SVT40- accuracy controls

I'm curious about the anecdotal stories of accuracy problems including wildly errant first shot so I decided to begin a little accuracy test of my own examples. For starters I thought I'd strip each of the four and attempt to see how the action/ barrel are bedded in these refurbs. The rifles are Tulas (two 41's, one '42, and one '44). Two have the groove at top of the bolt cover and are probable original snipers. All have very well preserved metal surfaces and show signs of quality work in the refurb. To be brief, all four show consistant bedding points as shown on the photo. With the stock installed all four have significant (5 lb+) up-pressure at the tip of the stock. This pressure is either entirely on the ring in the lower metal jacket or, in one rifle, on both metal and about one inch of the wood. I don't believe the metal jacket assembly is rigid enough to impart any up-pressure at its tip but, rather, will flex as the barrel oscillates. The cleaning rod is also "along for the ride". Rearward, the barrel to barrel re-inforce are free while the receiver ring and small flat forward of the cross-pin bear on the stock. Of great interest to me, three of the four display absolutely zero longitudinal free-play of action in stock with cross-pin and trigger assembly inplace. The fourth (a non-sniper) has considerable free-play (at least 0.008") which is what I get the impression some feel could lead to the big spread between first and second shots and which could be solved with shims. To me, the biggest unknown seems to be the effect of all the junk hanging on the front of the barrel (ie. forward of the tip of the stock). These parts are probably highly variable in fit from gun to gun. So, question to the accurizing gurus out there: How well thought out is the position of the stock-end up-pressure from a barrel oscillation point of view and what approaches might be worth considering for optimizing one of these rifles? I plan to take a couple to the range this weekend to start some tests. Love the design- simple, logical.

Ridolpho

You may be a trail blazer on the subject, at least in this hemisphere. I'm down to two and a few spare parts. Both are Finnish captures, so no Post-WWII rework. Looking forward to your findings!

Good thread, looking forward to the results..


The soldier above all others prays for peace, for it is the soldier who must suffer and bear the deepest wounds and scars of war.

Douglas MacArthur

Thank's guys. I'll be hitting the range tomorrow (Saturday) with a big pile of quality commercial ammo. Sunday we may get our first big snow of the season. I wish there was more written (in english) on the SVT38/40 but all it has received so far seems to be passing (but useful) mention in books about other rifles (for example, in "Hitler's Garands" by Weaver). Has anyone out there any knowledge about books in Russian that might exist- I've recently tracked down a Russian language prof. at the local University.

Ridolpho

jmoore: I forgot to ask- what, if any, repairs or changes did the Finlanders make to your two rifles?

Ridolpho

They did nothing more than mix some parts and add the SA mark, as far as I can tell. One is matching except for the trigger group, the other may have a few other mismatched parts, but both keep the parts to the same mfg.

Well, I can see this is going to be a lot tougher than I thought. Made it to the range with two rifles but ended up only shooting one ('42 Tula with sniper notch). This gun has very tight action body fit- no detectable free play but bore is only fair with dark, slightly pitted grooves/ decent rifling overall. The rest of the mechanicals look hardly used post refurb so strange the bore is as it is. Unfortunately the gun was not zeroed (way off) and the equipment I had with me wasn't up to the job of drifting the front leaf. Forced me to hold off to right on the targets I had which, I might say, weren't much good for these open sights. Then I had to play with the gas setting to get it cycling (totally reliable on 1.3). Main fact about this gun is long, heavy trigger pull- one of the worst I've run into. Photos show the two best (aargh) 100m 5 shot groups of the day. The one on the right is about 5 inches, the one on the left has 3 shots in about 1.25 inch and a fourth pulled and a fifth......? It slam-fired after number 4 and probably went well above the target. Went to put the scope on for a few groups only to find I'd misplaced the pin. End of session. The ammo that I used was "WPA" steel-case, 174gr fmj. It's my intention to establish typical groups with all four (well, now it's five) of my SVT's which have a variety of action fit, bore condition, trigger pull, etc. Three of the five will hold a scope and these will be shot both scoped and over the iron sights. Might try a few experiments like shooting without cleaning rod/ metal guards, shimming loose action bodies, etc. I'll revive this thread in a month or two when I've finished. You might want to buy stock in "WPA".

Ridolpho

I figured out how to lighten the trigger pull, but it requires relocating the spring seat on the sear. It's the strangest firing mechanism! If you go swapping trigger groups, watch that the disconnector pin in the receiver engages properly the safety bent at the front of the pack. Very often it won't work right without fitting.

There are a few slow motion videos of the SVT40 firing that might give you a hint as to what pressure points might be more important..

I think this is one but I'm unable to view it right now.
SVT-40 Slow Motion 10 rounds - YouTube

Quote:

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Originally Posted by jjjxlr8

There are a few slow motion videos of the SVT40 firing that might give you a hint as to what pressure points might be more important..

I think this is one but I'm unable to view it right now.
SVT-40 Slow Motion 10 rounds - YouTube

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Yup, that's the one..

jjjxlr8: that's certainly more entertaining than the Steelers game last weekend! What catches my eye initially is the abrupt downward bend of the barrel ahead of the forend tip upon firing. You can see the captive cleaning rod flexing as the barrel bends- is it me or does it actually contact the bottom of the lower metal guard? Love to see a super-slo mo of one in full auto mode. Going to be staring at this for a while.

Ridolpho

Foul early spring weather and I still haven't been to the range since October. I have, however, added to the collection and now have '41 and '42 original snipers with good bores. Each has been equipped with an aftermarket bracket and a real scope and both are bore-sighted and ready to go (photo shows the '41). In the meantime I've been using a '41 Tula that I bought for $200.00 before Christmas to play with bedding techniques. Seems to boil down to the through stock pin being an axis and forend tip pressure being adjustable from both ends. I've made shims out of 0.012 gasket paper for the rear that also snug up the action-body fit in the stock. At the front end I've used epoxy to tighten the fit between barrel and lower handguard. This one has about 6 lbs up-pressure now which feels right- but is that how they're supposed to be set up? There is a new book out in Russian and a gentleman from the Ukraine has told me it outlines original Russian armorers techniques for shimming and that the goal was to have significant forend tip pressure.
Also monitored various websites over the winter for anecdotal info (particularly north of 49 where a lot of people are shooting these things). Unsubstantiated claims have been made that 1) removing the cleaning rod improves accuracy; 2) that free-floating the barrel improves accuracy; 3) that the gas setting affects accuracy. That last one intrigues me as on my last range trip in November a '42 Tula that had been showing potential for 2 inch groups suddenly opened up to 12-15 inches coincident with erratic cycling at the setting that had worked well in Sept. I'm now convinced that the initial downward bending of the barrel in the ultra-slow motion film is not whip but, rather, bending due to inertia of the bolt/ carrier effectively pushing out on the piston. Then, if the carrier is sluggish due to congealed grease it would potentially affect shots somewhat randomly (call it a theory).
So, my first step is going to be a range session with the test-bed gun. I'll shoot it with various forend pressures (easily adjustable with the shims) and then I'll remove all shims and swap the handguard for one without the epoxy and compare results. I'm aiming to try to use one of the snipers in RangeRovers's vintage battle rifle shoot in June so I've got to get cracking.

This whole experiment has proven much tougher than I'd originally expected. A really crappy spring has left my club range unusable as recently as May 8 (2 ft of snow on the steep access road). Had 2 SVT's ready to go so went to the public range (dump?) next door which was a mud-hole. Managed to get a few groups (all 100 yards)from each so I've now got baselines on 3 guns. The previous test subject was a '42 (field conversion) sniper. With a tight fitting action to stock and 5 lbs up-pressure at the forend tip it was brutally innacurate.
.....First one tested this time was a genuine former '41 sniper. This one needed shim work to snug up action in stock and came from re-furb with a strongly free-floating barrel. This wasn't bad- target 1 shows two 5 shot efforts. The left was typical- 3 or 4 not bad then a flyer usually due to the horrific trigger. For the right side group I made a real effort to settle down and modify my pull to accomodate. Got my best group with an SVT so-far. Max 2 inch center to center with 3 in 3/4 inch. Target 2 was another that was going well (3 in 3/4 inch) then the old girl slam-fired! This rifle (floated) seems to have good potential, mainly limited by the incredibly long trigger pull (and the shooter). The best result is as good as I can do with my No.4 T. Next step for this one is to insert a cylindrical shim at forend tip which gives about 8 lbs up pressure and repeat. Note that the gas was set at 1.5 which gave very strong, reliable cycling.
.....Second tested was my $200.00 "parts gun" (final photo). Target 3 shows a 7 shot group (iron sights, of course). All 5 inside 5 inches and 4 inside approx 2.5 inch. This is better than I could do with the earlier tested '42 with scope. This one has strong (>5 lb) up pressure utilizing shims as shown in an earlier post. Next step for this one is to increase gas setting and retest as is, then remove all shims for a free-float. Trigger poor as with the sniper and I need to use targets more suited for open sights as these ones were pushing my vision.
.....For these tests the temp was about 60F with very light breeze. The '41 sniper rifle may have some original parts on it? The triggerguard is stamped and the, obviously well used stock, doesn't appear to be re-stamped. The replica scope mount fits perfectly and allows free movement on recoil. The bores on both these guns would be described as good, with strong rifling but somewhat dark grooves. They're certainly not the best.
.....These two have restored my faith in SVT's after the first miserable results with the '42. I've always found it tough to believe the Russians, usually quite practical, would spend as much time developing the SVT for sniping if it didn't have decent accuracy potential and I think these current results show that they do. In future efforts I'll retry the sniper with 5 shots from cold to see how the first shot deviates from the zero. I'd love to see some other folks results with their SVT's so please don't be worried about highjacking the thread.

Ridolpho

Greetings Mr. Ridolpho,

In all my righteous might, I'm determined to gain the inevitable upper hand and push on to absolute victory...err, I mean, get my 41 SVT-40 to shoot better. So I'm reaching out to you, and anyone else, who may have discovered a trick or two in tuning these babies for better accuracy.

I working on an idea regarding making a barrel insert to allow the barrel to be held firmly in the barrel band clamp instead of having the clamps tight but only being capable of securing the bottom of the barrel, leaving the upper portion open to "whip"

---------- Post added at 12:55 PM ---------- Previous post was at 12:48 PM ----------

Nice Brownells video. Check out the barrel "whip" at 1:25 ish.

From the Vault: Tokarev SVT-40 Rifle - YouTube

Good luck, I miss mine from years back. Interesting to see how the gas catch cup on the rod seems to have an effect (opposing reaction) on the barrel flex as well as the muzzle brake. Mine had the serrated slots. The problem I had with it was not the bedding, but that the resonation appeared to release the hammer so that it would pop off two for one pull. Needless to say, this also affected accuracy as the second round was off a bit.

Hey thanks man. I'm a dedicated tinkerer at heart and love a challenge. I've never read any thing with respect to the idea I want to try, so what the heck I have to at least try.

In your case, that's a bit of a melon twister. (self induced slam fire) Curious, was your hammer-sear engagement played with...a little too much? I ask because I've reduced the trigger travel on mine, and poundage wise its sitting around 5.5 pounds with what feels like about 25-30% less travel. Much nicer trigger. (and passes the drop test)

Attachment 99079PaulTT-33: Fully clamping the barrel at the forend tip is something I haven't tried. The original bedding approach was to have the barrel firmly bearing on the metal ring of the lower metal guard but free to move a bit before returning to the same configuration for the next shot. The Soviets concluded that the main problem with this setup was the ability of the lower guard (with the ring) to shift between shots, causing flyers. I am convinced that the Soviets switched over to fully floating barrel by '43 which is easy to do by means of a bit of inletting at the rear deck of the stock. Supporting this theory is the existence of a simplified type of lower guard which does not have the barrel support ring. I've had my best "accurizing" luck with the floated barrel so far. Your idea would be easy to test and one would think it would further dampen oscillation beyond just having up-pressure at the forend tip. One question would be how tight? If you clamp it too tightly will it cause problems as the barrel heats, etc? The attached photo shows some SVT targets (all 100m). Two are noteworthy- the '42 Sniper has so-far defeated my efforts but can't be floated without significantly modifying the stock. The target shown was shot with enhanced up-pressure- as it came from refurb it had no pressure and wouldn't group within a foot. The lower right target is from my most accurate SVT- a simplified '41 Tula with neither good bore nor good bedding. Unbelievably it made 5 shot groups like this time after time with Chinese surplus. Good luck with your efforts. can you show us what your "before" accuracy has been like?

Ridolpho

I really like the A.P.I circles on your target Ridolpho. Just like the Soviets did it. More relevant. Having said that, you're 41 "simplified" shoots very well. Correction, you sir shoot it very well. Credit where credit is due. You seem to have this rifles measure. Day by day I'm hope to as well.

Though I've owned this rifle for a few years now, I've only taken it out to shoot a couple of times a year. Which kinda puzzles me, because I really love this round! Seeking insight and getting actual hands on knowledge is great. So far everything's been trial (based on some theory) and error for me. That's why I value your's, and any one else's opinion(s). Like they say here in the sticks, "its aint braggin, if you can drag it out of the ditch"

However in my case the showing of before and after targets will be tough. After checking though my keepers, all I have are some I shot in January this year. And most of those were 25 yard sight ins. The 100 yard ones likely got 86'd out of frustration. However I did find the last one I shot. Come to think of it, it's probably why I haven't shot the old mule that much.

I have my 50 yard target and my 100 yard dispersal I'll include here....

Yesterday I was called away and had to leave the post unfinished, but I wanted to thank you for the question on how tight to make this area (under top barrel band) in relation to barrel heating. I realize there will need to be some "running clearance" but wondered what has been your experience here? And what gas setting are you running in the 41 simplified?

Anyway you get the direction I'm heading in, applying some down force on top of the barrel to keep it in place via an "insert" under the top hand guard, locking it all together. I plan on making a "proof of concept" from JB Steel Stik...should prove interesting, inexpensive, easy to make, so not a big loss if a complete failure. Just one little piece of the puzzle that is the SVT-40

I've previously removed a small up pressure point from the barrel channel. A locking screw on the tab used to catch and hold the bottom of the barrel band was protruding thru and making contact with the barrel. So naturally due to harmonics it was slightly gouging the bottom of the barrel. To further that I've relieved the barrel channel - free floated - to see what difference that might also make. I'm not expecting a miracle, but I was encouraged to read your comment on barrel floating this rifle. I'll take a nice little improvement from a tiny bit of effort if I can get it. My stock/action area is completely without any freeplay. I have perfect fit between the action and the trigger group, which is easy to remove, and goes back together with some - but not too much force. I did a little trigger work to reduce travel as well. I also made a slight change to the rear sight blade by applying flat black paint (like smoking your sight to aid with glare from the sun) along with a white painted front post and a dab of black paint on its tip, to improve contrast. (My eyes need all the extra I can give them.)
The more I examine this rifle the more it seems to break from the Russian way of thinking, where "best is the enemy of good enough" a - la the SKS, AK-47. However the b.band clamp area does seem an area that may respond to a little detail work. I'll keep you posted. (could take a bit though, its -29 C this morning)

---------- Post added at 09:08 AM ---------- Previous post was at 09:06 AM ----------

I forgot to include this earlier. Lots of historically interesting reading.

Tokarev SVT-40. Identifying, collecting and FAQ.

Good stuff. interesting to see that good group with the Chinese surplus. With a Molot PU I get 1.5" 5 shots groups regularly at 100yds with the Chinese stuff, frequently 3 shots grouping under an inch. Much better than I get with other makes of surplus 7.62x54R.I have not shot much With the warm in my SVTs though Contrary to everything I hear/read, detail disassembly/reassembly of SVT is a real pain for my old arthritic hands.With the warm weather I'll try and contribute some to your study.With the way the SVT writhes in your hands when fired , I have my doubts about ever getting great accuracy with these rifles.