I had Devon 10110 shink bad enough to cause accuracy issues on my rifles. Recoil lugs were no longer making proper contact on the sides so action was free to create slight rotational torque. re-torquing screws would not cure contact issues on the sides of lugs. Skim bedded over it with JB Weld and accuracy came back, and actually even a little better than it was before. I don’t use Devcon anymore, but because of that issue, epoxies shrinking does matter to me due to the evidence seen on targets.
I used to tape the side of the lugs to make stock removal very easy, but I always seems to have better overall results when I bed them tight. Especially over time. But I suppose a rifle can be tuned to a certain degree with pretty much any bedding method
Tested the tight/loose recoil lug sides on the Kodiaks, Pandas (with front recoil lug added aka: 'Pand-iak') and the 700-style round actions. Testing was at 100 and 200 with the 30BR. Based on that testing, recoil lug side clearance is my approach. Additionally, on a flat sided action (Panda for example), clearance around the entire periphery showed benefits. This is particularly true around the tang as being tight here can give the effect of a second 'recoil lug' which does nothing good for accuracy. Obviously, we're talking bolt ins, here.
Right on!!!!!
Say what? I can't hear you
Update to mixing with acetone to thin. As of yesterday afternoon (~24hrs after mixing) it was still soft enough to slightly push a fingernail into. This seems about normal. As of a bit ago (~36hrs) it's hardened up a lot but you can still get the slightest fingernail mark into it. Still seems normal. I'll see how it does after another day or two. If in the end it hardens up fine I may do a larger block and machine it flat on two sides to see how it holds up dimensionally after the acetone thinning.
I agree with both of you!!!
While I can agree in some of that, I disagree on rotational forces. Perhaps a 30BR or small 6mm variant doesn’t have much rotational forces, but try holding a bare 338 Lapua barreled action in your hand for that test. Even big fast 6.5s running 140gr bullets in excess of 3200 fps will jump and rotate violently or a bench when shooting from a bipod. I tested this on my 6.5 Remington Magnum which is a hunting weight rifle. On a concrete bench, if you were to just pull the trigger with no shoulder or wrist/hand support on the rifle, it would come back and and jump the feet of the bipod enough to flip itself right over on its side. It’s more about bullet size and speed, and perhaps weight of the rifle. A 30 BR has neither large size bullets or fast speeds and generally are built for BR exclusively which are heavier weight rifles.Alex, you know me...I have to test stuff.
As far as rotational force goes, there's really not much of that. I know that doesn't sound right but the reason is than the majority of all vectored forces are manifested in rearward motion (recoil). The only way rotational force could be enough of a player would be to literally have gun locked into position where it was unable to move rearward when fired. Jim Borden included this in one of his excellent articles in Precision Shooting. The clamping force of two 1/4-28 actions screws are well in excess of any real rotational forces during firing. For anyone that wants to test that, just hold a barrelled action in your hand and fire it. Which brings us to another area...that of the coefficient of friction between an action and the bedding compound and the amount of contact area. As you point out, many of the listed compounds will do a good job. As far as the shrinkage rate goes, that's a hard one to prove or disprove other than by actual use. Common sense tells us that for a glue in, we want a less viscous product than for a conventional pillar bed job. And if people doing glue ins aren't pre bedding first, there's a potential for a lot of permanent stress permanently built into the final product.
In the end, it's the target that matters. But we really have to test this stuff to know. Too many shooters won't look into things past the: "Do you want fries with that?" stage. And it's also good for those that test to go back and revisit things at times. Things evolve and shooters should, too. Matter of fact, after wringing out a new barrel on my HV 30BR, I'm going to tighten up the sides of the lug in the bedding and retest.
Just my opinion. -Al
I didn't mean to imply there's no rotational force...there has to be because of the rifling. The management of that rotational force in the stock is easily handled with the friction between the bedding and action and the action screws. If there's rotational movement of the action in the stock, there's bigger problems in play.
What you said about lot to lot variation is a fact. I was a marine tex guy at one time. But I started having problems with it shrinking. So bad it would suck down below the stock line as it cured. And I mean it would suck down a lot. I bed my stocks before I cut the trigger guard so it was not running out the bottom. I just couldnt fix it so I ended up back on Devcon. I go through a lot of epoxy, and have not seen much difference in the Devcon. Weighing the stuff is important, I wouldnt recommend mixing by volume. 9 to 1 for Devcon, I think marine tex was 6.3 to 1? Double check that. The initial shrinkage that happens while curing is far more than what happens over long periods of time in my experience. So thats my main focus.
I hear ya, but I don’t want the action screws handing that force on a receiver. That job is for a barrel recoil lug, bedding cut (XP cut) or bottom of a flat receiver
Yeah I haven’t used enough lots of Marine Tex to find bad variation or any major shrinkage, but I wouldn’t be surprised if I did receive a bad batch one day. So far my Marine Tex bedded stocks have stayed pretty dang tight and no issues over time.
