this conversation about bolt bounce is quite interesting and something I have thought could happen in almost any blowback operated semi-auto platform. I have never read much about this though until I read through all the threads here on this topic. I own a couple of dedicated .22LR AR rifles and is this bolt bounce problem something that occurs on all AR's of this nature, or just certain ones? I don't shoot hyper velocity ammunition in my rifles. Is purchasing one of these weight kits something everyone should consider doing to eliminate bolt bounce? Sorry for coming into the discussion late.

Rick H.
 
#40 · (Edited)
Is purchasing one of these weight kits something everyone should consider doing to eliminate bolt bounce?
Bolt bounce isn't a big problem for me. I shoot semi-automatic only, so an out of battery shot isn't a real danger for me. The dramatic bolt bounce seen in slow motion video arguably is hard on the extractor.

High bolt speed can be a problem for me. Very high bolt speeds in some of my two stage triggers can cause the disconnect to fail to catch the hammer, and can cause the bolt to beat or over-ride the bolt catch.

I think anyone who uses a Catch22 or Better Mag Adapter can benefit from the slower bolt speed. The weight also makes mounting a buffer easier.
 
#41 ·
I read this thread and bought a stainless steel weight from Bore Buddy. I did not realize CMMG sold a weight also (it has serrations on the weight for the forward assist). I did receive an email msg from Bore Buddy informing the buyers that his weight(s) work with CMMG bolts (round firing pin). I have not received mine yet (anticipate Jun 16 mailing) and I highly anticipate its arrival. Getting every bit of accuracy is important to me with less wear and tear on parts. I do have every Bore Buddy part except for the firing pin. I do have the CMMG bolt and barrel.
 
#44 ·
buffers

-The buffers I made were cut from a sheet so they will touch a bore buddy weight or my 49g weight, not the 43g. (this was to keep them cheap, but I abandoned them right off)

-The shore/durometer of the urethane was spec'd to handle a bolt without a weight.

-I was never sold on the buffer idea. Alone it's a band-aide, Used in conjunction with the weight it "compliments" function but isn't strictly necessary. The weight was, and still is, the answer.

-If your weight is correct for your ammo/barrel length combo the buffer won't be doing much (which is why you can use some Xtra squishy stuff if you insist)

-If the original thread was still up, you could see I brought all I could contribute to this. As far as I'm concerned, the mountain has been conquered. (and with the BoreBuddy weight system for sale, there's now a chateau at summit)
so
I've dropped the last 2 weights I'll make in the mail and I'm on to the next peak.

Conclusion: 48-49g gets me the everything I want out of the system.
("Exoticts" like velociters or "Hyper" ammo, or the SSS.... will require more or less and I'll look on here for the best combinations!)
 
#45 ·
Thanks for the replies gents, but I still have questions. My favorite dedicated .22 LR upper was one of the early DPMS 20" service rifle models. I don't shoot it a lot as parts are getting scarce for it as well as magazines. Anything I can do to make life easier on that platform is a plus in my book. Watching the videos of how bolts react from the round going off is indeed eye-opening. I simply had no idea .22 LR bolts were reacting in the manner shown, it's almost as if a round is being fired twice when the bolt returns if that makes sense. It also explains a lot of the marks that I see on the bolt after shooting only a few rounds. I am also surprised in some of these instances that the extractor is not pulling the round out of the chamber as the bolt bounces backwards.

So in my case, with having no high speed video of my DPMS setup being fired, would the consensus be to obtain one of these mechanisms to reduce or eliminate this issue? If so, which one would be best for my DPMS upper? Thanks again for any help and/or information.

Rick H.
 
#46 · (Edited)
Thanks for the replies gents, but I still have questions. My favorite dedicated .22 LR upper was one of the early DPMS 20" service rifle models.
Rick, I think your bolt differs from the Ceiner/CMMG pattern (the kind shown in post #14) so profoundly that none of these weights would work with your existing bolt. In the upside, the DPMS bolt looks like it's longer and therefore heavier to begin with.
 
#49 ·
Received my stainless steel bolt weight yesterday while I was on duty. Very nice quality, I did polish the bottom a little (to satisfy my OCD, lol) Installed it this morning, I can definitely tell a difference in the way it sounds and feels with the weight installed. Only shot a 25 round mag and had no malfunctions with the Winchester M-22. I will try some Remington subsonic tonight after the grandson leaves and report later.

Sent from my Pixel 3 XL using Tapatalk
 
#50 ·
I found something interesting out that I did not know before. I didn't realize that a 4.5" barreled pistol could be finicky. My pistol functioned fine with CCI Standard Velocity and CCI AR Tactical before installing the stainless steel weight from Bore Buddy. My pistol definitely did not function well with the CCI Standard after installing the bolt weight. Since I don't use a suppressor and the pistol still functions very well with high velocity, I'll stick with that. The pistol was smoother and cleaner with the added bolt weight. I didn't have near the amount of carbon inside the upper as I did before.

This was my first short pistol build.
 
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